Disclosure of Invention
The present invention is a powertrain for a hybrid electric vehicle, comprising: an internal combustion engine; a first motor-generator coupled to the internal combustion engine and adapted to start the internal combustion engine or to supply power to a second motor-generator; a second motor-generator that supplies traction to the wheels; a first electrical energy storage device; a second electrical energy storage device; a power converter; a controller and a charger.
The first electrical energy storage device is a battery that delivers or absorbs electrical energy when the vehicle is operating as a hybrid vehicle or when the vehicle is operating using only stored electrical energy.
The second electrical energy storage device is a flywheel, a capacitor or an ultracapacitor or a supercapacitor, or a battery, which only draws or delivers current when necessary to protect the first electrical energy storage device from currents exceeding the damage threshold of the first electrical energy storage device.
In response to the controller, the power converter transfers electrical energy from each electrical energy storage device or motor-generator to each other electrical energy storage device or motor-generator.
The controller has means to determine and control the power flow path through the power converter. The charger recharges either or both of the first electrical energy storage device and the second electrical energy storage device using externally supplied power.
The system includes (at least) a fuel powered engine or fuel cell, a battery, a fast energy storage system, a power converter, a controller, a drive motor, a power distribution system, and a transmission system.
One of the following three devices can be used for fast energy storage. (1) The flywheel device includes a rotor, a motor-generator, bearings, a housing, a power converter and controller, and auxiliary subsystems. (2) A small battery optimized for high cycle life. (3) The supercapacitor bank includes a plurality of electrostatic energy storage components.
Broadly speaking, the preferred embodiment of the apparatus includes a battery pack, a fast energy storage device, an engine, a transmission, power electronics and a control device. A preferred embodiment of the method includes using a fast energy storage device to perform short, frequent, high intensity charge and discharge functions, thereby keeping the battery providing average power for driving in the electrical mode only.
A power electronics package (package) includes a plurality of power conversion devices for managing power flow between various subsystems. A transformation device is used for the grid interface. The controller is associated with power electronics of a grid interface for managing bi-directional power flow between the vehicle and the grid, which includes equipment for communicating with a utility, independent system operator, an aggregate service provider (services), or other related entity.
The grid interface system includes some or all of the following elements:
GPS-based vehicle position sensor
Two-way data communication
Charging/discharging control unit
"plug-in" or link (hookup) device capable of bidirectional power flow
External (garage mounted) charger for bidirectional power flow
Chargers (multiple chargers) for parking lots and garages at workplaces
It is an object of the present invention to provide a plug-in hybrid transmission system that can produce at least 150000 miles of durability for passenger vehicles in normal use.
A second object of the present invention is to combine the battery and separate fast energy storage elements of a plug-in hybrid system to provide service to the distribution Grid when the Vehicle is connected to the Grid, wherein the Vehicle-to-Grid (V2G) system allows the power Grid to benefit from a plurality of small power sources randomly connected to it and dispersed throughout the locality. The regulation service has the best potential to take advantage of the capacity of the vehicle-based energy storage system to increase the value of the grid, while other ancillary services may benefit equally. Ancillary services provided by decentralized fleets are cheaper and more efficient than the regulatory services provided today by power stations. By providing or absorbing (sourcing or sinking) energy pulses, most V2G vehicles are able to perform frequency stabilization, thereby alleviating the need for frequent adjustment of the power plant output. For V2G applications, a major problem with existing conventional hybrid systems is that providing auxiliary services to the power distribution system may necessitate a sufficient number and depth of discharge-charge cycles to degrade battery performance and reduce battery life. This problem is exacerbated when cycling includes high current operation in a low charge state.
It is a third object of the present invention to provide distributed storage for unstable sources of electrical power, such as wind. Wind direction distribution in certain regions of the world (e.g., midwest and western texas in the united states) is such that wind is greater at night than during the day. Most V2G vehicles are able to absorb non-deliverable, off-peak wind power during energy-inexpensive off-peak hours to charge their batteries.
One advantage of the present invention is that the number of charge and discharge cycles of the battery is reduced, which correspondingly increases the battery life. This is accomplished by using a fast energy storage system that has a cycle life that exceeds the battery cycle life by at least a factor of 10, and is sized to provide or absorb brief, frequent pulses and provide most or all of the V2G auxiliary services.
A second advantage of the present invention is that the rapid energy storage reduces the life cycle cost of the battery. Without rapid energy storage, the battery would experience a large number of shallow cycles and occasional high current pulses when the battery is at a low state of charge. The present invention reduces the number of shallow charge cycles that the battery will experience, by 90% -100%, and protects the battery from high current pulses. In particular, fast energy storage systems protect batteries from the adverse effects of high discharge rates at low states of charge. In this way, the present invention extends the life of the battery so that no replacement is required over the life of the vehicle.
