An improved resonant DC link invertor for induction motor drives

The authors present a bidirectional initial current control concept which solves the voltage overshoot problem in the resonant link and establishes reliable zero-voltage crossing for smooth inverter operation. The resonant circuit is analyzed to establish the criteria for initial current selection. A circuit is proposed to establish the bidirectional initial current. The improved inverter permits successful operation at 50 kHz resonant frequency and can potentially operate up to 100 kHz. The control of the inverter, which involves prediction of the inverter input current, is formulated. A complete inverter-fed induction motor speed control system is simulated using PC-SIMNON. The simulation study at both 50 kHz and 25 kHz resonant frequency indicates the superiority of the inverter at higher resonant frequency.<>