Research On Optimal Configuration And Operation Of Energy Storage In AC And DC Hybrid Microgrid

With the increasing demand for new energy,microgrid has been widely concerned and applied as an effective way of utilization of renewable energy.In the face of the increase of distributed power and diversity of load types,it is necessary to access distributed power and the load to different types of microgrid in order to ensure the optimal economy of the system,which induce the AC/DC hybrid microgrid.However,due to the fluctuation of output power of renewable energy and load,it is necessary to configure a certain storage energy in the microgrid to achieve power and energy balance.The current research on energy storage allocation and operaiton of AC/DC hybrid microgrid is less,and seldom discusses the differences of allocation effect between centralized and distributed energy storage.This paper first analyses the influence of energy storage location,and proposes an optimized energy storage configuration method of AC/DC hybrid microgrid considering effect of energy storage location preferentially.The central point of net load is defined as the initial value of location optimization.And the minimum average voltage fluctuation rate with energy storage position as the variable is taken as the upper-level goal,and the minimum annual comprehensive cost of the energy storage system with the capacity as the variable is taken as the lower-level goal,thus a bi-level optimization model is constructed.The model is solved by genetic algorithm.The example analysis shows that the proposed optimization strategy can greatly reduce the power flow calculation and shorten the optimization time,and the bi-level optimization can simplify the computational complexity.Secondly,based on the analysis of cost,benefit and reliability of energy storage system,the optimal allocation effect of centralized and distributed energy storage in AC/DC hybrid microgrid is compared.The cost of energy storage system and the possible benefits is analyzed in detail,and the energy storage capacity optimization model is established with the goal of the investment benefit-cost ratio.By calculating the island running time of the microgrid,the reliability parameters of the system are obtained combining with Monte Carlo simulation.By comparing several kinds of scenarios,centralized storage system is suitable for the microgrid with large scale,small DC system and low reliability,while distributed energy storage is suitable for the microgrid with small scale,large DC system and high reliability.Finally,aiming at the economic problem of real-time scheduling of hybrid energy storage system,a real-time scheduling and economic operation method of hybrid energy storage system based on dynamic programming-genetic algorithm is proposed.Considering the reliability of power supply and the service life of hybrid energy storage system at the same time,a bi-objective optimization model of economic operation of hybrid energy storage is established,with constraints on capacity,power,discharge depth and charging and discharging time of energy storage system.Combining the spectrum analysis,dynamic programming and genetic algorithm,the power distribution of the hybrid energy storage is optimized,and the economic operation of the system is realized.The numerical example shows that the proposed method of real-time scheduling and economic operation of the hybrid energy storage system is feasible,and is more economical than the only dynamic programming.