Smooth shifting on hybrid pulse width modulation strategies for high power variable frequency AC drives

High power AC drives application has lower switching frequency due to the high switching loss of power devices, and many optimized pulse width modulation (PWM)strategies are proposed for the low carrier-frequency ration applications. In some variable frequency application, different PWM strategies are applied in different frequency range for better performance on harmonic current elimination or other optimal characteristics over the full speed range. The smooth shifting of hybrid PWM is a key issue for steady processing of the system. This paper works on the fundamental and harmonic component's transient state of the different PWM strategies during modulation strategies shifting, and propose a compensation algorithm using reference wave phase angle delay compensation and shifting timing selection to reduce the switching impact, and gives the simulation and experiment result under two level voltage source inverter.