Terje Gjengedal

The Effect of Large-Scale Wind Power on System Balancing in Northern Europe

Summary form only given. The on-going development in the electrical system and the transition from a mainly thermal dominated power system into a system, widely affected by renewable production resources, requires a revision of future balancing strategies facilitating the secure integration of renewable energy. Especially the increasing wind power penetration with its uncertain production on all time scales will largely affect the system operation, requiring a higher flexibility and thus more reserve capacity providing balancing energy.

Impact of large scale wind integration on power system balancing

With an increasing wind power penetration, more generation intermittency will be added to the power system, requiring higher flexibility and thus more regulating reserves. Based on high resolution numerical weather prediction models and wind speed measurements, the actual and the forecasted wind power production is simulated for five scenarios covering the years 2010, 2015 and 2020. These scenarios are taken as an input to an integrated northern European market model, analyzing the procurement of regulating reserves and their activation. Further on, the possible benefit of integrating the northern European regulating power markets for handling the intermittent production is investigated.

Design, operation and availability analysis of a multi-terminal HVDC grid - A case study of a possible Offshore Grid in the Norwegian Sea

Multi-terminal HVDC subsea cable grids have the ability to integrate offshore wind power and petroleum installations with the main land, as well as transferring energy in parallel with the onshore AC grid. Such grids have presumably lower investment costs than radial cables to each installation. It is shown in this paper that the reliability is higher as well. The operation of a multi-terminal HVDC grid calls for new methods for control and fault clearing. A case study with two land terminals and three offshore terminals is presented in this paper. The work is a part of Statnetts R&D project “Offshore Grid - design and operation.”

Options for large scale integration of wind power

This article demonstrates options for large scale integration of wind power. Two cases are considered. One is considering a connection of a large wind farm to fairly week regional grid, and the other is considering the power system balancing of large magnitudes of wind power. It is demonstrated that local control actions enables quite large wind farms to be operated at fairly week grids, and that marked based balancing copes well with large magnitudes of wind power.

Sequential timestep unit commitment

This paper presents a method for solving the unit commitment problem sequentially in time. By decomposing the problem in time, each timestep is solved individually using a free market model of the power system. The corresponding market clearing handles both energy demand, primary reserve demand and secondary reserve demand, and is performed using an extended economic dispatch algorithm that determines both the unit dispatch decisions and the unit commitment decisions. The paper focuses on describing the formulation and the solution of the problem, and includes explicit formulations of both the unit dispatch decision and the unit commitment decision as functions of the system prices. Comparisons with results provided by other methods show that the method is very competitive.

Ant colony optimization and analysis of time step resolution in transmission expansion computations for wind power integration

This paper investigates the necessary time step resolution in a transmission expansion planning algorithm based on ant colony optimization. A maximal and efficient wind power integration is the main motivation for the grid expansion, which requires a planning tool dealing with wind energy fluctuations. For the analysis a power system model for the Nordic area is used, including a wind power production scenario for 2030. A comparison of simulation results with different time step resolutions, including average and peak values for wind power production, is presented in this paper.

Improved method for integrating renewable energy sources into the power system of Northern Europe: Transmission expansion planning for wind power integration

This paper presents an improved algorithm for transmission expansion planning based on ant colony optimization, which is a heuristic optimization method showing several advantages compared to traditional methods. A grid model for the Nordic Area, Great Britain and a combination of both are used to show the performance of the optimization process. The focus of the work is to develop a tool for transmission expansion, especially regarding the new challenge of integrating renewable energy sources, especially large on- and offshore wind power. The results show that the algorithm is capable to deliver good solutions for relatively large systems up to several hundred buses, lines and generators.

Opportunities for Hydrogen Storage in connection with Stochastic Distributed Generation

This paper gives an overview of the opportunities that exist for the combination of stochastic power generation and hydrogen production, storage and end-use. It is described how hydrogen storage can be applied in both isolated and grid-connected systems, and how the produced hydrogen can be utilized for stationary energy supply and as a fuel for transportation. The paper discusses the benefits and limitations of the different hydrogen storage applications, and emphasizes the need for stochastic studies both for long-term planning and operation planning. A simulation case study of using excess wind power in a weak grid to produce hydrogen for vehicles has been presented. It is shown that the penetration of wind power can be significantly increased by introducing electrolytic hydrogen production as a controllable load

Modeling the northern European electricity market

In this paper we present the methodology of a market model simulating the European day-ahead, intraday and real-time power markets. In a first step the day ahead market is modeled as a common European market including a simultaneous reserve procurement for northern Europe. Secondly, the intra-day market is simulated using the day ahead market results as an input. To reflect the current state of the system, the intraday market is restricted to the Central Western European (CWE) and the Nordic area. The scheduled day ahead dispatch is successively adjusted based on a continues revision of load and wind power forecasts. In a last step, the balancing market is modeled as a real time power dispatch on the basis of intraday market results and remaining deviations. Transfer capacities, start-up costs, technical constraints of thermal power plants in combination with a high resolution wind power model are used as a data basis for the model.

Application of adjustable speed hydro (ASH) machines in the Norwegian power system

The main subject in this paper is the adjustable speed hydro (ASH) machine concept and its potential applications. The ASH machine gives a contribution to increased efficiency in the penstock/turbine system as well as an improved flexibility with respect to the electrical system. By means of its quick response to network events, the ASH machine is able to obtain an increased stability margin and thereby a more safe operation of the power system. On the other hand, this represents new opportunities for the power producer as well as for the system operator in utilising the transmission network even better. The paper has shown that transmission lines appearing as bottlenecks with respect to power demand may increase their transfer capacity as ASH machines are introduced in the network. In turn, this may lead to a postponement of high investment costs for new overhead lines. Furthermore, the paper has given a quantification of how much the power export out of an example region can be increased due to introduction of ASH machines.