Power electronics technology is a science that uses power electronic devices to study the control and conversion of electric energy. It is an interdisciplinary subject among the three main fields of electrical engineering-power, electronics and control, and has a wide range of applications in power, industry, transportation, aerospace and other fields. 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.
First, the development of power electronics technology
The development direction of modern power electronics technology is the transformation from traditional power electronics with low frequency technology to modern power electronics with high frequency technology. Power electronics technology began with silicon rectifier devices in the late 1950s and early 1960s, and its development has gone through rectifier era, inverter era and frequency converter era, which promoted the application of power electronics technology in many new fields. The power semiconductor composite devices with high frequency, high voltage and high current, represented by power MOSFET and IGBT, developed in the late 1980s and early 1990s, indicate that the traditional power electronics technology has entered the modern power electronics era.
1, rectifier era
High-power industrial electricity is provided by power frequency (50Hz) alternator, but about 20% of the electricity is consumed in the form of DC. The most typical ones are electrolysis (non-ferrous metals and chemical raw materials need DC electrolysis) and traction (electric locomotives, electric diesel locomotives, subway locomotives, urban trolleybuses, etc.). ) and DC drive (steel rolling, paper making, etc. High-power silicon rectifiers can efficiently convert power frequency alternating current into direct current, so the development and application of high-power silicon rectifiers and thyristors have been greatly developed in the 1960s and 1970s. At that time, there was an upsurge of establishing large-scale silicon rectifier factories in China. At present, large and small silicon rectifier semiconductor manufacturers in China are the products of that era.
2, the inverter era
In 1970s, there was an energy crisis all over the world, and the variable frequency speed regulation of AC motor developed rapidly because of its remarkable energy-saving effect. The key technology of variable frequency speed regulation is to convert direct current into alternating current of 0~ 100Hz. In 1970s and 1980s, with the popularization of frequency conversion speed regulating devices, thyristors, high-power transistors (GTR) and high-power inverter gate turn-off thyristors (GT0) became the protagonists of power electronic devices at that time. Similar applications include high voltage DC output, static reactive power dynamic compensation and so on. At this time, power electronics technology has been able to achieve rectification and inverter, but the working frequency is low, limited to the middle and low frequency range.
3, frequency converter era
In 1980s, the rapid development of large-scale and ultra-large-scale integrated circuit technology laid the foundation for the development of modern power electronics technology. Combining the precision machining technology of integrated circuit technology with high voltage and high current technology, a number of brand-new fully controlled power devices have emerged. First, the appearance of power M0SFET has driven the development of medium and small power supplies to high frequency, and then the appearance of insulated gate bipolar transistors (IGBT) has brought opportunities for the development of medium and large power supplies to high frequency. The appearance of MOSFET and IGBT marks the transformation from traditional power electronics to modern power electronics. According to statistics, by the end of 1995, power M0SFET and GTR have reached the same level in the market of power semiconductor devices, and it has been concluded that IGBT will replace GTR in the field of power electronics. The development of new devices not only provides high frequency for AC motor variable frequency speed regulation, which makes its performance more perfect and reliable, but also makes modern electronic technology develop to high frequency, which provides an important technical basis for efficient material saving and energy saving of electrical equipment, and realizes small, lightweight, electromechanical integration and intelligence.
Second, the application of power electronics technology
1, general industry
Various AC and DC motors are widely used in industry. DC motor has good speed regulation performance, and its controllable rectifier power supply or DC chopper power supply is a power electronic device. In recent years, due to the rapid development of power electronic frequency conversion technology, the speed regulation performance of AC motor can be comparable to that of DC motor, and AC speed regulation technology has been widely used and occupied a leading position. Power electronic AC /DC speed regulation technology is widely used in various rolling mills as large as several thousand kilowatts, servo motors of CNC machine tools as small as several hundred watts, and mine traction. In recent years, some large blowers with low requirements for speed regulation have also adopted frequency conversion devices to achieve the purpose of energy saving. In order to avoid the current shock when starting, some variable speed motors adopt soft starting devices, which are also power electronic devices. DC power supply is widely used in electrochemical industry, and electrolytic aluminum and electrolytic salt solution need large-capacity rectifier power supply. Plating equipment also needs a rectifier power supply. Power electronics technology is also widely used in metallurgical industry, such as high-frequency and intermediate-frequency induction heating power supply, quenching power supply and DC arc furnace power supply.
