Research On Control Strategy Of Hybrid Energy Storage For Microgrid With Tracking Dispatch Schedule

With the continuous development of renewable energy generation technology and the support of the national new energy policy,microgrid technology,which consists of distributed power,energy storage and load units,has been developed rapidly.With the increasing penetration of renewable energy in the grid,it brings new challenges to the stability of the grid,and the trend of microgrid receiving grid dispatch will be the development of high penetration grid of renewable energy.In this context,this paper focuses on the problem of microgrid tracking and scheduling plan,and actively carries out research work on microgrid scheduling plan planning,power allocation of multiple hybrid energy storage system and tracking and scheduling plan strategy,the main research contents are as follows:1.In order to maximize the consumption of renewable energy in microgrids and reduce the fluctuation of their grid-connected power with the grid,this paper proposes a microgrid day-ahead scheduling planning method with the objective of reducing the exchange of power with the grid.Firstly,the long-time scale prediction values of renewable energy power and load power are obtained,and the energy management objective function of the microgrid is designed to minimize the power exchange with the grid by combining the load state of the energy storage system.Secondly,the microgrid dispatching model is designed by combining the objective function and the constraint equations.Finally,the dispatching model is solved by a particle swarm optimization algorithm to obtain the optimal solution of the day-ahead dispatching plan.The experimental results show that the planned day-ahead scheduling plan can effectively reduce the amount of power exchanged between the microgrid and the grid,provided that the balance of power supply and load demand of the microgrid is ensured.2.In order to reduce the cost of hybrid energy storage systems and improve the service life of energy storage devices,a multivariate hybrid energy storage system and its power distribution strategy are proposed.According to the power fluctuation characteristics of microgrid,the power fluctuation is decomposed into random component,pulsating component and continuous component,and the supercapacitor,lithium iron phosphate battery and all-vanadium liquid flow battery are used to smooth these components respectively in combination with the characteristics of the energy storage device,and then constitute the multivariate hybrid energy storage system.A low-pass filter and a high-pass filter are used to design a three-stage power distribution strategy for the multiple hybrid energy storage system,and the two frequency dividing points of the three-stage power distribution are obtained by means of wavelet transform.The simulation results show that,compared with the hybrid energy storage system based on two-stage power allocation,the three-stage power allocation multiple hybrid energy storage system can effectively reduce the charging and discharging burden of supercapacitors and lithium batteries,prolong the service life of energy storage equipment and improve the economy of the hybrid energy storage system.3.The actual output power tracking and scheduling plan for microgrids is challenging due to the time-varying and uncertain nature of energy changes in microgrids as a result of the non-linear nature of source-load power fluctuations in time.To address this problem,based on the idea of using energy storage to regulate the tracking power error,a multivariate hybrid energy storage cell is used to construct a microgrid system.Combining the predicted value of source-load power in the microgrid with the SOC of the energy storage system to propose a hybrid energy storage control strategy that tracks the scheduling plan,in order to take into account the non-linear relationship between the SOC of the energy storage battery and the power fluctuations of the microgrid,a fuzzy controller is added to the case of the power allocation of the energy storage device,and a differential allocation algorithm between the predicted and actual grid-connected energy of the microgrid is designed to make real-time corrections to the active power reference value of the energy storage system,enabling the hybrid energy storage system to maintain a better SOC.Simulation results show that the microgrid can accurately track the grid-connected dispatch plan on a long time scale,and the energy storage device will not produce overcharge or over-discharge,which improves the safety and stability performance of the hybrid energy storage system operation;After adding the fuzzy control optimization,the lithium battery SOC has been kept fluctuating between 35% and 70% under the same working conditions,and the fluctuation range has been reduced by 12.6% compared with the pre-optimization period,indicating that the energy storage system has better SOC and prolonged the service life of the energy storage system.This paper takes the microgrid as the research object,takes into account the microgrid scheduling plan,the structure of the energy storage system and the energy optimization of the energy storage system,and realizes a way to control the microgrid by the grid scheduling from a long-time scale,which improves the stability and reliability of the microgrid and is of positive significance to promote the application of new energy.