Patent Application
20140379180
The present disclosure relates generally to power sharing and, more particularly, to power sharing for a locomotive consist.
A train consist often includes a lead locomotive and at least one trailing locomotive. The lead locomotive, although generally located at the leading end of the consist, can alternatively be located at any other position along its length. The lead locomotive generates operator and/or autonomous control commands directed to components of the lead and trailing locomotives. A typical locomotive of a consist will have a prime mover power source that includes a diesel engine and an alternator or generator that converts rotational output of the diesel engine into electrical power. The term “prime mover” is generally used to refer to the source of power used primarily for generating a tractive effort used in moving the vehicle. A prime mover power source may also provide power for parasitic or auxiliary loads that do not contribute to the tractive effort, such as air compressors, traction motor blowers, and radiator fans. In some cases an additional auxiliary power source is included on the locomotive to provide the power needed for parasitic or auxiliary loads. Electrical power output by the prime mover power source is used primarily to drive electric traction motors, which convert the electrical power back into rotational output that drives the axles and wheels of the locomotive. A typical locomotive may have two trucks that support the body of the locomotive, with each truck including two or three axles, and each axle being driven by one of the electric traction motors.
Tractive power for the locomotive is supplied by the traction motors. Each traction motor may be an alternating current (AC) traction motor or a direct current (DC) traction motor. The diesel engine drives an alternator/rectifier that provides the prime mover electrical power to an electrical power bus. The prime mover electrical power from the alternator/rectifier is DC power that is then converted to provide electrical power in the appropriate form for the traction motors. When AC traction motors are used, one or more inverters receive the prime mover DC electrical power from the electrical power bus and supply AC power to one or a plurality of locomotive traction motors to propel the locomotive. When DC traction motors are used, DC chopper circuits receive a constant DC electrical power from the electrical power bus on the same locomotive and convert this constant DC electrical power into a variable DC electrical power source appropriate for each DC traction motor. The conversion of DC electrical power for use by DC traction motors includes using a switching technique known as pulse width modulation (PWM). Each of the locomotive traction motors on a locomotive propel the locomotive in response to the prime mover electrical power.
Communication between the lead and trailing locomotives can involve a hard-wired multi-unit (MU) cable, which carries signals indicative of a desired power level for the consist. The MU cable includes several wires that carry signals indicative of different throttle notch settings (predefined discrete power levels). Most of these signals are binary indicators that either provide a voltage or no voltage to the wires. Known methods for controlling a consist of at least first and second locomotives include providing control signals from a lead locomotive over the MU cable to command discrete operating modes for each locomotive in a consist. Such a method is disclosed in U.S. Pat. No. 7,021,588 that issued to Hess, Jr. et al. on Apr. 4, 2006 (“the '588 patent”). The method in the '588 patent comprises receiving a control command and determining a power operating mode of the first locomotive and a power operating mode of at least the second locomotive as a function of the control command and an optimization parameter.
Although the system of the '588 patent may have improved communication between multiple locomotives in a consist, the system may still be problematic. In particular, the system may be limited to communicating power operating requirements and control signals to each locomotive in a consist, but without the capability of actually sharing electrical power generated by power sources on each of the locomotives.
The power sharing method of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.
In one aspect, the present disclosure is directed to a method of sharing power between locomotives in a consist. The method may include receiving a power demand signal at a controller on one of the locomotives, with the power demand signal indicative of a total power output requirement for the consist. The method may also include determining an amount of available power on an electrical power bus running through all of the locomotives in the consist, and determining the power generating capacity of all power sources on all locomotives of the consist that are electrically coupled to the electrical power bus. An allocation of power output requirements from each of the power sources that will meet a performance goal for the consist may also be determined. The method may further include activating one or more power sources on any one of the locomotives in the consist to provide electrical power to the electrical power bus for use by a load on a different one of the locomotives in the consist.
In another aspect, the present disclosure is directed to a locomotive consist power sharing system. The power sharing system may include a plurality of locomotives, with each of the locomotives including at least one mechanical power source producing a rotational output, an electrical power generator coupled to the rotational output of the mechanical power source and configured to generate electrical power when being rotated by the rotational output, and a plurality of electric traction motors driven by electrical power generated by the electrical power generator. An electrical power bus may also run through all of the plurality of locomotives, with the electrical power bus being electrically connected to each of the electrical power generators on each of the locomotives and to each of the electric traction motors on each of the locomotives.
