Analyzing the Effects of Micro‐Source Disconnection on Interactive Stability of Grid and Micro‐Grid with Series Inverters.

Owing to a lack of systematic mathematical models to represent the parameters related to micro‐source disconnection, the stability of interaction between a grid and a micro‐grid with series micro‐source inverters (SMSI‐MG) is difficult to analyze. In this study, the average ratio and the degree of imbalance of three‐phase micro‐source disconnection, denoted respectively by δ and ϵ, are defined, and the positive‐ and negative‐sequence impedances of the SMSI‐MG containing the two parameters are established using a combination of the harmonic linearization and the symmetrical component methods. Moreover, rules of the behavior of the SMSI‐MG after micro‐source disconnection as well as its mechanism of interaction with the grid are revealed by the impedance models. The results of analysis show that high‐frequency harmonic resonance was generated around the carrier frequency when δ ≠ 0, and both high‐ and low‐frequency harmonic resonances were generated when both δ and ϵ increased in the interactive system. Furthermore, three SMSI‐MGs containing five, 10, and 20 micro‐sources in a single phase were simulated, and the results verified the correctness, feasibility, and advantages of the simplified analysis of the impedance models. These insights can be used to apply the corresponding control strategies in a timely manner according to the given conditions of micro‐source disconnection to reduce the harmonic resonance and increase the stability of the SMSI‐MG and the grid. The results of simulations verified the effectiveness of such a control strategy. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]