Power inverter design for magnetic perturbation coils in nuclear fusion experiments

An economical, broad-band switched power inverter for supplying electrical current to magnetic perturbation coils in magnetic confinement nuclear fusion devices is designed and tested. The unit uses commercial IGBT blocks for a load current up to 1.3 kA at a DC-link voltage up to 500 V. Current is controlled by means of an embedded PC with real-time patched Linux operating system and commercial I/O boards. H-bridge and neutral point clamped (NPC) topologies are compared, both with standard and phase-shifted pulse width modulation (PWM). DC to 500 Hz bandwidth is demonstrated with good step response at full output current, making the system suitable for the supply of 16 in-vessel saddle coils of the ASDEX Upgrade tokamak. With multi-level topology and phase-shifted PWM the inverter design can also cover a planned additional coil set with DC to 3kHz bandwidth.