1. Field of the Invention
The present invention relates to electric and hybrid electric vehicles and, more particularly, a system and method for wirelessly charging vehicle batteries while stationary or in motion.
2. Description of the Related Art
The rapid development of a new electric vehicle fleet is being fueled by a “perfect storm” of pressures—to cut foreign oil consumption, reduce greenhouse gas pollution and revive USA based manufacturing. However a major impediment to the rapid growth of an electric vehicle fleet is the high cost, low reliability and performance limitations associated with vehicular energy storage—the battery. Other major components required to produce a low cost, high performance electric vehicle are currently ready for mass production—strong lightweight body, electric motor and associated electronic controller. Accordingly, there is a need in the art for utility-based power generation capacity that is capable of adapting to the electrical consumption posed by any reasonable growth in electrically powered transportation.
The U.S. Department of Energy is faced with the very difficult task of driving development that will transition the energy infrastructure of our nation from one primarily based upon early 20th century technologies to an infrastructure based upon early 21st century technologies. The key being that the required 21st century technology is only partially developed, with many missing pieces and not integrated. Transitioning the transportation sector to 21st century technology is one very important component that U.S. Department of Energy must address if it is to successfully drive this difficult transition.
Vehicle fleet electrification is a fundamental way for the U.S. Department of Energy to drive fuel efficient and low pollution electrical energy generation to ubiquitously change the present inefficient nature of fossil fuel consumption. The primary impediment to widespread adoption of electric bus, truck and automobile electrification is the disconnect between electric power generation and vehicle motors, currently bridged by battery technology that is costly, easily damaged and performance limiting. The U.S. Department of Energy is of course one of the important drivers of battery technology improvement, however this appears to be a long term developmental process. The U.S. Department of Energy thus needs an adjunct that can enable both current and longer term battery technologies to seamlessly transition into all modes of land transport. The focus upon higher and higher battery energy storage density at proportionately lower cost, volume and weight still ignores the difficulties associated with peak charging energy demands that grow larger with each improvement.
The present invention provides.
The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which:
Referring now to the drawings, wherein like reference numerals refer to like parts throughout, the present invention comprises a wireless automated vehicle energizing system, referred to hereinafter as WAVES. WAVES complements the current development of an electric vehicle fleet and provides a primary means for achieving national “energy security” for U.S. vehicular transportation. The present invention presents a clear path towards the near- and long term elimination of battery technology limitations regarding range, charging time and associated lifetime cost and real-time performance trades. The present invention also provides the U.S. with a way to leapfrog over potentially severe investments in conventional mass transit, by providing similar gains in efficiency and carbon reductions as it complements our currently flexible roadway transportation based infrastructure. WAVES can be a very large factor towards achieving U.S. international commitments regarding greenhouse gas reductions.
In general, the present invention provides a wireless means of charging “all electric” and “hybrid electric” vehicle batteries and is applicable to stationary and moving vehicles (in parking spaces and within the roadway). The present invention is also scalable for both new production vehicles and as an add-on to existing vehicles. Intra-city use is an initial target, with inter-city and inter-state follow-on. Consistent with the needs of both private and public transportation vehicles, the present invention also includes a fee-based system whereby charges are automatically levied in proportion to energy use.
The charging operation is automatic when enabled by the driver of vehicle 20, employing a wireless data communication links between PRMs 16 and each/any PTM 14 supplying power. PTMs 14 are in turn LAN (Local Area Network) and subsequently internet connected for energy billing. The intent of the static infrastructure of WAVES 10 is to provide energy “hot spots” whereby WAVES equipped vehicles can partially or completely recharge using individual parking area located PTMs 14. Dynamic charging is accomplished by the concatenation of additional PTMs as necessary to provide continuous wireless charging.
When dynamically charging, vehicle 20 is both recharged and energized on a continuous basis while in transit, providing a power transfer capability greater than that required by electric motor 22. The result being that subsequent to a long range trip, requiring perhaps many times the energy nominally available from battery 26, vehicle 20 leaves the highway with a battery in a high state of charge.
In either stationary or mobile mode, the driver can be automatically charged for energy use (and tolls as they may apply), such as in a manner directly analogous to the current EZ Pass system where a credit card account is periodically charged for usage fees.
It should be recognized by those of skill in the art that safety standards must be adopted for the effective implementation of WAVES 10 so that the various components of the present invention, including PTMs 14, PRMs 16, and associated grid power and internet interfaces, are designed for safe operation, meeting transportation, fire, electrical and magnetic field standards. For example, the Department of Transportation and National Traffic Safety Administration are pivotal sources of safety and compatibility standards that all U.S. based WAVES components must meet to insure roadway safety. Regarding magnetic field health standards, the present invention is designed to meet IEEE P1140 (a VDT standard) in the VLF band from 2 KHz to 400 KHz, with magnetic field strengths within the passenger compartment below 0.25 mG. Regarding electric field intensity health standards, WAVES meets IEEE P1140 with VLF band field strengths within the passenger compartment less than 2.5 Volts/Meter.
In a preferred embodiment, WAVES magnetic coupling fields alternate at a frequency at the upper portion of the VLF band. PTM 14 magnetic fields emanate through a Faraday shielded assembly with electrical fields of the power amplifier waveform and its harmonics attenuated to meet FCC radiated emissions limits. It is intended that all WAVES modules are U. L. approved as a first insurance of electrical safety. This implies that the design has been verified to prevent catastrophic fire and shock exposure under normal, worst case and failed modes of operation. Conservatively rated components, temperature control, rigorous power fusing, automatic shutdowns and fault detection and location are important design attributes in meeting overall electrical safety and reliability.
Reliable wireless data interlocking between PTM 14 and PRM 16 modules prevents power generation until a vehicle PRM 16 is in the immediate proximity of a given PTM 14. When immediate proximity is achieved, efficient power transfer is possible given that the vehicle has established a valid ID via two independent communications paths, i.e., a first proximity link 28 between the PRM 16 and PTM 14 and an internet or data link 30, as well as an additional and independent real-time check on vehicle presence via a valid second proximity link 32.
The inherently rapid attenuation of magnetic fields at distances beyond the 3 inch nominal roadway clearance between PTM 14 and PRM 16 means that the magnetic field strength is normally very weak at the floor level of vehicle 20. Free space magnetic attenuation can be expressed as proportional to 1/(distance ratio)3. Additionally, if the floor of vehicle 20 contains a suitably magnetically permeable material, such as iron or ferrite, this already weak magnetic field will be significantly further weakened by being shunted away from the passenger compartment. Furthermore, when PRM 16 is effectively coupling power from PTM 14, the majority of the magnetic field is shunted through the vehicle's PRM 16 with a significantly weakened field left to propagate across the remaining distance to the floor of the vehicle 20 (again at an attenuation factor equal to 1/(distance ratio)3). If desired, in-vehicle magnetic field sensing can be employed to alarm and otherwise inhibit a valid ID from being sent via the first proximity link, thus disabling PTM 14 power generation such as in cases of an accident.
Power transfer can only be enabled by the condition of two valid ID requests, one in relatively non-real-time via the Wi-Fi (radio) Data Link 30 and the other in real-time via the first proximity link (magnetic) 28. Note that first proximity link 28 operates through the same PTM coil 42 of PTM 14 utilized for magnetic power transfer to insure correlation with the power transfer footprint. The second proximity link 32 verification is an additional condition that must be met for power transfer. It operates independently from both the first proximity link 28 and the Internet access link 30 by utilizing a radio sensing subsystem. This 3-way enabling function in combination with Exciter Control criteria insure that no magnetic radiation occurs from any Power Transmit Module—Coil Electronics Subassembly (PTM-CES) 34 whenever there is not a PRM 16 directly above (or within adequate coupling range) of a PTM-CES 34. The requirement that all three conditions be met makes certain that there will be a valid vehicle PRM 16 ready to absorb energy and the presence of highly attenuated magnetic fringe fields due to the large range, vehicle PRM 16 absorption and chassis between PTM fields and vehicle passengers.
From the broader standpoint of traffic safety, WAVES 10 provides a basis for real-time comprehensive traffic density and speed data that are vital to an efficient traffic management system. This can include active feedback to individual vehicles or to traffic signals as well as to law enforcement.
WAVES Energy Requirements
The energy required by electric vehicles 20 traveling on a highway is dependent upon many factors including size, weight, speed, acceleration demands. At city traffic speeds below 50 mph the energy requirements are dominated by mass acceleration and tire/rolling losses. The average of these energy requirements, with dynamic braking significantly normalizing acceleration demands is, on average, less than the energy required at constant upper-end highway speeds. Therefore, WAVES 10 energy requirements are set by the more demanding high speed conditions. At approximately 40 to 50 MPH wind losses begin to dominate vehicle energy demands and wind losses increase disproportionately with increases in speed. Maximum highway speed as defined for WAVES 10 energy transfer purposes is set at 70 MPH, which is at or above most maximum legal speed limits within the continental US.
Electric vehicle miles per gallon equivalent is often expressed in electrical energy per mile or kilowatt hours per mile. The continuous required power for a vehicle 20 is then kilowatt hours per mile divided by hours per mile or “watts”. This continuous power requirement can be distributed equally across the number of coils within the vehicle's PRM 16 since its design efficiently combines individual coil powers to produce a single source of DC for vehicle battery 26 charging and motor energizing power. The vehicle PRM 16 insures that all of its pickup coils are energized (continuously) by sequentially enabling magnetic coupling from respective roadway PTM 14 transmitting coils as they pass under the PRM 16 pickup coils. It is then the net continuous power per PRM 16 coil that is at the core of the roadway electrical design requirement. The energy requirements for various scenarios may be seen in Table 1 below:
It should be emphasized that WAVES 10 provides significant utility in offsetting the normally high 26 to 86 kilowatt rates of discharge from vehicle batteries 20 during normal operation. Repeated high discharge rates can be especially problematic, leading to lack of capacity and early failure, as batteries age and as battery temperatures are lowered during winter. By continuously offsetting the need for long periods of high rates of discharge, WAVES 10 provides the ability to dramatically extend battery life as well as range. From the above chart it can be understood that the maximum continuous power per PRM 16 coil, a core requirement, is 2 kilowatts. This is for practical purposes identical to the peak PTM-CES 34 magnetic field power requirement. Average PTM-CES 34 magnetic field power is less, dependent upon the traffic density induced energization duty cycle.
WAVES Roadway and Parking Lot Installation
Roadway 36 installations for the present invention may range from entire highway systems such as interstates to all or portions of local or intrastate highways to parking lots. Smaller scale installations can include segments of highways such as at traffic signals, waiting lines and other cueing areas where traffic densities are high and vehicle dwell times are sufficient to allow significant, although transient, battery charging intervals.
In the overwhelming majority of installations, roadways and parking areas already exist. Therefore an emphasis is placed upon existing roadway installations in a way that makes such installations cost-effective and as minimally intrusive as possible. This implies a set of national standards, an automated means of implanting PTM 14 modules and reasonable access to grid 18 and internet connection points. New roadway installations can however engineer required interfaces in a rigorous manner, thus avoiding retrofits and other perhaps more indirect methods to accomplish interconnectivity.
In either existing or new cases, subsequent to a WAVES 10 installation, the roadway 36 must provide a seamless transition across PTMs 14, with no effects upon drivability and safety. This implies that PTMs 14 have an ability to support worst case traffic loads, present a skid-free surface and be resistant to sun, oil, fuel, water, ice, salt, sand and temperature extremes. During roadway 36 installation, PTMs 14 are preferably imbedded within a V-shaped channel 38 cut along the centerline of each driving lane to form a PTM lane 40. The walls of roadway channel 38 are lined with salt resistant concrete, coated with asphalt or tar. The corresponding V-shaped bottom of PTM 14 is designed to fully seat into the roadway channel 38, continuously sealed along both side-walls, with the top surface of the PTM 14 matching the level of the roadway 36. Vertical traffic loads are thus translated to forces perpendicular to the side-walls of the V-Channel as downward pressure is exerted upon PTM 14, thus securing it within the roadway channel. This triangular implementation provides a robust installation, given that the trussed triangular cross section throughout the length of each PTM 14 translates load forces with minimal deflection.
