Patent Application
20110320056
The EVSE, which is also referred to as supply equipment, a vehicle charger, a charging station, a charger, etc., may be realized in several different mechanical configurations. EVSE are frequently installed as wall-mounted units in garages and on buildings where vehicles can be parked inside or close to the building. In outdoor locations, especially parking lots and curbsides, EVSE are commonly installed on pedestals. EVSE may also take the form of a cord set which is sometimes referred to as a travel charger, portable charger, handheld charger, etc.
The connector 16 and inlet 18 typically utilize a conductive connection in which the electrical conductors in one connector make physical contact with the electrical conductors in the other connector. Other systems utilize inductive coupling in which energy is transferred through magnetic coils that are electrically insulated from each other.
To promote interoperability of vehicles and supply equipment, the Society of Automotive Engineers (SAE) has developed various standards that define mechanical configurations of connectors for charging vehicles, as well as the arrangement and function of electrical contacts within the connectors. One standard known as SAE J1772 is of particular interest because virtually every automaker in the U.S., Japan and Europe has announced plans to use J1772 compatible connectors for models sold in the U.S. This standard relates to conductive charging systems and covers both AC and DC connections.
Terminal 5 of the coupling connects safety grounding conductors in the EVSE and the vehicle. A control pilot signal is connected through terminal 6 and enables basic two-way communications between the EVSE and the vehicle. For example, the control pilot enables a charge controller 36 in the vehicle to determine the maximum amount of AC current available from the EVSE, while it enables the EVSE to determine if the vehicle requires ventilation for charging and if the vehicle is ready to receive power. The return path for the control pilot signal is through the grounding path which enables it to serve a safety function: if the safety pilot signal is not present, control electronics 42 in the EVSE assumes the ground path has been compromised and causes the CCID to interrupt the flow of AC power to the vehicle.
A proximity device 40 enables the vehicle to verify that it is mechanically connected to an EVSE system. The implementation details of proximity detection are left to the discretion of the manufacturer, but the J1772 standard identifies the use of magnetic proximity detectors as an acceptable technique. For AC charging, only terminals 1, 2, 5, and 6 are required. DC charging requires the use of optional terminals 3 and 4, as well as the establishment of a more sophisticated communication link through optional terminals 7-9 which are not illustrated.
The J1772 standard defines different types of charging including AC Level 1, which utilizes the most common 120 Volt, 15 Amp grounded receptacle, and AC Level 2, which utilizes a dedicated AC power connection at 208-240 Volts nominal and 32 Amps maximum. DC charging is defined as a method that utilized dedicated direct current (DC) supply equipment.
For convenience, the term electric vehicle will be used to refer to pure electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), and any other type of vehicle that utilizes electric charging unless otherwise apparent from context.
Some inventive principles of this patent disclosure relate to electric vehicle supply circuits for EVSE. An electric vehicle supply circuit is designed to provide power to an electric vehicle from a power source and includes at least an interrupting device and control circuitry to cause the interrupting device to interrupt the flow of power from the power source to the electric vehicle in response to conditions relevant to electric vehicles. Examples of conditions relevant to electric vehicles include a ground fault condition, an inoperable grounding monitor circuit, the absence of a vehicle connected to the EVSE, absence of a ready signal from the vehicle, etc.
The embodiment illustrated in
In the context of UL standards, the ground fault detector 244, and interrupting device 246, taken together, may be used to implement a charging circuit interrupting device (CCID) which is required to disconnect the source of power if the difference between the current flowing in the current-carrying conductors (differential current) exceeds a predetermined threshold. Any differential current is usually assumed to be caused by a ground fault which may present an electrocution hazard. This is essentially the same operating principle as a common ground fault circuit interrupter (GFCI) which is typically designed to interrupt the flow of power (trip) if the differential current exceeds 5 mA.
In the case of electric vehicle charging, however, 5 mA may be an unacceptably low trip point. Natural nonhazardous current paths through the vehicle to ground may routinely exceed 5 mA, thereby causing excessive nuisance tripping that interrupts the charging process. Therefore, UL standards allow a CCID to have a trip point of 20 mA if the system is equipped with a grounding monitor that interrupts the power circuit if it detects an inadequate grounding circuit. UL standards also require a CCID to allow for manual testing or automatic testing before each operation.
