The Grid Connection Control Strategy Of Compressed Air Energy Storage With Directly Driven Generator

With the development of society,the problem of environmental pollution and shortage of fossil fuels has become more and more serious,and the electric energy storage is one of the key technologies to adjust energy structure,protect the environment and improve energy security.Therefore,the research of large-scale energy storage technology has important theoretical and practical value.The compressed air energy storage(CAES)has been widely concerned because of its large capacity,long working time,good economic performance and long service life.However,there is a gearbox between the expander and the generator in traditional compressed air energy storage system,it will lead to large mechanical loss and high cost,while using the direct drive generator can solve this problem.Besides,the performance of the system can be improved through the coordinated control of the expander and the generator speed and the efficiency can be improved.Firstly,this thesis summarizes three kinds of grid connection modes that can be applied to compressed air energy storage,including the connection of compressed air energy storage with constant speed synchronous generator,doubly fed asynchronous generator and direct drive synchronous generator;analyzes the potential advantages and challenges of three grid connection modes,and proposes a system of compressed air energy storage with directly driven permanent magnet synchronous generator using electronic power transformer,which has the advantages of small mechanical loss,flexible control and high power quality.Then,based on the established mathematical model,the basic control strategy of the permanent magnet direct drive compressed air energy storage power generation system is designed,and the simulation design and experiment of the whole system are created in Matlab / Simulink.The simulation results show that the output voltage of the system is stable,and the active and reactive power can be output or absorbed in different operation modes according to the needs of the power grid with high controllability and high quality of output power,it has significant advantages over the traditional grid connection mode.Finally,the optimal control strategy of the permanent magnet direct drive compressed air energy storage power generation system is proposed.A maximum power tracking control strategy and algorithm for compressed air energy storage is designed,and the simulation results show that the output power of the generator is significantly improved when the maximum power tracking algorithm is used under different inlet pressures.In addition,a tracking control strategy and algorithm for the maximum efficiency of compressed air energy storage system are proposed.The simulation results show that when the power grid demand changes,the output power of compressed air energy storage system can track the change of demand power in real time,and the expander can work at the highest efficiency point,which can effectively improve the efficiency of the whole energy storage system.