Mitigation of High Frequency Oscillation in Converter Connected to Weak Distribution Network

High penetration of power electronic equipment in distribution system lifts a new stability concern, converter-driven stability. High frequency oscillation occurs when a converter is connected to a weak AC distribution network, this research discusses the principle of oscillation and mitigation method. The small-signal model of PLL reveals the interaction between converter and network, and finds the oscillation component feedback path in controller. A supplementary damping control is proposed to increase system damping through outer reactive power controller, and a virtual impedance compensation is suggested in inner current controller to promote the robustness of feedforward voltage. Simulation of a grid-connected converter system validates the oscillation principle and demonstrates the effectiveness of proposed mitigation methods.