Autonomous variable speed power generating system with five level cascaded converter

The paper presents a novel autonomous power generating system with a three-phase five-level cascaded inverter (5LCI) topology fed from a diesel engine with multiple-winding permanent magnet synchronous generator set (DE/PMSG) for UPS application. The power electronics system consists of six isolated windings which supply six full-bridge diode rectifiers with boost converters stabilizing the DC link voltages for a particular cell of the 5LCI. The five-level current mode control algorithm provides the high quality PWM waves which mitigate the high harmonic content and satisfy a robust output voltage regulation even under the unbalanced load conditions. The interfaced battery energy storage (BES), which constitutes an integral part of the entire ldquogen-setrdquo system, it supplies the DC link capacitor voltages to particular cells of the 5LCI in a standby emergency mode, when the DE/PMSG are off-line. The topology under discussion can be applied to medium or high power UPS systems.