An Adaptive BESS Controller for Stability Enhancement of Islanded Low Voltage Microgrids

Battery energy storage system (BESS), as grid-forming unit, can quickly regulate voltage and frequency for a 100% inverter-based islanded low voltage microgrid. However, due to some inherent characteristics of this network, such as: (a) coupling among voltage and frequency dynamics, (b) dynamics of dc source, and (c) timescale coupling among converter and network, small-signal stability is a major concern. This paper proposes an adaptive feed-forward compensation scheme for each BESS unit to reduce dynamic interactions among converters and network/load parameters. Additionally, the proposed scheme can enhance system damping capability for a wide range of operating conditions without the need for any prior/ continuous generation/network information or additional sensors. This technique can preserve the voltage/frequency regulation capability of the traditional (omega -P/V-Q) droop control scheme for any low voltage networks. The existing small-signal model is modified to include dc-source, dc link, and proposed feed-forward dynamics, which assists in analyzing the impact of dc-side, ac-side, and network parameters on system small-signal stability. The system performance is analyzed with extensive case studies conducted on a CIGRE TF C6:04:02 benchmark system. The proposed model is validated using a real-time digital simulator with hardware-in-loop setup.