DC Offset Error Compensation For a Hysteresis Current Controlled Induction Motor Drive For Electric Vehicles

A variety of factors, including thermal drift, age, and nonlinearity, can generate DC offset errors (DCOE) in electrical sensors and associated circuits. Regardless of a well-designed hysteresis current controller, the DCOE is unpredictable, resulting in undesirable torque ripples that degrade drive performance. An increase in ripples impacts an electric vehicle's efficiency and driving comfort. This study first experimentally establishes the value of the DCOE generated in real-time using hardware on an induction motor. Then the PI-based observer and integral compensator, observes and compensates the identified offset error. This also decreases torque ripples at the motor output while having no effect on the dynamic response of the system. Because the induction motor equations for a stationary reference frame incorporate rotor current terms, rotor current compensation is included. The overall compensation can be achieved without the necessity of any additional hardware. Using MATLAB/SIMULNIK, the torque ripple and speed ripple values in three scenarios: a) no compensation, b) with PI-based compensation, and c) with PI-based and rotor current compensation are compared. Without any compensation, total harmonic distortion is 1 % which is reduced to 0.08% with both PI-based and rotor current corrections, indicating the need to compensate offsets in electric vehicle applications.