Application of electrically peaking hybrid (ELPH) propulsion system to a full-size passenger car with simulated design verification
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An electrically peaking hybrid electric (ELPH) propulsion system is being developed that has a parallel configuration. A small engine is used to supply power approximately equal to the average load power. The operation of the engine is managed by a vehicle controller and an engine controller such that the engine always operates with nearly full load - the optimal fuel economy operation. An induction ac motor is used to supply the peaking power required by the peaking load (electrically peaking). The motor can also absorb the excess power of the engine while the load power is less than the peak. This power, along with the regenerative braking power, can be used to charge the batteries on board to maintain the battery state-of-charge (SOC) at a reasonable level. With the electrically peaking principle, two control strategies for the drive train have been developed. One is called MAXIMUM BATTERY SOC control strategy, by which the engine and electric motor are controlled so that the battery SOC is maintained at its top level as much as possible. This control strategy may be used in urban driving in which accelerating and decelerating driving is common and high-battery SOC is absolutely important for normal driving. The other control strategy is called ENGINE TURN-ON AND TURN-OFF control by which the engine is controlled to operate in a turn-on and turn-off manner. This control strategy may be used in highway driving. Based on the ELPH principle and the drive train control strategies, a drive train for a full-size five-seat passenger car (1700 kg of gross weight) has been designed and verified using the V-ELPH computer simulation package developed at Texas A&M University. The results show that the ELPH car can easily satisfy the performance requirement, and the fuel economy can be improved greatly over conventional vehicles.
