Switching frequency characterization of hysteresis control in a pump back test configuration

The pump back test is widely adopted in the industry for characterizing and qualifying the high-power converters. One popular pump back test mode is to tie the DC link of two converters together and circulate the current through the inductor connected between the AC terminals. In this mode, one of converter operates in voltage mode to generate the virtual grid and another converter regulates the circulating current. Hysteresis control could be applied to this test mode. However, the switching characteristic of the hysteresis control is unique due to the PWM type voltage being the virtual grid. This paper contributes to analyzing the switching frequency characteristics of the hysteresis control in a pump back test configuration. The switching frequency tracking phenomenon is for the first time revealed and reported in this paper. Theoretical analysis, simulation validation, and experimental demonstration are provided to support the major conclusions.