Enhancing Voltage Control Stability of Grid-Forming VSCs Under PWM Delays: A Study on Feedforward Damping Methods

Grid-forming converters have demonstrated their ability to enhance the operation of renewable energy resources by providing essential grid voltage and frequency support. However, control delays can cause the output impedance of the converter having a negative-resistance region, which potentially leads to high-frequency instability in voltage control. While passivity-based design is typically employed to shape the output impedance, aspects such as ease of implementation, robustness, and constraints related to LC-filter design have not been fully explored. To address this gap, this paper examines four feedforward damping methods with varying sampling rates, ultimately recommending sixteen-sampling capacitor voltage feedforward as the optimal approach. The effectiveness of proposed approach is validated through experiments, with grid current feedforward used as a benchmark for comparison.