Research On Sensorless Phase Voltage Compensation Strategy Of Acim For Electric Vehicle

Under the circumstance of energy and environment crisis, electric vehicle isconsidered as a valid solution to reform the energy structure of the transportationindustry. Electric drive system is a key part of EV and AC induction motor (ACIM) hasbeen commonly used in electric drive system of EV. To avoid the negative outcomes ofmounting speed sensors, much research effort has been focused on the sensorlesscontrol technology of ACIM for EV. To guarantee the efficiency, phase voltage errorcaused by inverter output distortion is also an urgent problem to solve. This paperconcentrates on the study of the two aforementioned subjects and is expected to provideuseful references for future design of high end EV drive system.Typical speed estimation methods and cutting edge solutions for phase voltagecompensation of ACIM are introduced. To explain the theory of field-oriented control(FOC), the model of ACIM and the T equivalent circuit are established. With the help ofequivalent circuit, the mechanism of torque generation and the process of current vectordecoupling is elaborated.This paper implements the Extended Kalman Filter (EKF) to study the sensorlessFOC of ACIM. The state-space model of ACIM suitable for flux and speed estimation isestablished and discretized. The iteration processes and applying instructions of EKFobserver are closely extended. Sensorless FOC simulation system of ACIM based onmentioned observer is built. The configuration of noise matrices are obtained throughsome trial and runs. In order to validate the effectiveness of speed estimation, severalrepresentative experiments are designed. From the analysis of waveforms of criticalvariables, system with EKF observer is proven ideal speed adjustment performance andstrong disturbance immunity.To analyze the negative effects aroused by VSI output distortion, the elementsrelated are listed and the expression of phase voltage error is deducted from its causes.With the expression of voltage error, a new compensation strategy is developedconcerning the two key points of current polarity and compensation time. The validityof the strategy is proven primarily in simulations. On the basis of sensorless controlsystem, phase voltage compensation mechanism is integrated. An experimental platformis established. Through experiments, the performance of compensation timemeasurement and current polarity judgment in the strategy is confirmed. Experimentsare designed from both transient and steady-state aspects. The strategy is validated inexperiments and the results prove the system improvement in waveform quality andcontrol performance.