The grounding monitor circuit 254 monitors the continuity of a grounding conductor and generates an output signal GMO in response to the state of the grounding conductor. A manual test input GMMT enables the operation of the grounding monitor to be tested manually. An automatic test input GMAT enables the operation of the grounding monitor to be tested in response to an automatic test signal from a controller 262. The output signal GMO is provided to the controller 262 as well as logic 264.
The ground fault detecting circuit 256 monitors the differential current through the current carrying conductors and changes the state of the output signal GFO if the differential current exceeds a threshold. A manual test input GFMT enables the operation of the ground fault detector to be tested manually, while a manual reset input GFMR allows the detector to be reset manually. Automatic test input GFAT and automatic reset input GFAR enable the controller 262 to test and reset the ground fault detector. The output signal GFO is applied to the controller 262 as well as logic 264.
The contactor circuit 258 is arranged to close the circuit between the power source and the vehicle connector 260 in response to a CLOSE input signal from logic 264.
The contact monitor circuit generates an output signal CMO in response to the state of one or more switches in the contactor circuit 258. An automatic test input CMAT enables the controller 262 to test and monitor the contactor circuit.
A control pilot connection 266 enables the controller to determine whether a vehicle is connected to the supply circuit, to determine whether the vehicle is ready to receive power, to communicate the current capacity of the supply circuit to the vehicle, etc.
Logic 264 may be configured for interlocking operation. For example, the logic may be configured to assert the CLOSE signal only if the GMO signal indicates that the grounding monitor circuit is operating properly, the GFO signal indicates that no ground fault is present, and the controller asserts the CTRL signal.
The controller 262 may be configured to operate any or all of the features illustrated in
The microcontroller 270 includes digital I/O lines coupled to the test, monitor and reset signals shown in
Indicators 274 such as LEDs, lamps, etc. enable the controller to provide a visual indication of the operating condition of the vehicle supply circuit, fault conditions, etc. Some example indicators include a vehicle charging indicator and an EVSE fault indicator.
Operator inputs 276 such as switches, keypads, swipe cards, RFID devices, etc., enable a user to control the operation of the vehicle supply circuit. Some example inputs include switches to start/stop charging, switches to increase/decrease amperage, etc.
A display 278 enables the controller to provide more information to a user than may be conveyed through simple indicators. For example, an alphanumeric display may display vehicle charging current, voltage and/or power, percentage of charging completed, elapsed charging time, cost of power, etc. A display may also provide more detailed information about fault conditions and/or instructions for correcting faults.
A power meter 280 or other device may provide functionality to measure the amount of power transferred through the vehicle supply circuit, obtain authorization for power usage from a utility or other provider, facilitate off-peak rate reductions and/or demand response functions, etc. The power meter may be utility-grade for billing purposes, or it may be a convenience feature. It may be integral with the controller or separate from the controller, for example, in a tamper-proof enclosure. The power meter may be implemented, for example, with a dedicated integrated circuit (IC) such as a Microchip MCP3909 which may be mounted on a main circuit board with the microcontroller 270. Alternatively, the power meter may be arranged on a separate circuit board that may be attached to the main circuit board through a plug-in header to facilitate implementation of the power meter as an optional feature.
A network interface 282 may enable the controller to interface to any suitable network such as a local area network (LAN), wide area network (WAN), home network, the Internet, a control area network (CAN) or other industrial type control network, etc., through any type of network media and using any type of network protocol. Examples include dedicated wires, power line modulation, radio frequency (RF), infrared (IR), and other types of media, Internet Protocol (IP), WiFi, LonWorks, ZigBee, Z Wave, and other types of protocols.
The inventive principles described above with respect to the embodiments of
In a 120 VAC system, L1, N and GND may designate the hot, neutral and grounding conductors, respectively. In a 240 VAC system, L1, L2 and GND may designate the two hot conductors and the grounding conductor, respectively. Other systems, for example 3-phase power systems, may include different combinations of live and grounding conductors. In the circuit of
Actuating the manual test switch interrupts the monitor current path and causes the optocoupler to stop pulling up the monitor signal GMO. The controller or other decision making circuit may respond to the change of state of GMO by interrupting the flow of power to a vehicle and/or any other suitable actions.
