Study On Relevant Control Strategies Of Photovoltaic Power Generation System In Microgrid

Different from the influence of distributed photovoltaic power generation on grid stability under high permeability background,photovoltaic power generation systems in microgrid require higher controllability in terms of high-efficiency energy supply capability,internal power balance capability,and guaranteed power quality.However,the volatility and randomness of the photovoltaic source may result in a decrease in energy supply efficiency,also may result in poor power quality when the load is bad.Therefore,based on the hierarchical control strategy of two-stage inverter circuit,this thesis studies the maximum power point tracking control and harmonic suppression.In order to solve the contradiction between tracking accuracy and speed during PV maximum power point tracking control,a maximum power point tracking method based on disturbance observation and Newton interpolation is proposed.The oscillation of the perturbation observation method near the maximum power point is divided into four modes.According to the distribution characteristics of the oscillation points in each mode,it is concluded that the oscillation point can satisfy the Newton interpolation node in the three-point oscillation mode.Then,the initial fitting interval and the logical criteria of oscillation point are determined.The Newton interpolation is used to establish the fitting function of the photovoltaic characteristic curve,and the maximum power point voltage is more accurately found.While ensuring the tracking speed,the tracking accuracy is effectively improved,and the optimization of the maximum power point tracking control is realized.In order to solve the problem of current distortion caused by nonlinear load in microgrid photovoltaic power generation system,an inverter grid-connected control method with harmonic suppression is proposed.The method combines the traditional grid-connected constant power control and harmonic suppression strategy.On the basis of not changing the topology of the inverter circuit,the instantaneous reactive power theory is used to detect the harmonics so that the output current of the inverter is superimposed on the basis of the constant power control.The nonlinear load side harmonics are suppressed,and the power quality of the incoming network is improved.In the Simulink simulation environment,the overall model of the photovoltaic power generation system in the microgrid is completed.The reliability of the improved maximum power point tracking control method is verified by changing the illumination intensity;the accuracy of the grid-connected inverter constant power control method is verified without the nonlinear load;and in the case of a system with a three-phase bridge rectifier circuit,the effectiveness of its harmonic suppression function is verified.