Capacity enhancement and operational flexibility are two of the important limitations of the centralized shunt APF (APFsh) unit.\r\nThese limitations can be conquered by the operation of multiple APF units in parallel and connected back to back by a common\r\nDC link capacitor. In that case, a circulating current (CC) flows within the APFsh units. This CC flow becomes out of control when\r\nthe APFsh units operate in hysteresis based current controlled mode. One of the difficulties of this CC flow control or reduction is\r\nthe variable switching frequency of the APFsh units. In this paper, themodel for CC flow is derived by the switching dynamics study\r\nof the APFsh units. It is found that the selection of design parameters plays an important role in the amount of CC flow. Detailed\r\nsimulation, analysis, and real-time performance show how the selection of design parameters affects the CC flow and the reduction\r\nof CC flow can also be achieved at an acceptable level by the proper selection of design parameters.
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