The solid state relay RL5 enables the ground monitor circuit to be tested automatically by a controller or any other suitable apparatus. A logic high on the automatic test signal GMAT turns the switch side of RL5 off, thereby interrupting the monitor current path and causing the optocoupler to stop pulling up the monitor signal GMO. This enables the controller to confirm the correct operation of the ground monitor circuit. In this case, rather than actuating a CCID, the controller may drive GMAT low again, and after confirming that GMO goes high again, return to a normal monitoring mode of operation.
The current carrying conductors L1 and L2/N both pass through a differential transformer T1 and neutral-ground (N-G) transformer T2, which are connected to a ground fault interrupter (GFI) circuit 268. The GFI circuit includes circuitry to detect differential currents flowing through L1 and L2/N and trigger the silicon controlled rectifier (SCR) labeled SC1 when the differential current exceeds a threshold determined by resistor R10. The GFI may be based on a commercial or special-purpose GFCI integrated circuit such as the LM1851 chip from National Semiconductor or the FAN1851 chip from Fairchild.
In a conventional ground fault detection circuit, the SCR actuates a latching relay arrangement. In the embodiment of
When SC1 is triggered in response to a ground fault detection, it latches in the conductive state and causes Q1 to turn off, thereby causing the ground fault monitor signal GFO to go low. SC1 may be reset by closing the manual reset switch. A normally-open solid state relay RL4 enables the GFI circuit to be reset automatically by a controller and/or other decision making circuit or suitable apparatus in response to a ground fault automatic reset signal GFAR. A logic high on GFAR turns on the LED on the input side of RL4 through a current limiting resistor R16. Light from the LED turns on the FET switches on the output side of RL4, thereby resetting SC1.
The circuit of
Another normally-open solid state relay RL3 enables the GFI circuit to be tested automatically by a controller and/or other decision making circuit or suitable apparatus by driving the ground fault automatic test signal GFAT with a logic high. A high signal on GFAT turns on the LED on the input side of RL3 through a current limiting resistor R15. Light from the LED turns on the FET switches on the output side of RL3, thereby causing a test current to flow through R14 without passing through the transformers T1 and T2.
The GFI supply +VS is referenced to a local ground connection at node N3 and may be provided, for example, by a rectifier bridge connected to the current carrying conductors L1 and L2/N. One or more resistors may be connected in series with the bridge to reduce the supply voltage to an acceptable level for the GFI circuit 268. For example, commonly available GFCI chips such as the LM1851 typically include an internal voltage regulator that clamps the supply voltage to about 26 Volts.
During normal operation, if the contacts of the monitored relay are closed and AC power is available, current flowing through the input side of optocoupler U19 turns on a phototransistor which pulls the contact monitor output signal CMO to a high logic level through resistor R68 referenced to a logic supply voltage +V and an associated logic ground. If the contacts are open and/or AC power is not available, no current flows through the monitor current path and the optocoupler stops pulling up the monitor signal CMO. The CMO signal may be monitored by a controller or other apparatus to confirm that the contacts are actually open or closed when expected.
The normally-closed solid state relay RL6 provides additional functionality by enabling an automatic test feature. During a time when AC power is expected on LINE 1 and LINE 2, the contact monitor automatic test signal CMAT may be driven high to turn the switch side of RL6 off, thereby interrupting the monitor current path and causing the optocoupler U19 to stop pulling up the monitor signal CMO. This enables a controller or other apparatus to confirm the correct operation of the contact monitor circuit.
In any of the embodiments of
Some additional inventive principles of this patent disclosure relate to fault circuit self-testing for EVSE. For purposes of illustration, some of the inventive principles are described in the context of a ground fault detector, but the inventive principles are also applicable to other types of fault circuits that may be used in EVSE such as arc fault detectors, over-current detectors, etc.
Ground/Neutral transformer T1 is connected to the IC through a capacitor network including C6 and C7. The differential sense transformer T2 is connected to the IC through a network including capacitors C8-C10, resistor R11 and voltage regulator diode Z2.
