Asymmetric Sampling Disturbance-Based Universal Impedance Measurement Method for Converters

This letter proposes a universal impedance measurement method for grid-connected converter (GCC) where asymmetric disturbances are injected in the sampling process. The goal is to provide a low-cost and easy-implemented impedance measurement technique that does not rely on actual disturbance sources or prior controller knowledge. In this method, only two-phase sampling channels are needed to measure positive- and negative-sequence impedances of GCC at the same time. This method works well with converters employing various control strategies, and its universality is proved by theoretical analysis. The effectiveness of the proposed method is verified by the results of hardware-in-the-loop experiment and the testing of real prototype.