Small-Signal Stability Analysis of Three-Phase AC Systems in the Presence of Constant Power Loads Based on Measured d-q Frame Impedances
The paper discusses how stable and unstable cases are created in the experimental system, shown in Fig. 1, based on the derived d-q frame average model of both the VSI and VSC. The constant power loads and instability conditions are also considered, but solely through the d-d channel. The d-q frame impedance measurement techniques and algorithm are then discussed. The experimental results, including time-domain waveforms and measured d-q frame impedances, like Fig. 2, validate all stability conditions. Because of its accuracy, using this approach to predict stability in both the frequency domain and time domain has the potential to enable the use of impedance specification as a design tool for future ac systems.