Compensation for Multilevel Voltage Waveform Generated by Dual Inverter System

A space vector modulation (SVM) technique of a dual inverter system feeding an open-end-winding PM motor and improvement technique of generated multi-level voltage waveforms with the system are proposed in the paper. In the proposed system, one of the inverters has a battery power source and the other has a capacitor across the DC-bus. The SVM must be achieved both to generate multilevel voltage waveforms to the motor and to control the capacitor voltage constantly at the same time by using redundant switching states of the system. In order to control the capacitor voltage, it is necessary to select the optimal switching state with SVM considering the instantaneous motor power factor. In addition, it is also necessary to eliminate error voltage vectors contained in outputted multilevel voltage waveform. The error voltage vectors are generated during the dead time when the switching devices in the same phase of both inverters are synchronously turned on or turned off. Therefore, the special dead time technique is need for the SVM of the dual inverter system. The paper demonstrates proposed SVM techniques through computer simulation and experimental tests.