Research On Control Strategy Of Photovoltaic And DC Microgri

The installed capacity of new energy power generation,which is dominated by clean energy,has increased significantly in recent years.In order to alleviate the impact of grid connection of distributed power,microgrid has become a research hotspot in the field of new energy.Dc microgrid has the technical advantages of low construction cost,low control difficulty and high energy utilization efficiency.However,due to the inherent randomness and volatility of new energy generation,it seriously affects the safe and stable operation of power grid.In this paper,the photovoltaic energy storage DC microgrid containing photovoltaic cells,energy storage units and grid-connected inverters is taken as the research object,with the goal of improving the stability of DC bus voltage,the control strategy of networking units and coordinated control of the system are studied.Firstly,a mathematical model of photovoltaic cells was established,and Incremental Conductance(INC)method was used to control the photovoltaic cells.The conductance increment method and least variance adaptive algorithm were combined to optimize the maximum power control.The stability of photovoltaic output power and the fast response of tracking speed are ensured.The method was verified by MATLAB/Simulink simulation..Secondly,the equivalent circuit Model of the energy storage battery in the DC microgrid was established,the Dual Active Bridge(DAB)converter was used to Control the battery charge and discharge,and the stable voltage of the DC bus was maintained through Model Predictive Control(MPC).Due to the existing problems of current stress and backflow power in the single-phase shift control mode of DAB converter,dual phase shift control is adopted,and the back-flow power and current stress are further optimized by combining the Carotid-Kuhn-Tucker condition and Lagrange multiplier method.Third,build the mathematical model of Voltage Source Inverter(Voltage Source Inverter,VSI),based on space vector modulation technology and software phase-locked loop technology for power converter analysis,build based on the power grid voltage oriented vector control converter model,for the current loop and voltage loop design,Verify the feasibility of the control strategy of voltage source grid-connected inverter.Finally,the working areas of each component in the DC microgrid are classified,and the switching conditions between working modes are given.The coordinated control strategy based on DC bus voltage stability is adopted to ensure that the photovoltaic DC microgrid system can operate normally in different working environments and switching states.In this paper,the system simulation model of DC microgrid is established to verify the effectiveness of the coordinated control strategy based on bus voltage stability.