Optimal state control for CSI superconducting magnetic energy storage system

This paper discusses the design and analysis of the multivariable optimal state current source inverter control (feedback and feed-forward) for a superconducting magnetic energy storage system (SMES) for use in a wind farm. In optimal control, the control strategy is sought that gives the best control performance. High stability and robustness against parameter changes are two important advantages of optimal control. By using the method of translating three phase bilogic PWM signals to three phase trilogic PWM signal, EMTP-RV simulations show that trilogic PWM signals produced by this method can optimally handle stabilizing feedback signals. The AC side inverter has been modeled within the separated d-q-frame. This proposed method enables the independent control of the active and reactive components of the supply current vector, and thereby the ability to adjust the grid real power and reactive power through control of the SMES. Comparisons with a voltage source inverter SMES show that the current source inverter exhibits faster recovery of the wind farm voltage following a disturbance in the wind farm transmission line than voltage source inverter SMES.