Symmetrical Load of Supply Capacitors with Reduced Switch Count Space Vector PWM for 3L-NPC Inverter

This paper presents modifications to the space vector modulation for 3L-NPC inverter which are oriented towards symmetric load of the supply voltage dividing capacitors. Modification are made upon the space vector modulation, that uses prediction algorithm and additional transistors' states corresponding to output voltages, to reduce the number of individual state changes in power transistors (switch count). Reduction of switch count can be used to lessen the commutation losses. Two modification of previous method of modulation, that equalize the load of supply capacitors, are shown. Both methods were implemented, measured and compared with previous method, which was fully oriented towards switch count reduction. Presented modifications do not weaken switch count reduction ratio.