Graduation Year

2024

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Zhixin Miao, Ph.D.

Committee Member

Lingling Fan, Ph.D.

Committee Member

Kaiqi Xiong, Ph.D.

Committee Member

Zhengyu Wang, Ph.D.

Committee Member

Hadi Gard, Ph.D.

Keywords

Dynamic Modeling, Grid-Following Inverters, Renewable Energy Resources, Stability Analysis

Abstract

As the inverter-based generation is the primary technology driving renewable energy sources such as solar photovoltaic and wind turbines, its penetration is increasing rapidly. Due to the high penetration, there are multiple situations of IBR misoperation due to any type of grid contingency. This dissertation focuses on exploring the response of IBR towards grid contingency.

The primary objectives of the study are as follows: 1. Conducting a harmonic analysis of inverter-based resources when subjected to balanced and unbalanced grid conditions, 2. The use of a circuit simplification method to streamline the analysis process and study the dynamic response of IBR when subjected to grid contingency. To achieve the first objective, test setups are built in MATLAB / SimPowerSystems and PSCAD / EMTDC software tools to perform electromagnetic transient study (EMT). The analysis model is built for both open-loop and closed-loop operation of IBR and the results are compared with the analysis models. In the case of the closed-loop system, a black-box approach is utilized to create an admittance model, and a circuit is constructed for analysis purposes. For the future study of the IBR response towards grid contingency, a hardware testbed is set up with different controllers. For the second objective, a mesh network system is simplified to a Th´ evenin equivalent using an admittance matrix, and the results from the mesh network and simplified Th´evenin equivalent model is validated using a balanced and unbalanced fault condition.

Moreover, an additional topic is added to the dissertation, which is related to the unbalance study in asynchronous motors. For this objective, a simplified equivalent circuit of induction motor is derived to explain the harmonics due to rotor unbalance. Since AC machines are important for the blackstart of the power grid, this study can be extended to study the blackstart with IBR.

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