Small Signal Stability Analysis of Power System with High Penetration of Converter Interfaced Generation

Professor Liu, Tao   (Principal Investigator (PI))

42

2022-01-01

440725

Small Signal Stability Analysis of Power System with High Penetration of Converter Interfaced Generation

dissipativity theory, dynamic networks, power systems, small signal stability

Power System

Engineering (E)

27206021

Early Career Scheme (ECS)

2021

On-going

1 Stability analysis with slow system dynamics. This objective is aimed to answer how the slow dynamics, such as the electromechanical dynamics of synchronous generators (SGs) and power controller dynamics of converter interfaced generators (CIGs), interact with each other in a network form to influence the small signal stability of power systems, which is closely related the slow-interaction converter-driven stability issues discussed in the new IEEE Power System Dynamic Performance Committee Task Force Report PES-TR77. In this objective, the whole system will be treated as a dynamic network with dynamic nodes and static links. A new system model, which only considers slow dynamics, will be established in the current-balance form of the network equations, where each device connected to a bus will be modelled as a dynamic subsystem and each transmission line as a static one. The advantage of this model is that all subsystems will be modularised with current and voltage as their input-output (IO) pairs, which are naturally linked to some well-established IO properties. Both the time-domain and frequency-domain stability analysis will be carried out from a network science point of view. Passive/dissipative properties and phase properties of each subsystem will be exploited and combined with the power network to develop new stability criteria under the framework of dissipativity theory and the newly developed small phase theory for time-domain and frequency-domain analysis, respectively. 2 Stability analysis with fast system dynamics. This objective is aimed to answer how the fast dynamics, such as the electromagnetic dynamics of SGs, converter dynamics and inner loop (voltage/current) control dynamics of CIGs, interact with each other in a network form to influence the small signal stability of power systems, which is closely related the fast-interaction converter-driven stability issues discussed in the Task Force Report PES-TR77. Under this circumstance, the dynamics of transmission lines have to be properly considered in the system model, which makes the system become a dynamic network with both dynamic nodes and links. A system model that only considers the fast dynamics will be built also using the current-balance form of the network equations, where each bus and transmission line will be modelled as subsystems with voltage and current dynamics, respectively. Again, all subsystems will be modularised with current and voltage as their IO pairs. By exploiting the related local IO properties of each subsystem and the power network, the time-domain and frequency-domain stability analysis will be carried out under the framework of dissipativity theory and small phase theory, respectively. 3 Stability analysis with both slow and fast system dynamics. Objective 1 and 2 study how the local dynamics work in a network form to influence the system stability by only considering the slow and fast dynamics, respectively. Therefore, stability conditions developed in these two objectives may only be necessary conditions for the whole system with both slow and fast dynamics. This objective is aimed to establish stability criteria for the whole system by answering the question how the interactions between slow and fast dynamics influence the system stability. It is closely related the converter-driven stability issues discussed in the Task Force Report PES-TR77. The system model built in Objective 2 will be augmented with the slow dynamics and used to describe the whole system with both slow and fast dynamics. The IO properties of slow and fast dynamics established in Object 1 and 2, respectively, will be used to find IO properties of the corresponding device. These properties together with those of the power network will be further used to infer the stability of the whole system by using dissipativity theory and small phase theory for time-domain and frequency-domain analysis, respectively. Moreover, singular perturbation theory and network science ideas will be integrated to build some reduced-order system model to balance the trade-off between the accuracy of the model and computation burden for stability analysis. 4 Simulation study via RTDS, DSP, and MATLAB. This objective is aimed to test correctness and effectiveness of the results obtained in the first three objectives by detailed simulation study. The IEEE standard test systems as well as some virtual synthetic power systems will be used. Nonlinear test systems with detailed slow and fast dynamics will be built by using Real Time Digital Simulator (RTDS) and the Triphase Distributed Power System (DPS). The corresponding linear system models established in Objective 1, 2 and 3 will be built by using MATLAB/Simulink. Comparison between solutions of the detailed nonlinear system model and different linear models as well as stability properties obtained by theoretical analysis and simulation study will be carried out under small signal disturbances. The simulation study will also be used to test the penetration limit of converter interfaced generation under different system models and discover new phenomena that are not studied in the theoretical analysis.