Modeling and bandwidth design of resonant controller for medium frequency inverter

Output voltage of inverters with excellent output characteristic descends little as load increases. Resonant controller is an effective method for improving output characteristic of inverter. This paper analysis stability condition of inverter under light load based on the small-signal modeling of three phase four legs inverter. Considering automatic control theory, this paper proposes that self-oscillation of inverter is caused by phase shift of resonant controller. And design basis of resonant controller is developed. Simulation and experimental results prove theoretical analysis right.