Research On Energy Management Of Dc Microgrid Hybrid Energy Storage System Based On Fuzzy Control

In recent years,the problems caused by the energy crisis and environmental pollution are becoming increasingly severe.Due to the rich clean energy and low transmission costs,distributed power generation has received extensive attention.DC microgrid system,one of those microgrids,has a simple structure and does not need to consider frequency and phase.Meanwhile,the system has small loss and high efficiency,thus it is suitable for the connection of DC micropower,energy storage unit and DC load.The energy storage system can well suppress the power fluctuation in the DC microgrid,stabilize the DC bus voltage,and ensure the power balance.However,a single battery energy storage element has the disadvantage of low power density,which is difficult to meet the requirements of microgrid power balance.Therefore,this paper combines a large specific power flywheel energy storage system and a large specific energy lead-acid battery to form a hybrid energy storage system.The complementarity of the two is used to improve the performance of the energy storage system and at the same time extend the service life of the battery.For the hybrid energy storage system,how to make full use of the advantages of different energy storage components and reasonably distribute the output power of each component;and how to control the energy management of the microgrid to make the system run more stable is the focus and difficulty of the current research.This article focuses on suppressing distributed power generation fluctuations,stabilizing the DC bus voltage,and optimizing the performance of energy storage components.On the one hand,a fuzzy control strategy based on the optimization of the energy storage state of the flywheel is proposed and a hybrid energy storage power distribution is designed accordingly.On the other hand,a hierarchical energy management strategy is proposed based on the DC bus voltage and energy storage element status.The specific arrangements are:1.The principle and mathematical model of the photovoltaic power generation system are briefly described.In order to improve the energy utilization rate,the maximum power point tracking control is adopted,and the output characteristics aresimulated and analyzed.Secondly,the working principle,the model of the energy storage battery as well as the flywheel energy storage that constitute the hybrid energy storage system are elaborated,and the charge and discharge characteristics of the lead-acid battery and the control strategy of the flywheel motor are analyzed.The permanent magnet synchronous motor is selected as the flywheel drive motor,using the space vector PWM to control the flywheel motor for charge and discharge simulation,and the simulation is carried out.The results prove the effectiveness.2.The control target and working mode of the hybrid energy storage system are analyzed in detail.In this paper,according to the relationship between the energy storage state of the flywheel energy storage process and the micro-grid DC bus voltage,a flywheel energy storage state optimization module based on the change of bus voltage is designed.The distributor can make better use of the advantages of the battery and the flywheel energy storage.At the same time,in order to better track the ideal energy storage state of the flywheel energy storage in real time,the secondary output of the battery output is distributed,and the battery is charged to the flywheel under specific conditions.Finally,a simulation model is built for further experiments.The results prove that this control strategy can improve the smoothing performance of the hybrid energy storage system,and meanwhile enhance the working efficiency of the battery and extend its service life.3.The topological structure of the photovoltaic DC microgrid in this paper is designed,and the role of each part of the system is introduced.The requirements for energy management will be different when the microgrid is in different working states.This paper has designed a DC bus voltage and energy storage The hierarchical energy management strategy of the component status,and the control strategy of each component in the system are designed.Finally,a simulation system is built to perform simulation experiments under different working conditions.The simulation results show that the control strategy in this paper can effectively stabilize the DC bus voltage.