Wind Turbine Generator System - Converts Kinetic Energy of Wind into Electricity

The wind turbine generator system includes a wind rotor and a generator; the wind rotor consists of blades, hubs, reinforcements, etc.; it has the functions of rotating the blades to generate electricity by the wind, and turning the head of the generator. The wind power supply consists of wind turbine generator systems, towers supporting the generators, battery charging controllers, inverters, unloaders, grid-connected controllers, battery packs, etc.

When the wind turbine generator system is generating electricity, it is necessary to ensure that the output frequency is constant. This is very necessary for both wind turbine generator system grid-connected power generation and wind-solar hybrid power generation. To ensure the constant frequency of wind power, one way is to ensure the constant speed of the generator, that is, the operation mode of constant speed and constant frequency. Because the generator is driven by the wind turbine generator system through the transmission device, this method undoubtedly requires constant wind turbine generator system speed. Speed, this method will affect the conversion efficiency of wind energy; another way is that the generator speed changes with the wind speed, and the frequency of the output electric energy is guaranteed to be constant through other means, that is, variable speed and constant frequency operation.

1. Introduction to wind turbine generator systems

The power supply of wind power generation consists of wind turbine generator systems, towers supporting generators, battery charge controllers, inverters, unloaders, grid-connected controllers, battery packs, etc.; wind turbine generator systems include wind rotors, generators; wind rotors It consists of blades, hubs, reinforcements, etc.; it has the functions of blades being rotated by wind to generate electricity, and the head of the generator turning. Wind speed selection: Low wind speed wind turbine generator systems can effectively improve the wind energy utilization of wind turbine generator systems in low wind speed areas. In areas where the annual average wind speed is less than 3.5m/s and there is no typhoon, low wind speed products are recommended.

When the wind turbine generator system is generating electricity, it is necessary to ensure that the output frequency is constant. This is very necessary for both wind turbine generator system grid-connected power generation and wind-solar hybrid power generation. To ensure the constant frequency of wind power, one way is to ensure the constant speed of the generator, that is, the operation mode of constant speed and constant frequency. Because the generator is driven by the wind turbine generator system through the transmission device, this method undoubtedly requires constant wind turbine generator system speed. Speed, this method will affect the conversion efficiency of wind energy; another way is that the generator speed changes with the wind speed, and the frequency of the output electric energy is guaranteed to be constant through other means, that is, variable speed and constant frequency operation. The wind energy utilization coefficient of a wind turbine generator system is related to the tip speed ratio (the ratio of the linear speed of the impeller tip to the wind speed), and there is a certain tip speed ratio that makes Cp reach the maximum value. Therefore, in the variable speed and constant frequency operation mode, the speed of the wind turbine generator system and the generator can be changed in a wide range without affecting the frequency of the output electric energy. Therefore, wind turbine generator systems often use the variable speed constant frequency method to ensure a constant output frequency.

2. Background on wind turbine generator systems

In recent years, the annual growth rate of global renewable energy utilization has reached 25%. The use of renewable energy will be dominated by the power sector, and the proportion of electricity generated from non-hydro renewable energy will be tripled. According to statistics, although the consumption of renewable energy was about 1.4 billion tons of oil equivalent in 2002, it will exceed 2.2 billion tons of oil equivalent in 2030. Wind power generation is the most mature renewable energy power generation except for hydropower, and its installed capacity accounts for the vast majority of the total installed capacity of renewable energy power generation. However, the limitation of the performance of power electronic devices has caused a certain bottleneck to the development and application of large-capacity wind turbine generator systems.

With the further development of powerful power electronic devices and energy storage equipment, wind power can compete with conventional energy sources in terms of total investment or power generation costs, and wind power technology will also get greater development.

In addition, as the capacity of wind farms continues to increase, when the grid voltage drops, it is even more important to ensure that the wind turbine generator systems do not run off-grid and maintain the stability of the regional grid. With the development of high-power power electronic devices and their control technology, the current low voltage ride-through problem faced by wind turbine generator systems will be well resolved.

According to the structure of the main transmission chain, wind turbine generator systems can be divided into double-fed wind turbine generator systems with multi-stage speed-up gearboxes, direct-drive wind turbine generator systems without speed-up gearboxes, and semi-direct drive wind turbine generator systems with one-stage speed-up gearboxes. Driven wind turbine generator systems can be divided into constant speed and constant frequency wind turbine generator systems and variable speed constant frequency wind turbine generator systems according to the speed adjustment method of wind turbine generator systems. Due to its high wind energy utilization efficiency, the variable speed constant frequency wind turbine generator system has become the mainstream model in wind power generation.

