Electrical two-speed propulsion by motor winding switching and itscontrol strategies for electric vehicles

摘要

Theoretical analyses and computer simulation studies lead thenauthors to propose: (1) a new electrical two-speed propulsion system fornelectric vehicles (EVs) by switching induction motor windings; and (2)nan improved fuzzy logic control-continuous defuzzification method fornthe control of this system. The two-speed propulsion is achieved bynconnecting the motor stator windings in series for starting an EV andnthen switching the windings to parallel connection for normal speednoperation. The method produces a high starting torque, yet maintains theninverter within its rated power range. As compared with star-deltanstarting of induction motors, the proposed series-parallel method offersnhigher starting torque and acceleration. The control strategies for thisnsystem are investigated. A comparison of fuzzy logic control with anconventional proportional-integral (PI) shows that a fuzzy logicncontroller (FLC) can be applied to EV propulsion systems. Simulationnstudies also demonstrate that an improved FLC method using a continuousndefuzzification technique provides smoother torque and leads to lowernharmonic components in motor currents, thus further enhancing this EVnpropulsion system