An Enhanced Power Regulation and Seamless Operation Mode Transfer Control Through Cooperative Dual-Interfacing Converters

Abstract

Both voltage control method (VCM) and current control method (CCM) have been well-developed to control DG units in a microgrid. Although conventional VCM has seamless operation mode transfer capability, it has slow power control dynamics in grid-tied operation. On the other hand, CCM features rapid power control but it can hardly provide voltage support during standalone operation of microgrids. To address these issues, a single DG unit is interfaced to the microgrid with two low power parallel converters. One converter is controlled by VCM while the other one is regulated by CCM. Through a new collaborative power control algorithm for these two converters in a single DG unit, the merits of both VCM and CCM are preserved. First, the power control dynamics of this DG unit can be significantly improved in grid-tied operation. Second, the load demand can be accurately shared by these two interfacing converters during islanding operation. Finally, a true seamless operation mode transfer is obtained at any time instant without preparations. Evaluation results from a three-phase prototype show that the proposed interfacing converter configuration and corresponding control algorithm are more suitable for microgrid applications.