Comparative Experimental Study of Predictive and Resonant Controllers of Grid-Tied Inverter under Unbalanced Grid Conditions

Abstract

Simultaneous and flexible reduction of active and reactive power (P and Q) oscillations during grid imbalance in distributed power generation system is quite complex and poses a major research challenge. Various control techniques such as proportional-integral, proportional-resonant (PR) and hysteresis control have already proved their effectiveness under unbalanced grid (UG) conditions. Out of the above control techniques, PR controller is considered to be the most popular controller due to its simultaneous tracking ability for both positive and negative sequence of grid current. The model predictive controller is relatively recent, and its performance has been evaluated for UG conditions. But, no comparative experimental study with the popular PR controller has been reported for flexible P and Q transfer to the UG. In this paper, a comparative practical study is presented for verifying the static and dynamic performance of the two controllers in a distributed generation system during grid unbalance. The paper also examines the impact of sampling time on the static and dynamic performance of the controllers. Discrete-time designs of the two controllers are included, and stability is ensured. A one-kilowatt experimental laboratory prototype has been built to validate the results.