Application of Power Electronics Technology in Power System

Power electronics technology is a new technology in electrical technology. It is a fusion of power and electronic technology (strong power and weak current technology). It has played a huge role in the national economy and will have a huge impact on the performance of future transmission systems. At present, the application of power electronics technology has involved all aspects of the power system, including power generation, transmission and distribution systems, energy storage systems and so on.

I. Power Generation The power generation of the power system involves multiple devices of the generator set. The application of power electronics technology is aimed at improving the operational characteristics of these devices.
(2) Static excitation control of large generators. The static excitation adopts the thyristor rectification self-excitation mode, which has the advantages of simple structure, high reliability and low cost, and is widely used by various power systems in the world. Since the intermediate inertia link of the exciter is omitted, it has its own rapid adjustment, which provides favorable conditions for the advanced control law to fully play its role and produce good control effects.

(2) Variable speed constant frequency excitation of hydraulic and wind power generators. The effective power of hydropower depends on the head pressure and flow. When the head changes greatly (especially for pumped storage units), the optimal speed of the unit changes. The effective power of wind power is proportional to the cube of the wind speed, and the speed at which the windmill captures the maximum wind energy varies with the wind speed. In order to obtain the maximum effective power, the unit can be operated at a variable speed. By adjusting the frequency of the rotor excitation current, it is superimposed with the rotor speed to maintain the stator frequency, that is, the output frequency is constant. The core technology of this application is the variable frequency power supply.

(3) Frequency control of the fan and water pump of the power plant. The power consumption rate of power plants is 8% on average, and the power consumption of wind turbines and pumps is about 65% of the total power consumption of thermal power equipment, and the operating efficiency is low. The use of low-voltage or high-voltage inverters to implement the frequency conversion speed regulation of the fan and water pump can achieve the purpose of energy saving. The low-voltage inverter technology is very mature. There are many manufacturers at home and abroad, and there are complete series of products, but they have

(4) Solar power generation control system. The development and utilization of endless clean new energy, solar energy, is an important strategic measure to adjust the future energy structure. High-power solar power generation, whether it is a stand-alone system or a grid-connected system, usually needs to convert the direct current generated by the solar array into alternating current, so the inverter with the maximum power tracking function becomes the core of the system. Japan's Sunshine Project is mainly based on 3 to 4 kW household grid-connected power generation systems. China's power transmission to the township project is dominated by 10 to 15 kW independent systems, while large systems have Siemens solar power plants in California ( 7.2 MW) and so on.

Second, the transmission link

(1) Flexible AC Transmission Technology (FACTS)

AC transmission or grid operating performance. The applied FACTS controllers include a static var compensator (SVC), a stationary camera (STATCON), a stationary fast exciter (PSS), a series compensator (SSSC), and the like. In recent years, flexible AC transmission technology has been applied in important UHV transmission projects in the United States, Japan, Sweden, Brazil and other countries. In-depth research and development of FACTS has also been carried out in China.

(2) High-voltage direct current transmission technology (HVDC)

Stream stations can be relocated, allowing medium-sized DC transmission projects to be competitive at shorter delivery distances. In addition, the inverter can be turned off, and the commutation failure can be avoided due to the use of the power electronics that can be turned off. There is no requirement for the capacity of the receiving system, so it can be used for isolated small systems (offshore oil platforms, Island) Power supply, which can be used in urban distribution systems for future access.

1. Tianshengqiao-Guangzhou HVDC Project (2001) Â±500kV, 1800MW, 980km
2. Three Gorges-Changzhou HVDC Project (2003) Â±500kV, 3000MW, 890km
3. Three Gorges-Guangzhou HVDC Project (2004) Â±500kV, 3000MW, 962km

In recent years, there has been a new development in direct current transmission technology. Light-duty direct current transmission uses inverters such as IGBTs to turn off power electronic components to form inverters, and uses pulse width modulation technology to perform passive inverters, which solves the problem of using DC power transmission to no AC power supply. The problem of power transmission at the load point. At the same time, the equipment is greatly simplified and the cost is reduced. The world's first industrial test of light-duty direct current transmission using IGBTs as voltage source converters was put into operation in 1997.

(3) Static var compensator (SVC)

The SVC replaces the electrical switch with a solid-state switch with a thyristor as its basic component, enabling quick and frequent changes to the admittance of the transmission system in a way that controls the reactor and capacitor. SVCs can have different loop structures, which are called thyristor switching capacitors (TSC), thyristor switching reactors (TSR) or thyristor control reactors (TCR), depending on the object to be controlled and the way they are controlled. China Power Transmission System

Third, the distribution link

It is a fast-growing sister-type new power electronics technology. The core of adopting FACTS is to strengthen the controllability of AC transmission system and increase its power transmission capability; the purpose of developing CP is to enhance the reliability of power supply and improve the quality of power supply in the distribution system. The common basic technology of CP and FACTS is power electronics technology. The respective controllers have the same structure and function. The difference is only the rated electrical values â€‹â€‹are different.

Fourth, other applications

(1) Synchronous breaking technology

The fundamental way to achieve synchronous breaking is to replace the mechanical switch with an electronic switch. Westinghouse has produced 13KV, 600A, solid-state switches consisting of GTO components for use in substations in New Jersey. GTO breaking time can be shortened to 1/3ms, which is unmatched by general mechanical switches. Nowadays, the "soft switching" of the power distribution system of capacitor banks consisting of solid-state switches has been introduced.

(2) DC power supply

Many loads must use DC power, 20-30% of the total power generation in the world.

(3) Uninterruptible power supply (UPS) and various AC-DC, DC-AC switching power supplies

Switching power supplies are widely used in program-controlled switching stations, computers, televisions, medical equipment, aerospace, marine vessels and home appliances. These switching power supplies use high-frequency technology to reduce their volume and weight, and energy consumption and materials are also greatly reduce. In order to increase the unit power density of the power supply, the high frequency of the switching power supply is the development direction. Various soft switching techniques have been developed to reduce the problem of increased switching losses due to increased frequency.

(4) All solid state AC power supplies of various frequencies

This is a variable frequency power supply for various industrial needs. In the late 1980s, there were about 200,000 60-200 KW high-frequency equipment in China. Now, the thyristor medium-frequency induction heating device has completely replaced the intermediate frequency generator. The domestic has formed 200-8000 Hz and the power is 100-3000 KW. Series products. In the high-frequency power supply, 1000 KW/15-600 KHz (Belgium) is manufactured by the power MOSEFT, and 1000KW/200KHz and 400KW/400KHz (Japan) induction heating devices are manufactured by SIT (Static Induction Thyristor), and the efficiency is over 90%. A 75KW/200KHz SIT induction heating device has been developed in China. This makes it possible to save energy by using an all-solid-state high-frequency induction heating device.

Single Wall Heat Shrink Tubing

Single Wall Heat Shrink Tubing,Heat Shrink Tubing ,Shrink Tube ,Heat Shrink Wrap

Cable Sleeve Co., Ltd. , http://www.nbshrinktubing.com