Real-Time Simulation-Based Continuous Thévenin Impedance Monitoring Using Phasor Measurements

The grid impedance of a power system is a significant parameter that characterizes the overall electrical behavior of the system. It is often used for assessing grid strength and can help to identify the sources of voltage profile drop, as well as fault detection and diagnosis. This paper presents an in-depth analysis of invasive and non-invasive methodologies for estimating grid impedance. It gives a review of both methodology types and evaluates their practicability for a continuous monitoring. In the paper a non-invasive method for the estimation of Thévenin equivalent (TE) impedance was selected, which employs data from Phasor Measurement Units (PMU) installed on the slack bus. The focus of the approach lies on the coupling of the evaluation with real-time (RT) simulation systems to continuously determine grid impedance under different scenarios. Since RT simulations allow the emulation of the dynamic behavior of electrical networks, a phase drift correction is implemented to compensate for the angular deviation due to frequency fluctuations. Selected results are presented to validate the effectiveness and general feasibility of the proposed method.