As seen in
The number of highway lanes and/or highway traffic density and type will determine the segmentation distance and the corresponding number of GPMIs 48 present. Combined Heat and Power (CHP) units 50 may be employed at GPMIs 48 to provide power backup to grid 18, peak power shaving for grid 18 during periods of intense overall usage (e.g. during rush hours and at noontime), or on grid 18 continuously, given favorable net metering contracting with the utility. It is not necessary to provide CHP 50 capability at each GPMI 48 to provide a significantly large margin of robustness to WAVES 10.
As seen in
Parking lots 54 can be served by single or multiple GPMIs 48. The power demands of vehicles 20 associated with parking lots 54 can be on the same order as the per vehicle power demands of a highway, since battery charging alone can readily be in the kilowatt level. CHP units 50 may also be employed at parking lot systems, as seen in
As noted within Table 2 below, parking lot individual car charging rates are conservatively limited to 15 KW while larger vehicles 20 are limited to 45 KW such that the continuous per PTM coil power is limited to approximately half of a coil's peak power rating. Note also that a 1 to 10 ratio of Plug-in Hybrid Electric Vehicle (PHEV) or all electric (EV) trucks & buses to cars has been maintained for the purpose of this analysis.
Given approximately a 70%-30% split between battery charging power and auxiliary power (e.g. air conditioning and heating) there remains significant power to provide upwards of 10 KW or 10 KWh/hour of battery energy recovery. This would be sufficient for approximately 20 miles of travel in a car traveling at 70 mph, or correspondingly, 160 miles of travel for an 8 hour work day charge. The ratio of battery charging to auxiliary power for trucks and buses may be different depending upon refrigeration and other demands.
It is useful to consider the case of retrofitting an average interstate highway system such as the New York State Thruway (I-90) as an example of the implementation of a WAVES 10 according to the present invention. The typical peak vehicle density for this particular highway under normal driving conditions is approximately 160 vehicles 20 per mile across a total of 4 lanes, 2 lanes running in each direction. With an average traffic mix of 90% cars and 10% buses or trucks traveling at 70 mph it is estimated that the instantaneous peak power demands of a one mile interval would be 5 megawatts. This 5 megawatt primary power demand is satisfied by a single power converter station or GPMI 48 that is grid interconnected at its input side and outputs multiphase power as primary power input to connected PTMs 14. Thus, a 6 phase GPMI 48 would produce 6 PTM primary power lines at 5 MW/4 Lanes/6 phases for approximately 200 KW per lane phase, as seen in Table 3 below:
Four kilovolts (4 kVAC) has been chosen as the PTM primary power distribution voltage as a reasonable compromise between the need for low (Î2)*R losses and requirements for high voltage safety and reliability. At 4 kilovolt per phase, the maximum current drawn by each lane phase would be 50 amperes which is sufficiently low to ensure low losses with modest gauge conductors. Note that the #10 gauge conductor reference in Table 3 is an “equivalent” reference and will be made up of individually insulated metal foils with sufficient area to achieve bulk resistance and skin effect losses equal to the DC resistance associated with a #10 gauge solid round copper conductor. Skin effect begins to be a significant loss factor for power transmission frequencies that are within the VLF band as detailed in Table 4 below.
A GPMI 48, spaced nominally at an interval of 1 mile along a highway, such as 1-90, forms a 4 lane PTM segment 46. In cases where peak power demands of a particular segment might exceed the capability of a given GPMI 48, the connectivity between GPMIs 48 along the multi-phase PTM primary supply lines provides a means for borrowing energy from adjacent segments when available. The multiphase wiring of the PTM primary supply line provides an additional degree of redundancy since individual phase failures gracefully degrade the power transmission capability of any affected PTMs 14.
From a backup power perspective, natural gas/fossil fueled micro-turbine electrical power generation may be used and spaced strategically, at perhaps 20 mile intervals, in conjunction with a GPMI 48 located perhaps at service/rest stop areas. For example, a micro turbine generator capable of 1 MW available from Capstone Turbine Corporation of Chatsworth, Calif. can be readily grid inter-tied to produce efficient (28% natural gas to electrical efficiency) and continuous grid power in parallel with an operating grid or as the case may be, emergency backup power for both a roadway segment and an associated service area. A 1 MW micro-turbine generator can also be configured as CHP unit 50, supplying the heating and air conditioning loads of the service area itself. A quantity of six such CHP units 50 can continuously provide 6 MW of electrical power (grid tied or backup) while also producing 100 million BTU per hour (@580 deg. F.) of thermal energy. Given the availability of natural gas or another suitable fuel, such CHP units 50 can pay for themselves during normal operating periods, while insuring the availability of vehicle charging power under grid failure conditions. During grid outages the availability of backup lane segments spaced every 20 miles gives vehicles 20 an opportunity to acquire a full charge at an associated rest stop parking area or, if sufficient energy exists within the vehicle's battery 26, continue on with the original journey with some assurance of periodic future boosts in charge.
From a renewable energy perspective, photo-voltaic (PV) powered grid inter-tied inverters, co-located along the highway, may be used to mitigate greenhouse gas generation as well as shave some of the peak grid loads during daytime periods. Shaving one half, or 2.5 MW of the GPMI's worst case vehicle traffic load, using PV power generation, would require an array (@ 20% efficiency) that is 1 mile long by 20 feet high (the entire segment length). This is not a totally unreasonable requirement for many areas along a typical interstate highway system and could readily pay for itself in energy savings alone over a 20 year period.
WAVES Household Installation
Referring to
Transmitting coils are located at the top-most portion of the rib-like midsection 62 of PTM 14 such that it reaches within 3″ of the vehicle's PRM 16 (while retracted). Rib 62 has a triangular cross-section pointed upward forming an easily cleaned top surface that prevents debris or animals from resting thereon. PTM 14 is designed to interface directly to 220 VAC 60 Hz power mains, and is capable of continuous vehicle charging at a rate of 6.6 kW. The design of household installation 56 could be similar to the electrical design of the current 3 coil demonstration prototype described below, with additional power amplifiers & Tank Coils, as also described below.
WAVES Light Rail and Electric Transit Bus Installation
WAVES technology according to the present invention provides a means for supporting light rail and electric bus systems by minimizing electrical and control infrastructure while enhancing efficiency. The use of PTMs 14 embedded within trackways or bus lanes facilitates the use of electric motor drives fed wirelessly, without overhead wires, hot rails or associated moving mechanical contacts. Control system automation uses the existing PTM data link 30 allowing spacing and other vehicle data to be managed in a way to provide real-time feedback for collision avoidance, scheduling and integration with other roadway traffic. Positional, velocity and vehicle ID data is particularly effective in maintaining safety in cases where light rail or bus traffic is interspersed with normal traffic. In such traffic, vehicles 20 of all types share a common PTM 14, however may have individual PRMs 16 optimized for particular applications. Batteries 26 on board light rail and bus vehicles 20 provide a means for storing braking energy and otherwise limit peak energy demands. Distributing PRMs 16, motors and energy storage within each “car” of a transit vehicle 20, inherently scales its ability to meet transport propulsion needs. In this way, long trains of many cars are possible with minimal added integration.
WAVES Return on Investment
It is important to consider how investments in WAVES infrastructure will be paid for, and the fairness doctrine that can be employed to insure long term acceptance. Grid energy has a cost that varies with the type and location of power sources which in turn can vary throughout the day and days of the week. The instantaneous cost of energy to the driver can and should be adjusted both to provide fair price to the grid but also as a way to provide adaptive choices that drivers can use to minimize their driving expenses while at the same time providing the power grid with greater capacity margins. Thus at peak driving times such as early morning, noontime and early evening, the cost per kilowatt-hour passed to the driver may be substantially greater than at other times of the day. The driver may in turn choose other commute times or avoid engagement the PRM during these times.
The cost of the grid supplied energy is however only one factor in determining the final cost per kilowatt-hour passed along to the driver. A toll can be assessed in addition, that reflects the long term investment infrastructure required to put WAVES in place on a given highway as well as shorter term maintenance costs.
A third factor added to the final cost per kilowatt hour is that of the peak power utilized by vehicle 20 such as to achieve optimum utilization of WAVES power supplying equipments. The objective of the peak power utilization surcharge is to reduce the probability of having to increase existing capacity or of over-stressing existing power generation and distribution equipments. Such a surcharge can be dynamic in that the charge is traffic density based with a utilization cost assessed as a factor of the energy used at any one interval of time and associated with traffic density or instantaneous electrical load on the system. Thus, higher energy users such as trucks and busses end up with higher costs for the energy that they use during times and locations of intense overall energy use.
On-board vehicle computer controller 24 can be programmed to consider all of these cost factors in deciding what route to take or when to activate the vehicle's PRM 16, which of course would include the vehicle's battery and its state of charge.
Parking lot located WAVES 10 offer some additional billing considerations. Parking lots associated directly with businesses may wish to incentivize use based to attract customers. The cost of delivered energy could be made artificially lower to accomplish greater visitation and/or be based upon a customer's purchases or history. Other factors that may be additionally attractive or simply deemed parking services, is that of supplying energy for vehicle air conditioning or heating while the vehicle is left unattended. This promotes safety and comfort while at the same time reduces the amount of energy required to overcome the accumulated environmentally induced loads once the vehicle leaves the parking area. WAVES 10 provides opportunities to employers wishing to pass along perks or incentivize certain employee habits by providing smart parking lots.
And finally, it must be stated that as with highway GPMI grid power backup, CHP micro-turbine generation can be used at businesses local to parking lots. This grid parallel inter-tie form of connection not only provides emergency backup electrical power for both business and WAVES during grid failure events, but also increases the level of overall net efficiency of heating, cooling and electrical power to nearly 90% for CHP GPMI associated businesses and highway vehicles 20.
It is also viable to consider the addition of renewable energy sources as a way to reduce environmental impacts associated with fossil fueled power generation and shave daytime load peaks from the grid. Specifically, regarding the use of PV renewable sources, it can be noted that typical parking areas represent extremely large areas of real estate, capable of receiving PV arrays with minimal impacts upon vehicle 20 use. Thus such a large amount of renewable energy, in direct proximity to point of use represents an efficient power source while at the same time offering an additional source of revenue and payback.
WAVES Grid Power Interface
Referring to
Normal grid power is in the form of high voltage and current 3 phase 60 Hz grid power to a set of lower voltage 480 VAC, 3-phase power, using 6 transformers 64 (or a single 3-phase transformer). A subsequent tie circuit 66 associated with each of the 480 VAC Phase Inverter 68 feeds allows for the decoupling of a given 60 Hz phase from the grid under failure or maintenance conditions, or the introduction of alternate sources of power. Such alternate sources can be an external CHP 50 whereby grid power 18 is supplanted entirely (grid failure mode) or simply “or-tied” for purposes of peak load sharing and net metering. Additionally, since the phase inverters 68 are insensitive to 60 Hz phase relationships (each having internal AC-DC rectification), there is the capability to simply bring in another source of 60 Hz power as a backup. The following set of 6 Phase Inverters 68 (A through F) are phase synchronized to produce properly phased relationships on their outputs that directly feed PTM 14 segments.
