Onshore and Offshore Transmission Expansion in the European Grid for Large Scale Wind Integration in the North Sea

摘要

The development and implementation of an offshore grid will have wide consequences to the onshore grid and its transmission expansion planning (TEP). A combined TEP for both on- and offshore is strongly necessary for large scale integration of wind energy in Northern Europe. Two TEP methodologies are presented in this paper: The Net-Op tool and the EMPS Investment Analysis Algorithm: i) Net-Op is a transmission expansion planning tool for power systems with large shares of renewable energy sources like e.g. wind. The offshore grid expansion optimization is formulated as a mixed-integer problem and Net-Op explicitly considers the benefit of transmission capacity between different price areas and the value of connecting offshore wind power to the grid versus the investment cost of power cables and auxiliary equipment. The methodology assumes that the locations and installed capacities of the wind farms are known, and finds a solution for the least-cost offshore grid structure and cable dimensioning, taking into account wind power and power demand variations, possible connection points to the shore and an aggregated description of the onshore power system. ii) EMPS (EFI's Multi-area Power market Simulator) is an electricity market model developed by SINTEF. It carries out a system optimization on basis of specified costs and capacities for production, demand and transmission for each area. Hydro power can be represented in detail. The optimization problem is solved by using a combination of stochastic dynamic programming for calculating strategies for hydro power, and linear programming for simulating each weeks and stochastic scenario. A functionality for carrying out investment-analysis has been developed. New capacities are phased in iteratively on basis of simulated prices in the previous simulation. For a transmission line, additional capacity is profitable if the price-differences between two connected areas are sufficiently large. The aim of this paper is to demonstrate how both these tools can be used for TEP in a case study of the North Sea region.