Research On New Combined Control Strategy Of Photovoltaic Generation And Active Power Filter

Under the background of the world energy crisis and environmental problems, solar energy has become one of the best clean energy sources in the world with its unique advantages, therefore, the photovoltaic technology has broad prospects and great value. However, in recent years, with the extensive application of various new power electronic devices, a large number of nonlinear and impact loads have sprung up, and the influence of harmonics on the grid is becoming more and more important. And the application of passive filtering technology has been unable to meet the requirements for power quality, APF has become a research hotspot at home and abroad with its good ability of harmonic governance.In this paper, for the problems of that grid-connected PV is vulnerable to light, weather and other factors, APF is expensive and difficult to popularize, topology, control method and many other aspects of them have been detailed studied, the theoretical basis for the unified control of the two party is obtained, so that the device can realize the function of grid-connected PV and APF, save equipment investment, improve equipment utilization, improve the quality of grid-connected power. The two key technologies of the unified control, namely the harmonic detection technology and the main circuit control technology, are deeply studied, the symmetrical component method is used to improve qpii- harmonic method based on instantaneous reactive power theory, the detection error of phase locked loop(PLL),and the precision of positive sequence voltage. The model of three-phase photovoltaic grid inverter and APF are established respectively and the similarity of the two mathematical models is studied to obtain the control strategy of the main circuit that is double closed loop control strategy of voltage and current. Voltage loop adopts proportional integral(PI) control based on constant power, ensure the stability of the DC voltage, current tracking control adopts quasi proportional resonance(QPR) control strategy based on voltage space vector(SVPWM), decreases the steady-state error of system, achieve static error tracking of current and designs parameters to quasi PR controller.Finally, this paper uses MATLAB/Simulink to build the simulation model of the unified control system. The simulation results show that the unified control system has the function of PV grid and APF, At the same time, superiority of the new harmonic detection method and correctness of the control strategy of the main circuit are verified. Besides, this article also conducted some experiments related to photovoltaic DC-DC at smart micro-grid lab.