The design of the Phase Inverters 68 may be based on a “transformerless” IGBT approach. In a concatenated roadway segment implementation, each Phase Inverter 68 will be phase-locked to its respective incoming phase from the adjacent segment, thus allowing for a direct inter-tie between segments. This is not a firm requirement because segments can be operated independently; however, by inter-tying segments, power can be passed between segments or otherwise directly shared, thereby enhancing overall robustness of the roadway energizing system. Furthermore, such an inter-tie prevents an open transmission line effect which may require active termination (variable load via multi-phase AC to DC to grid (or other) inter-tie inverter(s)) to reduce reflections back through the segment.
Alternative GPMI 48 designs can be configured that do not employ transformers. This promotes reductions in GPMI 48 cost, weight and size.
Power Transmit Module (PTM) Primary Power Distribution
Referring to
Ripple in Full Wave Rectified Waveforms for Multiple Phases
Each phase of a multiple phase system is full wave rectified and the outputs combined to provide a DC power source. When all six rectified phases are combined the resulting DC waveform has a ripple as shown in the subsequent waveform of
Historically, all high power multiphase generation was achieved with rotating machinery. Under these conditions, mechanical constraints on coil winding and placement in the alternator forced generated phases to be uniformly spaced over 360 degrees. That is, the phase increment between adjacent phases was 2 π/Nφ degrees, where Nφ is the number of phases. Thus a 3 phase system had 120 degrees between phases, a 4 phase system had 90 degrees between phases, etc.
With modern high-power solid state inverters, the interval between phases can have any desired value. This phase is no longer constrained as it was in the past with machinery based multiphase alternators. This flexibility is used within WAVES 10 to synchronize ripple peaks in the rectified dc output voltage with demands for maximum power transfer at the coil amplifier. This insures that maximum power transfer is achievable without energy storage or costly filtering requirements. In particular, in WAVES 10 it is desirable to have a phase increment equal half of what it would have been for rotating machinery. Table 5 below summarizes ripple peaks for electronic and rotating machinery generation, where Nφ=Number of Phases.
Thus, the number of ripple peaks per cycle is 2 Nφ for all combinations of phase intervals and even or odd number of phases, except for the larger phase interval combined with an even number of phases (where it is reduced to Nφ).
Power Transmit Module (PTM) Magnetic Power Transmission Control
Vehicle mounted PRMs 16 contain a first proximity wireless link 28 that is used to enable power transmission at each roadway PTM 14 as PRM 16 passes over them. This power enabling signal is demodulated at each PTM 14 subassembly to reveal the vehicle's ID that is used in conjunction with a valid vehicle ID obtained from a fiber cable based Data Link (routed internally within each PTM) to enable power transmission to vehicle 20.
The degree of power coupled to a given vehicle 20 is limited by the maximum power capability of each PTM 14, aggregated by the number of simultaneously enabled coils and their respective instantaneous magnetic coupling coefficient (as expressed between PTM 14 and PRM 16). Furthermore, due to the parallel resonant transformer primary formed at each PTM-CES Tank Coil 74, the power required by each coil driving amplifier within the associated PTN-CES 74 subassembly is directly equal (minus relatively minor losses) to the power coupled to the vehicle. The amount of energy (power×time) provided by each PTM 14 is thereby measured for each vehicle passage and reported over the internet for billing purposes, along with other status information that has been acquired both organic to PTM 14 and from wireless data link 30 derived data. It should be noted that PTM 14 segment power demands can be capped at a power limit, as for example during above normal traffic loading, by purposely inhibiting individual or groups of PTM-CES units.
There is seen in
A high bandwidth WiFi wireless Data Link 30 is maintained between vehicle PRM 16 and roadway PTMs 14 (providing 2-way internet access, using PTM 14 contained fiber optic cables) for purposes of supplying required vehicle validation, billing and Performance Monitoring and Fault Location (PMFL). Data Link 30 has sufficient additional capacity to provide vehicle occupants with direct access to the internet while en-route. The WiFi nature of Data Link 30 communications allows for continuous access while a vehicle is on a WAVES 10 equipped highway, even while crossing lanes or otherwise not in direct magnetic power coupling range of a PTM 14. It should be noted that all highway vehicles preferably need access to this wireless Data Link 30, whether WAVES 10 equipped, fossil fueled or otherwise. Universal Data Link 30 connectivity enables features associated with traffic control, law enforcement and general communications to be available from to and from all vehicles 20 on the highway. Traffic safety, efficiency and related labor cost reductions strongly drive for the universal adoption of a generic WAVES wireless Data Link 30 standard.
Control signals are also sent via PTM 14 contained fiber optic cables to enable or disable individual or multiple PTM-CES 34 within a lane as may be required for maintenance or other purposes. Control and monitoring functions can be highly automated, centralized and remotely located from WAVES 10 equipped highways. Performance monitoring at each PTM-CES 34 is used to insure safe power generation under worst case loading and transmitted power levels as well as to report failures for future maintenance. PMFL includes thermal, over current and over voltage sensing to insure safe amplifier operating conditions at each PYM 14 coil subassembly.
Power Transmit Module (PTM) Spectrum
In a preferred embodiment of the present invention, PTM-CES 34 coils are nominally operating at 360 kHz. This is roughly in the middle of the U.S. FCC VLF sub-band from 305 kHz to 405 kHz allocated for the dual purpose of both Aeronautical Communications (radio beacons) and Aeronautical Mobile (communications). WAVES 10 will be treated by the FCC under radiated and conducted emissions regulations/standards similar to that of other electrical appliances, as in electric vehicles, computers, TVs, inverters etc. that have internal high power electronics operating within this radio spectrum. WAVES 10 wireless power is coupled as a magnetic field, through a magnetic window, with electromagnetic shielding and filtering designed to avoid unintended emissions from both PTM and PRM. The power carrier itself is narrowband with PTM-CES tank coil 74 Q's greater than 10 during full power coupling. Standard EMI verification can be conducted (similar to tests that are routinely performed on military electronics) to insure that all demonstration tests will comply with FCC regulations for both fundamental and harmonics of the power carrier.
Primary Power Distribution (6 phase) Spectrum
Direct division of six of the PTM 14 operational frequency, thus nominally 60 kHz each phase. Due to National Time Code usage of the 60 kHz channel, the suggested operational frequency should most likely be just below or above the time code spectrum. Thus, PTM 14 operating frequency would be above and below 360 kHz by a factor of 6 times the difference in primary power frequency respectfully above and below 60 kHz. The cable shielding and multiple phase nature of the primary power distribution should greatly attenuate any unintended RF radiation at 60 kHz.
Power Transmit Module (PTM) Roadway Interface
PTMs 14 are sealed and ruggedly built triangular “conduit-like” modules 80 containing 50 individual PTM 14 coils and their associated PTM-CES 34. Each PTM 14 contains a concatenated line of pre-installed PTM-CES 34 units along with associated internal power and data cables. Weather-tight electrical and fiber optic feedthroughs at each end of a PTM 14 provide the means to rapidly chain PTMs 14 in series as they are installed within a roadway.
Referring to
Note that PTM-CES 34, pre-installed within each PTM 14, are designed to be separately removable/replaceable for in-field servicing of roadway installed PTMs 14. The multi-phase primary input power to PTM-CES 34 units utilize magnetically coupled transformer links and blind-mated electrical and fiber connections to promote ease and reliability of this process. Table 6 below details the preferred specifications for PTMs 14:
Power Transmit Module (PTM) Interface to Roadway Transformer Cable (RTC)
PTM 14 electrical components include multi-phase power wiring that supports not only the entire electrical power demands of a given PTM but also carries significantly higher levels of power required to sustain an entire lane segment. Utilizing high voltage AC power distribution minimizes currents and respective Î2R and skin effect losses associated with powering PTM 14 segments. Each PTM-CES 34 is connected to the multi-phase distribution running through a given PTM 14 by a set of six magnetically coupled transformer links 90 that serve to provide a safe, weather resistant, contact-less and reliable connector. Thus, this multi-phase power wiring is referred to as a Roadway Transformer Cable (RTC) 92. Magnetically coupled RTC transformer power connectors 94 are located below each PTM-CES 34 of a PTM 14. Each individual phase link forms a transformer with a physically separable core that enables a tight magnetic flux connection from primary to secondary when the core halves are brought together as PTM-CES 34 units are seated within the roadway. The primary side of each transformer link 90 is connected between one of the six multi-phase power lines to a neutral or paired ground conductors and performs a voltage step-down function (current step-up), in addition to the connection function, as a result of the ratio of turns between primary and secondary halves of the transformer.
To facilitate the manufacture of the RTC 92, individual transformer primary windings contain programmable taps 96 that are welded to respective phase conductors within the RTC 92. Each primary within a 6-phase sequence will select a unique ground/phase pair via programmable bonds thus allowing for a common transformer primary and associated cable construction. The use of multiple ground in parallel, paired with an appropriate phase allows for further reliability in these phase connections. Final molding of a surrounding insulating weatherproof outer jacket during manufacture encapsulates bonds, conductors and transformer primaries, as see in
Multiple PTM-CES 34 sets of magnetically coupled transformer links 90 are thus molded directly into the primary power phase lines during RTC 92 manufacture. They form repeating sequences of qty 6 phase transformer primary links that align with above secondaries respectively located within each PTM-CES 34 unit, as seen in
The employment of 6 multi-phase power lines allows the power frequency to be ⅙th that of a single phase power line while achieving the same rectified ripple percentage for an equivalent rectifier on each phase. This lowered power frequency in turn reduces skin effect losses on the power distribution cable and allows the Multiphase Power Interface Unit (MPIU) 96 to be designed using more readily available and lower cost components operating at higher operational efficiencies due to lowered switching transition losses at correspondingly lower phase frequencies. The relatively high operational power frequencies as compared to 60 Hz drive RTC phase conductors 94 to be able to compensate for the increased skin effect conduction loss. Phase conductors implemented as metal (e.g. aluminum) foil or thin film conductors can satisfy this requirement while simplifying cable manufacture and lowering costs. Such implementations include depositing a film conductor on insulating (e.g. plastic) ribbons, that can be sandwiched for lower cost and higher reliability. Large scale RTC 92 to PTM-CES 34 power interface connectors 94 can employ transformers at each phase to ensure safe, reliable voltage isolation combined with efficient voltage step-down within this power interface, such as that seen in
Some variants (e.g., a parking lot) of PTM-CES 34 can employ a more conventional direct wired connection to each PTM-CES 34 for smaller scale installations and lower cost alternatives, especially within initial prototypes and demonstrations, as seen
Power Transmit Module (PTM) Design Trades
A fundamental trade space surrounding PTM 14 design is that of design center gap distance between roadway/parking lot PTM 14 and vehicle mounted PRM 16 coils. This gap distance drives many design factors and related reliability and costs. The size of the coils within PRM 16 and PTM 14 can be relatively equal for wide ranges of gap distance however there exists a relatively linear relationship between coil size and gap distance for a fixed amount of power transfer/coupled power. The cost of roadway or parking lot installation is at least directly related to PTM 14 coil size in that a doubling of the width or cross-lane dimension of the PTM 14 coil doubles the amount of material that must be removed and doubles the physical volume of the PRM 16 assembly. Coil size also impacts the upper resonant frequency limitation of the associated Tank Coil 74 perhaps lowering this by a factor of 2 for each doubling of coil aperture area. Higher resonant frequencies reduce power supply ripple filtering requirements and allow efficient and small sized power transformers on the primary power side of PTM 14 ensuring the availability of magnetic connectors.
