PHIL-based Impedance Measurement for Electromagnetic Stability Analysis of Grid-following Converters

Inverter-based resources (IBRs) have a complex internal structure and internally use controllers and output filters with different dynamics. The increasing number of IBRs in modern power systems has led to a redefinition of the power system stability criteria, as it is necessary to assess stability under faster dynamics and disturbances imposed by the IBRs. A new class of power system stability called electromagnetic stability (EM) is introduced to evaluate the effects driven by the IBRs on power system stability. One of the major problems when assessing EM stability is the fact that the internal structure of the IBRs control loops is typically not available to those assessing the stability. The impedance-based stability assessment approach proves to be an effective way of evaluating the system’s EM stability, because no detailed knowledge of the internal structure of the IBR’s hardware or its control is needed in this case. In this paper, we illustrate the application of a 100- kVA commercial power hardware in the loop (PHIL) system to measure the output impedance of a grid-following converter (GFL) and the impedance of the voltage-source converter acting as a grid to which the GFL is connected.