Quasi-Z Source Superconducting Magnetic Energy Storage System Based on Passive Control Theory

In superconductivity magnetic energy storage (SMES) system the power exchange between power grid and superconducting magnet is realized by converter, however, traditional energy storage converter exists such defects as limited output voltage range and the switches located at the upper and lower bridge arms are easily interfered so that these switches are damaged due to direct through connection. To implement the secure and stable operation of SMES system, an SMES system based on quasi-Z source converter (QZSC) was proposed, and in allusion to the nonlinear and strong coupling characteristics of QZSC-SMES system, the passive control strategy based on the Euler-Lagrange (EL) model was adopted to the converter at AC side and the chopper at DC side in QZSC-SMES system. The effectiveness of the proposed QZSC-SMES topology and its control strategy is verified by simulation results, that is, the system can quickly and accurately track active and reactive power commands; comparing with traditional PI control, the proposed system possesses lower grid-connected harmonic content, better dynamic performance and stronger robustness.