Improvement on the series control strategy for ITER AC/DC converters

The Coil Power Supply System is one of the most critical systems in the ITER machine to provide controlled DC power to the superconductive magnets by large power AC/DC converters for the control of plasma initiation, shape and position. The AC/DC converter system leads to serious harmonic variation and risk of the low frequency oscillation, which has become a major concern. In addition, the deficiency of the voltage response for AC/DC converters could downgrade the performance of the plasma operation. This paper describes the configuration and series control strategy of the ITER AC/DC converter. Then, according to the theoretical analysis of the time-varying and broad-spectrum distributed ITER load harmonics, an improved hybrid control strategy is proposed based on the existing sequential control strategy. The hybrid control strategy can restrain harmonic current and improve voltage response performance by redistributing the voltage of each series connected unit. Finally, the representative simulation confirms the effectiveness of the control strategy.