Interconnection of microgrids (MGs) provides the opportunity of increasing loadability and enhancing reliability by allowing power exchange among individual MGs. Control of networked MGs requires coordination of distributed energy resources (DERs) within each MG such that the sum of the MG’s load and exported power is shared proportionally among DERs while maintaining power quality. This paper proposes a new hierarchical control scheme for accurate load sharing and power quality enhancement in networked MGs with unbalanced load currents. The proposed scheme is comprised of local DER controllers, MG control units, and Networked MG control center. The MG control units adjust the power exchange at the value specified by the control center and regulate the voltage at the point of common coupling (PCC) by means of a secondary control signal. At the DER level, droop control is adopted to enable load sharing with fast dynamic response. The droop controller output is combined with the secondary control signal and a correction voltage which eliminates the effect of line impedances on the current sharing accuracy. This way, accurate sharing of individual phase currents is realized without requirement of data exchange among DERs. Simulation and experimental results showcase the effectiveness of the proposed scheme.

中文翻译：

---

网络微电网电压不平衡补偿和精确负荷分配的二次控制方法

微电网 (MG) 的互连允许各个 MG 之间进行电力交换，从而提供了增加负载能力和增强可靠性的机会。联网 MG 的控制需要协调每个 MG 内的分布式能源 (DER)，以便在保持电能质量的同时，在 DER 之间按比例共享 MG 的负载和输出功率的总和。本文提出了一种新的分层控制方案，用于在负载电流不平衡的联网 MG 中实现准确的负载分配和电能质量增强。提议的方案由本地DER控制器、MG控制单元和联网MG控制中心组成。MG 控制单元根据控制中心指定的值调整电力交换，并通过辅助控制信号调节公共耦合点 (PCC) 的电压。在 DER 层面，采用下垂控制，实现具有快速动态响应的负载共享。下垂控制器输出与次级控制信号和校正电压相结合，消除了线路阻抗对均流精度的影响。通过这种方式，无需分布式能源之间的数据交换，即可实现单相电流的准确共享。仿真和实验结果展示了所提出方案的有效性。