Modeling and Stability Analysis of Inverter-Based Microgrid under Harmonic Conditions

Microgrids (MGs) operate under harmonic conditions due to the integration of nonlinear loads. The autonomous harmonic compensation control of inverter-interfaced DG has been proposed to successfully mitigate the harmonics. However, the small-signal analysis of harmonic compensation controls has not been investigated in the microgrid with multiple inverters. This paper develops the modeling and analysis of the inverter-based MGs under harmonic conditions. The concept of dynamic phasor (DP) is used to describe the fundamental and harmonic components of an ac waveform via dc variables. The developed model consists of droop-controlled distributed generators (DGs), diodes rectifiers (working as nonlinear load) and resistance loads. Virtual impedance control is considered in the droop-controlled DGs for the autonomous harmonic compensation. Based on the developed DP model, the dynamic behavior of the microgrid is investigated via small-signal analysis. It is observed that the virtual impedance for harmonic compensation brings inter-inverter oscillations on harmonic domain. Participation and eigenlocus analysis are performed to investigate the influence of parameter tuning of harmonic compensation on microgrid stability. Numerical simulations are carried out to validate the effectiveness of the proposed modeling method and the analysis results.