The Enhance Power Flow Control Capability (EPFCC) project will investigate the operating performance of existing Quadrature Boosters and use the resulting knowledge to better understand if new control strategies will allow more effective power flow control and help manage future network constraints. It will also explore how innovative solutions in phase shift transformer designs could deliver transportable modular solutions sufficiently flexible to cope with future demand and the power flow changes during the energy transition. It will also investigate how numerous suitably sized and optimally placed power flow devices can be effectively coordinated to maximise the power transfer capabilities of critical transmission boundaries, whilst minimising risk and ensuring resilience and reliability.
Benefits
The project investigates solutions to enable a wider range of tap moving in post fault action, a coordinated control of multiple QBs, and strategic sizing and location of the power flow control devices to fully utilise the capability of these QB devices and enhance power flow control capability in the network. It’ll bring significant benefits on reduced constraint management cost and increased boundary transfer capability of the transmission network, which could delay or reduce the need for new builds and bring cost savings to consumers.
Learnings
Outcomes
The following outcomes have been achieved so far:
- A technical report assessing QB techniques to control power flow has been delivered. This report detailed the factors impacting QB power flow control such as location, grid topology and QB impedance. Core saturation at extreme tap positions and the problems caused by slow tap-movement control have been identified as major operational constraints.
- A literature review report on coordinated control of multiple QBs has been completed. This literature review provides a foundation for future research on the coordinated control of QBs. Research included:
- Different methods to determine total boundary transfer capacity.
- An Optimal power flow model for the calculation of boundary transmission capacity has been reviewed.
- Key algorithms for solving the Optimal Power Flow problem are highlighted, including probabilistic simulation methods, metaheuristic optimisation methods, and linear methods.
- Improvements to existing QB tap operation guidelines were identified. Ultimately, this should enhance post-fault power flow control capability by allowing more bucking of power flow on overloaded lines.
- Results prove coordinated operation of multiple QBs will enhance power flow control capability and increase boundary transfer under severe contingencies in Future Energy Scenarios. A preventive-corrective security-constrained control algorithm has been proposed.
- A finite element model has been constructed and verified to study the saturation of QBs under bucking and boosting modes. The model has been proven to increase accuracies in determining the maximum flux density in both QB shunt and series units.
- A reduced circuit equivalence model was derived and used to assess the varying flux densities in the core leg and yoke under different operational conditions.
- A QB structure optimisation framework is proposed, which considers the relationships between the core diameter, QB power rating, operational flux densities in the leg and yoke, the structural parameters of the QB and their impacts on hot spot temperature rise and the insulation requirement.
Recommendations for further work
None at this stage.
Lessons Learnt
PSTs are essential for the reliable and resilient operation of an AC dominated meshed power system. The transition to a net zero electricity dominated future, will require numerous power flow control devices, each capable of manipulating hundreds of MVA especially when AC or DC feeder outages occur. The importance of power flow control on the GB grid will increase as more renewables are connected in the North and fossil fuelled generation declines in the South-East. The challenges are compounded by High Voltage Direct Current (HVDC) interconnectors to our European neighbours, offshore wind farms, and HVDC links or bootstraps between Scotland and England.
Dissemination
- A paper has been accepted based on the work of magnetic field analysis of QB.
- C. Chi, S. Shen, Z. D. Wang, P. Crossley, X. Ding. “Finite element Modelling of core saturation phenomena in phase shifting transformers: reduced circuit equivalence,” IEEE International Conference on High Voltage Engineering and Application (ICHVE), August 2024.
- Research outcomes related to magnetic field analysis of QBs will be disseminated in the 16th University High Voltage Network Colloquium (UHVNet) at University of Exeter on 9th and 10th May.
