Single phase and three phase P+Resonant based grid connected inverters with reactive power and harmonic compensation capabilities

Designing optimized and more efficient controllers for grid connected inverters is a challenge. Conventionally such controllers were established in dq or rotational frame; however, recently stationary or alpha-beta frame has found special interest due to some unique features that it can offer for grid connected inverters. On dq frame variables turn into constants after passing through transform matrixes, so PI controllers that have infinite gain on DC quantities are widely used. But PI controllers are unable to achieve zero steady state error in stationary frame and P+resonant controllers which have infinite gain on their resonant frequency have been implemented instead. This paper will explain step by step P+resonant based inverter controllers design for grid connected single and three phase inverters with reactive power compensation and then a novel approach for grid harmonics compensation will be implemented.