Wind turbines in weak grids - constraints and solutions (original) (raw)

Electrical limiting factors for wind energy installations in weak grids

… of Renewable Energy Engineering, 2001

In this paper the electrical limiting factors for installation of wind turbines have been used to determine which types of power quality problems that will dominate when wind turbines are installed in weak grids. The main limiting factors are static voltage level influence, the flicker ...

A Method for the voltage quality assessment in weak grids with wind power generation

A method to assess the impact of wind power generation on weak distribution grids and their local consumers is presented. The method addresses the influence of different factors as the wind turbine technology, the topology of the grid, the wind turbulence and the existence of local loads, that influence the quality of the power delivered to the grid. It is described how this method enables the application of the International Electrotechnical Commission (IEC) standard for the assessment of wind turbines power and voltage quality, currently under development for a single wind turbine, in the feasibility study phase of a wind park.

Contribution of a wind farm to voltage and system stability: results of a measurement campaign

CIRED - Open Access Proceedings Journal, 2017

The rising percentage of inverter-based generation poses new challenges to the grid. Approaching a majority share of inverter-based generation, technical issues in grid operation and the contribution to grid stability have to be analysed. A measurement campaign in a wind farm has been carried out in order to investigate the performance of a wind farm and its interaction with the grid. Due to a long feeder, the short circuit power at the connection point of the wind farm was low. The results are used to recognize technical challenges and to find adequate solutions. The main objective of this paper is an evaluation of the wind farm performance and a comprehensive comparison with requirements of grid codes and guidelines to contribute to reactive power balance and system stability.

Integration of wind farms into weak AC grid

2017

Large wind farms are usually located in remote and offshore areas. High voltage transmission systems that have long transmission distances are used to deliver the wind power to main grids. Weak AC grids have high impedance, low short circuit ratio (SCR) and/or low inertia compared to strong AC grids. The voltage stability of weak AC grids is a challenging issue that needs to be considered. This thesis compares weak and strong AC grids based on the voltage stability analysis. The steady-state characteristics of the weak AC grids are investigated. The power transfer characteristics of the wind farms that are connected to weak AC grids are studied under different voltage control technologies. The mitigation of the voltage recovery problems for weak AC grids is proposed by supplementary voltage control. The main characteristics of a weak AC grid are determined using P-V and V-Q curves. Different short circuit levels of the AC grid are presented with an increase in grid load and active p...

Wind Turbine Operation in Power Systems and Grid Connection Requirements

This paper discusses the impact of wind turbine generation systems operation connected to power systems, and describes the main power quality parameters and requirements on such generations. Furthermore, it deals with the complexities of modeling wind turbine generation systems connected to the power grid, i.e. modeling of electrical, mechanical and aerodynamic components of the wind turbine system, including the active and reactive power control. In order to analyze power quality phenomena related to wind power generation, digital computer simulation is required to solve the complex differential equations. Other important factors analyzed in this paper are grid connection requirements for connecting large wind farms to the power grid, specified by system operators all over Europe. The requirements, which include voltage and frequency stability, the ability to supply reactive power and responses to fault conditions, and active power control and power factor, are compared by the most important European wind power producers. Finally, a methodology for impact determination is proposed.

Grid Compliance and Power Quality Comparison of Wind Plants with Different Turbine and Grid Types

International Journal of Renewable Energy Research, 2018

In this paper, different grid integration and generators used for wind plants is compared by means of quality of the power generated in plant and impact to the power system. Annual energy production and cost of a given wind plant are basis of the comparison. Technical and economical values of different type wind turbine generators are quantitatively evaluated by providing necessary electrical and cost calculations. In technical examination, grid compliance of a 30 MW wind plant with 13 units of asynchronous geared type turbine is investigated by using power system analysis software as per Turkish Grid Code. Steady state conditions of the wind power plant are evaluated by calculating the reactive power capability, load flow and short circuit analysis at first part of the paper. Secondly, low voltage ride through capability, system frequency and voltage test of the wind park are assessed. Similarly, same plant is considered to be equipped with 3.0 MW direct drive type turbines and tec...

Power Control for Wind Turbines in Weak Grids

In many parts of the world and certainly in Europe large areas exist where the wind resources are good or very good and the grid is relatively weak due to a small population. In these areas the capacity of the grid can very often be a limiting factor for the exploitation of the wind resource.

