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Abstract

The content

Introduction

Interest in the problems of renewable energy sources (RES) is associated with a reduction in fossil fuel reserves.

At present, reserves of fossil fuels are being depleted and its use in increasing the volume leads to environmental pollution. Allocation of carbon dioxide, which leads to global warming. In the future, will inevitably reduce consumption of fossil fuels and replacing it with other energy sources. The use of renewable energy more attractive, since it does not violate the natural balance of energy received our planet. RES are solar radiation, wind energy, the energy of rivers, tides and ocean waves, the energy contained in biomass and organic waste. For Ukraine, promising is the use of wind energy resources.

Wind energy known to mankind at least 2,000 years in the last 10 15 years, rapidly expanding its use to produce electricity. To date, the world's installed wind power more than 20,000 units with a total capacity of more than 16 million kW[5]. Modern wind turbines (windmills) have units of power from kilowatts to several megawatts and can cost-effectively with a high degree of reliability to convert wind energy. Wind turbines can be used for various purposes, ranging from charging batteries (AB) and supply of various objects (houses, farms, etc.) to the electricity supply network in the central power.

Wind energy for a long time regarded as a clean inexhaustible energy source. Before the wind energy can bring significant benefits, must be solved many problems, chief among which are: high cost of wind power plants, their ability to operate reliably in an automatic mode for many years and to ensure uninterrupted power supply. Therefore, today the most important task facing the wind energy is to reduce the unit cost of electrical turbines. One way to reduce costs is to use a more efficient wind turbine electrical structures.

You also need to address issues of reactive power control of wind turbines and study modes of EPS when connecting to them large amounts of wind turbines.

1. Topicality

Increasing the share of wind turbines in the total power of the EPS leads to a change in modes of operation of the electrical system. Under certain conditions, including wind turbines with a decrease in power due to lack of wind, there may be a violation of the stability of the system. Therefore, research is needed that will identify areas of stability and measures necessary to ensure stability, improve the efficiency of wind farms, activities for optimization of wind farm.

2. The purpose and objectives of the study

The purpose of the work - the development of measures to ensure the specified modes of operation of electric power systems with a large share of the total capacity of wind power (control of reactive power, sustaining EPS)

3. Objectives of the study

The main objectives of the study are

  1. Determination of optimal operating conditions with the wind farm synchronous generators with permanent magnets.
  2. Creation of a mathematical model of a synchronous generator with permanent magnets for the stability studies of EPS.
  3. Definitions of optimal reactive power.
  4. Creation of a mathematical model of EPS with TPP and wind farm.

4. Analysis of advantages and disadvantages of modern types of wind turbines

Modern wind turbines – a set of interconnected equipment and facilities that convert wind energy into mechanical energy of a rotating wind turbine, and then into electrical energy.

The main features of the classification structures of wind turbines are:

Currently used in two basic designs wind turbines (Fig. 1): horizontal-axis and vertical-axis wind turbines. Both types of wind turbines are approximately equal efficiency, but the most widely used wind generators of the first type. Capacity of wind turbines can be from several hundred watts to several megawatts.

Figure 1 - The main types of wind turbines=

Figure 1 - The main types of wind turbines

In structure of both types of wind turbine includes the following main parts:

As this system is considered a promising convert mechanical energy into electrical energy of alternating current, based on the scheme shown in Figure 2, "a synchronous generator with permanent magnets - an active rectifier - inverter voltage." SGEE this type implements a full range of options required for the generation of systems of autonomous objects.

Figure 2 – Simplified diagram of electric wind turbines with a unit SGSM=

Figure 2 – Simplified diagram of electric wind turbines with a unit SGSM

Figure 3 shows the mode of start-up wind turbines with permanent magnets at idle resulting in a simplified mathematical model of the changing weather conditions (wind power).