The differential fault current threshold (sensitivity) for the IC is determined by the current flowing into the RES terminal (pin 6) through resistor R10. The timing or integrating capacitor C3 is charged by a fault current when the IC 271 detects a fault condition. When the voltage on C3 reaches a predetermined limit, the SCR output (pin 1) is driven high which triggers the SCR SC1 through resistors R7 and capacitor C2, which provides noise protection from accidental triggering.
To simulate a fault condition during an automatic testing process, a fault simulation circuit such as the auto test circuit including R15, RL3 and R14 shown in
A trigger connection TRIG may be provided to the gate of SC1 to enable the self-test controller to control SC1. For example, the TRIG connection may have three different states: a high-impedance state that enables the IC 271 to control SC1 as it normally would in a conventional operating mode; a low output or pull-down state that clamps the gate of SC1 to a low level to prevent it from triggering even if the IC 271 tries to trigger it; and a high output or pull-up state that triggers SC1 regardless of the state of the output (pin 1) of the IC 271.
A sense connection SENSE may be provided to enable the self-test controller to read the state of the SCR output (pin 1) of the IC 271.
A timing circuit 275 includes a transistor Q1 which turns on in response to a signal P_CTL and discharges the timing capacitor C3 through a resistor R270. This causes the timing capacitor to discharge more rapidly than it normally would under the control of the IC 271.
A zero crossing detection circuit 273 generates a zero crossing signal ZC which may enable a self-test controller to determine when the AC input voltage on L1 and L2/N crosses zero, as well as other information such as the line voltage, polarity of a half-cycle, etc. The zero crossing detection circuit may be implemented, for example, with a resistive voltage divider connected to the AC input voltage and referenced to the local ground node. If used in combination with a zero crossing detector, the optocoupler RL3 may be used to apply a fault condition to the system during any selected portion of a line cycle or half-cycle.
In some embodiments, the self-test controller may be implemented as a dedicated controller. In other embodiments, the self-test control functionality may be integral with other control functionality such as that provided by the controller 262 illustrated in
The apparatus illustrated in
If, however, the SENSE signal is activated earlier than expected, this may indicate that an actual external fault condition exists. The self-test controller may then release the TRIG signal immediately to enable IC 271 to trigger the SCR and open the contacts. Alternatively, the self-test controller may activate the TRIG signal to trigger the SCR and open the contacts.
In some embodiments, the self-test controller may activate the P_CTL signal at the end of a self-test process to enable the timing circuit 275 to rapidly discharge the timing capacitor C3. This may reduce the time required to put the fault circuit back online for detecting actual faults once a self test is completed.
In some embodiments, the self-test controller may be programmed to perform a self test across at least two different half cycles of opposite polarity. The determination of the timing of the self test may be based upon timing performed by the self-test controller in combination with the zero crossing detection circuit 273. Both the polarity and timing of a zero crossing are detected with the help of the zero crossing circuit 273. If a self test is conducted during the existence of an external fault that was below a trip limit, then this condition could result in a false failure of a self test. Because the system may be configured to conduct the self test across at least two different half cycles of opposite polarity, this self test may not be affected by the presence of a standing external fault. This is because with at least one of the embodiments described above, the self test simulated fault signal may be a rectified fault signal. If during the self test, the SENSE signal goes high at the half cycle or during a period of time when a test fault is not applied, this means that an external fault caused the tripping and the self-test controller will unblock the SCR to allow the IC chip 271 to trip the solenoid.
