This project will study and compare two different control strategies for offshore wind power plants connected to HVDC via diode rectifiers.
Network infrastructure connecting offshore wind power plants
(offshore WPPs, OWPPs) with onshore grids is needed to fully exploit Europe’s
offshore wind resources. High-voltage direct current (HVDC) is seen as the main
technology as distance from shore increases, but the high cost of power
converter technology is, among others, hindering the deployment of such
networks. In quest of lowering the costs of offshore wind energy, new control
strategies taking advantage of the type-4 (full-converter) wind turbines’
(WTs’) own power converters have been recently shown to enable the use of diode
rectifiers (DRs), instead of voltage source converters (VSCs), for connecting
OWPPs to HVDC networks.
Until now, HVDC-connected OWPPs have relied on the HVDC
offshore voltage source converters (VSCs) to form the offshore AC grids i.e., control
their voltage magnitude and frequency. This has enabled the use of WT and WPP
control schemes similar to those utilised onshore. DRs offer reduced costs and
increased reliability, but they lack the control capabilities of VSCs, and
their use relies on delegating the corresponding control functions to the WT
front-end VSCs. This requires fundamentally different WT and WPP control
schemes, changing their control philosophy from grid-following units to
grid-forming units. This project will study and compare two different
strategies for controlling such grid-forming type-4 WPPs/WTs. Some of the
corresponding tasks include:
- Reviewing the relevant literature related to
OWPPs connected to HVDC via DRs.
- Modelling the studied system in a dynamic simulation
tool e.g., Simulink.
- Implementing the two different control
strategies for the model.
Comparing the performance and robustness of the
control strategies for different operating conditions, system parameters and
L. Yu, R. Li and L. Xu, "Distributed PLL-based Control of Offshore Wind Turbine Connected with Diode-Rectifier based HVDC Systems", IEEE Transactions on Power Delivery
, Advance online publication.
Sound background in wind turbine/plant control; Knowledge of electrical power systems and control engineering; Command of Simulink Power Systems or similar; Good English speaking and writing skills