Robust Secondary Controller for Islanded Microgrids with Unexpected Electrical Partitions Under Fault Conditions

This paper presents a sophisticated centralized secondary controller tailored for inverter-based, islanded Microgrids (MGs) that are prone to unforeseen network partitions triggered by faults activating protective devices. In typical radialconfigured MGs, a line fault can cause protective devices to isolate the faulted line, thereby splitting the MG into two electrically independent sub-microgrids (SMGs), while retaining the existing communication and control framework. Diverging from both centralized and distributed traditional secondary controllers, which often fail to normalize the frequency in one of the split SMGs, the proposed controller exhibits exceptional performance. Through simulation studies on 6-bus and 13-bus islanded MG setups, our controller has demonstrated not only its ability to swiftly restore nominal frequency in both SMGs within a few seconds, but also to ensure fair power distribution among the distributed generators (DGs) serving the SMGs. This rapid frequency stabilization underscores the controller's effectiveness in maintaining stable frequency levels immediately following a fault.