Title

The Incidence of Inverter Incidents: Understanding and Quantifying Contributions to Risk in Systems with Large Amounts of Inverter-Based Resources

Date of Award

2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Electrical Engineering

First Advisor

Paul Hines

Abstract

Renewable energy is an important and growing percentage of the total power supply. Additionally, non-wires alternatives, which are meant to substitute for the construction of more transmission lines, are increasing in quantity as the demand for electrical power increases. Many non-wires alternatives take the form of renewable energy resources and batteries, and are distributed over short distances through neighborhoods and communities. Inverters are used to connect these DC resources to the AC grid.

However, there is growing industry concern that the disconnect function that is inherent to interconnection standards for inverter-based resources has the potential to result in a cascading failure if voltages deviate significantly from nominal.

This thesis studies the conditions under which a cascading inverter collapse of this sort could occur. More specifically, it identifies engineering design parameters, such as time constants, that influence the speed and nature of these cascades, using a new model called Time-Dependant Inverters Model (TiDIM). While this model is preliminary, the results suggest that risk increases with a number of factors including large transmission or distribution line impedances, a large variance in inverter voltage setpoints, and an inappropriate number of inverter-based resources that can contribute to supplying too much or not enough power. Next, the thesis characterizes the risk at which one may expect this sort of event to occur as a function of line impedance and the resultant voltage magnitude. It is found that a greater proportion of inverter-connected power in the grid is associated with a higher probability of collapse, and a greater variance in inverter behavior is associated with a wider transition band, which is defined in this thesis as the range of impedances/voltages where the probability of collapse is an uncertain. Lastly, the thesis identifies cost-effective strategies to reduce the likelihood of such an event.

Language

en

Number of Pages

68 p.

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