Power electronics technology is the study of the use of power electronic devices to achieve the control of electrical energy and the transformation of science, is between the three major fields of electrical engineering - power, electronics and control of the interdisciplinary between the three major fields of electrical engineering, in the electric power, industry, transportation, aerospace and other fields with a wide range of applications. The application of power electronics technology has penetrated into all aspects of industrial production and social life, and has become an indispensable key technology in traditional industries and high-tech fields, which can effectively save energy.
I, the development of power electronics technology
The development direction of modern power electronics technology, from low-frequency technology to deal with the problem of traditional power electronics, to high-frequency technology to deal with the problem of the main direction of the transformation of modern power electronics. Power electronics technology began in the late fifties and early sixties silicon rectifier devices, its development has experienced the rectifier era, inverter era and inverter era, and promote the application of power electronics technology in many new fields. The late eighties and early nineties development, to power MOSFET and IGBT as a representative of the set of high-frequency, high-voltage and high-current power semiconductor composite devices, indicating that the traditional power electronics technology has entered the modern power electronics era.
1, the rectifier era
High-power industrial power supplied by the frequency (50Hz) alternator, but about 20% of the power is consumed in the form of DC, which is most typical of electrolysis (non-ferrous metals and chemicals need DC electrolysis), traction (electric locomotives, electric drive of the internal combustion locomotives, metro railroad locomotives, urban trolley buses, etc.) and DC drive (steel rolling, paper making, etc.). Rolling steel, paper, etc.) three major fields. High-power silicon rectifiers can efficiently convert AC power to DC power, so in the sixties and seventies, the development and application of high-power silicon rectifier and thyristor to a great development. At that time, the domestic had set off - a share of silicon rectifier factory around the big boom, the current national large and small manufacturing silicon rectifier semiconductor manufacturers is the product of that time.
2, inverter era
The seventies appeared the world-wide energy crisis, AC motor frequency conversion speed due to energy-saving effect and rapid development. The key technology of frequency control is to invert DC power into AC power of 0~100Hz. In the seventies to eighties, with the popularization of frequency conversion speed control device, high power inverter thyristor, giant power transistor (GTR) and gate turn-off thyristor (GT0) became the main protagonist of power electronic devices. Similar applications include high-voltage DC output, static reactive power dynamic compensation. At this time the power electronics technology has been able to realize the rectifier and inverter, but the working frequency is low, only limited to the low frequency range.
3, inverter era
Entering the eighties, the rapid development of large-scale and ultra-large-scale integrated circuit technology, laid the foundation for the development of modern power electronics technology. The integrated circuit technology and high-voltage processing technology and high-current technology, the emergence of a number of new full-control power devices, first of all, the introduction of power M0SFET, resulting in small and medium-power power supply to the development of high-frequency, and after the emergence of insulated gate bipolar transistors (IGBT), and for the development of large and medium-sized power supply to the high-frequency development opportunities. The successive introduction of MOSFETs and IGBTs is a symbol of the transformation of traditional power electronics to modern power electronics. According to statistics, by the end of 1995, power M0SFET and GTR in the power semiconductor device market has reached the point of equality, and IGBT instead of GTR in the field of power electronics has become a foregone conclusion. The development of new devices not only for the AC motor frequency control provides a higher frequency, so that its performance is more perfect and reliable, but also to make the modern electronic technology continues to high-frequency development, for the power equipment, high efficiency and energy saving, to achieve a small lightweight, mechatronics and intelligence provides an important technical basis.
Two, the application of power electronics technology
1, general industry
Industry in the application of a large number of various AC and DC motors. DC motor has a good speed performance, to its power supply controlled rectifier power supply or DC chopper power supply are power electronic devices. In recent years, due to the rapid development of power electronics frequency conversion technology, so that the AC motor speed performance can be comparable with the DC motor, AC speed control technology is widely used and occupy a dominant position. As large as thousands of kW of various steel mills, as small as a few hundred W of CNC machine tools servo motors, as well as mine traction and other occasions are widely used in power electronics AC and DC speed control technology. Some of the speed control performance requirements are not high, such as large-scale blowers in recent years have also adopted a frequency conversion device to achieve the purpose of energy saving. There are also some motors without speed control in order to avoid the current impact of the start and the use of soft starting device, this soft starting device is also a power electronic device. Electrochemical industry uses a large number of direct current power supply, electrolytic aluminum, electrolysis of brine and other large-capacity rectifier power supply is required. Electroplating devices also need rectifier power supply. Power electronics technology is also used in the metallurgical industry, high-frequency, medium-frequency induction heating power supply, quenching power supply and DC arc furnace power supply and other occasions.
