Research On Capacity Optimal Design And Coordination Control Of DC Microgrid System

With the rapid development of the economy,the demand for energy is increasing,the depletion of fossil energy and environmental pollution have caused widespread concern around the world,and promoted the in-depth research and application of new energy power generation technology at home and abroad.Based on the requirements of independent microgrid,this paper studies the capacity optimal design of DC microgrid and the coordinated control of photovoltaic power generation unit and energy storage system.The main contents are as follows:Firstly,the topology of the DC microgrid is studied to meet the load and power balance of the system,and the basic structure of the DC microgrid is determined,including the photovoltaic cell-based power generation unit and the energy storage unit responsible for smoothing system power fluctuation.The output power model of each component is established by studying the working principle of each part,and the power allocation strategy of the microgrid system is formulated according to their respective advantages.Secondly,in order to improve the stability and flexibility of the DC microgrid,a DC microgrid structure based on a hybrid energy storage system is adopted,and a diesel generator is added.For the DC microgrid system consisting of photovoltaic cells,diesel generators,batteries and supercapacitors.The capacity optimization configuration model is established.The effects of load power shortage rate,new energy permeability and the excess electricity ratio on the economics and stability of the system are analyzed.The genetic algorithm is used to solve the multi-objective optimization model,and the new energy penetration rate is42.23%,and it can meet the microgrid system of 285795 kW load power for the whole year.The results show the capacity allocation result can meet the requirements of the system for economy and reliability,and provide a flexible and reliable capacity configuration method to users.Finally,the problem of coordinated control of DC microgrid is studied.The MPPT control is realized by using the disturbance observation method for photovoltaic cells,which improves the utilization of solar energy.A voltage outer loop PID controller and current inner loop PID controller are used for the battery to ensure the stability of the DC bus voltage.The current single-loop PID controller is used for the supercapacitor,which stabilizes the high-frequency components of the power fluctuations in the energy storage system andoptimizes the performance of the energy storage system.The model is built on Matlab/Simulink simulation platform to verify the effectiveness of the coordinated control strategy of DC microgrid system,further construction of the experimental platform verified the feasibility of the control strategy.