A New Bi-directional ZVS Inverter by Estimated Phase Shifting for Non-linear Loads

A new bi-directional ZVS-PWM full-bridge inverter with fixed high frequency switching is described. Proposed inverter contains a high frequency isolation transformer, zero voltage switching full-bridge converter, zero voltage switching cycloconverter, and output low pass filter. Switching routine is applied in a way that ZVS is obtained in the full load variations even in very low loads and low phase shifting of switching where high bi-directional power flow is obtained. Output voltage estimation is done to obtain next phase switching mode in each step by using a circuit model with a non-linear resistance, which is considered for prediction of duty cycle losses, switches, transformer and other losses. Recursive least square estimation routine is applied to obtain online estimating parameters during load variation, which cause well tracing of reference waveform and low ripple in output voltage even with input voltage and output current variations. A circuit model for 24 VDC to 220 VAC inverter has been simulated. The results are presented and they verify the analysis