A third advantage of the present invention is that the overall weight of the energy storage system is reduced. The combined weight of the battery and the fast energy storage device is less than the weight of the battery sized to handle frequent cycling and high current pulses.
A fourth advantage of the present invention is that the durability of the energy storage system is improved.
A fifth advantage of the present invention is improved fuel economy over conventional vehicles. The present invention achieves a 2-fold improvement in fuel efficiency and fuel economy, which is 5-fold that of a typical driver, depending on the drive cycle. Current hybrid systems provide fuel economy improvements of 30% -50%.
The present invention requires the integration of electrochemical, electrostatic and electrokinetic storage technologies. The device and its functions have applications as a distributed energy system.
Other aspects of the invention will become apparent from consideration of the drawings and ensuing description of the preferred embodiments of the invention. Those skilled in the art will recognize that other embodiments of the present invention are possible, and that the details of the invention can be modified in various respects, all without departing from the inventive concept. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.
Detailed Description
Referring to fig. 1, a preferred embodiment of the apparatus is disclosed. The invention comprises an engine 1 connected to a transmission 4. The engine 1 can be coupled by means of a clutch or by means of a fixed gear or a shafting. The first motor/generator 2 is connected to a shaft on the engine 1 or on the transmission 4 side of the engine/transmission interface. The transmission 4 transmits power from the engine 1 and the first motor/generator 2 through the transmission 4 to the drive shaft 15, the differential 9, and then to the wheel shaft 10 and the wheels 11. The second motor/generator 3 is connected to the transmission 4 at a point on the transmission 4 near the output. The transmission system may use no or one, two or three clutches to selectively disengage the engine 1 or the single motor/generators 2, 3.
The transmission system comprises a drive shaft 15 and a differential 9, which may be part of the transmission 4 or separate from the transmission 4, and also an axle 10 or a split shaft.
The motor/generators 2, 3 may be mounted in line with the transmission system or may be connected to the transmission system by gears, belts or chains or hydraulic techniques.
The battery 7 preferably uses lithium chemistry, or may also use NiMH, NiCAD or lead-acid. The fast energy storage device 8 comprises a flywheel, a capacitor or a high power battery. Preferably, the flywheel is driven using a high speed rotor housed in a vacuum chamber and integral electronics. Alternatively, the flywheel may be any type of flywheel that is incorporated into the rotor and built into the motor/generator so that energy can be stored and retrieved electrically. The capacitor may be any type of capacitor including ultracapacitors, and electrolytic capacitors. The fast energy storage device 8 has an energy storage capacity that is much smaller than the capacity of the battery 7.
In the preferred embodiment, the engine 1 is a gasoline-fired small piston engine 1. Alternatively, the engine 1 may be an internal combustion engine 1, and the internal combustion engine 1 may burn gasoline, alcohol, flex fuel, diesel, biodiesel, natural gas, propane, or hydrogen.
A fast energy storage device 8 and a battery 7 are connected to the power converter and controller 6. The power converter and controller 6 directs energy flow between a flywheel or capacitor 8, a battery 7, the first motor/generator 2 and the second motor/generator 3. All elements (2, 3, 7 and 8) storing or using power can provide or absorb power. The power converter and controller 6 comprises a single component or subassembly. These subassemblies may be configured within a single module, or they may be covered as separate modules. The subassemblies may be positioned together or dispersed throughout the vehicle.
The interface between the vehicle and the electrical grid comprises a plug and socket 12, wherein the alternating current power source of the vehicle can be converted into an on-board direct current power source. The ac power source may be single phase or three phase of 110V, 220V, 480V or other commercially supplied ac power. Alternatively, a fixed V2G interface 13 with bidirectional power handling capability may provide V2G services. The fixed V2G interface 13 may communicate with the utility to transmit V2G resources or to allow isolation through the utility. The fixed V2G interface 13 is connected to the vehicle via a dc or ac link and plug/socket 12.
Operation of the present invention includes driving in a number of different operating modes.
In the first drive mode, the engine 1 provides power to the wheels 11, while the first and second motor/generators 2, 3 are free to rotate but not energized.
In the second drive mode of operation, the engine 1 is turned off and all power is provided using either the first motor/generator 2 or the second motor/generator 3 or both. This mode may be referred to as EV mode. In this mode, electrical energy is supplied by the fast energy storage device 8 and the battery 7 in a combination determined by the power converter and controller 6.
In the third drive mode of operation, power is provided by both the engine 1 and the first motor/generator 2, the second motor/generator 3, or both. In this mode, electrical energy is supplied by the fast energy storage device 8 and/or the battery 7 in a combination determined by the power converter and controller 6.
