Power supply of the control coils of Wendelstein 7-X experiment

This paper presents the solution for the construction of power supplies to feed a group of coils for the new stellerator is being built in the Max-Planck Institute for Plasma Physics, IPP, in Greifswald. The 10 control coils in the stellerator are regulated by 10 power supplies, that must provide a controlled current compounded of direct current and 0–20 Hz bandwidth AC current in a range of almost 3 kA at low voltage, 30 V, in four quadrants. Positive and negative voltage and sinusoidal current with low harmonic distortion is required by load. Besides, all the sources must operate current synchronizated on time. The selected design is based on Switch-mode-power supply technology (SMPS) instead of classical thyristor based technology (SCR). This provide the system with a very high regulation response (very low current and voltage ripple) and excellent input power factor, keeping the grid Total Harmonic Distortion (THD) under minimum values. Due to low voltage and voltage drop requirements, the inverter is compounded of MOSFET transistors which allow also higher regulation speeds. Driver control and main tasks management is supported by Digital Signal Processing Technology (DSP) to achieve desired system response. The system in its entirety requires a high efficiency due to thermal considerations and reduced space. The presented system introduces a decisive solution for the future power supplies to superconducting or regular coils, where the regulation, precision and ripple requirements are a base of design.