A new method of frequency tracking and output power control for full bridge series load resonant inverter

Tracking the resonant frequency and adjusting output power are the key in full-bridge series load-resonant-inverter. In this paper, a new method of frequency tracking and output power control based on the mean-value of DC bus current polarity is proposed. The relationships between the DC bus current, load parameters, phase-shifted angle and the operation frequency are analyzed in detail under six modes of inverter. The expression of the mean-value of DC bus current polarity on load parameters, phase-shifted angle, operation frequency and formula of output power are given also. Because the maximum mean-value of DC bus current polarity corresponded to resonant frequency when the phase-shifted angle of the inverter is equal to zero, the inverter resonant frequency can be obtained by setting the phase-shift angle to zero periodically. The inverter output power varies with phase-shifted angle at the point of resonant frequency, so the inverter phase-shifted angle could be regulated using PI controller by the error between the reference value and the output power mean-value. The simulation and experimental results reveal that proposed method can well achieves tracking the resonant frequency and output power control of the full-bridge series load-resonant-inverter.