Research On Maximum Power Point Tracking Of Photovoltaic Generation And Coordinated Control Strategy Of Energy Storage

With the rapid development of the world economy for the past few years,the demand for traditional fossil energy is increasing.The continuous shortage of energy supply has brought many problems such as energy cost and environmental pollution.To solve the limitation and singleness of the existing traditional energy sources,renewable energy sources such as solar energy and wind energy have gradually been widely used.Photovoltaic energy has become one of the most popular research fields of new energy due to its inexhaustible and inexhaustible characteristics.How to efficiently utilize solar energy is the focus of photovoltaic power generation.Technical improvement of photovoltaic Maximum Power Point Tracking(MPPT)and the coordinated control of energy storage charge and discharge have gradually become way to improve the efficiency of photovoltaic power generation.In this paper,the grid-connected photovoltaic energy storage system is studied.Based on the output characteristics of photovoltaic cells,the advantages and disadvantages of the existing MPPT technology are analyzed.For uniform illumination conditions and local shading conditions,high-efficiency improved incremental conductance method(INC)and improved mayfly optimization algorithm(MA)are proposed.Research the control methods of energy storage systems and solar power grid-connected inverters under the change of external sunlight exposure,and conduct related simulation research based on MATLAB/Simulink.The main research contents are as follows:(1)According to the principle of photovoltaic cell power generation,the mathematical analysis model used in photovoltaic cell engineering projects has been scientifically researched.The effects of temperature and light intensity on the P-U and I-U output characteristics of photovoltaic cells are simulated and analyzed.Simulate the single-peak and multi-peak characteristics of the P-U output characteristic curve of the photovoltaic array when the sun shines evenly or partially blocks the light,to bring theoretical foundation to the analysis of new technologies for MPPT.(2)Aiming at the oscillation and misjudgment problems of the traditional INC algorithm,based on the combination of variable step size and power prediction,an improved INC algorithm is proposed.The algorithm step size is changed according to the location of the working point of the MPPT control and the variation range of the conductivity.When the solar light intensity changes drastically,the predicted power point and the next measured power point are approximately located on the same I-U characteristic curve based on the prediction model,improving the accuracy of the algorithm.By simulating and comparing traditional algorithms,the superiority of the improved INC algorithm in tracking time and accuracy is verified.(3)The power curve of the solar power generation array under the partial light blocking standard shows the multi-peak characteristics,which makes the traditional MPPT technology unable to guarantee the maximum power output of photovoltaic cells.Therefore,this paper proposes to apply the improved MA to maximum power tracking control.By introducing the gravity factor and limiting the search space of male mayflies,the optimization accuracy of the algorithm is enhanced,the oscillation of the algorithm near the maximum power point(MPP)is reduced,and the occurrence of premature maturity is avoided.Three test functions were chosen to validate the algorithm.Under the conditions of rapid change of irradiance and complex shadow occlusion,an MPPT model based on Boost circuit is established to verify the effectiveness of the algorithm.The simulation results show that the improved MA can validly converge to the MPP under complex shading conditions with high efficiency and accuracy.(4)Based on the topology and working principle of the bidirectional half-bridge DC-DC converter,the PI control strategy of the energy storage system is studied.Charge and discharge the energy storage system to control the adverse effects of random fluctuations of renewable energy on the system and reduce the impact of photovoltaic fluctuations on the power grid.The simulation results show that when the output of solar power generation is continuously changing,the response time of the energy storage system is fast,and the DC bus phase voltage can be stable around the rated value,meeting the energy flow requirements of the system.(5)Based on the mathematical model of the three-phase photovoltaic grid-connected inverter,the P-Q decoupling control of the grid-side voltage oriented according to the d-axis is realized by coordinate transformation.Based on the grid-connected inverter grid voltageoriented dual-loop control strategy,Based on the grid-connected inverter grid voltageoriented dual-loop control strategy,a photovoltaic-storage grid-connected system model is established,and the photovoltaic-storage coordinated control simulation analysis is carried out.The simulation results show that the strategy used can realize the unit power factor operation of the grid-connected inverter,the energy storage system can dynamically respond to the grid voltage change and power exchange after the photovoltaic grid is connected,and the grid-connected control effect is good.