Kriegers flak‐combined grid solution: coordinated cross‐border control of a meshed HVAC/HVDC offshore wind power grid

Abstract

The Kriegers Flak combined grid solution (KF CGS) will interconnect the eastern synchronous area of Denmark and Germany by extending the existing high-voltage alternating current (HVAC) offshore wind farm infrastructure in the Baltic Sea. In contrast to conventional point-to-point interconnectors, the extension creates a meshed submarine grid (MSG) which includes an interconnector and wind farm collectors to the countries using the same equipment. Denmark East as part of the Nordic system and 50 Hertz as part of the synchronous Continental European grid are asynchronous to each other, which makes a frequency transformation necessary. The interconnection will be realised by a high-voltage direct current (HVDC) back-to-back (BtB) converter in voltage source converter technology located at the German end of the interconnector. The BtB and the entire HVAC MSG between Denmark and Germany will be controlled by a so-called master controller for interconnector operation (MIO). The KF CGS will integrate offshore wind power generation, increase the security of supply and enhance integration of regionally produced renewable energy. This study describes the overall infrastructure of the KF CGS and the MIO functions. A model-based evaluation of those shows the behaviour of the HVAC/HVDC MSG in normal operation and in the case of contingencies.

Hierarchical control of offshore wind farm connected by parallel diode‐rectifier‐based HVDC and HVAC links

“…The HVAC link is rated at 150 kV and one‐third (400 MW) of the total wind power, which is connected with the wind farm via an offshore AC transformer. Two independent onshore AC grids are considered, one for the HVAC link and the other for the DR‐HVDC link, similar to the ‘Kriegers flak‐combined grid solution’ project [20, 21].…”

Coordinated voltage and reactive power control of offshore HVAC meshed grid and wind power

“…The Kriegers Flak combined grid solution (KF CGS) is a hybrid‐asset project of Energinet, the transmission system operator (TSO) of Denmark, and 50 Hz transmission, the German TSO, in the Baltic Sea [1]. The KF CGS is an offshore interconnector between the two transmission systems, which utilises the grid‐connections of the large offshore wind power plants (OWPP) [1]. Fig.…”

“…At present, the 150 kV terminal of the KFE platform serves as the point‐of‐settlement between Denmark and Germany with the nominal active power transfer capacity of ±400 MW and the permitted reactive power range of ±40 MVar [1].…”

“…Since Eastern Denmark (the Nordic synchronous area) and Germany (the Continental European synchronous area) are not synchronised, there is an high voltage direct current (HVDC) back‐to‐back (BtB) converter in the German Bentwisch substation. The active and reactive ratings of the BtB converter are 400 MW and 100 MVar, respectively [1].…”

Coordinated Voltage and Reactive Power Control Scheme of HVAC Meshed Offshore Grid of Offshore Wind Power Plant at Kriegers Flak

“…The Kriegers Flak Combined Grid Solution (KF CGS) is a hybrid-asset project of Energinet, the Transmission System Operator (TSO) of Denmark, and 50Hertz Transmission, the German TSO in the Baltic Sea [1]. The term hybrid-asset means that the KF CGS is an offshore interconnector between the two transmission systems, i.e., East Denmark and Germany, which utilizes the grid-connections of the large offshore wind power plants (OWPP) [2]. Fig.…”