Research On Control Strategy Based On Photovoltaic Grid Connected Power Generation System

With the large consumption of fossil energy and the tightening of the world energy situation,all countries are developing clean energy.Solar energy is becoming an important direction in the development of new energy because of its large reserves and no pollution.Under this background,this paper takes the single-phase photovoltaic grid connected power generation system as the research object,and deeply studies the output characteristics of the photovoltaic array,the maximum power point tracking technology,the control strategy of the grid inverter system and the islanding detection technology.First,this paper analyzes the working principle and characteristics of photovoltaic cells,establishes the mathematical model,and analyzes the influence of the external environment on the output characteristics of the photovoltaic cells by the simulation results,and verifies the correctness of the model.Secondly,aiming at the problems of the steady performance of the common maximum power point tracking algorithm and the poor tracking effect and the slow start process,the MPPT control method based on the extrapolation iteration method is put forward,and theoscillation and misjudgement of the disturbance observation method are analyzed,and the hybrid logic dynamic MPPT control method with the power prediction module is proposed,and the simulation results verify the calculation.The method has good control effect.Thirdly,the multi peak output peak of PV array under local shadow is studied,and the relationship between the series of photovoltaic arrays and the voltage of the parallel components under the local shadow is revealed.On this basis,the multi peak MPPT tracking algorithm based on the equal power curve scanning method is innovated.The algorithm has the advantages of the position of the extreme point of the premeasured power curve and the fast locking of the global maximum power point.Finally,the algorithm is two.The peak and three peak simulation experiments show that the algorithm can effectively track the global maximum power point.Compared with the existing scanning method,the algorithm has obvious advantages in tracking effect.Finally,the structure of the main circuit of the photovoltaic grid connected inverter system is analyzed,and the different control schemes are analyzed.The traditional PID control,the PID control based on the phase locked loop,the compound control based on the voltage feed-forward compensation and the phase locked loop,the digital PID control,the constant frequency hysteresis comparison and the no difference control are studied,and the reasons for the commonly used detection of the island are made.And the detection technology is introduced,and an improved voltage feedforward control and active frequency offset(AFD)islanding detection method are proposed.The same frequency phase of the grid current and the grid voltage is realized,and the expected detection function is basically realized.