Peak-to-peak torque ripple reduction and switching frequency variation control in hysteresis controlled VSI-Fed IM drives

This paper proposes an improved control strategy for switching frequency variation in hysteresis current controlled Voltage Source Inverter (VSI) fed induction motor drives, that provides the additional advantage of reduced peak-to-peak torque ripple, Te(p-p). The advantages of simple hysteresis controller, viz. simple implementation and fast dynamic response are added with the advantages of constant switching frequency and reduction in Te(p-p) 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. The voltage vector to be switched in the next sampling interval is identified by the boundary computed in the present sampling interval. The vector selection logic is designed to extract the features of VC-SVPWM based VSI fed IM drive whereby reduced Te(p-p) at higher modulation indices are obtained. A comparative simulation study of the Current Error Space Vector based controller resembling the characteristics of conventional VC-SVPWM based drive with the proposed controller based drive has been conducted using SIMULINK toolbox of MATLAB for steady state as well as transient performance analysis. Significant reduction in Te(p-p) has been obtained.