Event-Triggered Differential Delay Method for Current Sharing in Islanded DC Microgrids With Adaptive Droop Coefficient Regulation

Abstract

In islanded DC microgrids, various parallel distributed generation units (DGUs) are in voltage control mode, and mismatched line impedances always lead to inaccurate current sharing, which influences the normal and effective operation of power systems. To solve this problem, a distributed event-triggered differential delay method is proposed for current sharing in islanded DC microgrids. In this method, the master DGU is selected with the differential delay method, and then broadcasts its per-unit current via the communication network. When other DGUs have received this information, droop coefficients are adaptively regulated based on per-unit current errors, with which line impedance mismatches are eliminated. Furthermore, the communication and current sharing loops are activated with event-triggered control. With the proposed strategy, the current both in steady states and during load change transients is achieved with small droop coefficients, the bus voltage quality is hardly degraded. Besides, with the proposed event-triggered differential delay mechanism, both the date amount in communication and data exchange frequency are dramatically reduced. The convergence is analyzed and on this basis, the parameters in the triggering function are selected. Finally, hardware-in-loop test results in various conditions are presented to validate the effectiveness of the proposed strategy.