Power Control of Virtual Oscillator-Based Inverters Using Virtual Impedance and Model Predictive Control

This paper presents a control strategy to improve voltage regulation at the point of common coupling (PCC) and power control accuracy and achieve balanced power-sharing in microgrids controlled by dispatchable Virtual Oscillator Control (dVOC). Although dVOC effectively controls local voltage and frequency, it does not precisely regulate the PCC voltage, as it does not consider voltage drops across the LCL filter and transmission lines. This can result in less power being delivered to the load than the specified power set point. Additionally, in microgrids with parallel-connected distributed generators (DGs), unequal line impedances between DGs and the PCC lead to unbalanced power-sharing. To address these limitations, this paper proposes a controller that uses Model Predictive Control (MPC) and virtual impedance techniques to enhance the performance of dVOC-based DGs. In the proposed controller, the virtual impedance loop adjusts the reference voltage generated by dVOC, thereby ensuring accurate power-sharing. Meanwhile, MPC utilizes real-time measurements and system model to predict both voltage and inverter-side current, enabling more accurate voltage and power control. It also achieves higher robustness against load variations and a faster dynamic response. Simulation results validate the effectiveness of the proposed method in microgrids with multiple DGs operating under varying line impedances.