2, transportation
Electrified railways are widely used in power electronics. Electric locomotives in the DC locomotive rectifier, AC locomotives using frequency conversion device. DC choppers are also widely used in railroad cars. In the future magnetic levitation train, power electronic technology is a key technology. In addition to traction motor drive, vehicles in a variety of auxiliary power are inseparable from power electronics. Electric car motor by power electronics for power conversion and drive control, its battery charging is also inseparable from the power electronics. An advanced automobile needs many control motors, they also rely on inverter and chopper drive and control. Airplanes, ships need many different requirements of the power supply, so aviation and navigation are inseparable from the power electronics technology. If the elevator is also counted as transportation, then it also needs power electronics. Most of the previous elevators use DC speed control system, while in recent years AC frequency conversion speed control has become the mainstream.
3, the power system
Power electronics has a very wide range of applications in the power system. It is estimated that the developed countries in the user's final use of electrical energy, more than 60% of the electrical energy through at least one more power electronic converter processing. Power electronic technology is one of the key technologies in the process of modernization of the power system. It is no exaggeration to say that if we leave the power electronics technology, the modernization of the power system is inconceivable. DC transmission in the long distance, large capacity power transmission has great advantages, its sending end of the rectifier valve and receiving end of the inverter valve are used thyristor current converter. Flexible AC transmission (FACTS) developed in recent years also relies on power electronic devices to be realized. Reactive power compensation and harmonic suppression are of great importance for power systems. Thyristor-controlled reactor (TCR), thyristor-switching capacitor (TSC) are important reactive power compensation devices. In recent years, new power electronic devices such as static reactive power generators (SVG) and active power filters (APF) have superior performance in reactive power and harmonic compensation. In the distribution network system, power electronic devices can also be used to prevent transient grid outages, transient voltage dips, flicker, etc., in order to carry out power quality control and improve the quality of power supply.
In the substation, the operating system to provide reliable AC and DC operating power, charging batteries, etc. need power electronic devices.
4, electronic devices with power
A variety of electronic devices generally require different voltage levels of DC power supply. Communication equipment used in the program-controlled switching DC power supply previously used thyristor rectifier power supply, has now been changed to the use of fully controlled devices of high-frequency switching power supply. Large computers require power supply, microcomputer internal power supply are now also used high-frequency switching power supply. In a variety of electronic devices, previously used a large number of linear regulated power supply power supply, due to high-frequency switching power supply small size, light weight, high efficiency, has now gradually replaced the linear power supply. Because a variety of information technology devices need power electronics to provide power, so it can be said that information electronics technology can not be separated from power electronics technology.
5, household appliances
Lighting in household appliances occupies a very prominent position. Due to the power electronic lighting power small size, high luminous efficiency, can save a lot of energy, usually called "energy-saving lamps", it is gradually replacing the traditional incandescent lamps and fluorescent lamps. Inverter air conditioner is a typical example of the application of power electronics technology in household appliances. The power supply parts of electronic devices such as television sets, audio equipment and home computers also require power electronics. In addition, some appliances such as washing machines, refrigerators and microwave ovens also apply power electronics. Power electronics technology is widely used in household appliances make it and our lives become very close.
6, other
Uninterruptible power supply (UPS) in modern society is becoming more and more important, the amount of use is also growing, in the power electronics has a considerable share. Space vehicles in a variety of electronic instruments need power, manned spacecraft in order to survive and work, but also can not be separated from a variety of power, these are necessary to use power electronics technology. The traditional power generation methods are thermal power generation, hydroelectric power generation, and later the rise of nuclear power generation. After the energy crisis, a variety of new energy sources, renewable energy and new power generation methods have been increasingly emphasized. Among them, solar power and wind power are developing faster, and fuel cells are attracting more attention. Solar power and wind power generation is subject to environmental constraints, the quality of the power issued is poor, often requiring energy storage devices to buffer, the need to improve the quality of power, which requires power electronics technology. When it is necessary to network with the power system, power electronics technology is also indispensable. In order to rationally utilize hydroelectric resources, pumped storage power plants have been given attention in recent years. The starting and speed regulation of large electric motors in them require power electronics. Superconducting energy storage is a kind of energy storage in the future, which needs a powerful DC power supply, which is also inseparable from power electronics technology. Nuclear fusion reactor in the generation of a strong magnetic field and injection of energy, the need for high-capacity pulse power supply, this power is the power electronics. Scientific experiments or some special occasions, often need some special power supply, which is also the place of power electronics technology. Previously, the application of power electronics technology in favor of medium and high power. Now, in the following 1kW, or even dozens of W below the power range, the application of power electronics technology is also more and more extensive, and its position is also more and more important. This has become an important development trend that deserves people's attention.
In short, power electronics technology has a wide range of applications. From mankind's exploration of the universe and nature, to the various fields of the national economy, to our food, clothing, housing and transportation, the existence and great charm of power electronics technology can be felt everywhere. This has also inspired generations of scholars and engineers to study and research power electronics technology and make it develop rapidly. Power electronic devices to provide the load is a variety of different DC power supply, constant frequency AC power supply and variable frequency AC power supply, so it can also be said that power electronics research is also the power supply technology. Power electronics technology is important to save power. Especially in large fans, pumps using variable frequency speed control, in the use of a very large amount of lighting power supply, etc., power electronics technology, energy saving effect is very significant, so it is also known as energy-saving technology.