| With the rapid development of the global economy,the problems of energy crisis and environmental pollution have become more serious.The new energy power generation technology represented by photovoltaic has been widely used.Due to the influence of light intensity and temperature,there are some intermittent and volatility problems in photovoltaic power generation,which will cause fluctuations in the bus voltage of the photovoltaic and energy storage DC microgrid.If the situation is serious,the whole microgrid system will be more likely to collapse.Based on this,this paper deeply analyzes the operating state of the photovoltaic and energy storage DC microgrid in island mode,and studies the droop control strategy of energy storage system to stabilize the DC bus voltage fluctuation and make full use of photovoltaic side energy.The control of the DC bus voltage was studied.Specifically,the research content of this paper is as follows:(1)Analyzed the overall structure of the photovoltaic and energy storage DC microgrid,including photovoltaic power generation module,battery energy storage module,load module and grid side converter module.(2)The working principle and mathematical model of photovoltaic cell were studied.The output characteristics were analyzed under different working conditions.At the same time,the maximum power point tracking(MPPT)technology was studied for the purpose of maximizing the use of solar energy.In addition,the mathematical model of lead-acid battery in battery energy storage module is studied,and its charge and discharge characteristics are analyzed.(3)The control of the bus voltage under the island mode of photovoltaic and energy storage DC microgrid is studied.A distributed power coordination control strategy based on DC Bus Signaling(DBS)is proposed.Under the control strategy,the photovoltaic power generation module operates in the MPPT mode,but when the bus voltage is higher than the set upper limit value,in order to ensure the safe operation of each load in the system,the photovoltaic power generation module is changed from the MPPT mode to the drooping constant voltage mode..(4)Aiming at the problem of bus voltage drop caused by the traditional droop control strategy of battery energy storage module,an improved droop control strategy based on bus voltage compensation is proposed.(5)The small-signal model of the photovoltaic and energy storage DC microgridis established.The parallel impedance method is used to analyze the small signal stability of the photovoltaic and energy storage DC microgrid at steady state equilibrium.The theoretical analysis of the influence of parameters on the stability of the system provides theoretical guidance for the stability design of the photovoltaic and energy storage DC microgrid.Finally,the photovoltaic and energy storage DC microgrid simulation model is built in MATLAB/Simulink.The voltage control strategy of the proposed bus voltage is verified by changing the power of load and input of the photovoltaic side.On this basis,DSP28335 is designed as the main Control the photovoltaic and energy storage DC microgrid experimental platform of the chip,and write the corresponding system control program.The simulation and experimental results are basically consistent,indicating the feasibility and effectiveness of the proposed control strategy. |
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