On the other hand over four times the reactive PTM 14 transmit power is required if the power transfer between PTM 14 and PRM 16 is to be maintained over a doubled gap distance. This increased reactive power is in turn a primary stressor for PTM 14 electronics reliability and raises component costs perhaps by a factor of 8. The chosen design center for PTM 14 to PRM 16 coil gap within the current design is 6 inches which is sufficient to allow a net roadway clearance of approximately 5 inches. Clearances greater that this will result in a rapidly decreasing falloff of power transfer. Clearances less than 5 inches will cause a disproportionately greater coupling factor between PTM 14 and PRM 16 coils resulting in the need to regulate or “fold back” the reactive power within the PTM 14 coil to maintain a fixed power. Therefore the 6 inch gap specification really determines the maximum gap at which a specified maximum power can be transferred. Initial experimentation has been with PTM 14 (Tank) coil dimensions of approximately 12 inches long (along lane) by 16 inches wide (across-lane) allowing a nominal 16 inch wide trench requirement for roadway or parking lot installation. It is possible to gain some design margin or reduction in reactive power (a main cost driver for PTM 14 implementation) by increasing the PTM 14 coil aperture, to perhaps a 16 inch by 16 inch dimension without significantly impacting the ability to operate at currently high magnetic power frequencies, specified maximum power transfer or roadway installation costs. This could result in an estimated 25% reduction in reactive power for the same gap specification. Table 7 below depicts an attempt to rationalize a set of basic ratios of PTM 14 size and power to cost.
PTM Assembly
PTM 14 is comprised of included PTM-CES 34 units which are themselves individually environmentally sealed. In the preferred embodiment, separately manufactured and individually tested PTM-CES 34 units are attached to one another, in numbers that establish the modularity desired (e.g. 14 for parking lots and 50 for roadway installations). Note that certain PTM-CES 14 end-caps contain a locking mechanism which both draws the entire PTM 14 down into trench and while also securing it into position, as described in further detail herein. While a minimum of 2 locking mechanisms at each end of a PTM 14 may be adequate for the short parking lot PTM 14 configuration, this may be too few to be adequate in continuous roadway PTM 14 applications. It therefore is desirable to maintain a periodic spacing of the locking mechanism (that is fixed, perhaps to the parking lot PTM 14 interval) within the roadway PTM 14 configuration. Gasketing and fasteners are employed to additionally seal interfaces between PTM-CES 34 end caps and locking mechanisms shell. Each of the PTM 14 contained PTM-CES 34 exterior allows the enclosed electronics from the lower apex of each PTM-CES 34 to protrude into the trench bottom thereby allowing it to maintain direct thermal contact with the trench walls and with the power cabling directly below, within the apex of the “V” trench 38. Use of metal thermal through-wall vias into each PTM-CES 34 enclosed electronics area promotes good thermal transfer of heat generated from internal electronics while also providing possible electrical grounding and electromagnetic shielding for contained PTM-CES 34 electronics. For certain installations it can be desirable to “pre-mate” RTC 92 or other power cabling to the bottom of the PTM 14 assembly prior to installation within its trench. This insures proper physical and electrical mating while not inhibiting the “blind mating” capabilities of the PTM 14 during maintenance swapping, once initially installed.
PTM-CES Assembly
Individual PTM-CES 34 units are designed to be structurally rugged, with an internal truss structure that fully supports worst case traffic loading without significant deformation or degradation from environmental and load cycling. The top of the PTM-CES 34 incorporates a Tank and Link Coil 74 filled containment cavity which produces a flat and well supported underlayment for the top roof/roadway surface area PTM-CES 34 within a typical roadway installation. The Tank and Link Coil 74 underlayment is further sealed against moisture by the incorporation of an electrical insulating and encapsulating agent such as a resin, wax or oil filling, that ensures mechanical and electrical stability under all operating conditions. The Tank and Link Coil 74 subassembly further contains spacer material that adds compressive and shear strength to the truss supported roof structure, as seen in
PTM Trench Installation
A “V” trench 38 is used to mount PTMs 14 flush with the roadway surface. Preparation of the trench proceeds by initially rough cutting a “V” cross-section with saws or other means into the road bed or parking lot bed. This is followed by a finishing coat such as concrete to achieve accurate, smooth and debris free sidewalls. Vibrating forms can be used to compress and rapidly form this finish coating. To prevent water intrusion once PTMs 14 are installed (mainly for freeze and corrosion protection), a waterproofing sealant coating can be applied to the side walls of the trench prior to PTM 14 installation. (Note: appropriate gasketing as applied to the exterior of PTM 14 may accomplish the same sealing property) If desired a power cable can be separately laid into the bottom of the trench with connectors facing upward at a spacing that mates with each PTM 14 or PTM-CES 34 as the given configuration requires. Otherwise the power cable can be pre-attached to PTM 14 prior to installation within the trench. PTMs 14 are then mechanically secured within the “V” trench at strategic locking points, including at minimum PTM 14 ends, as well as periodically along the length of PTM 14 in cases where longer PTM 14 lengths, with greater numbers of PTM-CES 34 units are employed. Locking also secures all primary power connections. The locking mechanism allows PTM 14 to be drawn down into the trench while simultaneously being secured to the trench walls as the locking mechanism is tightened. The locking (and unlocking) mechanism is operated from the roadway surface for both installation and maintenance.
An alternative to separately applying a finishing concrete or other appropriate material to the initially cut trench wall, necessitating the use of separate forms and possible added time, a more rapid finishing may be obtained by use of PTM 14 itself as the form. In this way a release coating can be applied to the sides of PTM 14 prior to it being pressed into the Trench which has had newly applied finishing material (e.g. concrete). PTM 14 locking pads or pawls are extended from their unlocked position upon installation, and serve as elements of the “selfform” for creating sidewall detents. Removal of PTMs 14 requires that these locking pads/pawls are first retracted away from Trench side walls and vertical mechanical force applied to lift PTM 14 out of the Trench.
PTM Locking Mechanism Design
The thread pitch and starting depth of the locking assembly is such that the vertical movement is sufficient to fully draw the PTM down into the trench being securely braced by both pads against respective side walls, conversely securing the PTM, within and against the trench, against traffic loads and other forces. The PTM is removed simply by a counterclockwise rotation of the screw rod inducing the reverse of the afore described locking action. A “detent” providing a more positive sensory indication of proper screw rod and pad depths, greater tolerance in the locking range and an enhanced locking force can be produced by an introduction of suitable parallel grooves down the entire length of each sidewall within the trench. Such grooves can mate to the top of each pad, fixing the desired PTM seating depth while accommodating significant locking by pad tilting and resultant detention of the pads within the side walls during installation/locking. Such grooves can be produced by cutting into finished, cured and/or partly cured side walls during trench formation.
The use of a recessed screw rod head, when combined with a uniquely keyed head and mating rotating tool or tool sets can provide a fundamental level of theft protection. Other electronic means and mechanical key locking means at sporadic intervals can provide a further deterrent.
Alternative PTM Locking Mechanism Design
Another embodiment of the end cap locking mechanism 116 is depicted in
Integrated Tank and Link Coil Design
Tank and Link Coils 74 can be integrated within a common assembly as shown in
The Tank Capacitor 120 can also be integrated within the assembly of Tank Coil 74 as seen in
WAVES Power Transfer Regulation
The loosely coupled air core resonating design of the WAVES power transformer dictates the generation of high reactive power within the PTM Tank Coil 74 and associated Tank Capacitor 120. This is problematic from a safety and reliability standpoint as it increases the costs and development difficulties of these key components. Further adding to operational difficulties on one hand is the significant variability in magnetic coupling to the user vehicle and on the other hand the need for regulated, standard power waveforms at the vehicle charging or energizing interface. This prompts the need for an automated feedback based regulation approach developed for WAVES 10. There are two main aspects to this approach: first, the maintenance of a “safe operating area” for the PTM based power amplifier and, second, generation of a regulated standard voltage and frequency output to the user vehicle and associated electrical systems. These aspects are related to each other in the sense that the time varying vehicular waveform and load demands as modulated by varying magnetic coupling across the roadway gap will in turn reflect a time varying load demand upon the PTM Tank Coil 74 and associated amplifier which needs to be included within its “safe operational area” capabilities. This is further complicated by the loosely couple air-core design utilized by WAVES 10 as it avoids the use of high-permeability materials.
The key is that the voltage waveform experienced by the Power Amplifier/Tank Link side of the Tank Coil 74 may not indicate the waveform expressed by the Tank secondary winding which may experience significantly more variable voltage swings especially under light loads. To insure safe the establishment of a safe operational area, the Power Amplifier Drive 122 needs to be inhibited by feedback whenever this voltage waveform exceeds specific limits. Additionally, power amplifier current sampling infers real power (not reactive power) delivered in real-time. An added feedback loop around this current sampled signal can also inhibit the Power Amplifier Drive 122 thereby accomplishing regulation (and/or safe high current shutdown under failure or faults) that is inclusive of both vehicle loading and safe area operation. On the vehicle side, a time varying waveform may be generated by active circuitry within the PRM 14. This circuitry can also self regulate within an acceptable operational range of power transfer to insure proving a standard power waveform to the vehicle e.g. 220v @ 60 Hz. The demands of PRM load power (waveforms et. al.) are, of course, reflected back to the PTM Power Amplifier 122 as a time varying real power demand that requires seamless incorporation within its regulation.
WAVES PTM Tank Capacitor Design
Referring to
Referring to
Extruded PTM-CES Construction
Individual PTM-CES 34 units can be constructed from a continuous plastic or other insulating material extrusion that is subsequently sliced to the proper length to form the chassis for PTM-CES 34 units. Such an extrusion process allows the inclusion of internal 3D structure designed to be structurally rugged while minimizing overall weight. Extrusion promotes the low cost, mass-fabrication of PTM-CES housings. End Caps with appropriate gasketing then provides environmental sealing to contained integrated electronics. Single or multiple PTM-CES 34 containing units can be formed within each extruded slice, to be environmentally sealed by end caps during assembly. Heat sink and electrical vias can be formed with machining of chassis penetrations. Heat sink components can be inserted from internal and external areas of each PTM-CES 34 electronics area, through sealed penetrations to be subsequently joined or riveted together during unit assembly to form a complete thermal path from internal electronics to trench side walls. PTM-CES 34 contained units are separately tested and numbers of such completed units mechanically held together to form a PTM 14 assembly suitable for parking lot or roadway installation within prepared trenches.
Power Transmit Module (PTM) Environmental Heat
PTM roadway and parking conditions are exposed and can receive heat loading from ambient air temperatures and direct solar absorption. This heat gain can result in severe temperatures at the surface of the PRM 16 which can lead to lack of mechanical stability of related housing materials, especially when combined with vehicle traffic weight loading. The addition of reflective material along top PRM 16 surfaces may help reduce such increases in concert with appropriate housing material choices. This “cover” material could also have thermal insulation properties that isolate internal housing structure from potentially significant surface temperatures. Another possibility is a more active method of cooling, based upon phase transfer of heat at a common temperature, located within the internal housing volume. Materials such as wax absorb considerable heat in transitioning from a solid to a liquid. An active pumping system can be employed within the housing that allows a fluid (e.g. oil) to convey heat to from the exposed top area of the PRM to lower/subsurface areas. Heat sink vias located within these areas can then conduct heat to exterior side wall areas of the Trench that are at significantly lower temperature.
PTM & PRM Fabrication Material
High Density Poly Ethylene (HDPE) has important properties that are suited to the manufacture of PTM-CES 34 and PRM 16 housings. Fastening is one option, but various parts are preferably joined by hot air or nitrogen welding. Also, ultrasonic, laser, and infrared welding may be used. HDPE can be injection molded as well as being available from recycled sources at lower costs. Glass material can be embedded within the top layers to enhance strength and achieve a proper degree of UV and thermal protection. Furthermore the excellent electrical properties make it possible to create high voltage/high frequency resonating capacitors within the housing structure itself, inserting conductive plates within slot cavities formed within the housing material, thus eliminating the need for separate dielectric materials or associated mechanical fixturing. The lack of glue-ability does not preclude the use of glue or rubber-like compounds between components that serve in a sealing gasket function so long as additional mechanical means are employed to hold components together.
