Date of Award

6-1-2023

Publication Type

Dissertation

Degree Name

Ph.D.

Department

Electrical and Computer Engineering

Keywords

Fault type classification;Microgrid Control;Phase Selection

Supervisor

Maher Azzouz

Rights

info:eu-repo/semantics/embargoedAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

Renewable energy sources (RESs) are permeating the power grid due to their importance in reducing air pollution and fuel consumption. These sources require synchronization with the power grid using inverters that must meet grid code (GC) requirements. During fault conditions, GCs enforce inverter interfaced RESs (IIRESs) to follow reactive current generation (RCG) requirements to enhance grid stability. However, it could adversely affect protection functions, e.g., phase selection methods (PSMs), operations. The main objective of this dissertation is to enhance the power system resiliency by determining the faulty phase(s) accurately. This is achieved by investigating the root causes behind the failure of the commercial PSMs when fault currents are supplied from IIRESs. Consequently, accurate PSMs are achieved by two approaches. The first approach is enhancing the relay algorithm to guarantee correct faulty phase determination during different IIRES controllers. The second approach is fulfilled by controlling IIRESs to achieve PSM and RCG requirements, simultaneously. Short-circuit analysis is performed to investigate the effect of various fault conditions, including arc resistances, on phase selection. Hence, A new current-angle-based PSM that adaptively adjusts the conventional zone bisectors is proposed to confront the exotic IIRES fault current signatures. Compensation angles are added to the zone bisectors to mitigate any differences in the sequence impedance angles affecting relays emanating from IIRESs. In addition, new zone boundaries are proposed to cope with various fault resistances. Furthermore, a comprehensive analysis is performed to determine the effect of various IIRES controllers on the relative angles between sequence voltages measured at the fault and relay locations due to the voltage drop occurred on the transmission line. Thereafter, a comprehensive PSM based on comparing the angles of sequence voltages is proposed. In the proposed method, new zones are defined to guarantee precise phase selection during various fault conditions. On the other hand, two dual-current controllers (DCCs) are designed to secure a correct operation of the conventional PSM and meet positive-sequence RCG requirements. First, initial reference angles of the negative- and positive-sequence currents are determined according to the grid-side zero-sequence current angle and RCG requirements, respectively. Then, these angles are adjusted to secure correct operation of PSM without violating RCG requirements. Thereafter, the reference currents are calculated to achieve the reference current angles and keep the current magnitude within permissible limits. Lastly, the current-angle-based PSM is analyzed when the IIRESs follow GCs with positive- and negative-sequence RCG requirements, which reveals their inability to ensure correct PSM operation. Consequently, a new DCC is designed to guarantee the correct operation of commercial PSM without violating these GCs and achieve maximum current limit requirements. First, the negative-sequence-current angle is designed to guarantee injecting the minimum negative-sequence active current that ensures correct PSM based on the relative angle between the negative- and zero-sequence currents. Subsequently, the positive-sequence current angle is designed to allow maximum positive-sequence active current injection without violating PSM requirements. Finally, the positive- and negative-sequence current magnitudes are determined to inject the maximum current limit.

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