A Virtual-Flux Decoupling Hysteresis Current Controller for Mains Connected Inverter Systems

This paper proposes a new simple method of three- phase, sensorless mains voltage, power control with near constant switching frequency based on a decoupling hysteresis current controller (DHC), and the virtual-flux concept. The virtual flux method is used to extract the mains voltage from the switching state, dc voltage, and line currents. From the desired real and reactive powers the three-phase currents are generated using a DHC. The DHC avoids the switching interaction between the phases, and when a variable hysteresis band is employed a near constant switching frequency is achieved. The method is also extended for high power inverter applications that include an inductance- capacitance-inductance output filter, where some undesirable characteristic, such as filter resonance, have to be compensated. Theoretical analysis is presented and the performance of the proposed method is experimentally verified.