Study On Technologies And Characteristics Of Large-scale Photovoltaic Power Plant Connecting To The Grid

Energy crisis and environmental pollution on an international scale are providing an opportunity for the development of new energy industry. And solar power as one of the new energy is gained widespread attention for its advantage of renewable, widely distributed and zero pollution. As one environmentally friendly method in solar power utilization, the rapidly developing of grid-connected Photovoltaic(PV) power plant will ease the existing electric power system pressure, improve the reliability of power generation effectively. In this paper, the technique and characteristics of large-scale PV power plant connecting to the grid are in-depth analyzed and researched.The main content contains:1) The structure and characteristics of PV power plant is described; According to the equivalent circuit of the photovoltaic cells, a mathematical model of PV array used in the simulation is proposed and its properties are analyzed.2) The structure and function of grid-connected inverter is introduced; the key technologies of grid-connected PV power plant are elaborated in detail, including the inverter control method, maximum power point tracking method and islanding detection technology, particularly, the details of double closed-loop controlling, which is a current decoupled controller based on input-output variable feedback linearization is designed as current inner loop, PI controllers are used in the outside loop in inverter control strategy, the incremental conductance method in maximum power point tracking method, and the active frequency drift(AFD) method in the islanding detection technology. All of these have provided a theoretical basis for the key technologies in simulation of grid-connected PV power plant.3) Using the PSCAD/EMTDC simulation platform to study key technologies of PV power plant connect to the grid which have previous mentioned. and related simulation waveforms are analyzed to lay a foundation to next step simulation study of the dynamic response of network which including actual grid-connected PV power plant.4) The simulation models of a distribution network with large-scale PV power plant were built in PSACD/EMTDC. Simulation analysis of the dynamic responses of PV power plant in the condition of common faults happened and external factors (temperature, irradiance) sudden changed were illustrated. Considering the voltage transient behavior of the point of interconnection (POC), siting of PV power plant was studied on. The simulation results have some reference value to further research of impacts to distribution systems made by PV plants, and help to find corresponding schemes and strategies.