Research On Integrated Control Strategy Of Photovoltaic Grid-Connected Generation And Reactive Power Compensation

Solar energy is a representative one among the various renewable energy sources.The photovoltaic system(PV system)which converts solar energy into electrical energy photovoltaic power generation mode has been widely promoted in various countries.Its share has increased in the power generation because of its characteristics of no pollution,renewable and low operation cost.But the PV system also has some defects,such as power low generation efficiency,vulnerable to environmental impact and rapid voltage fluctuations.The control strategies of PV generation system from generation to the grid are focused on in this paper.In this paper,the mathematical model of photovoltaic cells is studied.And its complicated mathematical model is simplified to obtain the engineering model of photovoltaic cells.Based on the engineering model,the output characteristics of the PV array are studied under normal operating conditions and partial shading conditions by establishing the simulation model.The results show that some local maximum power points appeared in the output characteristic curves of PV array under partial shading conditions.This would create difficulties in maximum power point tracking.Then,the maximum power point tracking(MPPT)of PV system is studied.Based on the perturbation and observe method and the improved particle swarm optimization,a maximum power point tracking method based on perturbation and observe method and improved particle swarm optimization is proposed.By comparing with the performance of perturbation and observe method and particle swarm optimization,it can be found that the proposed MPPT method has better effects on the tracking time and tracking accuracy.Therefore,it can be considered that this method has a practical significance for improving the power generation efficiency of PV system.Finally,the control strategy of the inverter in the PV system is studied.The normal operation control mode,the reverse power control mode,the cloudy control mode and the night control mode are respectively set for different weather conditions that the PV system may encounter.And then through the switching method of these four control modes,a photovoltaic grid-connected power generation and reactive power compensation integrated control strategy is put forward.The simulation results show that the integrated control strategy can decrease the deviation rate of the voltage from its standard value to about 2%.Therefore,it can be considered that the control strategy can effectively suppress the voltage fluctuations of the PV system.Based on the above results,it can be concluded that the research in this paper not only helps to improve the power generation efficiency of PV system,but also can effectively mitigate the voltage fluctuations in PV system.It is of great significance for better promotion of photovoltaic power generation technology and maintenance of power grid Operational safety and stability.