Modelling virtual oscillator-controlled microgrids

• Published in: IET generation, transmission & distribution Vol. 13; no. 11; pp. 2173 - 2181
• Main Authors: Shi, Zhan, Li, Jiacheng, Callegaro, Leonardo, Nurdin, Hendra I, Fletcher, John E
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 04.06.2019
• Subjects: ac cycle; ac microgrids; average dynamics; average power; average real power; average VOC dynamics; average VOC model; distributed power generation; eigenvalues and eigenfunctions; emerging nonlinear technique; filtered power; invertors; linearised model; low‐pass filter; low‐pass filters; modelling virtual oscillator‐controlled microgrids; newly developed linearised VOC model; oscillators; power generation control; precise small‐signal stability; previous literature; reactive power; small‐signal linearised models; small‐signal models; Special Issue: Emerging Technologies for Virtual Power Plant and Microgrid; stability; stability studies; studying stability; three‐phase inverter subject; transient analysis; transient dynamics; transient response; transient responses; virtual oscillator control; virtual oscillator‐controlled inverters; virtual oscillator‐controlled inverter‐based microgrids; voltage control; stability studies; transient responses; transient response; average real power; power generation control; three-phase inverter subject; transient dynamics; ac cycle; distributed power generation; newly developed linearised VOC model; ac microgrids; average power; eigenvalues and eigenfunctions; invertors; virtual oscillator-controlled inverter-based microgrids; average dynamics; low-pass filters; low-pass filter; filtered power; stability; modelling virtual oscillator-controlled microgrids; oscillators; average VOC dynamics; linearised model; virtual oscillator control; emerging nonlinear technique; previous literature; small-signal linearised models; studying stability; average VOC model; reactive power; virtual oscillator-controlled inverters; transient analysis; small-signal models; voltage control; precise small-signal stability
• ISSN: 1751-8687; 1751-8695
• DOI: 10.1049/iet-gtd.2018.5737

Virtual oscillator control (VOC) is an emerging non-linear technique to control the terminal voltage of inverters in ac micro-grids. This study compares two small-signal models of VOC, obtained from average VOC dynamics over one ac cycle. The first model from previous literature is based on the approximation of real and reactive power in the average dynamics by the corresponding instantaneous values of power. The second model proposed in this study, in contrast to the first, approximates the average power by filtered power from a second-order low-pass filter. The two models are evaluated by eigenvalue and participation analyses. Simulations and experimental results are used to verify the models, by observing transient responses of a three-phase inverter subject to a step change in the load. The proposed linearised model can tracks transients of the output voltage and current more accurately than the existing technique both in the simulations and experimental tests. The proposed linearised VOC model enables a more precise small-signal stability and transient analysis of the average VOC dynamics. In conclusion, this improvement benefits stability studies when system parameters are changed or load disturbances are added to virtual oscillator-controlled inverter-based micro-grids.