Superconducting magnetic energy storage for voltage stabilizer in electric power systems

Superconducting magnetic energy storage (SMES) which consists of a 6.7 H superconducting coil and a 50 ampere 36 volt three-phase power converter has been developed. The bidirectional converter uses a single bridge IGBT. The independent control of active and reactive power is achieved by controlling the phase and modulation index using the PWM method. The SMES system was connected to a simple power system model consisting of: a three-phase isolator power transformer connected to the power utility; three 28 mH inductors as a transmission line model; and a 1/2 hp induction motor as a disturbance source. The PWM pattern, synchronized with the power system, was generated by a hardware circuit to have a fast response. A hardware circuit to calculate RMS voltage, and the active and reactive power of the system has also been developed. They were interfaced to a personal computer, in which two proportional integral (PI) control loops were calculated to keep the superconducting current and the voltage of power system model at their target values. By running the induction motor, a voltage drop was created; using SMES system, the undervoltage was quickly compensated. In this paper, the experimental performances of the SMES system are presented