Study On The Power Conditioning System Of Superconducting Magnetic Energy Storage System

Superconducting Magnetic Energy Storage(SMES)is a technology for storing electromagnetic energy that is converted from electrical energy. The energy is stored in superconducting coil and can be returned back to the grid or the load when needed. This technology was first proposed by Ferrier in1969as a new type of energy storage. It has been paid more and more attention to because of its merits such as improving the stability of power system and the power quality, its high efficiency of energy store and rapid response, and etc.The converter is a bridge which connects the superconducting coil in the SMES to the grid.Generally, the converter with its controlled circuit called Power Conditioning System (PCS) is the unit to convert the energy between the superconducting coil and the grid.So,to improve the function of the PCS is one of the most important technologies in system of SMES.At present, the strategy of PWM is used in system of adjusting the power. It can rapidly, independently control the four-quadrant active and reactive power, with characteristics of fast response and restraining of harmonic waves and so on.According to the circuit topology, there are two basic kinds of the power adjusting system,the one is Current Source Converter (CSC)and the other is Voltage Source Converter (VSC).This paper separately describes the basic principles and the topology of the CSC and the VSC device. When studying the VSC, the establishing of the mathematical model of it and its chopper are mentioned at first.And then follows design of the dual closed-loop with feed forward decoupling control of PWM rectifier control system and its simulation in MATLAB/SIMULINK.The mathematical model of SCS is established and the discrete state feedback decoupling control strategy is used to analysis the model.The outer controlled loop is the superconducting magnet current and the inner one is the active and reactive current. Improved double-loop control method is used to design the CSC system,and also is simulated in MATLAB/SIMULINK.Finally, simulation results demonstrate the feasibility of the PWM rectifier closed-loop in the power adjusting system and its small total harmonic distortion (THD) when injecting to the grid.