Optimizing BUSSARD: The new 16-phase inverter system of ASDEX upgrade

BUSSARD is a new inverter system at the nuclear fusion experiment ASDEX Upgrade for mitigation of so called “edge localized modes” (ELM) (Suttrop et al., 2011a,b) [1], [2] and execution of other, physics related experiments. The concept and first results have been presented in detail (Teschke et al., 2015). Four-phase operation was routinely done during shot campaign 2015/16 and much experience in operation was gained. Now, the completion of BUSSARD is finished and many improvements have been adopted. 16-phase operation with up to 16 × 1.3 kA coil current of arbitrary waveform controlled by 16 independent real-time controllers at 500 Hz bandwidth, 5 kHz switching frequency and about 1 MW/10 Mvar total real/reactive power was commissioned within the last campaign. In this publication it is discussed the power stage, PSpice simulations and the fully revised predictive controller with special focus on a (first time published?) numerical method to reduce systematic errors in current measurement. This ends up in an effect comparable to loop latency reduction.