Pulse Width Modulation Control Based on Pulse Encode and Pulse Rotation for Cascade Neutral Point Clamped Inverter

Cascade neutral point clamped(NPC) inverter is more suitable for high voltage,high power applications,but the power and voltage balances are crucial in practical uses.This paper proposed an effective sinusoidal pulse width modulation(SPWM) control scheme for a cascade NPC inverter in which a pulse encode and pulse rotation are fulfilled for all modulation indices.The module voltage and power,and series-capacitor voltage of each module are perfectly balanced,and each module has low switching frequency providing high pulse frequency of phase voltage.The proposed scheme is applied to the 1 MVA 6 000 V 17-level cascade NPC inverter,and the simulations and experiments are carried out.The simulated results and experimental results verify the proposed scheme.