Follow-up control method in a resonant DC link inverter

This paper describes a new follow-up control method in which a simple digital proportional-integral-differential (PID) filter is applied to a resonant DC link inverter and used as an estimator in the controller. Primary follow-up control can determine the polarity of each resonance voltage at every resonant cycle, and the simple PID filter can allow a high resonant frequency. This results in fast control of the output voltage and allows the inverter to use a smaller AC filter. The output voltage and the distortion factor characteristics are discussed with integral and differential gain as parameters and the stability of the inverter is analyzed by using the state space averaging method. Good agreement between the theoretical and experimental results is obtained.<>