An Adaptive Active Damping Method for Grid-Connected Voltage-Source Converters to Achieve Passive Input Admittance

The dynamic interaction between voltage-source converters (VSC) and the grid may lead to high-frequency destabilization (HFDS). It has been shown that HFDS can be effectively avoided if the VSC input admittance (VIA) is compensated to be passive at all the frequencies below Nyquist frequency (NF). The effective approaches, auxiliary current feedback and advanced control sequence (i.e., oversampling or delayed sampling), are limited for cost-sensitive applications. Without the above approaches, full-range passive VIA is hard to achieve, even if existing self-tuning active damping methods are used. Therefore, this article proposes an adaptive parameter switching voltage-feedback active damping control (AFVC) method. Both positive and negative feedback are used to design preset AFVC parameters, making VIA passive in different ranges, which overlap and cover the frequencies below NF. Parameter switching is triggered by fast Fourier transformation (FFT). The data sequence length of FFT is designed to balance the speed and frequency spectrum resolution. Sampling frequency aliasing and PWM sideband frequency coupling challenge the admittance/impedance based stability analysis around NF, so they are modeled and proved to be negligible for high-frequency stability. The effectiveness of the proposed method is verified by both simulation and experiment.