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Single - Stage Single - Phase Grid - Connected Photovoltaic System with Current Ripple Mitigation Based on Nonlinear Control

Abstract:

Due to the high-scale penetration of single-phase photovoltaic (PV) systems in distributed generation, a single-stage single-phase grid-connected PV system, with a nonlinear control strategy is presented in this paper. Using the general structure for synchronous dq0 frame, the controller is developed to obtain maximum power from the PV array regardless of the atmospheric conditions without the requirement of a DC-DC converter and to control the active and reactive power supplied to the grid. The nonlinear controller is combined with adaptive control to estimate the unknown disturbances that physically could appear in the circuit. Moreover, since the double-frequency ripple on the DC bus is the main disadvantage of single-phase grid-connected inverters, a method to mitigate the current ripple is added in the model. A Lyapunov analysis is developed to show the stability and boundedness of signals in the closed-loop system. Simulation results validate the performance and robustness of the controller.