Secondary Power Sharing Regulation Strategy for a DC Microgrid via Maximum Loading Factor

Abstract

Conventionally, additional control levels are often introduced in a dc microgrid (MG) to ensure equal power sharing among distributed energy resources (DERs). To achieve this, it is necessary for the supervisory controller to collect multiple operation signals of all DERs. Thus, the burden of communication increases with increased usage of DERs. Additionally, high requirements on communication links decrease the flexibility and reliability of dc MGs. In this paper, an improved secondary control strategy with maximum loading factor (MLF) for accurate power sharing in dc MGs is proposed. In this method, the MLF is used to achieve an auto-selection of the leader converter with differential delay methods. Additionally, the compensation value for power sharing improvement is calculated at the secondary control level. In contrast with the conventional approaches, the only signal transmitted in the communication link corresponded to the MLF, and thus power sharing is realized with ultra-low bandwidth communication. After receiving the MLF signal, the compensation value is calculated in the local converter. Thus, the centralized secondary controller or master controller is not required. Finally, performance of the proposed control scheme with different time latencies is verified via hardware-in-the-loop tests for different scenarios.