Рисунок 3– Режим пуска ВЭУ с постоянными магнитами на холостом ходу=

Figure 3 – Mode of starting permanent magnet wind turbine at idle

5. Analysis of the modes of modern wind turbines in the ES

Introduction to the new wind power and solar plants in Ukraine suggests the gradual development of the electricity sector. In the near future, the impact of these stations on the work of electric power systems (EPS) will increase significantly. New problems can be anticipated, and suggest possible solutions. The first step is to evaluate the basic concept of the EPS as an increase in their share of ES on the use of renewable energy sources (RES).

At the present time it is necessary to consider the traditional centralized EPS, which connect ES concentrated on the basis of renewable energy, increasing the total power generation system and without changing the existing structure of the system. Another way of EPS is that the system of ES RES give only part of the generated electric energy, and most of these stations cover the needs of the nearby power consumers.

The second path is now electricity in Germany [1]. An important factor is the presence of a local load, the power that is commensurate with the power sources and generation of sufficient power reserve in the EPS to be decreased due to the deterioration of ES RES weather conditions. Further growth of the total capacity of ES RES will lead to the need for electrical energy generation to meet gaps related to weather conditions. As a result of these changes will happen in the EPS decentralized sources of generation and perhaps the emergence of decentralized storage facilities. There will be new links directly to the sources of generation and load, while eliminating the need to use a large number of available lines, will be a change of the internal structure of the EPS.

At present, Ukraine should be considered the first option. Both the first and second path requires the use of new management techniques, the so-called intelligent. This is primarily due to the need for rapid redistribution of flows of active and reactive power.Almost regardless of whether introduced into the work of the new RES ES or not, at present in all countries have introduced modern methods of control modes in the whole of the EPS, and their individual elements. The application of these methods by the need to improve the efficiency of the existing EPS and sustainability of their work at various perturbations.

It is obvious that in the coming years for wind power stations as the main types of generators will be used by the synchronous generator with permanent magnets [2]. Their lack of moving electrical contacts is one of the most significant advantages. In addition, the use of the output voltage inverter unit 50 Hz eliminates the use of a mechanical gearbox. All this can significantly increase the reliability of wind turbines.

The use of powerful ES RES exacerbates the problem of voltage regulation, ensuring the sustainability of the EPS (lines of communication with the EC RES EPS), relay protection against short-circuits, and in some cases, the voltage quality for consumers. It should be borne in mind that in accordance with the Rules of connecting wind farms [3], these rules apply to WES, the minimum capacity of not less than 100 MW. In the near future on the coast of the Azov Sea is planned to build several wind farms with total capacity of about 1,200 MW.

Figure 4 - Alternative schemes to connect wind farms to the electrical system

Figure 4 - Alternative schemes to connect wind farms to the electrical system

In the event of a unified energy system of Ukraine's wind power is removed and transferred to an autonomous mode of operation [3]

The main factors that will require changes in the implementation of protection relays ES RES

Necessary is to estimate the static and dynamic stability of the EPS, which is connected to the WES. Communication line with the RES wind farm power system should provide maximum power transfer. In order to ensure static and dynamic stability in power supply provides the necessary arrangements and facilities, including emergency power reserve РAB. EPS steady state is characterized by certain power flows on the inner sections of the EPS, which correspond to the calculated field resistance. Connect the power RVES will change and redistribution of power flows and, consequently, a change to the maximum cross-flow РМ.Д.. the various sections

To evaluate the stability margin in accordance with the Methodology for assessing the sustainability of energy systems is determined by the factor of safety of the КР. The coefficient is calculated taking into account the irregular oscillations of active power [4], which must be attributed, and possible changes in wind farm output due to changing weather conditions.

Findings

This master's work is devoted to modes of operation of electric power systems in the presence of a significant proportion of these wind farms. We made the development of a mathematical model of wind turbine with a synchronous generator with permanent magnets and model EPS with wind turbines. The problems of reactive power control of wind turbines and study modes of EPS when connecting to them large amounts of wind turbines, as well as the stability of EPS when the weather conditions (wind power).

List of sources

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