PMU based Monitoring and Mitigation of Delayed Voltage Recovery using Admittances

TL;DR

This paper presents a novel PMU-based method for monitoring and mitigating delayed voltage recovery by analyzing load admittance, enabling online detection and control using local measurements, validated on the IEEE 162 bus system.

Contribution

It introduces a new admittance-based monitoring and mitigation approach for delayed voltage recovery, with analytical expressions and practical schemes for online application.

Findings

Effective detection of stalling onset using load admittance.

Mitigation scheme ensures voltage recovery within desired time.

Validation on IEEE 162 bus system confirms approach viability.

Abstract

This paper analyzes the delayed voltage recovery phenomenon by simplifying the Western Electricity Coordinating Council (WECC) composite load model using the load admittance and the thermal relay dynamics. From this analysis, a closed form expression approximating the recovery time is derived and the key load parameters impacting the behavior of voltage recovery are identified. A monitoring scheme based on the measured load admittance is then proposed to detect the onset of stalling, even in the presence of voltage oscillations, and estimate the duration of the delayed voltage recovery. A mitigation scheme utilizing smart thermostats and offline learning is also derived to ensure that the voltage recovers to the pre-contingency voltage within a specified time. Both the monitoring and mitigation schemes only need local measurements at a substation making them promising for online applications. Results for the monitoring and mitigation schemes are described in detail for the IEEE 162 bus system validating the various assumptions used for the analysis and establishing the connection between the delayed voltage recovery phenomenon and load admittance.