Alternative PTM-CES Laminate Construction
Individual PTM-CES 34 units can be constructed from a set of cross-sectional wafers, as seen in
The Tank & Link Coil 74 is integrated with strong winding separators and a strong central core to form a robust component that slips into and fills the associated PTM-CES 34 cavity during assembly (from an open side of a PTM-CES 34 unit). Additional intervening sealant then completely fills the cavity which when enclosed by end caps, the coil completes the formation of a solid strength member parallel to the its roadway exposed surface, being supported immediately below by truss-work within PTM-CES 34. The utilization of truss-work as opposed to solid cross sections is three-fold, high vertical strength at significantly reduced weight, overall material savings and the ability to form internal cavities and structure that fixture and fabricate internal components.
Heat Sink Via Designs Suitable for Laminate and Extrusion Implementations
The first embodiment is an I-beam configuration that neatly fits into prepared (2D) indentations within a laminate slice and is further captured and sealed by an opposing laminate slice within the stack of slices comprising a PTM-CES 34 unit. The second embodiment is a T-beam configuration for insertion through a relatively narrow opening through a PTM-CES 34 chassis side wall. In this instance the outside (or perhaps interior side) heat flow surface must be suitably fastened to the penetrating “T” end section to form the via 128. Suitable fasteners include riveting or otherwise cold forming T material or spot welding or screw fasteners. The intent is to provide a flush exterior with good sidewall contact for heat flow and minimal inclusions that may serve to inadvertently lock the PTM 14 in place preventing future extraction. An additional attribute to the second design is that of being capable of strapping across the multiple slices of a stacked laminate constructed PTM-CES 34, such as to provide individual unit integrity before being strapped or otherwise secured into a given PTM 14 configuration prior to subsequent installation.
Power Transmit Module (PTM) Electrical Specifications
PTM 14 electrical specifications include peak and average power for the entire module as well as average power dissipations from electrical/electronic losses which is manifested as heat. Heat will be conducted away from the PTM 14 along two paths, one is to the subsurface of the roadway (primary path) and the other is through the transmitting coil at the roadway surface interface (secondary) which will only be significant when roadway surface temperatures are well below subsurface ground temperatures. Table 8 below details the electrical specification for PTM 14:
It should be noted that the nearly 200 watts (peak) per foot dissipation is a significant amount of heat within a confined (0.75 cubic foot) volume as exists within a one foot long triangular section. This implies the need for a good thermal path between internal electronics within PTM-CES 34 components as well as a good thermal path to and through the side walls of the PTM 14 to the roadway subsurface. Also note that during the summer and in areas of direct sunlight the top or roadway surface of the PTM 14 is a potential source of high heat loading that must be avoided. Underlaying thermal insulation immediately below each PTM-CES 34 coil prevents this path being a major heat load to electronics below.
PTM-CES 34 units are the common denominator for transmitting the magnetic fields that are the source of power coupled to vehicle mounted PRMs 16, as well as the source for control and critical communications links to those vehicles. Multiple PTM-CES units 34, when simultaneously energized by a reasonably aligned passing PRM 16, couple increased power to the associated vehicle in direct proportion to the number PTM-CES 34 units energized, as seen in
PTM-CES 34 electrical specifications include required peak and average or continuous electrical power as well as loss related dissipation, manifested as heat. Heat is conducted internal to each PTM-CES 34 by both structure and insulating oil to its apex or lower triangular point. This apex area is thermally conductive and in good thermal contact, through adjacent PTM 14 side walls, to the sub surface at the bottom of the roadway trench. In this way cooling is maintained without sacrificing environmental integrity of the PTM 14 and its subassemblies.
The secondaries of magnetically coupled transformer links, located entirely within each environmentally sealed PTM-CES 34, feed rectifiers for the generation of DC power used by internal electronics. DC power is at nominally low voltages and moderate currents (see Table 9). Transmitting tank coil and capacitor AC voltages are however quite high due to associated Tank Coil Link transformer step-up and resonance effects. This is especially true when the Tank becomes lightly loaded under worst case low magnetic coupling instances. Therefore coil and capacitor components are high voltage insulated within the PTM-CES 34 by an internal oil bath and there is no direct exposure from coil to roadway as a result of employing a magnetic window material seal at this interface. The electrical specifications for PTM-CES 34 are set forth in Table 9 below:
The determination of the exact number of PTM-CES 34 units that are energized at any one time is in turn the role of the proximity links. The first proximity link is initiated by a magnetic field based data transmitter located within the vehicle PRM, such that PTM-CES 34 fields are only produced when there is the potential for adequate coupling to the PRM 16. The first proximity link data transmitter within vehicle PRMs 16 operate on a frequency separate from that of the PTM 14 and employ a pseudo-random modulation designed to limit power carrier interference. The signaling frequency is made appropriate to be easily combined with all coils of PRM 16 in a manner that each PRM 16 coil radiates a magnetic field from vehicle to roadway having a spatial shape and coupling factor nearly identical to that of the PTM 14 power carrier (emanating from roadway to vehicle). This independent signaling frequency allows first proximity link receiver within each PTM-CES 34 to detect a proximity signal in the same coil used for power transfer to the vehicle and in the presence of a power carrier, thus insuring that the pickup coupling is analogous to that experienced during power transmission. Filter networks within the first proximity link receive path of each PTM-CES 34 and each transmit path of the PRM 16 are designed to be anti-resonant at the power carrier frequency but series resonant at the signaling frequency. This design effectively isolates subsequent signaling components from the high level power carrier, allowing reliable signaling carrier to interference ratios. Furthermore, the bandwidth of the signaling channel thus formed is made sufficiently broad (nominally 30 kHz) to accommodate transmission of multiple copies (10 minimum) of a psuedo-random modulated vehicle ID word within the minimum interval of a single PRM 16 coil to PTM 14 coil passage (nominally 0.01 seconds).
Since the proximity link 28 function is critical to both human safety and to the proper operation of PTM-CES 34 modules, insuring adequate magnetic coupling is always present before energizing, additional proximity link hardware is included such that two valid proximity links are required in real time to generate an enabling signal. This second (additional) proximity link operates on an entirely different principle and employs a separate PTM-CES 34 UHF transmit signal and receiver analogous to that employed in store antitheft security systems, wherein a very simple chip is embedded within each vehicle PRM 16 coil that is activated as it passes over an interrogating PTM-CES 16 coil. Thus, three separately generated enabling signals must be present before any energy activation occurs
Referring to
Referring to
The MOSFET H Bridge configuration utilized as a power amplifier output stage derives its name from the “H” formed when two sets of vertically stacked transistors are joined horizontally between their respective center connections by the load. The load in this case being the Tank Link Coil 74.
The use of a transformer coupled H Bridge MOSFET configuration 70 for the power amplifier allows the presence of an exciter output to directly enable the amplifier's power generation. With no exciter driving signal, all four of the amplifier's MOSFETs are turned off and virtually no current flows. This is true whenever the exciter output is gated off. Thus a (low level) “Transmit Enable” logic level signal is used as a low power, low voltage gating of the exciter output to energize each PTM-CES 34.
When the amplifier is gated on, diagonally opposite MOSFET pairs of the H bridge 70 (pair #1—upper left & bottom right; pair #2—upper right & bottom left) are alternately switched on and off during each half of the power carrier cycle (one pair switched on while the other pair is switched off). This switching arrangement causes high alternating currents to flow within the Tank Link Coil 74, currents that switch direction at each half cycle in unison with alternating MOSFET pair conduction. The resulting alternating magnetic field of the link coil 132 is tightly coupled to the resonant tank coil 74, a coil having a significantly larger number of turns than the Link Coil 132. This turns ratio produces a large voltage step up from link to tank. The tank circuit is made parallel resonant at the switching frequency by the paralleled Tank Capacitor 120. Therefore, the net result is that the tank voltage builds rapidly with each cycle of link current. In normal operation, tank circuit loading is primarily from nearby (passing) vehicle PRM 16 coils which act as a loosely coupled transformer secondary winding. Reactive currents within the tank circuit are passed alternately from Tank Coil 74 to Tank Capacitor 120 as the magnetic field collapses through the Tank Coil 74 and back to the Tank Coil 74 as the increased rate of Tank Capacitor 120 charge occurs on the next half cycle. The relatively loosely coupled vehicle PRM 16 coil presents an increasing real power load in proportion to the level of reactive power exchanged within the tank circuit, until the amount of real power coupled to the PRM 16 load matches the real power provided by the MOSFET amplifier Tank Link Coil 74 circuit (less minor losses). At this point constant maximum real power is exchanged wirelessly by the alternating magnetic field coupling between Tank Coil 134 and PRM 16 coil. Once the PRM 16 coil moves out of range as determined by the Proximity Link 28 to the PTM-CES 34, the PTM-CES 34 is gated off again and de-energized, allowing the tank resonant energy to rapidly decay to zero based on residual coupling to PRM 16 and tank circuit losses. It should be noted that a vehicle PRM 16 may be many coils long, therefore a given PTM-CES 34, once enabled, will remain energized for the entire duration of passage (several PRM 16 coil times). At 70 mph, with a 14 coil PTM, this energization would be for a time duration of 0.11 seconds.
Power Transmit Module (PTM) Charge Controller Function
The vehicle charge control function can be addressed wholly or in part by the PTM-CES 34 units within the PTM 16. When a vehicle is coupling energy whether statically or dynamically there must be a throttle on the amount of energy transferred, such that the vehicle's battery is not overcharged or discharged when sufficient power is available, or charged at a rate that exceeds specifications. An on board, vehicle based charge controller can accomplish this battery charging control by inhibiting the flow of power in the battery charging circuit to exactly match the instantaneous needs of the vehicle. If the vehicle is in motion there are motor power demands added to battery charging power demands. There may also be demands from vehicle accessories such as lights and air conditioning. The charge controller monitors the battery's state of charge and motor power to establish a battery terminal voltage that continuously balances wireless power input with the needs of the combined total vehicle electrical load. This implies that there will be a variable amount of wireless power coupled to vehicles under both static and dynamic roadway conditions. If the PTM-CES 34 units were to do nothing in response, the tank coil and capacitor voltages would be higher under light loads and lower with heavier loads as they are energized by the passing vehicle. A range of loading is acceptable so long as tank and pickup coil voltages are maintained at safe levels and the fringe fields above the pickup coil are sufficiently attenuated before reaching vehicle or occupants. Over-voltage conditions at the PTM-CES 34 tank can be sensed and made to gate the amplifier drive to better match amplifier output energy to light loads. Sensing means can be a sense coil within the Tank Coil 134 field or a capacitive or resistive AC voltage divider from the ungrounded side of the Tank Coil 134. A spark gap in conjunction with a fast acting over-current shut-down can be further employed as an added safety feature that puts an ultimate limit on tank voltage swings.
Current monitoring can be effectively monitored using a current sampling transformer in either or both of the Link Coil 132 leads to the high power amplifier. The resulting AC waveform can be rectified and filtered if necessary to be used in comparison with control derived threshold voltages to inhibit amplifier drive and thereby power.
A particularly interesting mode to consider is the incorporation of a greater degree of charge controlling functionality within each PTM-CES 34 such as to shift the majority of this function from vehicle to roadway or parking lot. This provides a means to simplify vehicle charge controlling while archiving a degree of commonality from vehicle to vehicle. This works by using the WAVES Data Link 30 to transmit vehicle power needs in conjunction with vehicle ID such as to allow programing of PTM-CES 34 amplifier drive gating. Programming will in turn cause the proper amplifier power output when it is subsequently enabled by the WAVES proximity links 28 and 32 during vehicle passage. This in effect produces a closed loop around the magnetic power coupled to the vehicle battery and motor (dynamic). In the dynamic case, the Data Link 30 is sufficiently real-time to prime upcoming PTM-CES 34 units with the proper power level, in advance of their being enabled by the passing vehicle. Since this forms a closed loop, errors in coupled power (from instance to instance) can be corrected by changing power level programming of power transfers from continuously engaged PTM-CES 34 units (static) or subsequently enabled PTM-CES units (dynamic). In initial applications, wherein parking lot and household operation is sufficient, a static charge control function is all that is necessary.
