An observer-based control of a three phase inverter

An observer-based cascaded control of the inverter of a three phase UPS system is presented. Instead of measuring the currents of the filtering capacitors, these currents are now estimated by an observer. The assumptions for developing an appropriate mathematical model of the inverter are explained. On the basis of the mathematical model, the design principles of the observer, the capacitor current controller and the voltage controller are described. Finally, experimental results are presented which are obtained from a realisation of the presented control concept in an UPS system with an apparent power of 60 kVA