Compensation of voltage flicker at the output of wind turbines based on induction generator by Statcom to improve power

Dissertation for Master's Degree in Electrical Engineering

Power Orientation

Abstract:

The use of renewable energy to generate electrical energy has been increasingly increased with the expansion of the use of flexible alternating current transmission systems. (FACTS), in order to compensate for the quality of power and voltage, has increased the range of use of these energies. The use of various types of wind turbines to generate electricity has become common in recent years, and many countries use it. In this project, the use of static synchronous compensator (STATCOM) in the continuous operation of a wind farm has been evaluated, and the effect of the presence of STATCOM has been investigated and modeled. The simulation results show that the network power improves with the presence of STATCOM and wind turbines. Fixed speed turbines significantly affect the quality of the voltage of the electrical network connected to them due to the fluctuating nature of their output power. Rapid voltage fluctuations produced by these turbines cause voltage flicker in the network. According to the simulation done, it is possible to check the effect of different parameters of the electrical network on the amount of voltage flicker emitted by wind turbines. To evaluate the amount of voltage flicker emission, the flickermeter program was written based on the IEC 61400-4-15 standard. The study and simulation was done in the MATLAB/SIMULINK environment and considering three 3 MW turbines based on the induction generator in a wind farm.

Introduction

The issue of power quality, which is still one of the most important issues in power systems, has been raised since the past, and power companies around the world have been working on this issue for several decades.

In 1970, power quality was raised as one of the important goals in the design of industrial power systems. In addition to safety, servicing with high reliability and reducing initial and current costs were also topics that involved electrical engineers. Almost at the same time, the issue of "voltage quality" was raised in the Scandinavian countries and in the former Soviet Union, whose main goal was to control low-range voltage changes.

1-2: Factors affecting the increase in the importance of the issue of power quality

Today, several factors have caused that the issue of power quality and the supply of electricity with appropriate quality to consumers is considered one of the important issues, some of which are mentioned below. Be:

Equipments and devices have become more sensitive to voltage disturbances. Power equipment has become much more sensitive in the last 10 to 20 years. Mr. Thomas Kay discusses the problems of voltage disturbances on the performance of electronic equipment in 1978. In addition to the sensitivity of equipment, companies also show more sensitivity to this problem due to the loss of time and decrease in income due to problems related to power quality phenomena. In an ideal electrical energy network, the continuous supply of electricity is a basic right for the intended subscribers, as a result, any power outage will face more objections than in the past, even if it does not cause any damage or physical damage. [5]

Different equipment and devices alone cause voltage disturbances. Modern power electronic devices are not only sensitive to voltage disturbances, but also cause voltage disturbances themselves. The increase in the use of converters (from consumer electronic equipment and computers to speed control equipment in engines) has led to an increase in disturbances in voltage. The main issue here is the non-sinusoidal current of rectifiers and inverters. In addition to having the main frequency of the network, the input current of these devices also contains harmonics. which are considered an important problem for the network due to the increase in their use.

Increasing the need for standardization and performance criteria: in the old days, the consumer of electric energy was considered simple from the point of view of many electricity companies, power outages and voltage disturbances were considered a normal thing, and the aforementioned company also acted according to its wishes, and any subscriber who needed higher quality and reliability had to pay an additional fee, but today, electricity supply companies look at the consumer as a "customer". Electricity is known as a product with its own characteristics that can be measured, predicted, guaranteed, improved and so on. This issue is due to the trend towards privatization and changing the structure of the electricity network. Free competition in electricity markets makes the matter of convenience even more complicated. In the old days, the consumer would sign a contract with the local electricity company and that company would provide the consumer with electric energy with its own quality and capability, but today, in the restructured systems and with the expansion of the electricity market, customers can buy electric energy from any company they want, so an organization is successful in this regard that can deliver electricity to customers with better quality and reliability. Therefore, the discussion of power quality and reducing its adverse effects shows its importance.

Power quality can be measured: with the availability of electronic devices to measure and display waveforms, power quality has received more attention. In the past, measuring power quality indicators was difficult and was limited to measuring the effective value of voltage, frequency, and long-term outages. But today, with the advancement of technology and availability of power quality monitoring equipment, it is also possible to provide Appropriate indicators and methods, evaluation and measurement of various phenomena of power quality can be done easily. 1-3: What is power quality? As an example, a power company considers power quality more than reliability, or from a manufacturer's point of view, power quality is the specification of power supplied for the proper operation of production devices.

Dictionary of the International Association of Electrical Engineers in the IEEE std 1100 standard defines power quality as follows: "power quality is the electrification of sensitive equipment for the proper functioning of that equipment" a more comprehensive definition stated in reference [5] of power problems It states: "Any problem in the supplied electricity that occurs in the form of deviation of current, voltage or frequency and leads to failure or improper operation of the subscriber's equipment". widely used are the IEEE1159 and IEC-61000 series, the famous phenomena introduced by these standards are described below [4, 5, 6]:

1-4-1: Transient states:

The term transient is usually used for sudden changes in a sinusoidal waveform. The word shock is used to describe transient waves caused by Lightning arises is used. The IEC61000-2-5-1990 standard divides transient waves into two subgroups depending on the sources that cause these disturbances:

1-4-1-1: Shock transients:

Sudden transients are a sudden change in stable current, voltage or both conditions and with a frequency different from the network frequency and unidirectional polarity. It means. Impulsive transient states are usually known by two characteristics "Decay Time" and "Rise Time" as well as their spectral contents.