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Energy storage (ES) has become increasingly important in modern power system, whereas no single type of ES element can satisfy all diverse demands simultaneously. This study proposes a hybrid energy storage system (HESS) based on superconducting magnetic energy storage (SMES) and battery because of their complementary characteristics for the grid integration of wind power generations (WPG). This study investigates the mathematical model and the topology of the proposed HESS, which is equipped with a grid-side DC/AC converter, a battery buck/boost converter and a SMES DC chopper. The advanced control strategies comprised of device level and system level are designed. The control strategy for the converters which can be considered as device level is briefly discussed. The significant contribution of this study is proposing a novel system-level control strategy for reasonable and effective power allocation between SMES and battery. According to the control objectives, a fuzzy logic controller optimised with genetic algorithm is adopted. The detailed controller designs are described, meanwhile system stability and HESS operation performance are evaluated. MATLAB simulations are presented to demonstrate the effectiveness of the proposed strategies.

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This paper proposes a Superconducting Magnetic Energy Storage (SMES) based excitation system for doubly-fed induction generator (DFIG) used in wind power generation. The excitation system is composed of the rotor-side converter, the grid-side converter, the dc chopper and the superconducting magnet. The superconducting magnet is connected with the dc side of the two converters, which can handle the active power transfer with the rotor of DFIG and the power grid independently. Utilizing the characteristic of high efficient energy storage and quick response of superconducting magnet, the system can be utilized to level the wind power fluctuation, alleviate the influence on power quality, and improve fault ride-through capability for the grid-connected wind farms. According to the system control objective, the system can contribute to the stability and reliability of the wind power grid-connected system. Using MATLAB SIMULINK, the model of the SMES based excitation system for DFIG is established, and the simulation tests are performed to evaluate the system performance.Index Terms-Doubly-fed induction generator (DFIG), superconducting magnet, superconducting magnet energy storage (SMES), wind power generation.