Common-Mode Voltage Elimination of Three-Phase Multilevel Voltage Source Inverter by Means of Quarter-Wave-Symmetric Space Vector PWM Approach

Abstract

AbstractThe new common-mode-voltage-eliminating (CMVE) space vector PWM algorithm for three-phase multilevel voltage source inverter (MLVSI) of any arbitrary topology with any arbitrary number of generated equal voltage levels is proposed. This technique employs all the approaches and attributes of the recently offered quarter-wave-symmetric space vector PWM algorithm but, unlike the latter, operates with quantities in the coordinate frame of the relative values of the MLVSI phase load voltages, referred to the three-phase load common star point (phase-to-neutral load voltages). The applied MLVSI voltages space vectors are the selected space vectors which produce the zero value of the three-phase common-mode voltage, understood as the voltage across the neutral point of the load and the inverter system ground point. Similar to the baseline algorithm, intended for shaping the high-quality MLVSI output voltages and currents, the new CMVE algorithm generates enough high-quality output power, thanks to keeping the quarter-wave symmetry of the star (phase-to-neutral) and delta (phase-to-phase) voltages. The dependences of the THD and low-order weighted THDs values on the phase voltage amplitude modulation index are obtained by PSIM-simulation for the three low, multiple of 6, values of frequency modulation index.KeywordsCommon-mode voltageMultilevel voltage source inverterSpace vector PWMWeighted THDPSIM-simulation