Application of quasi proportional resonant scheme in grid-connected inverter

The traditional proportional resonant (PR) regulator is sensitive to the frequency fluctuation of the power grid, and the gain is very limited for the non-resonant frequency. Therefore, in this paper, a quasi-PR controller easy to be implemented is proposed. The frequency feedback is introduced in order to increase bandwidth, and the frequency fluctuation of the power grid is controlled by the phase locked loop. The solar grid-connected inverter based on the PR controller had some advantages, such as making use of the controller infinite gain in the resonance frequency and eliminating the steady-state error. The simulation model of the grid-connected inverter is constructed to verify the theoretical analysis. The PR control algorithm can selectively make certain frequency enhancement, so as to achieve the effect of harmonic filtering.