基于虚拟同步机的并网逆变器不平衡电压灵活补偿策略

With a large number of power electronics devices connected to the power grid, there are problems, such as inertia and damping decreasing. To improve the frequency stability and power quality of the unbalanced grid, this paper proposes a flexible compensation control strategy of unbalanced voltage based on virtual synchronous generator (VSG). When the frequency of the grid is oscillating, VSG can provide active power support to enhance the stability of power system. By using the feed-forward compensation control of negative sequence voltage, it can restrain the unbalanced voltage at the point the of common coupling and improve the power quality. By building the model of VSG under unbalanced grid, this paper proposes a suppression strategy of unbalanced voltage by using the voltage feed-forward compensation. Then, the performance of voltage feed-forward compensation strategy is analyzed and the compensation coefficient setting method of the unbalanced voltage is studied. The method can realize flexible control, which changes the compensation coefficient automatically according to the goal of voltage unbalanced factor and the remaining capacity of instrument. Finally, simulation results validate the correctness and effectiveness of proposed control strategy.