3. Small wind turbine generator system structure for wind turbine generator systems

Although there are many types of small wind turbine generator systems. But its structure can be roughly divided into two parts. The mechanical part includes: wind wheel, transmission mechanism, speed limiting or speed regulating mechanism, brake mechanism, machine base rotary tower, etc.; the electrical part includes: generator, power distribution box or controller, battery, inverter, etc. The function introduction of each part is as follows:

Wind wheel The wind wheel is the energy conversion device of the wind power generating set. Its function is to convert the wind into mechanical energy, and use the rotation of the wind wheel to drive the generator to generate electricity. The wind rotor is an important component of a wind turbine generator system, mainly composed of three parts: blades, petioles, and wheel stages.

Transmission capacity The speed change mechanism between the wind wheel and the generator. Its function is to change the transmission direction and speed change. For hundred-watt micro-miniature wind turbine generator systems, because the generators are all low-speed generators, the transmission device is generally omitted, and the direct connection between the wind wheel and the generator is adopted.

Speed-limiting mechanism and speed-regulating mechanism The working environment of wind turbine generator systems is relatively harsh, and is greatly affected by natural wind conditions, and sometimes it is subject to sudden gusts or strong winds. In order to ensure the safe and reliable operation of the wind turbine generator system and make the wind rotor work within a limited speed range, it is necessary to set up the necessary speed regulating and speed limiting mechanisms. Common speed regulating mechanisms include centrifugal torque converter, wind wheel side deflection, nose pitch, aerodynamic damping, wind wheel eccentricity, counterweight tail and other forms.

Frame rotator The structure of the frame rotator is very simple, but it is one of the important components of the wind turbine generator system. Its function is to support the entire nose (wind wheel and generator, etc.) and make it rotate freely on the upper end of the tower.

The function of the steering mechanism is to keep the blade surface of the wind rotor in a vertical state with the incoming wind, so that the sail can obtain the maximum wind energy to achieve the maximum power output. High-speed propeller-type wind turbine generator systems are divided into two types: upwind type (also known as windward type) and downwind type (also known as leeward type) according to the spatial position of the wind wheel and the incoming wind.

Towers are generally divided into suspension type, simple type and single rod cable type. Hundred-watt-level small wind turbine generator systems mostly adopt the single-rod cable type.

Generator The generator is the working device of the whole wind power generation system. Its function is to convert the function into electrical energy. Commonly used generators include DC generators and silicon rectifier generators. Silicon rectifier generators are divided into permanent magnet type and excitation type. Compared with DC generators, silicon rectifier generators have the characteristics of small size, light weight, simple structure, and good low-speed charging performance.

Power distribution box or controller The power distribution box or controller is an indispensable part for wind turbine generator systems to maintain normal external power supply. For wind power generators, because the natural wind is sometimes strong and sometimes weak, and sometimes not, the generator cannot be used to directly supply power to the electrical equipment, but must be used together with the battery to ensure stable output voltage. For batteries, overcharging or overdischarging will reduce their service life. Therefore, there must be necessary protection devices in the distribution box to ensure the normal use of the generator set.

Battery The battery in the wind power generating set is not only an energy storage device, but also plays a dual role in stabilizing the output voltage. According to the different electrolytes, it can be divided into two types: acid storage battery and alkaline storage battery. Commonly used are lead-acid batteries, iron-nickel batteries, and tin-nickel batteries.

Inverter An inverter is a device that converts direct current into alternating current. The output voltage of micro wind turbines generally has 12v, 24v, 36v, which can only be used by DC electrical appliances of the corresponding voltage. At present, most household appliances such as TV sets, washing machines, refrigerators, motors, etc. use 220V AC. Therefore, an inverter must be used to convert DC power into AC power for use in home appliances.

4. Classification and characteristics of wind turbine generator systems

4.1 Constant speed and constant frequency wind turbine generator system

Constant speed constant frequency wind turbine generator systems are mainly divided into cage induction generator constant speed constant frequency wind turbine generator systems and electric excitation synchronous generator constant speed constant frequency wind turbine generator systems.

Has the following characteristics:

4.1.1 The unit has a simple structure and is suitable for working in field environments;

4.1.2 Due to the constant speed. The maximum power point tracking control cannot be carried out, and the power generation efficiency is reduced.

4.1.3 When the wind speed increases rapidly, since the speed remains unchanged, the wind energy will be transmitted to the main shaft, gearbox, generator and other components through the blades, resulting in a large mechanical stress, which will cause fatigue damage to these components. Due to its low efficiency in low wind speed areas, this type of wind turbine generator system is mainly used in systems with low power and unit capacity below 600kw.

During the normal power generation process of the constant speed and constant frequency wind turbine generator system, the stator winding of the generator is directly connected to the power grid, and its speed is determined by the frequency of the power grid. The speed of the wind turbine generator system remains constant over the entire operating wind speed range.

