Power Conditioner Design and Control for LCL-based Grid Connected Photovoltaic System via LCL Filter Based on Inverter and Grid Side Currents Feedback

Solar energy, as an unlimited, clean and cost-effective source of energy, can be converted into electrical energy using photovoltaic arrays. In this paper, design, control and stability analysis of inverter-based power conditioner, which is connected to the low voltage grid via LCL filter, are presented to manage power injection of the photovoltaic system. Since the PV arrays generated voltage is lower than the grid voltage, DC-DC converter is utilized to increase the PV output voltage. The LCL filter is employed to improve injected current quality and to reduce interface inverter output voltage distortions. This filter can cause to occur resonance and system instability. Current double feedback control method, which is used inverter side and grid side currents as feedback current, is proposed to damp the resonance and to improve harmonic eliminations. The systematic design procedure of the proposed control strategy parameters is presented considering resonance damping, stability margin and grid-connected features to ensure the system stability in a non-ideal and weak grid. The proposed power conditioner system is simulated in MATLAB/Simulink to verify model performance and proposed control method. The simulation results show good performance of the proposed system in managing PV power flow into the grid, high quality of the injected current, and system stability against the grid impedance change disturbances.