Performance analysis of random pulse-width modulated Z-source inverter with reduced common mode switching

This paper proposes and comparatively evaluates a number of different pulse-width modulation (PWM) schemes that can be used for Z-source inverter control to achieve buck-boost energy conversion with random and reduced common mode (RCM) switching. The presented schemes are developed systematically by firstly identifying an appropriate RCM PWM scheme. Unlike a traditional voltage-source inverter, Z-source inverter does not require dead-time protection, and therefore various RCM alternatives can be used with each giving rise to different capacitive ripple current, THD and WTHD. Analytical formulas for calculating these performance indexes are derived and presented in the paper. The performance of the modulation schemes is next refined by integrating an appropriate random PWM scheme developed from different random modulation concepts. These concepts include random switching frequency (RSF) PWM, pulse frequency modulation (PFM) and a newly proposed random shoot-through time (RST) PWM that can only be used with a Z-source inverter either as a standalone module or with RSF PWM to form a dual random modulation scheme. The developed PWM schemes are lastly tested in Matlab simulation and experimentally using a laboratory prototype with the captured results presented sequentially in the paper.