面向构网型变换器的阻感型虚拟阻抗精度与稳定性评估

Modifying the output impedance of a grid-forming converter can improve stability of the grid-forming control and help shape the converter output impedance. A virtual impedance (VI) modifies the output impedance through control only, thus saving the cost of additional hardware. Furthermore, the parameters of a VI can be modified on-the-fly, making VIs suitable for current limitation. Typically, a VI represents a series connection of a resistor and an inductor: around the fundamental frequency, this most closely matches the impedance of most grids, resulting from the transmission lines and other grid nodes. The VI should not introduce any instability and behave as similarly as possible to the impedance it is intended to emulate. This work starts with an overview of multiple VI strategies from literature. The most promising VI strategies in terms of accuracy and stability are then investigated in measurement and numerical analysis. This work provides guidance to those seeking to incorporate a VI into their application.