As shown in
Control computers 130, 132, 134 may be provided on each of locomotives 120, 122, 124, and may be communicatively coupled through a common control bus 170 extending through all of the locomotives to control modules on each of the power sources. Each control computer may include an engine control, electrical power output control for an associated alternator or generator, electrical power control for an associated traction motor, and a locomotive control, and may additionally include an exhaust aftertreatment system (ATS) control if ATS hardware is included on the associated locomotive. A lead locomotive of the consist may include a lead control computer communicatively coupled over a multi-unit (MU) cable 160 to control computers on each of the trailing locomotives, and/or to additional consists of locomotives that may be connected in the train in a trailing position and separated from the lead consist by additional rail cars. Each control computer or controller may include one or more processors, or various combinations of software and hardware, or firmware configured to execute instructions, such as routines, programs, objects, components, or data structures that perform particular tasks or implement particular abstract data types.
Various energy management protocols implemented by one or more of the control computers may designate one or more periods of time when only one auxiliary diesel-electric power source is operating on only one of the locomotives in the consist to provide electrical power to electrical power bus 180. The electrical power provided to power bus 180 by the one small diesel-electric power source on one of the locomotives in the consist may provide all the power that is needed during designated periods of time to operate traction motors 20 on any of locomotives 120, 122, 124, and provide power to any parasitic loads such as traction motor fans, onboard air conditioning, air compressors, or other non-tractive loads. These low power demand periods of time may occur, for example, when the train is traveling down a steep grade, and each of traction motors 20 is in a regenerative braking mode. Energy management protocols initiated by one or more of control computers 130, 132, 134 may enable the selective operation of one or more power sources on any or all of the locomotives in the consist. Various implementations of this disclosure may allow for operational situations when any particular locomotive in the consist may be able to obtain an extra boost of power from electrical power bus 180 even though the power sources on the particular locomotive are also operational. A locomotive with a temporarily malfunctioning power source may also be able to continue to meet auxiliary and/or tractive power needs by drawing power from electrical power bus 180. The power sharing arrangement in accordance with various implementations of this disclosure may also allow for all power sources on some of the locomotives to be turned completely off during periods of time when both tractive and auxiliary power demands on each locomotive are being met by power obtained from the common electrical power bus 180.
In some implementations of this disclosure the electrical power provided to electrical power bus 180 by one or more of the power sources on the consist may be controlled to maintain a certain minimum voltage on the electrical power bus at all times. As one non-limiting example, a minimum voltage falling approximately within the range from 600 volts to 1200 volts may be maintained on electrical power bus 180 at all times. One or more of control computers 130, 132, 134 may be configured to receive input data and provide command control signals for operating any of the power sources on any of the locomotives in the consist to maintain this minimum voltage on electrical power bus 180. Input may be provided to the control computers from operators onboard the locomotives, or from other command control centers or wayside stations. Additional signals received by the control computers may include signals indicative of operating parameters for each traction motor 20, operating parameters and power generating capacities of each alternator or generator, duty cycles for each alternator or generator, track profile information including track grade, curvature, elevation, tunnels, speed limits, road crossings, and switchyards, power available on electrical power bus 180, trip plan information, and actual power utilization rates on each locomotive for both tractive effort and other parasitic or auxiliary loads.
The control computers may be configured to process the information received from various sensors and other inputs providing the data discussed above and maintain the minimum voltage on electrical power bus 180 by controlling one or more power sources as needed. Maintenance of a minimum voltage on electrical power bus 180 at all times may provide a benefit in that ancillary power on any of the locomotives for air compressors, traction motor blowers, radiator fans, and other parasitic loads is available from electrical power bus 180 at all times. Furthermore, maintenance of at least a minimum voltage on electrical power bus 180 may help to reduce power losses over the power bus by allowing for a lower current through the bus. Because of the relationships between power (P), voltage (V), current (I), and resistance (R), in a power bus with a resistance R, where V=IR, P=IV, and accordingly P=I2R, the power loss over the power bus may be referred to as an I2R loss. A higher potential or voltage (V) in a power bus having a substantially constant resistance (R) may result in substantially the same amount of electrical power (P) transferred through the bus at a lower current (I). A lower current translates into lower power losses, and may also enable the use of an electrical cable with a smaller cross sectional area, which may further reduce costs by cutting down on the amount of copper needed to produce electrical power bus 180.
One or more control computers on any of the locomotives may also be configured to transfer excess electrical energy from electrical power bus 180 to various energy storage devices. One or more of the locomotives in the consist may include an energy storage device, which may include electrical storage batteries, capacitors, flywheels, accumulators, or other mechanisms for storing energy.
