Analysis of Dynamic Power Angle Oscillation and Its Suppression Strategy for the Droop-Controlled Grid-Connected Inverter
Xing Zhang, Hang Zhang, Ming Li, Zixuan Guo, Yuhua Hu, Qiaodi Chen, Xiaoxi Liu, Fei Li
Abstract
The power angle characteristic is not suitable for describing the power transmission character of the droop-controlled grid-connected inverter due to the small inertia and fast response of the power electronic system. Therefore, it is of great significance to study the dynamic model of the power transmission circuit and put forward the strategy to suppress the dynamic power angle oscillation. However, the existing dynamic model only considers the line impedance but ignores the influence of the closed-loop output impedance of the dual-loop control. Also, the existing virtual resistance damping strategy for suppressing dynamic power angle oscillation has the problem of increasing power coupling. This article analyzes the dynamic model of the power transmission circuit considering the influence of the closed-loop output impedance of the dual-loop control, and the dynamic power angle oscillation frequency is extended from the fundamental frequency point to the low-frequency range. Then, a novel virtual impedance damping strategy is proposed, which can suppress the dynamic power angle oscillation without affecting the steady-state performance of the system. Finally, the properties of dynamic power angle oscillation and the effectiveness of transient virtual impedance damping strategy are verified by experiments.