A nonlinear approach to control instantaneous power for single-phase grid-connected photovoltaic systems

This paper presents a novel nonlinear control algorithm to connect a single-phase distributed generation (DG) system to the utility grid using a power electronic converter. The control system receives the commands of active and reactive powers and generates an appropriate reference signal for the converter to ensure desired injection of the power to the grid. The proposed technique is based on controlling the instantaneous power and avoids double-frequency ripples which are observed in the conventional controllers. The mathematics of the control algorithm and guidelines to adjust the parameter values are presented. The method is then successfully applied to a photovoltaic (PV) system and the robustness of the proposed method is verified through different operating conditions and uncertainties. A controller based on internal model principle (IMP) is implemented and optimally designed using the LQR concept in this paper. The performance evaluation results are presented to validate the controller concept.