Control Strategy Of Three-phase Grid-connected Photovoltaic Generation System

With the rapid development of national economy and pollution-free advantages, solar energy has been widely concerned. Photovoltaic (PV) grid power generation system is a main form of solar energy utilization, and grid-connected inverter, as the core component of the system, not only determines the stable and reliable operation of PV grid power generation system, but also affects the life of the whole system. Therefore, grid-connected inverter is a hotspot of current research. In this paper, based on the basic structure of PV grid-connected power generation system, introduces the structure, control strategy and simulation of the DC/DC and DC/AC (grid-connected inverter).Under the condition of ideal grid voltage, in abc??? and dq frame three-phase PV grid-connected inverter's mathematical model was deduced. Through comparing their advantages and disadvantages of control strategies, decided using dual loop control strategy, with the DC bus voltage outer loop and current inner loop in dq frame. The voltage outer loop adopts proportional-integral (PI) control strategy, which is used to keep DC bus voltage stable and provides the reference of the current inner loop; The current inner loop is to ensure the output quality of grid current. Based on the traditional PI control strategy, the paper introduces resonance (R) control strategy, which offers an infinite gain at a specified frequency, thereby suppresses the grid current distortion arising from the grid voltage distortion, and analyzes the system dynamic and steady-state performance under the control strategy. Finally, in order to validate that PI-R control strategy can output high quality grid current under the ideal and unbalanced grid voltage, the simulation model is built in Matlab/Simulink.Simulation results show that PI-R control strategy proposed in this paper of PV grid power generation system can output current with the same frequency and phase of grid voltage, and when the grid imbalance occurs, the control system can also output performance of grid current, and ensures the stable operation of PV grid power generation system, and improve the life of the system.