The advantage is:

There is no need to use high-power full-control switching devices for frequency conversion control, which reduces the cost and control complexity of the entire unit;

weakness is:

The speed of the whole wind power generating set is constant, so that the unit cannot operate at the speed ratio of the blade tip in the low wind speed range, resulting in energy loss in the low wind speed range.

4.2 Variable speed constant frequency wind turbine generator system

The speed of the variable speed constant frequency wind turbine generator system can change with the change of the wind speed. It can ensure that the unit can obtain the maximum wind energy utilization string in the low wind speed area. Its efficiency is much higher than that of constant speed and constant frequency wind turbine generator systems.

At present, variable speed constant frequency wind turbine generator systems are mainly divided into double-fed asynchronous wind turbine generator systems, permanent magnet direct drive wind turbine generator systems and electric excitation synchronous semi-direct drive wind turbine generator systems. Objective: The doubly-fed asynchronous wind turbine generator system is the mainstream model among variable-speed and variable-frequency wind turbine generator systems.

During the normal operation of the variable-speed constant-frequency wind turbine generator system, its rotational speed changes with the wind speed.

The advantage is:

Below the rated speed, the speed of the wind generator set changes with the wind speed to ensure that the unit operates at the best blade tip speed ratio point, so that the unit can obtain the maximum wind energy utilization rate in the low wind speed range;

weakness is:

Since the frequency of the power grid is basically constant, but the speed of the unit changes within a certain range, it is required to add a fully-controlled converter between the generator and the power grid. In order to realize the decoupling control between the grid frequency and the generator speed, the cost and control complexity of the wind turbine generator system will increase accordingly.

Since the wind speed of wind farms is below the rated wind speed for most of the year, improving the wind energy utilization efficiency of wind turbine generator systems below the rated wind speed is a key factor to increase the annual power generation of the unit. In addition, the emergence of high-power full-control power electronic devices makes most modern wind turbine generator systems use variable-speed constant-frequency wind turbine generator systems.

5. Repair and maintenance of small wind turbine generator systems

In areas far away from the grid or lack of electricity, small wind turbine generator systems have been rapidly promoted. At present, the majority of users feel that there is a lack of knowledge about the continued repair and maintenance of the unit. Here I will introduce this knowledge to you.

Wind turbine generator systems include wind rotors, steering gear, generators, batteries, charge and discharge controllers, towers and other accessories. The maintenance of the unit can be divided into first-level maintenance, second-level maintenance and third-level maintenance (ie, first, second and third guarantees).

The first guarantee is to quickly eliminate the found faults and replace or repair some damaged parts quickly and timely, which is an extremely important part to prolong the service life of the unit.

The second guarantee refers to the operation of the unit for about one year. To disassemble the fan blades, steering gear and other components, clean the putty. If the parts are damaged, replace or repair them, and add an appropriate amount of calcium-based lubricating oil (butter) to each bearing and moving parts.

Three guarantees mean that the unit has been in operation for three to five years, and a comprehensive inspection and maintenance must be carried out. If any parts are damaged, they must be replaced or repaired.

6. Advantages of wind turbine generator systems

Since wind power belongs to the category of new energy, there is still a big gap in terms of cost and technology compared with traditional thermal power and hydropower. Therefore, the rapid development of wind power requires strong support from national policies. Throughout the countries with rapid wind power development, such as Germany, Spain, and India, all of them have given huge preferential policies to the wind power industry without exception. China's policy support for wind power has been around for a long time, and the intensity is getting stronger and stronger. The object of policy support has also shifted from focusing on power generation in the past to focusing on supporting domestic wind power equipment manufacturing. National policy support will be the fundamental guarantee for the rapid development of the wind power equipment manufacturing industry. With the continuous strengthening of the independent manufacturing capacity of China's domestic wind power equipment, the country's policy support will also increase. The wind power equipment manufacturing industry is facing a rare historical development. opportunity.

China is in a good time for the development of wind power, and the market demand for wind power equipment is increasing. In addition, in addition to the increasing demand for complete wind power equipment, the supply capacity of wind power equipment components such as blades, gearboxes, large bearings, and electronic controls still cannot fully meet the demand, and the market growth potential is huge. Therefore, China's wind power equipment manufacturing industry continues to thrive.

7. Current status of wind turbine generator systems

In recent years, wind power in emerging markets has developed rapidly. Under the background of national policy support and tight energy supply, China's wind power, especially wind power equipment manufacturing industry has also risen rapidly, and has become the most active place for wind power in the world. In 2006, 9% of the global wind power funds were invested in China, with a total amount of 1.62 billion euros (about 16.27 billion yuan). In 2007, China's wind power installed capacity ranked fifth in the world.

