Power Quality Improvement Based on Third-Order Sliding Mode Direct Power Control of Microgrid-Connected Photovoltaic System with Battery Storage and Nonlinear Load

In this work, robust control of a microgrid system composed of a three-phase multifunctional double stage with energy storage for power quality enhancement purposes is presented. A comparative study is conducted between two versions of nonlinear control: super-twisting sliding mode (STSMC) and third-order sliding mode (TOSMC). The DC side is composed of a photovoltaic system with battery storage. Both are controlled by the proposed strategies (STSMC and TOSMC) to track the maximum power point regardless of normal and abnormal conditions from solar panels and to guarantee optimal management of grid-connected photovoltaic (PV) system battery storage. The AC side is composed of a two-level voltage source inverter associated with a parallel active power filter connected to the grid and supplies a nonlinear load. The shunt active power filter is controlled by direct power control with space vector pulse-width modulation based on the proposed strategies (STSMC and TOSMC). The proposed microgrid system control will overcome degradation caused by the integration of renewable energy sources in the grid. The main expected actions are the elimination of harmonic currents created by nonlinear loads, the compensation of the reactive power, and the PV power transmission into the electrical grid. Simulation results show that the TOSMC provides the best solution in terms of power quality enhancement, tracking performance, and robustness against varying solar irradiance and nonlinear load conditions.