| Photovoltaic power generation is one of the most important forms of new energy power generation.Microgrid theory and technology provide an ideal control mode for the application of photovoltaic power generation.In grid connected microgrid,gridconnected/off-grid control of converter is a key work,which is directly related to the normal operation of grid connected microgrid.Based on the theory and technology of microgrid,this thesis studies the control method and grid-connected/off-grid switching control strategy of the integrated photovoltaic energy storage converter in the power generation system composed of photovoltaic and energy storage equipment.On this basis,the integrated photovoltaic energy storage converter is designed and the relevant control strategies are verified by experiments.Based on the study of the working characteristics of photovoltaic array,disturbance observation method is selected to realize the maximum output power tracking control of photovoltaic array.Combined with the working mode of the battery,in order to meet the requirements of fast charging and discharging and prolong the service life of the battery,a constant voltage and constant current twostage charging and discharging control strategy is adopted in the control mode of Bidirectional DC-DC converter.In order to improve the grid-connected/off-grid control performance of the main power grid and photovoltaics and energy storage integrated converter and achieve the effect of smooth switching,an improved droop control grid-connected/off-grid switching strategy is studied and adopted.The correction algorithm of phase successive approximation is added in the control strategy,so as to improve the smoothness of switching and the control performance.On the basis of theoretical research,MATLAB software is used for simulation analysis.The correctness and effectiveness of the battery charging and discharging control strategy,the smooth switching control strategy of grid-connected mode and off-grid mode of photovoltaics and energy storage integrated converter are verified.On the basis of the above theoretical research and simulation analysis,based on the corresponding technical requirements of the project,photovoltaics and energy storage integrated converter is designed with TMS320F28335 chip as the core controller.Based on the analysis of the system composition,the hardware circuit of the system is designed.The software workflow and control algorithm implementation are analyzed.On the basis of software and hardware design,20 k W photovoltaics and energy storage integrated converter is built.The battery charging and discharging control strategy and the switching control strategy between grid-connected mode and off-grid mode are verified on the experimental prototype and the output power quality is analyzed.The experimental results show that the control strategy can effectively control the grid-connected/off-grid switching smoothly and the operation of the experimental prototype is reliable and stable. |
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