The "Panoramic Evaluation and Development Trend Research Report of China's Wind Power Generation Units" analyzes China's huge wind power market and cheap labor costs, attracting a large number of foreign wind power giants to set up factories in China, or to adopt joint ventures with domestic enterprises, and the products produced are all Labeled Made in China. Wind power equipment products made in China are occupying an increasing market share, and wind turbine generator system products are undergoing a transformation from global manufacturing to Chinese manufacturing.

As a clean and renewable energy, wind energy has been paid more and more attention by countries all over the world. China's wind energy reserves are large and widely distributed, and the wind energy reserves on land alone are about 253 million kilowatts. In the past five years, the world wind energy market has been growing at a rate of 40% every year. It is estimated that in the next 20-25 years, the world wind energy market will increase by 25% every year. Now, the cost of wind power generation has dropped to 1/5 of what it was in 1980. With the advancement of technology and the development of environmental protection, wind power generation will be fully competitive with coal-fired power generation commercially. As the competition in the electric power industry continues to intensify, excellent domestic electric power companies pay more and more attention to the research on the industry market, especially the in-depth research on the industrial environment.

With the rapid development of the wind power industry in recent years, the current domestic large-scale wind turbine generator system manufacturing technology has become mature, and as the core technology of wind turbine generator systems, wind turbine generator system control technology is monopolized by foreign countries; The grid problem has become another major bottleneck restricting the development of wind power, and it is imminent to solve the problem of large-scale wind power grid connection.

This project aims to study the two major technical fields of wind turbine control system control and wind farm grid connection that restrict the development of wind power in my country, and develop a 2.0MW wind turbine generator system with independent intellectual property rights. System simulation test platform and converter full power test platform. Developed a wind farm grid-connected full-dynamic reactive power compensation device to effectively solve the problem of wind power grid-connected power quality, and built a wind farm grid-connected full-dynamic reactive power compensation device test platform. At the same time, an online monitoring and fault diagnosis system for wind turbine generator systems has been developed to provide guarantee for the safe operation of wind turbine generator systems.

On August 19, 2022, the world's largest onshore impeller diameter 7.X MW-195 wind turbine generator system independently designed by China Energy Group United Power won the type certification issued by Beijing Jianheng Certification Center. This certification is a comprehensive evaluation and recognition of the reliability and safety of the wind turbine generator system, indicating that the performance of the wind turbine generator system has reached the industry-leading level.

8. Development of wind turbine generator systems

According to the "2013-2017 China Wind Power Generating Set Industry Market Prospect and Investment Strategic Planning Analysis Report", the power generation of each type of generating set in May 2012: According to the type of generating set: hydropower generating capacity of 222.6 billion kwh, A year-on-year increase of 7.8%, due to the better flow of river water, the growth rate has rebounded significantly; thermal power generation was 1,577.6 billion kwh, a year-on-year increase of 4.1%, and the growth rate continued to fall; nuclear power generation was 39.4 billion kwh, a year-on-year increase of 12.5%, an increase of The speed was lower than that of the same period of last year; the wind power generation was 42.4 billion kwh, a year-on-year increase of 24.2%, and still maintained a rapid growth.

Power generation by generator set type in December 2012: by generator set type:

The hydropower generation capacity was 864.1 billion kwh, a year-on-year increase of 29.3%, achieving a substantial increase throughout the year;

Thermal power generation was 3910.8 billion kwh, a year-on-year increase of 0.3%, achieving a slight increase;

The generating capacity of nuclear power was 98.2 billion kwh, a year-on-year increase of 12.6%, and the growth rate was lower than last year;

Wind power generation was 100.4 billion kwh, a year-on-year increase of 35.5%, maintaining rapid growth.

9. Installation site selection of wind turbine generator systems

Changes in wind speed and direction have a great impact on the power generation of wind turbine generator systems. Generally, the higher the tower, the greater the wind speed, the smoother the airflow, and the greater the power generation. Therefore, the siting of wind turbine generator systems should be carefully considered. Every installation is different, and factors such as tower height, distance from battery packs, local planning requirements and obstacles such as buildings and trees must be considered. The specific requirements for fan installation and site selection are as follows:

The recommended minimum tower height for wind turbine generator systems is 8 meters or more than 5 meters away from obstacles, and there should be no obstacles within 100 meters of the center of the installation range;

The installation of two adjacent fans should be kept at a distance of 8 to 10 times the diameter of the wind rotor; the location of the fans should avoid turbulent flow. Choose areas with high annual average wind speed, relatively stable prevailing wind direction, and small diurnal and seasonal changes in wind speed;

The wind speed shear in the vertical direction within the height range of the wind turbine generator system should be small; choose a place with as few natural disasters as possible;

Safety is the primary concern when choosing an installation location. Therefore, even if a wind turbine generator system is installed in a place where wind speed resources are less than ideal, the wind rotor blades must not rotate during installation.