Output filter simplification based on random PWM for medium frequency power supply

Based on the analysis of electric inverter control model,the single-pole double-frequency PWM and the random PWM are used to modulate the inverter waveform,which improves the equivalent switching frequency of inverter and reduces the amplitude of discrete harmonics at switching frequency.The influence of random signals on the power spectral density characteristic of switching function is studied and a practical design of randomized PWM is proposed.The cut-off frequency of improved inverter output filter can be set higher to ensure the bandwidth of control system and improve the waveform quality of inverter output voltage.Simulation and experiment show that,the discrete harmonics with higher amplitude at switching frequency extend as the continuous harmonics with lower amplitude within a certain bandwidth,which verifies its effectiveness.