Simultaneous Active and Reactive Power Control of Superconducting Magnet Energy Storage Using GTO Converter

By using GTO´s (Gate Turn-Off Thyristor) in place of ordinary thyristors in a conventional six pulse Greatz bridge converter, forced commutation is possible, so in the usage of ac-dc power conversion the reactive power of not only lagging but also leading phase can be absorbed. This feature enables superconducting magnet energy storage (SMES) to control reactive power in the wide range between lagging and leading phases. By virtue of this control ability , SMES will be applicable for a power system stabilyzer. A GTO converter which mainly consists of six GTO´s was developed and tested. In this GTO converter, the energy stored in leakage inductances of the transformer is handled by voltage clipper circuit. Then, by using two sets of these GTO converters, we carried out some experiments of simultaneous active and reactive power control of SMES. The experiments on the developed control system were successfully performed and the ability of controlling reactive power in the wide range between lagging phase and leading phase was verified.