Power Receive Module (PRM) Design
PRM 16 is required by any electric vehicle choosing to receive magnetically coupled power from roadway or parking lot embedded PTMs 14. Referring to
PRM 16 length varies with the vehicle to be able to match driving power requirements. Two lengths are suggested 11 feet for mid-sized car vehicles, and 34 feet for trucks and buses. The width, 3 feet, is the same in each case to accommodate 3-coil rows, to make pickup coupling less sensitive to lane position errors. The 4 point actuator allows PRM 16 to quickly swing down, in a road-surface parallel manner, towards the roadway during deployment. Similarly, when disabled actuators swing PRM 16 quickly back up to securely nest into a cushioned pocket located along the horizontal underside of the suspension. This “gears up” action can be manually initiated by the driver or automatically initiated by improper roadway clearance and debris. Part of the automatic retraction can be accelerated by the inherent up-swinging motion induced by physical pressure exerted by obstructions during forward motion of the vehicle. A forward facing PRM brush 144 normally clears the roadway surface under normal driving conditions. This brush may augmented by an additional brush or “air dam” like appendage mounted directly beneath the front of the vehicle, in line with, but apart from, the PRM 16. In this way small roadway debris can swept away without retraction. Major debris, obstructions or unsafe clearance conditions will however cause the brush to trigger a retraction thereby preventing serious harm to PRM 16. The heads-up display provides an indication of the state of PRM 16 deployment or retraction. Table 10 below provided the physical specifications for a preferred PRM 16.
A further consideration is the use of a “brush” mounted in a “V shaped cowcatcher” fashion at the front of the vehicle and/or on the leading edge of PRM 16 in a manner as to just clear the roadway, brushing small debris away from PRM 16 as well as assisting in and triggering the vertical movement of PRM 16 away from roadway obstructions as might occur at slower speeds. In this manner, PRM 16 vertical distance to the PTM-CES 34 is safely maintained at nominally 3 inches. Both PTM 14 and PRM 16 coils are sealed and covered with a thick layer of tough plastic, fiberglass, carbon fiber, asphalt or other like material, made magnetically permeable by being heavily loaded with ferrite. Table 11 below sets forth the preferred PRM electrical specifications.
The output voltage and currents shown above are nominal and can vary from vehicle to vehicle as a specific vehicle's battery charge controller interface requirements may dictate. A worst case power dissipation can occur when the vehicle is parked or static over an activated set of PTM-CES 34 coils. In these instances there may be no moving air to assist in cooling. Therefore parking lot magnetic power transfer is limited to 1 KW per coil. Secondary power is supplied to the PRM 16 to power internal electronics such as actuators, proximity links and Data Link.
Power Receive Module (PRM) & Vehicle Interfaces
A vehicle's PRM 16 consists of a set of pickup coils, each with associated inductive reactance canceling AC capacitor and following high frequency bridge power rectifier and series parallel wiring of DC outputs to the vehicle's battery charge controller. Three wireless links—two proximity links and a data link provide for energy transfer interlocking, billing data and passenger internet communications. These components are housed in a rugged weatherproof enclosure that when enabled for power transfer by the driver, is lowered and suspended below the vehicle at a nominal 3″ fixed distance above the roadway.
Mechanical interface is accomplished by a suspension from the vehicle's front and rear axels and further augmented by roadway brushes that normally end 1″ above the roadway that serve both as a means for debris removal and as a means to trigger raising of the PRM 16 to a “stow” position when major obstructions are encountered, such as a bump at moderate speeds or a rough roadway condition at normal highway speeds. The front and rear ends of PRM 16 are tapered to a V-shape to further limit the impact from roadway debris under all conditions. A dash panel control is used by the driver to lower PRM 16 towards the roadway and otherwise enable PRM power transfer. The mechanical actuator and controller for this deployment mechanism is located within PRM 16 itself and operates through the mounting points where the vehicle's axel extensions meet PRM 16.
PRM control electronics insures that actual power transfer occurs only when the vehicle's ID has been deemed valid and PRM 16 is in a proper alignment with PTM 14 coils as determined by the proximity links 28 and 32. Proximity links 28 and 32 include a low frequency magnetic signaling transmitter that utilizes the vehicle's power pickup coils themselves as transmission elements. This arrangement naturally limits the coupling coefficient of the proximity signal to a given PTM 14 coil in a manner that corresponds closely to that of the actual power transfer coupling coefficient between PTM 14 and PRM 16 coils. This insures an efficient transfer of energy. Additionally, the Proximity Link 28 signal from the vehicle is modulated with the vehicle's ID, that is demodulated at each PTM-CES 34 within local magnetic coupling range. This allows a further check on the validity of transferring power during the period of a PRMs 16 actual proximity to a given PTM-CES 34 coil. Normally each PTM-CES 34 coil maintains a dynamic stack or list of valid IDs in its neighborhood as established via the Data Link 30, a wide band LAN based communications link between vehicles and the roadway. Real time Proximity Link IDs are then matched from within this list to enable real-time power transfer. Eventually, IDs are dropped from the ID list as a vehicle leaves a given PTM-CES 34 neighborhood and new IDs are stored from approaching vehicles. In this manner there is a real time ID determining element having a non-complex and low data rate requirement.
The data link 30, with its greater flexibility, is dedicated more towards non-time critical functions of enabling and billing functions and vehicular internet communications. The data link 30 is a wireless microwave RF link between PTM-CES 34 mounted and vehicle PRM 16 mounted transceivers with associated antennas. PTM 14 segment interfaces then contain necessary routers and network adapters that link PTM 14 fiber data lines (with data to and from passing vehicle PRMs 16) to the internet network in a manner that effectively achieves continuous connectivity between vehicles and the internet. The PTM 14 power control logic may be seen in
The DC power output from PRM 16 is at a voltage and current which is directly compatible with the vehicle's battery charge controller. The charge controller is capable of handling the combined power for both battery charging and the vehicle's electric propulsion motor demands while underway. The vehicle's battery supplies energy in parallel with the charge controller, and is therefore able to cover peak power demands of the vehicle, leaving PRM 16 driven charge controller to supply the average demand for both battery charging and propulsion. This cooperative energy sharing arrangement takes advantage of the best of both energy sources while minimizing stressful requirements. The resulting net efficiency of the WAVES energy transfer is therefore high, nominally 80%. This efficiency can be broken down into two multiplicative components: (1) PRM 16 and magnetic field generation; and (2) PRM 16 and charge controller efficiency, both of which are better than 90%.
As explained above, there are both static and dynamic applications for WAVES 10. From a market development perspective it may be advantages to begin with static parking lot or household charging applications since they avoid the need for comparatively large effects upon infrastructure, cost and government involvement. Given that initially there will be no electric or electric hybrid vehicles available with an integrated PRM 16, PRM 16 may be offered as a manufacturer add-on or as an aftermarket add-on to the vehicle. As such it is important to minimize mechanical and electrical interfaces to the production vehicle thereby minimizing costs. Especially regarding electrical interfaces, it is useful to consider that PRM 16 be able to supply voltages and currents that are directly compatible with the vehicle's existing “plug-in” battery charging port, thus eliminating the need for vehicle charge controller modification and warrantee restrictions.
One way to accomplish this is to allow PTM 14 to be amplitude modulated (AM modulated) at 60 Hz such that the rectified and power carrier filtered PRM 16 output delivers 60 Hz standard voltages e.g. 110 VAC/220 VAC and currents e.g. 15 A/30 A. Note that this offers respectable charging rates of 1,650 watts/6,600 watts. AM modulation is simply and directly accomplished within each PTM-CES 34 by a 60 Hz logic level gating of the power carrier using the exciter “Carrier Enable” control signal. In this manner the parking lot or home market is served in a manner transparent to the magnetic link coupling employed by WAVES. Vehicle ID data within the PRM's Proximity Link 28 determines the use of this modulation. Thus the same PTM roadway 36 embedded hardware is made to work with both early static market PRMs 16 and later, dynamic and vehicle integrated PRMs 16 without change thereby providing a seamless path towards the end goal of a ubiquitous roadway infrastructure.
Power Receive Module (PRM) Magnetic Power Coupling and Control
PRM 16 unit is suspended below the vehicle in a manner that allows vertical deployment towards the roadway when the driver enables WAVES to be used to couple power from the roadway. It is preferred that PRM 16 be flexibly suspended such that roadway obstructions cause an immediate and dampened retraction and preferable that the main suspension be from the wheel axels as opposed to underbody to minimize vertical motion effects from the vehicle's suspension. In this manner PRM 16 vertical distance to PTM 14 coils can be safely maintained at nominally 3 inches. It can be noted that both PTM 14 and PRM 16 coils are sealed and covered with a thick layer of tough plastic or other like material, made magnetically permeable by being heavily loaded with ferrite. This magnetically permeable layer forms a rugged Magnetic Field Window that removes the Tank Coil 74 from the physical environment at the roadway surface while virtually magnetically displacing coil 74 to the very top surface of the roadway thereby maintaining the smallest possible coupling gap to the vehicle PRM 16. In this manner the coils on both roadway and vehicle are protected without adding the thickness of the plastic to the air gap through which magnetic coupling occurs.
PRM 16 consists of several coils made resonant at the PTM operational power frequency to cancel the inductive reactance of each coil and thereby maximize coupled power. The total power coupled is the sum of coupling to all the PRM coils at any one time. By arranging PRM coils in a contiguous line down the center of the vehicle, from front to back, one can achieve this maximum power coupling with a similarly arranged line of PTM coils, located along the middle of the driving lane, by centering the vehicle within the lane. The more PRM coils that are in alinement, the more power is coupled. This highly useful attribute of WAVES to essentially provide greater power coupling in proportion to a larger number of coupled coils, such as on larger vehicles, inherently matches power demands across a range of vehicle types utilizing a common roadway PTM.
Integrated Power Receive Module (PRM) Design
An integrated pickup coil and rectifier assembly for PRM 16, as shown in
Additional coils can be integrated within PRM 16 sheet assembly to serve as magnetic signaling pickup sensors that for instance can enable roadway or parking lot power transfer or transmit vehicle ID and/or other data from the vehicle to PTMs 14. One interesting design using multiple overlapping PTM 14 coils an minimize scalloping or misalignment losses during power transfer from associated PTM 14 coils. Rectifier/DC outputs from such interstitial and overlapping coils are or tied with other outputs to achieve graceful power summation as alignments between PTM and PRM change, sometimes continuously. Separate coil channels can be made from both sides of an electrical insulating sheet as one way to achieve coil overlap consistent with the previous implementation.
Note that the sheet material within which PRM 16 Pickup Coils are embedded can contain ferromagnetic material designed to enhance the concentration and coupling of the received magnetic field as well as provide the overall electrical insulation properties required.
It is possible to integrate pickup coil resonating capacitors within each coil to reduce size and cost. Furthermore such capacitors can be fabricated within the same material utilized to form the PRM 16 chassis (e.g. HDPE) and could be compactly located within the center area of each pickup coil. One such fabrication is to mill vertical slots into the (insulating) chassis material to into which metal capacitor plates are subsequently inserted to form the resonating capacitor. The separation between plates forming the required dielectric separators between opposing plates of the capacitor.