The alternators or generators included with each diesel-electric power source may be, for example, alternating current (AC) induction generators, permanent-magnet generators, AC synchronous generators, or switched-reluctance generators. In one implementation, each alternator or generator may include multiple pairings of poles, each pairing having three phases arranged on a circumference of a stator to produce an alternating current with a frequency of about 50-60 Hz. Electrical power produced by each alternator may be rectified to convert the power to DC power, and the DC electrical power may be supplied to electrical power bus 180.
DC traction motors 20 may be generally operable to receive DC power from electrical power bus 180 that may be pulse width modulated by DC chopper circuits. A DC chopper circuit may include a high speed switch such as an insulated gate bipolar transistor (IGBT) and/or a thyristor, and a free-wheeling diode. The free-wheeling diode may help to eliminate any sudden voltage spikes that may occur across an inductive load such as may be present in traction motor 20 when supply voltage to traction motor 20 is suddenly reduced or removed. AC traction motors may be used in alternative implementations where the DC power from electrical power bus 180 is converted for use by the AC traction motors using inverters. Traction motors 20 may additionally be operable to receive mechanical power from the wheels and axles they are mechanically coupled to and use the mechanical power to generate electrical power in a regenerative braking mode, if desired.
As traction motors 20 on each locomotive 120, 122, 124 and any auxiliary loads on the locomotives draw more or less electrical power from electrical power bus 180, the voltage of the electrical power bus may fall or rise proportionally. A control computer associated with a locomotive may include a power source control module and associated throttle position sensors and voltage or current sensors. A lead control computer on a lead locomotive, or any of the control computers on any of the lead or trailing locomotives may be configured to affect an output of each diesel engine and alternator on each locomotive in response to a detected change in electrical characteristics of electrical power bus 180. As traction motors 20 on any one of the locomotives in the consist draw more power from electrical power bus 180 and the corresponding voltage of the power bus begins to drop below a minimum threshold, any one or more of the control computers may be configured to receive signals from a power bus electrical characteristics sensor indicative of these changes in voltage or current. Upon making a determination that the available voltage has dropped below a minimum desired voltage on electrical power bus 180, one or more control computers may be configured to transmit control signals to any of the power sources on any of the locomotives in the consist.
The tasks performed by one or more of control computers 130, 132, 134 may also be performed by remote processing devices that are linked through a communications network . In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices. These local and remote computing environments may be contained entirely within the locomotive, or adjacent locomotives in a consist, or off-board in wayside or dispatch centers where wireless communication may be used. This method and system may be applicable to sharing power and communicating data between any of the linked locomotives 120, 122, 124.
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Each control computer may be further configured to receive other information or data relevant to the instantaneous operating performance of each locomotive in the consist, such as current fuel levels for each locomotive, ambient conditions at each locomotive, wear levels of various components on each locomotive, and track conditions being experienced by each particular locomotive. One or more control computers may be still further configured to include a system that may provide information on upcoming conditions such as track conditions and grade over the next 50 miles. Such a system may acquire data from GPS receivers and/or maps of the upcoming areas, and provide additional information to a control computer that may be used in determining specific energy management protocols for controlling the various power sources on each of the locomotives.
The control computers may be configured to control the prime mover power sources and the auxiliary power sources of each locomotive 120, 122, 124, and other operating parameters based on input from a vehicle operator or other command control center as well as input received from various sensors. Information may be received from a plurality of engine sensors, fuel level sensors, electrical power output sensors, voltage sensors, current sensors, and/or exhaust aftertreatment (ATS) sensors, and each control computer may be configured to send control signals to a plurality of engine actuators, electrical power actuators or controls such as automatic voltage regulators associated with the alternators, traction motor controllers, and/or ATS actuators on each locomotive. As one example, engine sensors and/or ATS sensors may include exhaust gas sensors located in, or coupled with one or more exhaust manifolds for each of one or more engines provided with each locomotive, exhaust temperature sensors located upstream and/or downstream of various emission control devices, and intake regulated emissions level sensors. Various other sensors such as particulate sensors for a diesel particulate filter (DPF), additional pressure, temperature, flow, air/fuel ratio, and alternate regulated emissions sensors may be coupled to various locations on or in the one or more engines provided with each locomotive. As another example, engine actuators and/or ATS actuators may include fuel injectors, hydrocarbon (HC) dosing injectors, reductant injectors used in conjunction with a selective catalytic reduction (SCR) process to reduce NOx levels, and throttle or notch controls. Other actuators for controlling mechanical and electrical components or flows, such as a variety of additional valves, voltage regulators, contactor or electrical relay actuators, and current regulators may be coupled to various locations in each of one or more engines, alternators, the electrical power bus, and traction motors associated with each of the locomotives.
