A Conservatism-Free Large Signal Stability Analysis Method for DC Microgrid Based on Mixed Potential Theory

Large disturbance scenarios such as pulse power load operation and load switching are commonly seen in the operation of DC microgrids. The mixed potential theory-based large-signal stability (LSS) analysis is a simple and practical method for investigating the LSS of DC microgrids. However, this method is characterized by conservatism, and produces conservative stability criterion results. When they are applied to the parameter designs of DC microgrids, they create excessive control parameter redundancies; when used for running status estimations, they may cause the system to be misjudged as unstable, and trigger unnecessary protective actions when the system runs into the conservative region. This paper presents a comprehensive analysis of the conservatism, revealing its main causes to be the idealization of the load converter's response characteristics, and the lack of refined models. It then proposes a novel, improved analysis method for transient response characteristics of the load converter. Experimental and simulation results using the improved method have validated it by showing that the conservatism of the traditional method had been eliminated, and the stability criterion obtained was more accurate.