PRM to Vehicle Interface Design
Initial PRM 16 design and demonstration development focuses upon static charging capability, capable of supplying up to approximately 6.5 kw of continuous power through the vehicles conventional 60 Hz AC power connection. A PRM output interface can be provided that duplicates 220 VAC 60 Hz input such as to minimize wiring changes to the vehicle's charging circuitry. This can be accomplished by PTM waveform control wherein either the magnetic power carrier waveform is modulated or preferably, PRM 16 rectifier outputs are switched in polarity at a 60 Hz rate to form a (filtered) square wave suitable for direct connection to the vehicle's grid compatible input. Regulation to maintain standard peak to peak AC voltages can be accomplished by circuitry within PRM 16 (e.g., duty cycle modulation of rectified output) or within a feedback loop to PTM 14 magnetic waveform power regulation or both.
As requirements to demonstrate greater energy transfer to the vehicle are presented, there will be a need to interface high DC power transfer to the vehicle's propulsion battery. Depending upon the vehicle's existing charge controller design and battery technology, separate charge controlling circuitry may be required within PRM 16 battery interface, along with associated wiring, software and circuit changes within existing vehicle components. The issue becomes one of making sure that the battery is always protected from receiving more energy than it can safely or effectively use. If the vehicle is under motion, some or perhaps all of PRM 16 power can be utilized by the vehicles motor with any excess power available for battery charging.
The preferred embodiment is that an additional (Class III) charging port is available within the vehicle's onboard charge controller and that this can be enabled while the vehicle is underway. In this way significantly high power charging can occur at all times and under proper supervision to insure safety and battery lifetime. PRM 16 electronics would then appropriately interface to this port as required (e.g. several hundred VDC at high currents netting high power transfer capability). Baring the availability of such a high capacity port, it may be possible to slave PRM 16 charge control circuitry to the vehicle's charge controller current regulation signal or other proxy signal such that a parallel battery charging circuit can be wired directly from PRM 16. This parallel circuit would of course be separately fused and current controlled to inhibit catastrophic failure from occurring. Alternatively, there may be a way to essentially mimic the operation of the vehicle's dynamic braking energy recovery system wherein associated circuit paths can be energized by PRM 16 in lieu of the vehicle's motor-as-generator energy source.
Dual Mode—Power Receive Module Charging or Physical Plug in Charging
There may be a need to be able to support both wireless and hardware plug in charging at a common parking site. This could be a way to ease market penetration, especially during the early phases of market acceptance where the majority of EVs are set up to only interface with plug charging. Referring to
Conversely, when the wireless mode is desired, the vehicle's PRM 16 is utilized, the Plug and associated WiFi is disabled and PTM pickup coil within PRM 16 simply idles with essentially no power being supplied to an external (plug) load. The influence of the imbedded idling PTM pickup coil can be controlled in terms of capacitance within the design by appropriate spacing from the Tank and Link coils 134 and 132, respectively. Furthermore, due the availability of significantly greater coupling between these co-embedded coils, one may dispense with a resonating cap on the internal pickup coil, thereby decreasing it's influence in this regard, even further.
Roadway Intersection Installation
Intersection installations as depicted in
Referring to
Note that the future is very bright with regards further driving automation. Since individual PTM-CES 34 modules relay real-time vehicle ID and position within the roadway and operate as a 2-way data link to the vehicle, a highway system could indeed issue real-time commands to the vehicle to control steering, velocity and spacing to adjacent vehicles. This type of system would of course require safety backups such as now being deployed with vehicular radar, in a manner that produces a truly robust automated system.
Referring to
For the 1.0 foot wide×0.8 foot long coils at both PTM 14 and PRM 16, the useful lateral driving accuracy requirements are 1.0 foot (+−0.5 foot) per line of parallel PRM 16 coils. The nominal number of parallel PRM 16 coils on a vehicle is 3, yielding a 3 foot driving accuracy requirement for optimum power coupling, or +−1.5 feet either side of the center of a given lane. This is a minimal system for accommodation of driving errors and could be linearly expanded by the addition of parallel lines of coils with minimal additional cost to PRM 16.
An appropriately designed interconnection non coherently combines the AC power from separately roadway coupled individual PRM 16 coils. First the AC power carrier frequency resonant PRM 16 coils are individually rectified to produce DC power at nominally 200 V RMS @ 10 A RMS per coil. Then, individually rectified (potential) coil power sources are then parallel wired laterally across the three lengthwise running (column) PRM 16 lines of coil rectifiers to instantiate the required widened coupling aperture. This widened aperture is achieved since any one or more of the three lateral (row) coil sources can feed DC power to the PRM's output. This paralleling of coil rectifiers creates Row-DC power outputs, one for each row of PTM 14 coils (laterally across the vehicle's direction of travel). Row-DC outputs are then wired in a series parallel arrangement to achieve the desired voltage and current for input to the vehicle's battery charge controller.
WAVES 10 is a way to immediately normalize peak battery energy demands to allow them to become, at most, average energy demands for the majority of driving modes and applications. This energy normalization increases overall transportation system efficiencies while at the same time eliminates electric vehicle “range anxiety”, charging time and effort. Thus WAVES accelerates DOE's critical drive to electrify ground transportation by the promotion of a broader and more robust electric vehicle market through lowered cost, increased performance and convenience.
Wireless Automated Vehicle Energizing System (WAVES) Prototype
An aggressive prototype development program has resulted in the design, construction and testing of a 3 Coil Demonstration Unit (3CDU). 3CDU Prototype Performance—Testing has produced a compact 115 VAC powered prototype capable of being transported to a non-laboratory based meeting where 115 VAC 20 A fused standard wall plug power is available. It is capable of wirelessly transmitted (magnetically linked) power transfer of approximately 1.5 kW across a 6″ gap to a resistive load bank consisting of 36 incandescent light bulbs. The operational frequency is nominally 360 kHz. In addition to the power transfer function, power management circuitry is incorporated to maintain a fixed power transfer at gaps less than 6 inches so as to maintain a safe power level at these closer coupling distances. Internal remote actuation, GFI and fusing are added safety features embodied within the design. The overall operational efficiency is estimated to be greater than 90% based upon light brightness and DC power levels input to amplifier modules. Lack of significant heating in power electronics and Tank Coils and Capacitors provides confirming evidence of very high operational efficiency.
3CDU Prototype Detailed High Level Design
3CDU Prototype Power Amplifier Schematic
The use of an H-Bridge 70 effectively doubles the voltage swing on the Tank Link as related to the HBPA DC supply voltage, thereby allowing a factor of 4× power increase over single ended switch configurations. This is very important in reducing PA primary supply voltages for any given power output demand. Furthermore the ratio of Tank Coil 74 turns/Link (or autotransformer primary) turns is a further source of voltage increase and resultant V̂2 increase in reactive power availability within the Tank Coil 74 field. Thus, by halving the number of Link turns for a given Tank Coil 74, the reactive/magnetic field power will increase by 4. This of course places voltage related stresses upon the Tank Coil 74 and Tank Cap 120 and corresponding insulation requirements all around, including link to Tank Coil 74 insulation. Furthermore, not immediately obvious, the net reactive energy cycling and stored within the parallel resonant tank circuit, similarly increased by such means, and available for (PRM) load coupling can also feed back in reverse, back to the power MOSFET switches during periods of normal (gate drive modulation for power control) and abnormal (load failure or rapid changes) conditions. Thus stored energy related transients can generate reverse voltage spikes and current surges that can be immediately and catastrophically destructive to MOSFETs within the HBPA. Reverse voltage spikes can defeat the nominal capability of intrinsic MOSFET diode designs and stimulate the parasitic generation of a destructive avalanched transistor within the FET junction monolithic structure, permanently destroying said structure and producing severe current surges in surrounding components. Furthermore, gate “shoot through” due to before mentioned load related “spikes” can also destroy FET junctions with similar catastrophic results. High-voltage ultra-fast diodes have been paced in reverse bias across each MOSFET to inhibit the introduction of reverse voltage “spiking”. Direct gate transformer drive connections are also made to a low inductance secondary and low voltage step up toroid transformer driven by a low impedance bipolar transistor driver configuration as a means for reducing the possibility of “gate shoot through”. Additionally (discrete and other) capacitance has been reduced surrounding each MOSFET and high voltage rated (2× to 4× supply DC) MOSFETs are employed to reduce transient current requirements while increasing intrinsic voltage standoff capability. It has also been learned that it is important to maintain phase matching between (especially) adjacent HBPAs and associated Tank Coils 74 in order to reduce the possibility of outer Tank Coil winding to adjacent Tank Coil arcing and transient generation. This phase match is controlled by both HBPA drive signal phase relationships and by Tank resonant frequency matching (not immediately obvious). Future designs can mitigate such Tank to Tank phase shifts by closing a phase locked loop solution around a measurements of instantaneous phases within each tank magnetic field such as to accommodate load dynamic and circuit related phase mismatch.
3CDU Tank Coil Design
3CDU Prototype Tank Cap Design
3CDU Prototype Pickup Coil Design
3CDU Prototype Pickup Coil Resonating Cap Design
3CDU Prototype Power Amplifier Control Electronics
3CDU Prototype Variable Frequency Electronics
3CDU Prototype PTM Chassis Layout
3CDU Prototype PRM Chassis Layout
It is significant to note that metal foil covered plastic has been used in the construction of the 3CDU Prototype. Rectangular cell sheets of plastic were covered with aluminum foil tape and electrically connected to power and module grounds to form a cohesive termination of residual ground current loops and shielding to help attenuate any unintended RF radiation. The additional use of individual heavy aluminum foil covers over control electronics at each PA 122 module is a means to protect sensitive electronics from power carrier magnetic field induced interference. The use of such foil conductive materials is a fundamental means for reducing weight and cost, while allowing the use of plastics and other lightweight, tough and flexible structural materials for the body of PTM 14 or PRM 16 construction. The use of foil materials are especially relevant to a resultant conduction verses weight efficiency match to the relatively shallow skin depth of the majority of conducted currents at Power Carrier frequencies.
Note that the completed prototype was successfully operated and total coupled power levels were estimated to be in excess of 1000 watts, while the operational efficiency was estimated to be greater than 90% from line to load over a 6″ air gap.
Power Transmit Module Energy Transfer and Waveform Management Features
One important aspect of the present invention is the inclusion of fail-safe & self-protection features integrated within each PTM-CES 34 enable low failure rates, performance monitoring and autonomous fault location. Included among these are the automated power fold-back and/or shutdown to protect against abnormal load conditions or component failures.
Another important feature of the present invention is the soft adaptability to flexibly meet Differing Vehicle Interfaces and Operation with minimal or no added vehicle hardware are provided by the RF Data Link 30 interactivity with vehicle electronic control systems. Critical real-time operational control is facilitated (via software) to accommodate variations in battery state of charge, apportionment of energy between battery and motor, acceleration and braking operations, traffic status and other. The ability of PTM 14 to electronically modulate bursts of energy to create 60 Hz/50 Hz or other AC power frequencies and voltages as direct output from PRM 16 allows direct charging or vehicle powering from conventional “plug in” interfaces. A “smart roadway” and “smart parking area” is created by such an environment, delivering only appropriate levels and formats of energy to the vehicle or otherwise effecting vehicle systems behavior to achieve the safe and efficient operation.
Yet another important aspect of the present invention is the high power generation efficiency achieved by power amplifier gating and parallel resonance within the Tank Coil 74. The Power amplifier 122 remains gated off when no vehicle loads are present or enabled. The MOSFET amplifier configuration allows near zero power dissipation whenever gate drives are removed. The inhibiting of Power Amplifier 122 gate drives for all times except for when the vehicular load is present is therefore a primary way of limiting losses. Additionally, the use of a parallel resonant tank circuit as the magnetic radiator allows losses at this high power point to be a percentage (small) of the power coupled to the vehicular load and not constant, thus further facilitating efficiency.