In the fourth drive mode of operation, the vehicle is decelerating to a degree and regeneratively recovering energy. In this mode of operation, braking torque is applied to the transmission 4 by the first motor/generator 2, the second motor/generator 3, or both. In this mode of operation, one or both of the motor/generators acts as a generator and converts the recovered kinetic energy of the vehicle into electrical power. This power is delivered to a fast energy storage device 8 or battery 7. The flow of electrical power to the energy storage device is directed by the power converter and controller 6. In this mode of operation, the engine 1 may or may not rotate.
In a fifth drive mode of operation, the engine 1 drives the first motor/generator 2 such that the first motor/generator 2 generates electrical power to charge the battery 7 or the fast energy storage device 8 or both in a combination determined by the power converter and controller 6. In this mode, the vehicle may be stopped or moving.
Performing V2G services includes a variety of different V2G modes of operation.
In the first V2G mode of operation, the grid supplies energy to the plug/socket 12, and subsequently to the power converter and controller 6, via the fixed V2G interface 13. The controller 6 uses this energy to charge the fast energy storage device 8 or the battery 7 or both.
In the second V2G mode of operation, energy from the fast energy storage device 8 is extracted by the power converter and controller 6 and supplied to the grid 14 via the plug/receptacle 12 and the fixed V2G interface 13.
In the third V2G mode of operation, energy from the battery 7 is extracted by the power converter and controller 6 and supplied to the grid 14 via the plug/receptacle 12 and the fixed V2G interface 13.
In the fourth V2G mode of operation, energy from the engine 1 is converted to electricity by either or both of the motor generators 2 and 3, then extracted by the power converter and controller 6 and supplied to the grid 14 via the plug/socket 12 and the fixed V2G interface 13. Any of the V2G modes of operation may be governed automatically by software resident in the vehicle, or may be governed by an external entity such as a utility, independent system operator, package service provider, or any other end user.
The fast energy storage device 8 tolerates frequent cycling and high power operation, but the battery 7 does not. In all modes of operation, the power converter and controller 6 generally directs the flow of energy such that the number of charging and discharging events experienced by the battery 7 is minimized. Additionally, the fast energy storage device 8 is operated to minimize the magnitude and extent of high power operation of the battery 7. By protecting the battery 7 from excessive cycling and excessive high power operation, several advantages can result. The durability of the combined energy storage system is improved compared to using the battery 7 without the fast energy storage device 8. The battery 7 may operate at a deeper depth of discharge than would be possible without the need to protect the fast energy storage device 8. Thus, a given full electrical stroke range can be obtained with a smaller battery 7 than would be possible without the protection of the rapid energy storage device 8.
Many other modes are possible, wherein the functions of the five defined modes may be used in combination.
Many variations of the invention will occur to those skilled in the art.
Referring to fig. 2, a first variation is to use one or more clutches 5 to selectively disengage the engine 1, the first motor/generator 2 or the second motor/generator 3.
Referring to fig. 3, the second variation is a parallel configuration in which only one motor/generator (first motor/generator 2) is used. The transmission 4 may be an automatic or a manual transmission which does not comprise or comprises one or two clutches 5.
In the first or second variant, the transmission 4 may support a two-wheel drive as shown. Alternatively, the transmission 4 may have full or dual four-wheel drive capability.
With reference to fig. 4, a third variant completely eliminates the transmission 4. In this case, the first motor/generator 2 is directly connected to the engine 1. The first motor/generator 2 functions primarily as a generator, but may also function as a motor that can be used to start the engine 1. The second motor/generator 3 directly or indirectly powers the wheels 11. The second motor/generator 3 is directly connected to the differential 9, the drive shaft or the wheels 11. The second motor/generator 3 may be connected through a fixed gear arrangement or other compact and constrained drive train component or subassembly. All power is electrically transmitted from a point of generation or storage to the drive motor. This configuration is a plug-in hybrid system or a series hybrid system in series.
Referring to fig. 5, a fourth variation uses multiple drive motors instead of a single second motor/generator 3.
Referring to fig. 6, a fifth modification uses the above series hybrid configuration and utilizes a fuel cell to generate electricity. The fuel cell replaces the engine 1 and the first motor/generator 2. In this variant, a fast energy storage device 8 and a battery 7 are connected to the power converter and controller 6. The power converter and controller 6 directs power flow between the fast energy storage device 8, the battery 7 and the second motor/generator 3. All elements (3, 7 and 8) that store or use power can provide or absorb power. In this variant, the fast energy storage device 8 protects the battery 7 from violent or frequent charging and discharging events. Additionally, in this configuration, the fast energy storage device 8 protects the fuel cell 16 by providing direct power for acceleration, where the fuel cell has poor throttle response and may be damaged due to such events.
