Impedance shaping for whole-system small-signal stability enhancement via co-operation between Grid and IBR operators
File(s)
Author(s)
Smith, Fredrik
Type
Thesis
Abstract
The transition to an electric grid powered largely by Inverter-Based Resources (IBR) is changing the tools required by an Electricity System Operator (ESO) to ensure stable operation of the power grid. Recent research has revealed that measurable system residues relate changes in apparatus impedance to the damping of the oscillation modes which define the whole-system small-signal stability.
This thesis describes a process where an IBR operator and an ESO co-operate with shared information to guide changes in the impedance of the IBR, to improve the system stability. Three main barriers to the implementation of the proposed process are identified and investigated.
The first barrier investigated is the unknown capability of grid-following IBR to provide the required modification in its impedance spectrum shape. A study is presented assessing the most suitable parameters for impedance shaping and the constraints imposed on the shape-ability by ensuring satisfactory performance of the IBR DC voltage control.
A second barrier is identified as the need to ensure stability of the system when the change in mode damping after the parameter change is different to that initially predicted. A method called the "minimum delta rho path constraint" is proposed to account for changes in the relationship between the impedance and the parameter in the neighbourhood of a mode to calculate an updated constraint on the allowed parameter change.
The third barrier considered is the effect of measurement noise on the modes and residues estimated with vector fitting. A novel version of vector fitting - referred to as "constrained vector fitting" - is proposed to improve the identification performance.
Taken together, the techniques proposed to address the identified barriers could improve the effectiveness of cooperation between an ESO and IBR operators, such that whole-system, small-signal stability can be more effectively enhanced through alterations of IBR control parameters.
This thesis describes a process where an IBR operator and an ESO co-operate with shared information to guide changes in the impedance of the IBR, to improve the system stability. Three main barriers to the implementation of the proposed process are identified and investigated.
The first barrier investigated is the unknown capability of grid-following IBR to provide the required modification in its impedance spectrum shape. A study is presented assessing the most suitable parameters for impedance shaping and the constraints imposed on the shape-ability by ensuring satisfactory performance of the IBR DC voltage control.
A second barrier is identified as the need to ensure stability of the system when the change in mode damping after the parameter change is different to that initially predicted. A method called the "minimum delta rho path constraint" is proposed to account for changes in the relationship between the impedance and the parameter in the neighbourhood of a mode to calculate an updated constraint on the allowed parameter change.
The third barrier considered is the effect of measurement noise on the modes and residues estimated with vector fitting. A novel version of vector fitting - referred to as "constrained vector fitting" - is proposed to improve the identification performance.
Taken together, the techniques proposed to address the identified barriers could improve the effectiveness of cooperation between an ESO and IBR operators, such that whole-system, small-signal stability can be more effectively enhanced through alterations of IBR control parameters.
Version
Open Access
Date Issued
2024-03-13
Date Awarded
01/03/2025
License URL
Advisor
Green, Tim
Gu, Yunjie
Chaudhuri, Balarko
Sponsor
Engineering and Physical Sciences Research Council
Publisher Department
Department of Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)