Stability Investigation and Control of a Hybrid Microgrid

Abstract

A microgrid can be considered a low- or medium-voltage localized power system with distributed energy sources, storage, and loads. Converter-dominated microgrids are now replacing the conventional inertial-based power system due to the numerous advantages they provide. The first and foremost is the integration of renewable energy sources with distributed storage and control units. This is significant since it directly contributes to an emission-free environment which has been a constant concern in the power industry. Based on the distribution system a microgrid can be classified into three main configurations, namely- AC, DC, and hybrid. Hybrid microgrids are developed particularly for overcoming the effective power regulation difficulties encountered in standalone microgrids by combining the advantages of individual AC and DC configurations. Hybrid microgrids are now gaining high popularity due to the compactness they inherently provide for integrating the AC and DC loads with a lower number of power conversions compared to the individual types. Hence the economic feasibility is appreciable compared to the individual AC or DC microgrids. Despite the advantages that microgrids, especially hybrid types provide, there are still several technical challenges to be addressed in the operation and control of microgrids in the autonomous mode of operation. Since microgrids are equipped with power electronic interfaces, unlike the conventional system, maintaining voltage stability, frequency stability, and power management is challenging and requires a different approach as compared to a conventional power system. In a hybrid microgrid with AC and DC subgrids, the interlinking converter (IC), is the key element connecting the two subgrids. The performance of the interlinking converter is adversely affected by improper coordination among the DG units, a wide range of load dynamics issues, and perturbation instability issues due to the d and q-axis impedance interaction in the inner control loops of the control system....