The development of a multi-terminal (MT) high voltage DC (HVDC) grid based on voltage source converter (VSC) technology has been envisaged as a key development for harnessing the vast offshore wind production potential of the North Seas. In this paper, market integration of a centrally dispatched MT HVDC Grid based on droop control is examined. Particular emphasis is given on the management of onshore imbalance volumes due to offshore wind power forecast errors. The economic importance of the control choices of the operator of such an active transmission grid is highlighted, and regulatory implications are briefly discussed. The main contribution of the paper is the coherent development of a droop-controlled MT HVDC grid scheme that integrates optimal power flow (OPF) dispatch, and imbalance volume management.Index Terms-Control strategy, imbalance settlement, implicit auctions, load flow control, market integration, multi-terminal high voltage DC (HVDC) transmission, offshore wind farms, voltage source converters (VSC).

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Wind power has experienced an enormous growth in the last years, not only in its installed capacity, but also in its great technological development. Today, wind power forecasts are necessary for the large-scale integration of wind turbines into the electrical grid due to this intermittency nature. Forecasting tools are also necessary to limit the use of spinning reserves, increasing even more the environmental benefits of this kind of energy. Wind power forecasts are necessary to participate in the electricity markets too. The work developed in this thesis is devoted to improve the performance of statistical models used in actual wind energy forecasting tools. To do so, we have begun from a particular case-Sipreolico. The main contributions of this thesis are the following: first, we estimate the parameters of the models by maximum likelihood through the Kalman filter and smoother instead of imposing them ad-hoc. This parameter estimation allows us to capture the operating conditions or characteristics of each wind farm to some degree and obtain significantly lower root mean square error (RMSE). Second, we propose new specifications for the state equation, including multivariate models, to capture, through the correlation of the elements of the state vector, the effect caused by omitted inputs. The relationship between wind and generated power is highly nonlinear and timevarying, so it is very common to use alternative models based on different assumptions about the variables involved. We proposed a novel forecast combination procedure through multivariate dimension reduction techniques. We check the strategies shown throughout this thesis in the Sotavento wind farm. At last, all the work developed is included as part of a real time forecasting tool with minimal expert intervention.

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