Generalized Scalar Approach for the Generation of Reduced Common Mode Voltage PWM Algorithms for Indirect Vector Controlled Induction Motor Drive
This paper presents a simple generalized scalar approach based reduced common mode voltage pulsewidth modulation (RCMV-PWM) techniques for indirect vector controlled induction motor drive. The classical space vector PWM (SVPWM) algorithm gives superior waveform quality. But, the complexity is more due to several calculations and also it gives large common mode voltage (CMV) variations due to the usage of zero states. Hence, to reduce the complexity and CMV, a simple scalar approach is presented for the generation of various RCMV-PWM techniques such active zero state PWM (AZSPWM) and near state PWM (NSPWM) techniques. In the proposed scalar approach, the modulating signals for the RCMV-PWM techniques are derived by adding a suitable zero sequence signal to the phase voltages. Then, based on the region (sector), suitable triangular wave (positive or negative) is selected for the comparison with modulating signal. The intersecting points will give the pulse pattern for the proposed RCMV-PWM techniques. The RCMV-PWM techniques did not use the zero states, which results in the reduction of CMV variations. With the proposed RCMV-PWM techniques the CMV will be reduced from Vdc 2 to Vdc 6 when compared with the SVPWM technique.
The proposed RCMV -PWM techniques have been verified by conducting simulation tests and results are presented and compared.
Keywords - AZSPWM, common mode voltage, NSPWM, SVPWM, vector control.