A novel superconducting magnetic energy storage system design based on a three-level T-type converter and its energy-shaping control strategy

Superconducting magnetic energy storage (SMES) has been widely used to stabilize the power fluctuations of wind farms to achieve efficient grid connections. However, conventional converters can rarely satisfy the high power quality requirements of a power grid. Compared to other convertors, a three-level T-type converter (3LT2C) can improve the output performance and operating efficiency of a system and reduce the voltage stress and conduction loss of power switches. Therefore, the 3LT2C has broad application prospects for electric power storage. A precise control strategy is also necessary for the practical application of an SMES system, which has significant nonlinear dynamic characteristics. Energy-shaping (ES) control is a nonlinear control method that is based on the theoretical design of interconnection and damping assignment (IDA), which considers both the nonlinear nature of a system and the energy perspective. This study proposes an ES control strategy for an SMES system based on a 3LT2C. Mathematical models and port-controlled Hamiltonian (PCH) models of the SMES are established. The ES control strategy of the SMES system is designed based on a feedback interconnection structure through analysis of the novel SMES topology. Finally, the effectiveness of the control strategy and the proposed topology are verified through simulations.