Fig. 7, 8 and 9 disclose details of the power converter and controller 6. Fig. 7 shows the nomenclature of the switch 17, the switch 17 comprising a diode 29 and a solid state switching device 30. Preferably, the solid state switching device 30 is an Insulated Gate Bipolar Transistor (IGBT), although other switching devices may be used. The switch 29 is commanded to open or close by a signal from the controller to the gate drive 27.
Figures 8 and 9 show the controller 28 issuing commands to each switch 29 in the system. For clarity, only some representative connections are shown. In effect, all switches 29 receive input from controller 28. Additionally, the controller 28 may receive information from each switch 29 including temperature, status (open or closed), and fault conditions (clear, warning, fault).
Each switch 29 is switched to be open or closed in response to a command from the controller 28. Switching is implemented to activate or deactivate components or subsystems for rectification, limiting, or to synthesize an ac waveform. The power rating of the accessory device varies. The respective power ratings of the associated switches 15 will also vary to allow the overall size, weight and cost of the power converter and controller 6 to be minimized.
The power converter and controller 6 has a dc bus with one bus 18 at a boosted potential and a second bus 19 at a common potential. The H-bridge lead comprises two switches 29 connected in series, wherein a pair of switches 29 connects the two busbars 18, 19 of the dc bus, and the point between these switches is connected to one phase lead of the connected ac device.
The dc bus capacitor 20 serves several purposes, either individually or simultaneously. The bus capacitor 20 primarily provides the kinetic energy storage required for the motor drive and buck-boost (buck-boost) functions implemented by the converter legs. A single dc bus capacitor 20 serves all phase legs in the power converter and controller 6.
The power converter and controller 6 provides or absorbs power in ac form from the motor/generators 2, 3, 31, the flywheel fast energy storage device 26 and the charging port 24. The H-bridge leads of the power converter and controller may operate as a rectifier, an active rectifier, a motor drive or an ac inverter to connect these devices.
The H-bridge lead may also be used as a circuit breaker (chopper), or any other power process performed by the switch, such as those used for dc-dc conversion. These configurations are used for the interface of the battery 7 and the fast energy storage capacitor 8.
An inductor is required for the buck-boost function and is part of the motor drive circuit. The motor has a non-negligible inductance, which is sufficient for this purpose. For devices with low intrinsic inductance, such as the battery 7 or the storage capacitor 8, the inductor 21 may be incorporated into the circuit.
For the motors MG 12, MG 23, MGR 31 and the motor/generators in the flywheel 26, portions of the power inverter and controller 6 function as a bi-directional motor drive. Three-phase drive is typical, but other numbers of phases may be used. Fig. 3 and 4 show a three-phase drive configuration. To generate torque, a variety of control strategies may be implemented, including Pulse Width Modulation (PWM), space vector control, and single commutation.
Buck/boost converters perform dc-to-dc voltage conversion by inducing a dynamic response in the inductor using high frequency switching. Capacitor 20 eliminates transients associated with the switching frequency of the converter. Inductor 21 or inherent inductance, capacitor 20 and switch 15 are required to perform either a buck or boost function. Fig. 8 and 9 show the buck/boost circuit of the battery 7. Fig. 8 shows a buck/boost circuit of the flying energy capacitor 8. In these examples, the use of two switches 17 for each buck/boost phase allows the inductor 21 and capacitor 20 to be used for either buck or boost operation without reconfiguration.
Buck/boost converters are used for dc-dc conversion of higher power accessory devices. The ac link 23 and the transformer 22 are used for ac voltage conversion at the charger port 24. The internal ac link 23 is used to allow for transformation to a lower voltage so that the individual inverter subassemblies can provide a lower voltage output (12V, 42V) at the dc power supply port 25.
The charger port 24 is shown as a single phase system, but a three phase system may also be used. When the vehicle is stationary and connected to the utility grid, the charger circuit may deliver energy to the dc buses 18, 19 and thence to any accessory devices. During operation of V2G, energy from the battery 7, the fast energy storage system 8, 26, or the engine 1 via the MG 12 may be delivered to the grid.
The dc output port 25 is energized by a small active rectifier operating at a voltage different from the voltage of the main dc bus 18, 19. The active rectifier uses a switch 17 of the type used throughout the power converter and controller 6 and communicates with a controller 28. The configuration shown in fig. 8 and 9 is capable of providing low power dc at two voltages, preferably 12V and 42V.
All such variations are intended to be within the scope and spirit of the present invention.