Power System for Offshore Wind Power

Transcription

1 Wind-Kraft Journal. German Offshore. 1. Auflage S. 2-3 und Wind-Kraft Journal. German Offshore. 5. Auflage S Outlook in the future of German North Sea 2020 ower System for Offshore Wind ower Boris Valov stitut für Solare Energieversorgungstechnik (ISET e.v.), Kassel, Germany reamble The future of wind energy production belongs to Multi MW wind-powered devices and to large offshore wind farms. However, if all planned wind farms in the North Sea come into operation, the task of wind power transportation from offshore to continent and its optimal distribution between different connection points of the German ower Transmission System will play a particular important role. ISET s developed concept of the High Voltage ower System in the North Sea shows a possible way for future large-scale integration of offshore wind farms into the German Transmission System and the UCTE-network. This proposed concept reduces the total costs of the offshore energy system and the impairment of protected areas in the North Sea. The technical feasibility of ISET s concept has been confirmed by extensive network computations. It is oriented towards the expected offshore wind power in the year 2020 and beyond. Legend: 1 - Offshore Bürger Windpark Butendiek; 2 - Dan Tysk; 3 - Sandbank 24; 4 - Nördlicher Grund; 5 - Amrumbank West; 6 - Nordsee Ost; 7 - Offshore North Sea Windpower; 8 - Borkum West; 9 - Borkum Riffgrund; 10 - Borkum Riffgrund West; A Uthland; B - Weiße Bank; C - Vento Tec Nord I; D - Offshore Windpark Austerngrund; E - Offshore-Windpark Deutsche Bucht; F - Vento Tec Nord II; G - Global Tech I; H - Hochsee Windpark Nordsee; I - Hochsee Windpark Hedreiht; K - BARD Offshore I; L - Gode Wind; M - Borkum Riffgat; O - Offshore Windpark Nordergründe; Meerwind. Fig. 1: ISET s concept for the German offshore High Voltage ower System / ISET s Konzept des Hochspannungs-Energiesystem in Nordsee 1

2 roblems The grid connection points (GC) of all wind farms to the German ower Transmission System are defined in [1]. The internet page [2] always presents the actual state. general it is planned to arrange all Offshore wind farms to some clusters and to connect them via separate sea cable traces to the German ower Transmission System. But investigations carried out by ISET [3] shown that in this concept: - loading of GSs of German ower Transmission System will not be balanced (Fig. 2) and - number of sea platforms (Table 1) and equipments of internal infrastructure are superfluous. Furthermore it can also be expected that: - flexibility of operating control of German ower Transmission System and of wind park clusters on sea is limited, - reliability of systems with several in series connected components [2] will be low, - possibility of support among wind farms in extreme case, black start etc. is limited. Fig. 2: ower ratio Leistungsverhältnisse K = S / the GCs / k Ein k K = S / an den Anschlusspunkten 2

3 roposal for Approach Fig. 2 shows an example the ratios of short circuit power S k (380 kv ) to total feed-in power at the GCs K = Sk (380 kv ) / = 40GW / for a nominal voltage of 380 kv. As the real values of short circuit power S k (380 kv ) are less than 40 GW [4], the effective ratios are even lower. Thereby it should be considered that the higher this ratio the lower the negative influence of wind farms on the grid power quality (voltage increases, flicker etc.). From Fig. 2 follows that at the GCs Diele and Boexlund the feed-in power is nearly to the short circuit power. The ratios K = 2, 85 for Diele and K = 4, 79 for Boexlund in year 2020 may not be high enough to ensure high grid stability and low influences of wind power on the grid. The above-named problems could successfully be solved by laying extended cross connections between the clusters. However until 2010 instead of numerous separate sea cable traces from wind farms in cluster III to continent only one trace L-NK4 should be laid. During the second extension phase ( ) the cross connection between wind farms Gode Wind (L) and Meerwind () should be laid in order to achieve a possibility of load balancing between GC2 and GC4 and to spare grid reinforcement of these GCs. Within the third extension phase (after 2015) the High Voltage ower System at sea is reinforced with three additional cross connections G-B-4, B-A and B-5. Consequently the named extreme difference of load at GCs can be balanced: the hardly loaded GC Conneforde and lower loaded GC Brunsbüttel now can take the excessive wind energy from the highly loaded GCs Diele and Boexlund. this concept the possibilities for support between wind farms concerning black start, emergency power supply, data transfer and cost reduction in fault cases also more flexibility for operation of High Voltage ower System are avaible. Moreover the necessary number of sea platforms could be reduced too (Table 1). Table 1 gives an overview of the forecasted trend for increase of wind power and the necessary numbers of sea platforms in two concepts of High Voltage ower System at sea. Time horizon Zeithorizont Wind turbine generat ors Windkraftanlage n Wind farms Windparks Total number of Gesamtzahl Sea platforms with Seeplattformen Separate interconnect ion of wind farms Separate Anbindung der Windparks Clusters with cross connection Cluster mit Querverbindu ng GW , , ,5 3

4 Table 1: Trend of development of wind farms at North Sea of Germany / Tabelle 1: Entwicklungstrend von Windparks auf der deutschen Nordsee Each superfluous sea platform means additional cost and prolongation of construction time of wind farms. Through balancing and attenuation of intensity of power fluctuations due to changes of wind speed over the large sea area the developed concept opens possibility for voltage stabilisation, too. Economic efficiency and technical feasibility of the developed concept have been demonstrated due to relevant calculations. The calculated estimated values of investments and power losses are given in the diagrams of Fig. 3 und 4 [5]. The extended cable cost of cross connection at sea can be lower than the additional costs of necessary grid reinforcements in the German Transmission System. Fig. 3: The calculated estimated values of investments (1 billion=10 9 ) Fig. 4: The calculated estimated values of power losses As a further positive social aspect of the proposed concept an increased acceptance particularly by the local population can be expected due to only single instead of multiple encroachments on flora and fauna in the area of national nature parks. Conclusions The developed Offshore High Voltage ower System presents an extension of today s trend of planning the energy transportation at the North Sea of Germany. A completion of the system with cross connection opens a lot of possibilities for enhancement of stability, feasibility and flexibility of system operation as well as for reduction of investments. Acknowledgement This concept has been developed in ISET within the project tegration großer Offshore- Windparks in elektrische Versorgungssysteme FKZ Nr C funded by Forschungszentrum Juelich GmbH - TJ 4

5 References [1] Dena-Studie. Energiewirtschaftliche lanung für die Netzintegration von Windenergie in Deutschland an Land und Offshore bis zum Jahr Deutsche Energie-Agentur GmbH (dena). Berlin, Mai [2] Bundesamt für Seeschifffahrt und Hydrographie (BSH). CONTIS-formationssystem. Offshore-Windparks (ilotgebiete). CONTIS_maps/NorthSeaOffshoreWindfarmsilotrojects.pdf [3] German roject tegration großer Offshore-Windparks in elektrische Versorgungssysteme FKZ Nr C [4] EN (VDE 0532) Leistungstransformatoren. Teil 5: Kurzschlussfestigkeit. [5] Valov B., Lange B., Rohrig K., Heier S., Bock C. 25 GW Offshore - Windkraftleistung benötigt ein starkes Energieübertragungssystem auf der Nordsee. Wind-Kraft Journal. 2008, H. 1, S Kontaktperson Dr./OAK Moskau Boris Valov, stitut fuer Solare Energieversorgungstechnik ISET e.v., Koenigstor 59, D Kassel, Germany, hone : , Fax: , mailto: [email protected] 5