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Delegates are invited to meet and discuss with the poster presenters in this topic directly after the session 'Storage & grid integration' taking place on Wednesday, 12 March 2014 at 16:30 -18:00. The meet-the-authors will take place in the poster area.

Andreas Grøsvik Laukhamar Ramboll, Denmark
Co-authors:
Andreas Grøsvik Laukhamar (1) F P Lorenzo Zeni (2) Poul Ejnar Sørensen (3)
(1) Ramboll, Copenhagen S, Denmark (2) DONG Energy Wind Power and DTU Wind Energy, Copenhagen, Denmark (3) DTU Wind Energy, Roskilde, Denmark

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Andreas Grøsvik Laukhamar was born in 1988 and holds a BEng degree in energy technology from Bergen University College (Norway) and an MSc degree in wind energy from the Technical University of Denmark. His MSc thesis focused on control of offshore wind power plant with HVDC grid connection, which was carried out in cooperation with DONG Energy Wind Power and DTU Wind Energy. He is currently working in the Automation & Electrical Systems department for Ramboll Denmark.

Abstract

Alternatives for primary frequency control contribution from wind power plants connected to VSC-HVDC intertie

Introduction

It is widely recognized that the future wind power development in the Nordic region will to a large extent be offshore. The most promising technology for connection of remote wind power plants is the voltage source converter based high voltage direct current (VSC-HVDC). This paper addresses the control of VSC-HVDC and an offshore wind power plant connected thereto, with the objective of providing primary frequency support to the onshore AC power systems interfacing an HVDC intertie. A new method for communication and control that facilitates wind power plant participation in the primary frequency control through an HVDC intertie is proposed.

Approach

The simulation results are provided by a simplified model in Matlab Simulink of a three-node HVDC system interconnecting two onshore AC power systems and an offshore wind farm. The simulations are assuming steady-state incoming wind speeds. Moreover, fast electrical (e.g. converter) dynamics are neglected. The model is, however, sufficiently detailed to dynamically describe state variables such as the onshore AC frequencies, DC node voltages, DC currents, and the wind turbine’s mechanical and electrical power extraction, which allows for acceptable accuracy in terms of frequency control studies.

Main body of abstract

The DC connection decouples the three frequencies of the two onshore AC power systems and the power collection grid in the wind farm. Therefore, a frequency disturbance in one of the AC power systems will neither be supported by speed governors in the other AC power system nor by frequency control of the wind farm. A mutual frequency support can, however, be achieved by means of communication links, coordination of onshore AC frequencies and DC voltages or a combination of these two methods. This paper investigates the former and latter method, where the latter is implemented in the control of the onshore converters. It is discovered that a coordinated DC voltage and AC frequency droop control leads to a high level of sharing of primary reserves between the onshore AC power systems and enables the wind farm to contribute to the frequency control. The implications of this mutual frequency support from a power system perspective are discussed in the paper. From a system perspective, the simulation results provided by the three-node HVDC system show that the deviation between the different communication and control schemes is marginal with respect to the total power supplied to the disturbed onshore AC power systems.

Conclusion

This paper presents different methods on how offshore wind power plants, as well as different synchronous areas can contribute to the short-term active power balancing demand of the onshore AC power systems interfacing the HVDC intertie. The solutions are discussed looking at their effect on the power system balancing and compared based on control and communication needs.


Learning objectives
Besides describing different methods on how offshore wind power plants with HVDC interconnections can, similar to conventional power plants, participate in the primary frequency control, this paper also deals with power flow control and power flow demand in very simple multi-terminal HVDC (MTDC) grids, which are more likely to be implemented in coming years with respect to extensive meshed DC grids.