Assessment of Power Quality Characteristics of Wind Farms

2007

In this paper the main parameters to assess the power quality of grid embedded wind farms are presented. International standards to assess and quantify the power quality of grid connected wind turbines exist for some years now, and are here extrapolated to wind farms aggregates when possible being the correspondent methodologies identified in the document. Recently, the grid code requirements posed a novel challenge to this technologic area, particularly since they were issued with national or local objectives and without particular normalized global concerns. The form how the international standards are evolving in order to cope both with the power systems industry local requirements, but also with the global wind turbine manufacturers principles is addressed in the paper.

An overview of wind energy-status 2002

Renewable and Sustainable Energy Reviews, 2002

The paper provides an overview of the historical development of wind energy technology and discusses the current worldwide status of grid-connected as well as stand-alone wind power generation. During the last decade of the twentieth century, grid-connected worldwide wind capacity has doubled approximately every three years. Due to the fast market development, wind turbine technology has experienced an important evolution over time. An overview of the different design approaches is given and issues like power grid integration, economics, environmental impact and special system applications, such as offshore wind energy, are discussed. Due to the complexity of the wind energy technology, however, this paper mainly aims at presenting a brief overview of the relevant wind turbine and wind project issues. Therefore, detailed information to further readings and related organisations is provided. This paper is an updated version of the article 'Wind Energy Technology and Current Status: A Review', published in Renewable and Sustainable Energy Reviews, 4/2000, pp. 315-374. This update was requested by Elsevier due to the large interest in wind power.

Technical and Regulatory Exigencies for Grid Connection of Wind Generation

Wind Farm - Technical Regulations, Potential Estimation and Siting Assessment, 2011

