Kazuhiro Imaie

Control strategies for multiple parallel current-source converters of SMES system

Multiple structured current-source converters are applied for a superconducting magnetic energy storage (SMES) system. Suitable control method and control block diagram are proposed by taking much use of the advantage of this multiple structure. A multi-modular pulse width modulation (PWM) control strategy of current-source converters for the purpose of higher efficiency and less harmonic distortion is developed with an idea for practical application. A design of a multi-reduced instruction set computer (RISC) controller is presented to put the proposed control blocks into practice. The results of the digital simulation by Electromagnetic Transients Program (EMTP) and the experimental results of the test module are provided to validate the proposed control method of SMES power conditioning.

A triple redundant controller which adopts the time-sharing fault recovery method and its application to a power converter controller

A novel fault recovery method, in which memory copy from a normal system to a fault detected system is executed in time-sharing fashion, has been implemented in a triple redundant controller. This method reduces data copy bandwidth required for recovery of the fault detected system, and allows non-stop fault recovery with only a little hardware overhead, even when the controller contains multiple processors and operates at a very short operating period. The developed controller contains triplicated processing units, each of which consists of seven 60 MIPS processor boards connected by a 30 MHz 4 byte bus. One processor board contains a bus arbiter, and each of the remaining six processor boards contains three sets of 100 Mbps two-way optical links, which can be utilized for inter-system memory copy as well as for connecting to 10 units. This controller has been applied to a power converter controller, and a 104 microsecond operating period was achieved.

Direct‐connected multiple current‐source converters for SMES system

The superconducting magnetic energy storage (SMES) system would be a valuable system for power line stabilization. It would increase stability by supporting peak energy and compensating generation shortage. With the development of a large-capacity GTO thyristor suitable for 20-MW-level power conversion systems, it is possible to control the four-quadrant real power (P) and the reactive power (Q) condition by self-commutated power converters with high performance. This paper describes a new direct-connected multiple current-source converter, and also explains suitable control strategies for the pilot plant of an SMES system. The feasibility of the control strategies is demonstrated by EMTP simulation results.