PWM and capacitor voltage balance control strategies for hybrid 9-level inverter

PWM and capacitor voltage balance control strategies for hybrid 9-level inverter are investigated in this paper. A direct PWM method based on decomposition of reference voltage for hybrid 9-level inverter is proposed. The 3^rd, 9^th and 15^th order zero-sequence voltages are injected into the reference signal of hybrid 9-level inverter to control the capacitor voltage balance of H-bridge inverter. Dead-time effect of hybrid 9-level inverter is analyzed in detail and a modified compensation method available to hybrid 9-level inverter is proposed. Experimental results demonstrate the validity of the proposed control strategies. The abnormal pulses induced by the dead-time effect are completely compensated through the proposed modified dead-time compensation method. Hybrid 9-level inverter outputs better waveforms for the total harmonic distortion (THD) of output voltage is small than 3%.