An enhanced stationary reference frame control for grid-connected distributed power generation systems

This paper presents an enhanced stationary reference frame control scheme that enables the grid-connected distributed power generation systems (DPGS) to provide high quality electric power under unbalanced input voltage conditions. In the proposed scheme, the positive and negative sequence components of currents are regulated based on stationary frame current references. Since the current references are expressed in α-β frame, proportional-resonant (PR) controllers are employed to achieve zero steady state error. Detailed mathematical derivation is presented. A fast and accurate active notch filter based (ANF-based) symmetrical component extractor is employed to extract the symmetrical components of the 3-phase voltages and currents. An extra module is introduced and added in order to enhance the system to compensate the grid harmonic currents. Simulations results verify the validity of the proposed control approach and its performance.