During charging, the voltage on timing capacitor C3 grows, and when it reaches its threshold value, pin 1 on the IC 271 goes high, and causes triggering of the SCR SC1. The triggering of the SCR provides current to the pilot solenoid RL2 of
In some embodiments, the SENSE signal from the fault detection IC 271 is coupled to the self-test controller to enable the controller to determine that the fault detector IC 271 has detected a fault. In this case, during a fault, either external or internal, when fault detector IC 271 generates a fault signal, the output from fault detector IC 271 flows not only to the SCR but also to the self-test controller to indicate to the self-test controller that a fault has occurred. The SENSE input to the self-test controller is significant because if during a test cycle, there is no active signal from pin 1 of fault circuit IC 271 into the self-test controller, then this result would provide an initial indication that fault circuit IC 271 has failed or at least that another component monitored by the self test has failed. In this case, self-test controller is programmed to conduct a self test over at least two different half cycles of different polarities. In at least one embodiment, these different half cycles can be consecutive half cycles. The simulated fault signals that are generated are introduced by the self-test controller in combination with the fault simulator such as RL3 in
In some embodiments, a temperature sensor 277 may be included. The temperature sensor 277 can comprise a circuit utilizing a resistor, a thermistor, or any other known sensor circuitry for determining the ambient temperature of the device. If necessary, the self-test controller can include an additional connection to this temperature sensor to form a closed circuit. The temperature sensor is used to determine the ambient temperature of the device, wherein the self-test controller includes programming to trip the contacts in the event it detects that an operating temperature, or an ambient temperature sensed by temperature sensor 277 is too high or too low.
Some additional inventive principles of this patent disclosure relate to communications between EVSE and a utility.
The electric vehicle supply circuit 348 may be realized with any suitable circuitry including, for example, any of the embodiments described above and illustrated with respect to
The apparatus 346 may be realized in any suitable form including a Level 1 EVSE cord set or hardwired device, a Level 2 EVSE device, a portable apparatus such as a plug-in adapter, etc. In some embodiments, the apparatus 346 may include a revenue-grade (or utility-grade) meter to enable power usage reporting and revenue collection through the communication link 354 between the apparatus 346 and the utility collection point 352.
Revenue-grade (or utility-grade) metering is provided by a metering IC 364 such as a Microchip MCP3909, a Teridian 71M65xx, or any other suitable device. The metering IC detects load current and voltage through a current transformer CT1 and voltage transformer T1, respectively. The output from the voltage transformer T1 may also be used to generate one or more DC power supplies for the microcontroller 360 and other support circuitry. A manual or air-gap switch may also be connected in series with the relay RL1. The metering IC may communicate with the microcontroller 360 through a serial interface 366 or any other suitable interface.
Communications capabilities may be provided by one or more network interface modules, ICs, etc. In the example embodiment of
Using the ZigBee Smart Energy 2.0 standard may enable Wi-Fi compatible wireless connectivity through the ZigBee module 372. This may reduce the overall system cost, design effort, power consumption and system requirements, while still providing the flexibility of Wi-Fi connectivity.
The embodiment of
Nodes 380 and 388 are comprised of, or included in, home area networks (HANs), while nodes 382 and 386 are comprised of, or included in commercial building area networks (BANs). EVSE 384, which may be realized for example with the embodiment of
Depending on the implementation, EVSE with the ability to function as a node in a mesh network may provide various benefits. For example, an EVSE system may be the first mesh-capable device introduced into a certain household in a neighborhood. This may greatly expand the interconnectivity and reach of a utility mesh network. This may be understood by reference to
As with other embodiments described above, the mesh-capable EVSE nodes 384 and 390 may be realized in any suitable physical form including a Level 1 EVSE cord set or hardwired device, a Level 2 EVSE device, a portable apparatus such as a plug-in adapter, etc. The communication technology may be based on a ZigBee Smart Energy interface or other interface using spread spectrum or other wired or wireless technology. Using a ZigBee Smart Energy 2.0 wireless interface may facilitate a direct link to a utility without the need for a gateway.
For example, in one embodiment the device may not be able to disconnect the receptacle 312 from the blades 310. The device may only have monitoring circuitry to display charging voltage, current, power, etc., on a display 314. Buttons 316 may enable a user to select a parameter to view, scroll through various parameters or menu items, etc.
In another embodiment, the plug-in device of
In other embodiments, the device of
The EVSE of
Referring to
The system enters State B shown as element 502 if a vehicle is connected to the EVSE and no faults are detected. In State B, the contactor is off, a 1 KHz pulse train is applied to the control pilot conductor with pulse width that indicates the current available from the EVSE. The vehicle charge control circuit maintains the pulses at +9/−12 VDC to indicate that the vehicle is not ready to accept energy. In State B, a wireless connection is established with utility, user, monitoring system, or other networked device. The system may return to State A and terminate the wireless connection if the vehicle is disconnected from the EVSE and no faults are detected.
