project will study the small-signal stability characteristics of 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 tech-nology 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 correspond-ing 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 the small-signal stability
characteristics of such an offshore AC grid based on several aggregated grid-forming
type-4 WPPs/WTs. Some of the corresponding tasks include:
I. Bernal-Pérez, S. C. Añó-Villalba, and R. M. Blasco-Giménez, “Stability
Analysis of HVDC-Diode Rectifier Connected Off-shore Wind Power Plants”, in Proceedings of the IEEE Industrial
Electronics Society 41st Annual Conference (IECON 2015), Yokohama, Japan,
9th–12th Nov. 2015, pp. 4040–4045.
- Reviewing the relevant literature related to
OWPPs connected to HVDC via DRs.
- Developing/deriving nonlinear state-space models
analytically/symbolically for the corresponding subsystems.
- Deriving the corresponding small-signal models by
linearising the state-space models analytically/symbolically.
- Validating the models by means of dynamic simulations
e.g., in Simulink.
- Studying the small-signal stability
characteristics of the studied system through eigenvalue/modal analysis of the validated
Sound mathematical background; Knowledge of electrical power systems and control engineering; Programming skills in MATLAB or similar; Good English speaking and writing skills