Improved switching frequency variation control in hysteresis controlled VSI-fed induction motor drives for reduced line current ripple

This paper proposes an improved control strategy for switching frequency variation in hysteresis current controlled Voltage Source Inverter (VSI) fed induction motor (IM) drives. The advantages of simple hysteresis controller like simple implementation and fast dynamic response along with nearly constant switching frequency and reduction in current ripple are obtained in the proposed controller. Elimination of look up tables is possible since boundary computation is performed online with estimated stator voltages calculated using current errors along the orthogonal axes thus making implementation easier. This paper proposes to reduce the complexity of algorithms that already exists by utilizing only the sampled magnitudes of reference phase voltages. Vector selection logic is designed to extract the features of Voltage Controlled-Space Vector PWM based VSI fed IM drive whereby reduced current ripple is obtained for the entire linear modulation range. Extensive simulation study of the proposed controller based drive has been conducted using SIMULINK toolbox of MATLAB for steady state as well as transient performance analysis. Significant current ripple reduction has been obtained. The simulation results have been validated experimentally on a 3phase, 2.2kW, 415V Induction Motor.