The system enters State C shown as element 504 if the vehicle remains connected, no faults are detected, and the vehicle charge control circuit maintains the pulses at +6/−12
VDC to indicate that the vehicle is ready to accept energy and that no indoor charging area ventilation is required. In State C, the contactor is turned on, and the wireless connection is maintained.
State D, which is shown as element 506 is similar to State C except that the vehicle charge control circuit maintains the pulses at +3/−12 VDC to indicate that the vehicle is ready to accept energy, but indoor charging area ventilation is required. In State D, the contactor is turned on after the EVSE provides a signal to turn on the ventilation if the EVSE is listed for indoor charging of vehicles.
The EVSE may enter State E shown as element 508 from several different states if the EVSE is disconnected, utility power is not available, or another EVSE problem is detected. In State E, no pulses are driven onto the control pilot conductor which is maintained at a 0 VDC nominal voltage. The wireless connection is terminated, and the contactor is turned off.
The system enters State F shown as 510 if a fault occurs while the vehicle is connected. For example, the EVSE may not be available or another EVSE problem may occur. In State F, no pulses are driven onto the control pilot conductor which is maintained at a −12 VDC nominal voltage. The wireless connection is maintained, but the contactor is turned off.
A lockout state 512 may be entered when a continuous fault is detected. In the lockout state, no pulses are driven onto the control pilot conductor which is maintained at a −12 VDC nominal voltage. The wireless connection is terminated, and the contactor is turned off.
The interface 402 may include any suitable mechanical interface to accept a communication module including a slot, bay, socket, etc., and any suitable electrical interface to enable the EVSE to communicate through the module including a card-edge connector, plug and receptacle, ribbon cable, etc., to establish serial data connection, parallel data connection, etc. with the module. A module may be realized in any suitable mechanical and/or electrical form to operate with the interface.
Having modular communications may provide a flexible solution that enables the EVSE to adapt to changing market conditions, supply conditions, user preferences and/or needs, etc. For example, a specific type of communication protocol such as Z-Wave may be popular in a particular market where the local utility is promoting a new standard such as ZigBee Smart Energy 2.0. The local utility may require new EVSE to include the new standard, but hardware for the new standard may not be widely available yet, it may be prohibitively expensive, or it may lack user acceptance. By providing a modular interface, an EVSE manufacturer or supply may initially ship a unit with the more common or acceptable Z-Wave module, but still enable the conversion to the new standard when required by the utility or accepted by the user.
The inventive principles relating to WiFi may be implemented even without a modular interface. Current EVSE products typically have non-WiFi communication such as ZigBee, which is oriented to specialized applications such as automation and control systems and cannot interoperate with WiFi. However, WiFi has become popular with the general public WiFi routers have been installed in homes and businesses on a widespread basis. To promote acceptance of electric vehicles by the general public, it may be advantageous to enable consumers to interact with EVSE through a familiar interface such as WiFi. Thus, some of the inventive principles contemplate an embodiment of an EVSE system with a WiFi interface, which may be modular or built into the EVSE, that enables a user to check, for example, the charge status of an electric vehicle from a WiFi enabled computer or phone, while utilizing existing WiFi infrastructure.
Another embodiment of a communication module according to some of the inventive principles may operate on any version of the ZigBee Smart Energy standard including version 2.0. Such an embodiment may combine wireless and power line carrier (PLC) technology in a modular form that may be utilized for locations or utilities that require a ZigBee interface.
Another embodiment of a communication module according to some inventive principles may provide Z-Wave compatible functionality. An benefit of a Z-Wave compatible module is that is may enable an EVSE to interoperate with a wide range of existing products such as remote controls, serial communication modules, etc., many of which may be consumer oriented products that users may have developed a level of comfort and acceptance with.
The inventive principles of this patent disclosure have been described above with reference to some specific example embodiments, but these embodiments can be modified in arrangement and detail without departing from the inventive concepts. For example, even though some example embodiments are described in the context of EVSE systems, the inventive principles may also be applied to other types of power distribution systems. Thus, any changes and modifications are considered to fall within the scope of the following claims.
