Responsibility Identification for Harmonic Oscillation Issues in the Parallel Grid-Connected Inverters System

The responsibility identification for harmonic oscillation issues, caused by the interaction among the inner control loops of power electronics converters and passive components in renewable energy systems, can provide guidelines to the harmonic oscillation suppression. However, the identification method using the impendence-based stability criterion has not been fully discussed. In this paper, two methods based on a sum type impedance-based stability criterion are proposed to identify the responsibility of each inverter. The proposed Method-1, which is called the result-oriented method, calculates the system state quantitatively assuming one of the inverters is removed from the system and the responsibility of each inverter can be obtained when the calculation is done removing each inverter. The proposed Method-2, which is called the cause-oriented method, employs the calculation of the original system state and the inverter state using the combination weighting method to analyze the responsibility of each inverter on system instability. The former method is more accurate while the later one is more suitable in the large-scale system due to less computation. Finally, simulation and experiment results validate the effectiveness of the proposed methods and analysis.