Pollution problems such as the greenhouse effect as well as the high value and volatility of fuel prices have forced and accelerated the development and use of renewable energy sources. In the three last decades, the level of penetration of renewable energy sources has undergone an important growth in several countries, mainly in the USA and Europe, where levels of 20% have been reached. Main technologies of renewable energies include wind, hydraulic, solar (photovoltaic and thermal), biofuels (liquid biodiesel, biomass, biogas), and geothermal energy. Within this great variety of alternative energy sources, wind energy has experienced a fast growth due to several advantages, such as costs, feasibility, abundance of wind resources, maturity of the technology and shorter construction times (Ackermann, 2005). This trend is expected to be increased even more in the near future, sustained mainly by the cost competitiveness of wind power technology and the development of new power electronics technologies, new circuit topologies and control strategies (Guerrero et al., 2010). However, there are some disadvantages for wind energy, as wind generation is uncontrollably variable because of the intermittency of the primary resource, i.e. the wind. Another important disadvantage is that the best places to install a wind farm, due to the certainty and intensities of suitable wind, are located in remote areas. This aspect requires of additional infrastructure to convey the generated power to the demand centres. Unfortunately, in several countries the regulatory aspect does not follow this fast growth of wind possibilities. Many countries do not have specific rules for wind generators and others do not make the necessary operating studies before installing a wind farm (Heier, 2006). Power system operators must consider the availability of these power plants which are not dispatchable and are not accessible all the time. Today, developing countries, such as Argentina, are subjected to an analogous situation with wind energy, having perhaps one of the best sources of such energy around the world. Nowadays, there are several operative wind farms and others in stage of building and planning. Similar to other countries, in Argentina there is a lack of regulatory aspects related to this topic (Labriola, 2007). This chapter thoroughly presents a revision of wind generation, including the following sections. In the first part, a brief history of the wind energy developments is presented. Following, some remarks related to the modern wind energy systems are made. Then, a survey of modern structures of wind turbines is carried out, including towers and foundations, rotor, nacelle with drive train and other equipment, control systems, etc. www.intechopen.com Wind Farm-Technical Regulations, Potential Estimation and Siting Assessment 4 Subsequently, major wind turbine concepts related to fixed and variable speed operation and control modes are described. Eventually, technical and regulatory exigencies for the integration of wind generation into the electrical grid are discussed in detail, including a study of selected countries grid codes. 2. Overview of wind energy technology 2.1 A brief history of wind energy development Since ancient times, man has harnessed the power of the wind for a variety of tasks. Indeed, humans have been using wind energy in their daily work for some 4 000 years. In 1700 B.C., King Hammurabi of Babylon used wind powered scoops to irrigate Mesopotamia. Some other civilizations, like the Persians (500-900 A.D.), used the wind to grind grain into flour, while others used the wind to transport armies and goods across oceans and rivers. Sails revolutionized seafaring, which no longer had to be done with muscle power. More recently, mankind has used the power of the wind to pump water and produce electricity. So the idea of using wind, a natural source, is not new (Rahman, 2003). The discovery of electricity generated using wind power dates back to the end of last century and has encountered many ups and downs in its more than 100 year history. In the beginning, the primary motivation for essentially all the researches on wind power generation was to reinforce the mechanization of agriculture through locally-made electricity generation. Nevertheless, with the electrification of industrialized countries, the role of wind power was drastically reduced, as it could not compete with the fossil fuel-fired power stations. This conventional generation showed to be by far more competitive in providing electric power on a large scale than any other renewable one. Lack of fossil fuels during World War I and soon afterward during World War II created a consciousness of the great dependence on fossil fuels and gave a renewed attention to renewable energies and particularly to wind power. Although this concern did not extend for a long time. The prices for electricity generated via wind power were still not competitive and politically nuclear power gained more attention and hence more research and development funds. It took two oil crises in the 1970s with supply problems and price fluctuations on fossil fuels before wind power once again was placed on the agenda. And they were these issues confronting many countries in the seventies which started a new stage for wind power and motivated the development of a global industry which today is characterized by relatively few but very large wind turbine manufacturers (Vestergaard et al., 2004). Wind turbines that generate electricity today are new and innovative. Their successful history began with a few technical innovations, such as the use of synthetic materials to build rotor blades, and continued with developments in the field of aerodynamics, mechanical/electrical engineering, control technology, and electronics provide the technical basis for wind turbines commonly used today. Since 1980, wind power has been the fastest growing energy technology in the world. 2.2 Modern wind energy systems The beginning of modern wind turbine development was in 1957, marked by the Danish engineer Johannes Juul and his pioneer work at a power utility (SEAS at Gedser coast in the Southern part of Denmark). His R&D effort formed the basis for the design of a modern AC wind turbine-the well-known Gedser machine which was successfully installed in 1959. www.intechopen.com Technical and Regulatory Exigencies for Grid Connection of Wind Generation 5 With its 200kW capacity, the Gedser wind turbine was the largest of its kind in the world at that time and it was in operation for 11 years without maintenance. The robust Gedser wind turbine was a technological innovation as it became the hall mark of modern design of wind turbines with three wings, tip brakes, self-regulating and an asynchronous motor as generator. Foreign engineers named the Gedser wind turbine as 'The Danish Concept' (Chen & Blaabjerg, 2009). Since then, the main aerodynamic concept has been this horizontal axis, three-bladed, upwind wind turbine connected to a three-phase electric grid, although many other different concepts have been developed and tested over the world with dissimilar results. An example of other concepts is the vertical axis wind turbine design by Darrieus, which provides a different mix of design tradeoffs from the conventional horizontal-axis wind turbine. The vertical orientation accepts wind from any direction with no need for adjustments, and the heavy generator and gearbox equipment can rest on the ground instead of on top of the tower (Molina & Mercado 2011). The aim of wind turbine systems development is to continuously increase output power. Since the rated output power of production-type units reached 200 kW various decades ago, by 1999 the average output power of new installations climbed to 600 kW. Today, the manufactured turbines for onshore applications are specified to deliver 2-3 MW output power. In this sense, the world's first wind park with novel "multi-mega power class" 7 MW wind turbines was manufactured by the German wind turbine producer Enercon (11 E-126 units) and put into partial operation in Estinnes, Belgium, in 2010 (to be completed by July 2012). The key objective of this 77 MW pilot project is to introduce a new power class of large-scale wind energy converters (7 MW WECs) into the market with potential to significantly contribute to higher market penetration levels for wind electricity, especially in Europe. On the other hand, sea-based wind farms are likely to mean bigger turbines than on land, with models that produce up to three times power of standard onshore models. Series production of offshore wind turbines can reach to date up to 5 MW or more, being the largest onshore wind turbine presently under development a 10 MW unit. At least four companies are working on the development of this "giant power class" 10 MW turbine for sea-based applications, namely American Superconductors (U.S.), Wind Power (U.K.), Clipper Windpower (U.K.) and Sway (Norway). Even more, it is likely that in the near future, power rating of wind turbines will increase further, especially for large-scale offshore floating wind turbine applications.