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The increased penetration of renewable energy sources into the power system has resulted in a need for dispatchable control for the inverters. Dispatchable generation enables intelligent use of power sources thus enhancing the system's efficiency, reliability and reducing the stress on the distribution lines. In this article, a dispatchable control for virtual oscillator controlled-inverters is presented to achieve simultaneous regulation of both the active and reactive power in a single-phase system of $\boldsymbol{m}$ -controlled and $\boldsymbol{n}$ -uncontrolled inverters. Further, a set of security constraints is derived to determine the achievable power set-points for each controlled inverter present in the system. The dispatchable controller parameters corresponding to the desired power set-point can be determined using the presented control laws. A technique to design the control parameters and line impedance for the uncontrolled inverters is presented to enable optimal power sharing proportional to their power ratings. Simulation and experimental results are presented for the power regulation of multiple virtual oscillator controlled-inverters connected to a load through respective line impedances. The proposed dispatchable control strategy effectively regulates both the active and reactive power of the controlled inverters for a number of cases and in a wide operating range. [ABSTRACT FROM AUTHOR]

This paper compares transient responses of virtual oscillator control (VOC) to the conventional droop control method, under various inverter terminal voltage amplitude and frequency regulations. The system of interest is an islanded microgrid of three three-phase inverters sharing a resistive load. By letting the two controllers have similar steady-state droop characteristics, the virtual oscillator and droop controlled systems are compared in a small-signal framework with the aid of eigenvalue analyses. The analytical results are verified by simulating the two systems in MATLAB/Simulink. In the simulations, the third inverter in each system is connected to share the load when the other two inverters are already synchronized. Transients are compared by examining synchronization time after the third inverter is connected. The key finding is VOC outperforms droop control in terms of time responses when the terminal voltage frequency regulation range is allowed to be wide; otherwise, the droop control responds faster than the VOC technique. The same conclusions are found for two other load types: constant power load and nonlinear load. In addition, transient energy losses are investigated, which shows positive correlation with the time response. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]