Peter Børre Eriksen

A Large Wind Power System in Almost Island Operation—A Danish Case Study

In Denmark, incorporation of wind power into the power system is increasing whereas power generation from the large conventional power plants is reducing. The common concern has become maintenance of reliable and stable operation of the Danish power system with a large amount of wind power - the large wind power system. At present, maintaining the voltage stability of such a large wind power system relies on strong ac connections to neighboring power systems with sufficient reactive power and voltage control and on control of central power plants in Denmark. This paper presents the results of a stability investigation carried out by the Danish transmission system operator (TSO), Energinet.dk, for the case of almost island operation of the Western Danish wind power system. The main ac lines connecting Western Denmark to the synchronous area of the Union for the Co-ordination of Transmission of Electricity (UCTE) were out of service and the wind power generation was high. The investigation has shown that the reactive power and voltage control of the domestic power plants is essential for maintaining short-term voltage stability of the Western Danish wind power system and becomes even more relevant when ac connections to the strong transmission system of the UCTE are out of service. The results presented in this paper may also be relevant for the operators of the power systems that are in island ac operation and with plans for significant commissioning of wind power - Great Britain, Ireland, Tasmania, etc.

Where the wind blows

The power systems in Denmark, Spain, Ireland, and New Zealand have some of the highest wind penetrations in the world. The management of the different power systems to date, with increasing amounts of wind energy, has been successful. There have been no incidents in which the wind has directly or indirectly been a major factor causing operational problems for the system. However, there are a number of parameters that are being monitored that indicate the need for active management in the near future (and in some cases already today). In this article, we briefly describe the situations in these four countries, giving special emphasis to the market integration of wind power, the use of wind forecasting, and curtailment experience. The final section provides an overview of the main wind forecasting methodologies and challenges.

EcoGrid EU — A prototype for European Smart Grids

The EcoGrid EU is a large-scale demonstration on the Danish island Bornholm. The aim is to demonstrate a Smart Grids solution to operate a power system with more than 50 % renewable energy, including a mix of variable distributed energy resources (i.e. wind, solar, biomass, biogas, and CHP) and energy storage technologies such as heat pumps, district heating and batteries from EVs. Out of the 28 000 electricity customers on Bornholm, 2000 residential consumers will participate with flexible demand. A major part of the participants will be equipped with residential demand response devices with intelligent controllers, enabling customers to respond to real-time prices and allow users to pre-program their automatic demand-response preferences. This paper presents the concept of a real-time market and information architecture, which gives numerous small end-users and local producers of distributed energy new options for offering TSO additional balancing and ancillary services.

Toward a Benchmark test system for the offshore grid in the North Sea

In an effort to protect the environment despite the projected development of the electrical power system, the European community is focusing on a significant increase in the installed wind power capacity up to the level of 300 GW by the year 2030 throughout Europe. Most of the planned installations - about 150 GW - are going to be realized in the offshore sector, a large part of which will be located in the North Sea. Such development will lead to new challenges regarding integration of the bulk offshore wind power into the power systems and will require a comprehensive analysis concerning various aspects such as optimal planning and operation taking into account new concepts, as multi-terminal VSC HVDC. In this paper the establishment of a test system for analysis of the offshore DC grid behavior is proposed taking into account the recent structural and technological concepts on this field as well as the national plans. Hence, in the first step the configuration of the analyzed offshore grid was defined, which includes a mix of AC and DC system. Further, the assumptions for the system parameters will be discussed and the implementation of this test system into a power system simulator as well as some exemplary calculations will be shown.

Selected studies on offshore wind farm cable connections - challenges and experience of the Danish TSO

The Danish power system is characterised by a high share of wind power production. Most of the wind power has so far been distributed onshore and connected to the lower voltage levels. The recent tendency is to group it in large offshore wind farms. The wind farms are often connected directly to the high voltage network via long AC cable lines compensated by shunt reactors. These cable connections impose some additional challenges that should be considered in the planning stage. This paper presents the recent experience of the Danish TSO with long cable connections of wind farms and shows the results of selected simulation studies made of the planned Horns Rev B wind farm connection.

Currents of change

The power systems in Denmark, Portugal, Spain, Ireland, and Germany have some of the highest wind penetrations in the world, as shown in the paper. In this article, the situations of five countries with high wind penetration are briefly presented, with special emphasis given to their future needs with respect to accommodating targeted wind power amounts. The final section provides an overview of offshore grid developments and plans in Europe.

Integrating dispersed generation into the Danish power system - present situation and future prospects

Since the early 80s a huge amount of dispersed generation (DG) has been implemented into the Danish power systems. Today the Danish system has a share of 18.5% electricity consumption produced by wind turbines and 26.5% produced by combined heat and power units (CHP), of which the biggest part is installed in the western part of Denmark. The paper shows the technical measures as well as utilization of market mechanisms applied by the Danish system operator, Energinet.dk, to handle the challenging situation of safe and reliable system operation. Future prospects with respect to the internationally growing wind power capacity and respective need for a market for ancillary services are presented

Managing critical weather conditions in a large-scale wind based European power system — The twenties project

Experience from existing large offshore wind farms show that the geographical concentration of wind power leads to increased wind power variability, and that the response to storm front passages raises new issues: this may lead to a sudden shut down of the wind farm when the wind speed exceeds the cut-off wind speed (typically 25 m/s). Experience has shown that a large offshore wind farm in this way can be shut down from full power to zero power in less than 5 minutes. Thus, in the planned offshore development in the North Sea, several GW of wind power could be shut down within less than one hour as a result of a storm passage, which may impact the security of the whole European electric system. The storm passages will be a threat to the whole system reliability and stability, unless the wind power shut down is carefully coordinated.

Offshore Power System Operation Planning Considering Energy Market Schedules

This paper analyzes selected issues concerning operational strategies for multiterminal dc offshore power systems (OPSs). In the first section, the main challenges regarding the operation of such an OPS are discussed, and a proposal is given for a new observer-based management system (OBMS) used for operation coordination using references from the energy market. In the second section, different operational scenarios for the OPS are investigated in order to present the OBMS application. For this purpose, a test system that considers the expected European future wind power development is introduced. Then, using reference power flows from the hourly market, the influence of the OBMS optimization process on the power flows aiming at minimum deviations from the reference energy market signals will be presented. Some exemplary test simulations are performed and recommendations are given.

European test field: VPP Denmark

The Danish power system is characterized by a high share of wind power production as well as production from local scale combined heat and power units, both called dispersed generation (DG). Today, with respect to market terms, these units work together as virtual power plants. Currently also the technical aspects are further developed. According to the Danish Governmental Strategy renewable energy — mainly wind power — is expected to cover 50% of the Danish electricity consumption by the year 2025. Thus the Danish TSO currently investigates the possibilities of how to successfully reach this target by increased integration of wind power by adapting several sectors exploiting among others the benefits of virtual power plants.