A high-performance 2×27 MVA machine test bench based on multilevel IGCT converters
In this paper, a high-performance 22 MW/27 MVA machine test bench using pumpback topology is introduced. It proposes a cost-effective concept that works reliably even with a weak grid. A paralleling concept of two three-level IGCT converters is presented. It generates a five-level pulse pattern with low harmonic distortion at 600 Hz carrier frequency and 80 Hz load frequency. The selected magnetic device minimizes the circulating current, which ensures the full power utilization of IGCT converters. Moreover, vector control concepts for machines are presented that work reliably at 7.5 times of carrier-to-load frequency ratio, while there is a sine filter between the converter and load machines. This test bench has been experimentally validated at the customer site.