Studies on power conditioning system for SMES in ITER

The International Thermonuclear Experimental Reactor (ITER) draws huge power from utility power grid and it may cause some problems in the power system. Especially, the power required to control the movement of plasma caused by some instabilities of the plasma is suitable for compensation by SMES, because the time duration is a few seconds although the required power is around 100 MW. In this system, the design of the power conditioning system is one of the keys. As a power conditioning system, two systems were studied; one is the system using line commutation and light triggered thyristors, another is the system of multi-series converters using forced commutation and gate turn-off devices such as GTOs. Feature of the former circuit is the inter-phase DC reactor-less configuration. Thyristor rectifiers are directly connected in parallel at DC side, primary side windings of rectifier transformers are connected in series in order to ensure equal sharing of current between rectifiers. Reactive power can be compensated by TSC (thyristor switched capacitors). The performances of two proposed circuits were studied by computer simulation.