The electric power system is facing several challenges; from large-scale renewable power generation, increasing demand of long-distance power transfer between grids due to trading in electricity markets, and difficulties in building new transmission lines for system reinforcement. High Voltage Direct Current transmission system with Multi-terminal based on Voltage Source Converter (MT VSC-HVDC) is considered as an effective way to handle these challenges, thanks to its unique advantages (e.g., highly flexible power flow and voltage control, ability for power reversal control, independent control of active and real power, etc.). When a MT VSC-HVDC is embedded into an ac grid, it offers additional controllabilities to power system operation in effective damping power oscillation, bus voltage support, optimizing power flow, and so on. Thus the electric power system can be operated in a more stable and optimized way.
The overall aim of this project is to investigate the potential benefits in operation and planning of electric power systems by utilizing embedded MT VSC-HVDC. The following aspects will be treated in the project, which are to:
- Understand the technical benefits of operation of the transmission system with the MT VSC-HVDC link, such as the benefits from South West Link.
- Propose optimal operation strategies for the operation of transmission system with multi-terminal VSC-HVDC links. An expected outcome from the project would include proposing approaches to support the TSO (Transmission System Operator) to utilize its resources in the best way when maintaining system integrity and reliability.
The project consists of the following main tasks:
1. Formulation of optimized operation strategies of mixed ac/dc system based on a mixed ac/dc optimal power flow (OPF) framework:
- Identification and development of appropriate steady-state model of multi-terminal VSC-HVDC system.
- Development of a mixed ac/dc OPF model
- Using the model to analyze operation strategies with different TSOs objectives, including, e.g., minimum power losses, minimum operation cost, congestion management.
2. Analysis of dynamic performance of the ac/dc system and their interactions:
- Development of dynamic model of MT VSC-HVDC which is suitable for the dynamic study at the system level.
- Dynamic studies of mixed ac and dc system and identification of interactions between ac and dc systems such as voltage and transient stability of the system due to large disturbances from both ac and dc side.
- Suggestions of improving the system stability and operation keeping desired level of reliability.
Feng Wang (Ph.D. student), Lina Bertling Tjernberg (Examiner and supervisor), Tuan Le (Assistant supervisor), Anders Mannikoff (Assistant supervisor, SP), Anders Bergman (Assistant supervisor, SP)