One or more control computers may be further configured to store data and information about each of the power sources on each of the locomotives in a memory device to assist communication with other control computers located onboard the consist. A control computer may also be configured to use this data and information to assist in a determination of which power sources on the consist may be best utilized at any particular time for maintaining a desired minimum voltage on the electrical power bus. One or more control computers may also store data and information on the electrical power output characteristics of the various alternators or generators, and electrical power consumption characteristics of traction motors 20, and maintain this information in continually updated logs of the performance characteristics of the various electric drive components on each locomotive.
Input devices may be located onboard a lead locomotive of the consist, and may include any component or components configured to transmit signals to one or more components of the consist. In some implementations, an input device may include components that an operator can manipulate to indicate whether the operator desires propulsion of the consist by traction motors 20 and, if so, in what direction and with how much power the operator desires traction motors 20 to propel the consist. For example, an input device may include an operator input device with which an operator may indicate a desired consist performance to be received by a lead control computer. In an alternative implementation, an input device may be a computer-based system that may allow the consist to operate automatically without requiring an operator. One or more of the control computers may include circuitry and/or algorithms that enable the one or more control computers to receive and process information in real time from all locomotives, operator inputs, sensors, databases, look-up tables, and/or maps. The control computers may also be configured to determine from this information exactly what power outputs should be requested at any particular time from each of the power sources on each of the locomotives in the consist. Goals may include optimization of fuel efficiency for the entire consist, reduction of emissions, re-allocation of load requirements, equalization of fuel consumption, or precise control of the electrical power outputs of each locomotive as a function of operating parameters, constraints, and objectives. The ability to share power between locomotives may significantly increase the flexibility of the entire system in meeting power demands while improving performance and achieving other desired operating goals.
To facilitate effective control of the supply of electricity from electrical power bus 180 to traction motors 20 on each locomotive, one or more of control computers 130, 132, 134 may be configured to monitor various aspects of engine operation, generator operation, traction motor operation, and/or transmission of electricity within the system. For example, the control computers may monitor engine speed, engine fueling, and/or engine load for their respective engines. Likewise, the control computers may be configured to monitor the voltage, current, frequency, and/or phase of electricity generated by their respective alternators and conveyed over electrical power bus 180. Additionally, the control computers may be configured to monitor the electricity supplied to and/or consumed by traction motors 20, a torque output of traction motors 20, wheel or axle rotational speeds, individual wheel slippage, and/or total tractive forces of each locomotive. The control computers may also employ sensors and/or other suitable mechanisms to monitor the operating parameters. For example, one or more control computers may monitor an actual performance of the consist with one or more sensors, where the actual performance of the consist may include total electrical power consumed by all traction motors 20 during a particular time period or travel distance.
In situations where fewer than all of the locomotives in the consist are required to meet desired performance characteristics, one or more control computers may be configured to automatically improve fuel efficiency for the consist by transmitting a command to one or more other control computers, instructing the associated one or more locomotives to virtually isolate itself or themselves. In an “isolation” mode, a locomotive may essentially take itself electrically offline as a result of the command received from a lead control computer. In isolation mode a trailing locomotive may no longer respond to throttle or power commands from a lead control computer, and may instead receive start-up and shut-down commands from an Automatic Engine Start-Stop (AESS) system on the trailing locomotive. In various non-limiting implementations, the AESS system may monitor conditions on the trailing locomotive such as the electrical charge in batteries, air pressure in brake line reservoirs, and engine temperatures. Based on these monitored local conditions, the AESS system may start-up and shut-down the trailing locomotive completely independently from any command received from a lead computer, as independently determined by the AESS system to maintain desired local conditions on the isolated locomotive. The transfer of electrical power over common electrical power bus 180, which is maintained at or above a set minimum voltage may also enable an isolated locomotive to continue to draw all of the auxiliary power it may need from electrical power bus 180.
One or more control computers 130, 132, 134 may be further configured to receive inputs from various engine sensors, electrical sensors, ATS sensors, and locomotive sensors, process the data, and trigger the engine actuators, generator electrical power control actuators, traction motor actuators, ATS actuators, and locomotive actuators in response to the processed input data. The one or more control computers may be configured to take these actions based on instructions, look-up tables, one or more maps, or programmed code or algorithms corresponding to one or more routines. For example, a control computer may be configured to determine a locomotive trip plan including locomotive power outputs and brake settings, engine operating parameters, and the precise levels of electrical power output expected from each generator on each locomotive based on the locomotive operating conditions and current environmental conditions for each locomotive.
