Control strategies for a high-performance 2×27 MVA machine test bench with multilevel IGCT converters

In this paper, control strategies of a 22 MW / 27 MVA machine test bench using pumpback topology are introduced. The current loop design at extremely low pulse ratios (e.g. 600 Hz carrier frequency / 80 Hz load frequency) is developed. The system stability and dynamic response are analyzed. The challenges for high-power machine control with a sine filter and a transformer connected between the voltage-source-inverter and the machine are listed and solutions are given. Afterwards, some specific test modes are introduced as well. Finally, the control strategy is validated with the motor test at the customer site.