A Triple-Droop Control Scheme for Inverter-Based Microgrids

In this paper, a power management control scheme based on triple-droop control strategy is proposed for low-voltage microgrid system. The proposed control method is based on traditional P/f and Q/V droop control, but adds two other levels of droop control in response to the DC bus voltage conditions. One of them regulates the output power of micro-source (MS), while the other adjusts the output parameters of Droop Control 1. With this control scheme, the output power of MS can be adjusted automatically without the need for communication among the MS systems. The proposed control scheme is proven as capable of operating in both autonomous mode and grid-connected mode. In addition, the droop-controlled VSI systems ensure a smooth transition from grid-connected mode to autonomous mode without the need for mode-switching or communication. The design methodology of the triple-droop control scheme is presented in this paper. The effectiveness of the proposed scheme and design methodology are verified by simulation results on PSIM.