In one example, a control computer may be configured to determine a trip plan including precise electrical power output requirements for each locomotive based on the current voltage and/or current in electrical power bus 180, individual engine operating conditions, generator electrical power output capabilities, traction motor electrical power requirements, age of the equipment, and operator preferences. Individual locomotives and/or one or more consists of locomotives in a train may be operated in accordance with particular power duty cycles that specify the time spent at each power level or range of total power outputs as a fraction of total time of operation. In various implementations, for example where the diesel engines of prime mover power sources 140, 142, 144, and auxiliary power sources 150, 152, 154 are most efficient and achieve best possible brake specific fuel consumption at or near full power, a control computer may provide commands for electrical power output from each of the power sources that will result in the engines on each locomotive operating close to full power for as large a portion of total operating time of each engine as possible. Based on possible differences between the trip plan's time in a particular power duty cycle and a reference duty cycle (such as an EPA duty cycle), one or more control computers may reconfigure the trip plan. For example, based on the differences, a particular control computer may be configured to readjust parameters set during trip planning. These parameters may include electrical power output requirements for each alternator, electrical power consumption or draw by each traction motor 20, fuel injection settings for each engine, ignition timing, and other engine operating parameters and exhaust aftertreatment parameters. In one example, as an actual duty cycle for one or more of the locomotives starts deviating from a reference duty cycle, thereby possibly leading to increased exhaust emissions or reduced fuel efficiency, a control computer may provide instructions to readjust electrical power output requirements for one or more locomotives for a trip plan that imposes fuel economy and exhaust emissions as constraints. Any one or more of the control computers may be configured to customize a trip plan. The trip plan may be modified during a particular trip based on network data and/or non-network data received from one or more of an operator, remote dispatch center, onboard sensors including engine operating sensors, electrical sensors, and locomotive sensors, and wayside sensors including hot box detectors, impact detectors, and hot wheel detectors.
In various alternative implementations, operator input may include a total wattage power output goal, a fuel efficiency goal, an emissions level goal, a tractive power goal, or a performance goal for each of the locomotives or for the consist as a whole. Any one or more of the control computers may be configured to determine the electrical power output desired from each of the power sources on each of the locomotives at any particular time, or over any particular period of time, in order to improve fuel efficiency for the entire consist, reduce emissions, re-allocate load requirements, or otherwise vary the power outputs of each locomotive as a function of operating parameters, constraints, and objectives. This determination may be made by calculating from one or more algorithms, or by reference to a look-up table, one or more maps, or other data obtained over a network or stored in memory.
The disclosed locomotive power sharing system may enable operation of the various power sources throughout the consist in ways that may improve overall fuel economy, reduce emissions, increase engine life, reduce noise, and efficiently and effectively meet a wide range of power demands and tractive efforts called upon under a wide variety of conditions experienced by the consist. The transfer of electrical power from one power generating locomotive to another in the consist along a common electrical power bus running through all of the locomotives may provide flexibility in the operation of the various power sources that would not be available when simply transferring control signals between the locomotives. The disclosed power sharing system may be applicable to any number of vehicles and/or different types of vehicles having electrical power drive in various arrangements. For example, the consist could include additional or fewer locomotives, passenger cars, freight cars, tanker cars, or other rail or non-rail vehicles having electrical power drive.
At step 202 in
At step 204, any one or more of the control computers may determine an amount of available power on an electrical power bus running between all of the locomotives in the consist. This determination may be made from signals received from power bus electrical characteristic sensors such as voltage sensors and current sensors. The control computers may also take into consideration upcoming conditions such as changes in track profile, weather, anticipated loading, or other factors that may affect the power draw on the electrical power bus.
At step 206, any one or more of the control computers may receive signals indicative of a power generating capacity of each power source on all locomotives of the consist that are electrically coupled to the electrical power bus. These signals may include current operating parameters for each power source, rated capacities for each power source, desired operating ranges for each power source to provide improved fuel efficiencies, reduced emissions, or various combinations of these parameters, and historical or empirical data obtained from various data sources including maps or tables specific to the engines and alternators or generators of each power source. Although
At step 208, any one or more of the control computers may determine an allocation of power output requirements from each of the power sources that will meet a performance goal for the consist. Performance goals may be based on a variety of factors including, but not limited to, improved overall fuel efficiency for the consist, reduced emissions, improved engine life, reduced noise, increased power, reduced drawbar pull, increased traction, or any combination of these and other operational parameters.
At step 210, any one or more of the control computers may activate one or more power sources on any one of the locomotives in the consist to provide electrical power to the electrical power bus for use by a load on a different one of the locomotives in the consist. The power sharing system in accordance with various implementations of this disclosure may allow some of the locomotives in a consist to temporarily shut down all power sources, while still receiving power needed for tractive effort and/or auxiliary loads from electrical power bus 180.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed power sharing system. Other implementation will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed methods. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
