Dynamic State Estimation for Load Bus Protection on Inverter-Interfaced Microgrids

TL;DR

This paper investigates the effectiveness of dynamic state estimation (DSE) for load bus protection in inverter-interfaced microgrids, addressing challenges posed by inverter behavior during faults to improve protection reliability.

Contribution

It extends DSE load protection analysis to include short-circuit conditions with grid-forming inverters exhibiting current-limiting behavior, which was not previously studied.

Findings

DSE can effectively detect faults during inverter short-circuit conditions.

Inverter current-limiting behavior impacts DSE accuracy.

The proposed approach enhances microgrid protection reliability.

Abstract

Inverter-interfaced microgrids results in challenges when designing protection systems. Traditional time-overcurrent, admittance, and differential protection methods are unsuitable on account of lack of fault current, excessively short lines, or a prohibitive number of protective devices needing to be installed. Current practice is to force all inverters to shut down during fault conditions, weakening resilience and reducing reliability. Dynamic state estimation (DSE), which has been explored for both line protection and load bus protection before, is a potential solution to these challenges to create widely utilizable, highly reliable protection systems. However, it has only been tested for load protection with ideal voltage sources, which do not capture the short-circuit behavior of inverter-interfaced generation, notably low fault current and unbalanced output voltage. This paper aims to extend the state-of-the-art on DSE load protection: the performance of DSE during short-circuit conditions with a grid-forming inverter with current-limiting behavior during fault conditions is investigated.