Current overload protection features of hybrid inverter drives

Hybrid drive circuit topologies are presented which contribute to the development of voltage source pulse width modulation (PWM) inverter drives with inherent self-protection against fault currents. The central feature of the hybrid drive is to automatically decouple the DC link capacitance from the drive power converters during fault conditions. The author shows how one of the three forms of the hybrid drive minimizes the current rating of the DC link inductors. Where required, the buck-type hybrid drive can be used to minimize the size of the inductors together with the DC link capacitor. The PWM rectifier hybrid drive permits unity input power factor operation and control of the DC link inductor current during output overhead current conditions. Extensive simulation results are used to demonstrate the performance of the drive during steady state operation and during output short circuit fault conditions