A further advantage of the present invention is the closed loop charging power regulation via interactivity between PTM 14 and PRM 16 over the Data Link 30 with data from vehicle charge sensors providing a means for controlling delivered power and consequently reducing the need for vehicle charge control hardware while increasing safety and efficiency. In this way PTM-PRM power is transmitted directly to battery 26 without passing through added high power electronic control systems onboard the vehicle, in the amount dictated by real time battery storage and environmental needs.
As seen in
Roadway Physical Locking can be accomplished by a centralized vertical bolt with special keying to inhibit theft at each PTM-CES 34 module. This bolt travels within central reinforcement structural strength member that is environmentally isolated from internals of module. The bottom end of bolt engages with bottom of roadway trench to secure module to roadway. The attachment to roadway trench can be indirect via the RTC wherein the RTC is independently and periodically secured to the roadway trench and provides an appropriately located and spaced socket for the vertical bolts from the top of PTM-CES 34 modules.
The present invention also involves Faraday and non-resonant shielding of PTM 14 and roadway surface located Tank Coils by the use of nonmagnetic metal skins, including foils and films that surround individual PTM-CES 34 and PTM 14 components. The purpose being to significantly reduce the unintended emission or radiation of RF energy, especially at the GPMI and power carrier frequencies and related harmonics and sidebands, without significantly effecting magnetic field coupling to vehicles, either at power or signaling frequencies. The use of a metallic skin overlay over the top (roadway level) of the Tank Coil is especially significant in this regard, this skin can be patterned to provide RF attenuation while at the same time remain transparent to magnetic fields utilized by WAVES. Patterning in effect can be non-resident at power carrier and magnetic signaling frequencies thereby minimizing respective induced currents.
The present invention also includes thermal transfer and high voltage insulation by the use of an oil that surrounds high voltage & high power components (especially power carrier components such as Tank Coil Cap 120, high power amplifier components and perhaps Tank Coil 74). Oils such as silicon based oil have both excellent thermal conduction/convective/distribution properties and excellent high voltage insulating properties that when properly employed internal to PTMs 14 allows corona suppression and heat dissipation to outer and lower subsurface areas of the roadway trench where lower temperature promote efficient heat transfer at correspondingly lower operational temperatures. Such a design limits moisture penetration ant related corrosion and electrical conduction issues. Furthermore the potential exists to eliminate solid dielectrics within critical capacitors such as within the Tank Cap 120. Such oils can serve this function directly while again promoting heat transfer from high power capacitors.
The “V” Shaped PTM 14 of the present invention promotes efficient design for heat transfer from “V” bottom areas of PTM 14 to external side-walls and trench. The “V” shape is also an efficient volumetric match to the needs for a relatively large surface for roadway-level Tank Coil 74 at the top of the “V” and the relatively smaller dimensioned and volume associated with power electronics potentially located lower down within the “V” cross-section. The Tank Cap 120 could be conveniently integrated as a distributed capacitance within the Tank Coil 74 itself or given the need for added capacitance could be a separate component located directly below Tank Coil 74. High area as available within this region of the “V” is an advantage in lowering the cost and mounting of such capacitors especially at the frequencies nominally employed by the power carrier. Advantage can also be made of the vertical dimension of the “V” for such Tank Cap 120 location while overall volume is conserved over other perhaps rectangular cross-sections. The “V” cross-section also promotes ease of installation minimizing additional or difficult filing of roadway material both at surface and subsurface of PTM 14. Additionally, and critically, The “V” cross-section is inherently mechanically strong, easily internally cross-brace able to further strengthen and allows direct downward weight and related traffic loads to be distributed to the vertical side-walls of the receiving trench, providing crush resistance with minimal distortion. Such “V” trench sidewalls can readily receive sealant/cushioning/tolerance absorbing/weatherizing/sealing/heat conducting material during installation to insure proper installation and tolerances to roadway surface.
Primary Power Distribution Features
The present invention includes an efficient PTM-CES 34 power distribution architecture that minimizes GPMI 48 conversion losses from the grid 18 and/or CHP 50 and associated roadway or parking area transmission cable 92 and related PTM 14 primary power losses. The high voltage transformer-less design of GPMI 48 reduces conversion losses and the modularity allows subdivision of the load by the number (or effective number) of phase lanes of provided as load. This subdivision reduces GPMI 48 design requirements to where current technology is able to cost effectively implement this function. This subdivision also introduces redundancy within the transmission and load architecture where phase failures represent a “soft” system failure, degrading PTM 14 power generation in a more or less linear fashion. The ability to electronically optimize GPMI 48 phase power generation, based upon roadway loading, increases conversion efficiency. The provision of multiple phases at transformer primaries within RTC 92 reduces current by the number of phases thereby making the size and material of each related phase transformer practical and cost effective. The relatively high frequency (60 kHz nominal) makes the implementation of each phase transformer practical for this application. The design of RTC 92 negates skin effect losses associated with this relatively high frequency by the use of metalized plastic or metal foil conductors that in turn can provide a low cost light weight alternative to conventional cabling such as copper wire. Further geometry considerations within RTC 92 cabling allow a shielded transmission line ducting of transmitted energy enhancing EMI shielding and reducing losses. Furthermore, internal geometry of foil conductors facilitates connections to imbedded transformer primaries thereby enhancing reliability and lowering costs of manufacture. The ability of high speed turbines as utilized within current CHPs allow the migration of some or all GPMI 48 power conversion into CHP 50 function with appropriate associated electrical generator design.
The present invention also encompasses grid back-up configurations with distributed generation and peak shaving that is facilitated by the CHP 50 grid inter-tie functionality and WAVES 10 ability to “smartly” interact with vehicle loading. Grid inter-tie further enhances reliability beyond load sharing to being able to completely supply roadway or parking needs under periods of grid failures or vice-versa under CHP failures. RTCs 92 can be terminated into RTCs 92 in adjacent roadway or parking segments to produce a combined network of power distribution and distributed generation and grid connectivity that further enhances redundancy for failure mitigation. The phase locking mechanisms within each GPMI 48 readily facilitates such segment to segment inter-tie.
The present invention also provides inherently weatherized interconnection to PTM-CES 34 units by utilizing magnetic fields as the power transfer mechanism and thus allows liberal use of waterproof electrical insulation surrounding RTC 92 imbedded phase transformer primaries and associated secondaries within PTM-CES 34 units. Only the physical parting interface is exposed to the roadway/parking environment. Such magnetic material is readily formulated and/or coated to resist corrosion at these parting interfaces with minimal effect upon power transfer efficiency.
The present invention further accomplished simplified and efficient PTM 14 coil and related electronics implementation due to the modularity and construction of individual PTM-CES 34 units. The relatively large number of PTM-CES 34 units activate able per vehicle (nominally 14 for small vehicles) allows the use of low cost and electrically efficient power generation and control electronics such as power MOSFETs and diodes etc. The Tank Coil 74 is a critical component in the establishment of the roadway/parking magnetic field source for energy transfer. Since the operational frequency is in the region where skin effect is an important source of losses (nominally 360 kHz) the design of this component requires careful consideration. Current Litz wire 126 construction can be replaced with metal foil implementation wherein a spiral of metal foil and associated interwinding dielectric or other geometry coil is fabricated. The depth of this coil from the roadway can be made to accommodate the foil width required, to suitably reduce resistive losses (bulk conduction and skin effect). Furthermore, the design of this coil can be tuned to resonance at the operational power frequency through the control of dielectric spacing and material and by the number of foil turns within the coil. This can accommodate the Tank Coil 74 and all or part of the Resonating Tank Capacitor 120 function thereby decreasing cost and overall volume while simplifying the architecture.
Power Receive Module Features
The present invention may provide for passive driving error mitigation by the use of multiple PRM 16 receive coils. The energy received by two or more PRM 16 receive coils on an plane parallel to the roadway and on an axis relatively perpendicular to the vehicle's direction of travel can be coherently (AC) or noncoherently (DC) combined such as to effectively increase the PRM's energy receiving aperture in direct proportion to the combined area of the individual receive coils. In this manner, driving errors can be mitigated with minimal loss in efficiency and no physical tracking by PRM 16.
The present invention may additionally provide simplified physical and electrical integration vehicle steering sensory feedback adjuncts via the sensing of roadway magnetic fields in relation to vehicle path enables feedback to both driver and automated steering systems onboard vehicles to either allow errors to be sensed and easily manually corrected or fully automated steering. This includes automatic alerting and drive mitigation with regards adjacent lane or fore and aft vehicles in a WAVES connected roadway environment. Knowledge gained from energized PTM-CES 34 units can be collected, aggregated and disseminated by the WAVES (system) to roadway vehicles to address roadway navigation and safety issues.
The present invention further provides an integrated pickup oil and resonating cap combined into a common single integrated component utilizing conductive foil or otherwise high area conductors with dielectric spacing to establish parallel resonance. This approach minimizes high voltage wiring and high voltage PRM Resonating Cap 120 requirements (note that foils can readily serve as effective conductors within both capacitors and coils at the frequencies nominally employed within power electronics). Foil construction is especially relevant to maintaining low weight and cost while reducing skin effect losses associated with AC current transfer.
The present invention includes parallel and otherwise resonated load specific to the power carrier frequency(s) employed allow for selective power transfer to vehicle loads. This represents a fundamental means for limiting power transfer to non-intended loads such as passive metallic objects on the roadway or vehicles. This feature can be employed to selectively supply energy to specific classes of vehicles or to otherwise differentiate the power transfer mechanism.
Like the roadway surface, the present invention includes Faraday and non-resonant shielding of PRM 16 and located pickup coils by the use of nonmagnetic metal skins, including foils and films that surround individual PRM 16 and PRM 16 components. The purpose being to significantly reduce the unintended emission or radiation of induced RF energy, especially at the power carrier frequency and related harmonics and sidebands, without significantly effecting magnetic field coupling to the vehicle and roadway, either at power or signaling frequencies. The use of a metallic skin overlay over the bottom (roadway level) of PRM 16 coils is especially significant in this regard, this skin can be patterned to provide RF attenuation while at the same time remain transparent to magnetic field frequencies employed by WAVES 10. Patterning in effect can be non-resident at power carrier and magnetic signaling frequencies thereby minimizing respective induced currents.
The present invention also employs imbedded DC rectification with power summing capability for the passive mitigation of driving errors and the accommodation of different voltage/current outputs to meet differing EV energization needs. Or-tying of power carrier rectified power can in turn sum respective outputs from several PRM 16 coils with minimal loss from coils not fully excited magnetically. This is deemed non-coherent power summation. Series parallel combinations of rectified coils, in turn, provide combinations of voltage/current outputs from PRM 16 to meet differing EV energization requirements.
Referring to
By phase synchronizing drive signals (transformer isolated) to the power carrier waveform as received by PRM 16 from PTM 14, the polarity of the output can be controlled in both static and dynamic senses by way of the switching of appropriate power MOSFETs on each side of the output circuit. Furthermore, gate drives can be duty-cycle modulated or otherwise shaped to effect net instantaneous power transfer to the output, thereby allowing sinusoidal or other net waveform generation at sub-carrier output frequencies (e.g. 60 Hz) including DC. Note that power carrier related components of the output are smoothed/integrated/filtered/sufficiently eliminated by carrier filter capacitors or other output filtering that leave desired sub-carrier waveform intact.
WAVES Strapping Approach to PTM Assembly and Fabrication
Referring to
The present application is a non-provisional of U.S. Provisional Application No. 61/463,717, filed on Feb. 22, 2011 and U.S. Provisional No. 61/573,750, filed on Sep. 12, 2011, both of which are hereby incorporated by reference in their entirety.
Number | Date | Country | |
---|---|---|---|
61463717 | Feb 2011 | US | |
61573750 | Sep 2011 | US |