Step 2 transport
Power electronics technology is widely used in electrified railways. DC locomotive in electric locomotive adopts rectifier device, and AC locomotive adopts frequency conversion device. DC chopper is also widely used in railway vehicles. In the future maglev train, power electronics technology is a key technology. In addition to traction motor drive, various auxiliary power sources in vehicles are also inseparable from power electronics technology. The motor of electric vehicle is controlled by power electronic devices for power conversion and driving, and the charging of its battery is also inseparable from power electronic devices. A limousine needs many control motors, which are also driven and controlled by frequency converters and choppers. Aircraft and ships need many different power sources, so aviation and navigation are inseparable from power electronics technology. If the elevator is considered as a means of transportation, it also needs power electronics technology. In the past, most elevators used DC speed regulation system, but in recent years, AC frequency conversion speed regulation has become the mainstream.
3. Power system
Power electronics technology is widely used in power system. It is estimated that more than 60% of the final electricity consumption of users in developed countries has been treated by power electronic converters at least once. In the process of power system modernization, power electronics technology is one of the key technologies. It is no exaggeration to say that without power electronics technology, the modernization of power system is unimaginable. Dc transmission has great advantages in long-distance and large-capacity transmission, and both the rectifier valve at the transmission end and the inverter valve at the receiving end adopt thyristor converter devices. The FACTS developed in recent years are also realized by power electronic devices. Reactive power compensation and harmonic suppression are of great significance to power system. Thyristor controlled reactor (TCR) and thyristor switching capacitor (TSC) are both important reactive power compensation devices. In recent years, new power electronic devices such as static var generator (SVG) and active power filter (APF) have better reactive power and harmonic compensation performance. In the distribution network system, power electronic devices can also be used to prevent instantaneous power failure, instantaneous voltage drop and flicker, thus controlling power quality and improving power supply quality.
In the substation, power electronic devices are needed to provide reliable AC and DC operating power for the operating system and charge the battery.
4. Power supply of electronic equipment
Various electronic devices generally need DC power supplies with different voltage levels. The DC power supply used by program-controlled switches in communication equipment used to be thyristor rectifier power supply, but now it has been changed to high-frequency switching power supply for fully controlled devices. High-frequency switching power supply is also used for working power supply required by large computers and internal power supply of microcomputers. In all kinds of electronic equipment, linear regulated power supply was widely used in the past. High frequency switching power supply has gradually replaced linear power supply because of its small size, light weight and high efficiency. Because all kinds of information technology equipment need power electronic devices to provide power, it can be said that information electronic technology can not be separated from power electronic technology.
5. Home appliances
Lighting occupies a very prominent position in household appliances. Power electronic lighting power supply is often called "energy saving lamp" because of its small size, high luminous efficiency and energy saving, and is gradually replacing traditional incandescent lamps and fluorescent lamps. Frequency conversion air conditioner is a typical example of power electronics technology applied to household appliances. Power electronics technology is also needed for the power supply of TV sets, audio equipment, home computers and other electronic equipment. In addition, some washing machines, refrigerators, microwave ovens and other electrical appliances have also applied power electronics technology. The wide application of power electronics technology in household appliances makes it very close to our life.
6. Others
Uninterruptible power supply (UPS) plays an increasingly important role in modern society, and its consumption is increasing, which has occupied a considerable share in power electronic products. All kinds of electronic instruments in the spacecraft need power supply, and manned spacecraft also needs all kinds of power supply for people to survive and work, which must adopt power electronics technology. Traditional power generation methods include thermal power generation, hydropower generation and later nuclear power generation. After the energy crisis, all kinds of new energy, renewable energy and new power generation methods have been paid more and more attention. Among them, solar power generation and wind power generation have developed rapidly, and fuel cells have attracted much attention. Solar power generation and wind power generation are restricted by the environment, and the quality of power generated is poor, so energy storage devices are often needed to buffer and improve the quality of power, which requires power electronics technology. When it is necessary to connect with the power system, it is also inseparable from power electronics technology. In order to make rational use of hydropower resources, pumped storage power stations have been paid attention to in recent years. Among them, the starting and speed regulation of large motors need power electronics technology. Superconducting energy storage is a kind of energy storage method in the future, which requires powerful DC power supply, which is also inseparable from power electronics technology. When a nuclear fusion reactor generates a strong magnetic field and injects energy, it needs a large-capacity pulse power supply, which is a power electronic device. Scientific experiments or some special occasions often need some special power supply, which is also where power electronics technology plays a role. In the past, the application of power electronics technology mainly focused on medium and high power. At present, in the power range below 1kW, even below several tens of w, the application of power electronics technology is more and more extensive and its position is more and more important. This has become an important development trend and deserves people's attention.
In a word, power electronics technology has a wide range of applications. From human exploration of the universe and nature, to all fields of the national economy, to our daily necessities, we can feel the existence and great charm of power electronic technology everywhere. This has also inspired generations of scholars and engineers to study and study power electronics technology and make it develop rapidly. Power electronic devices provide different kinds of DC power supply, constant frequency AC power supply and variable frequency AC power supply to loads, so it can also be said that power electronic technology studies power technology. Power electronics technology is of great significance for saving electric energy. Especially in the variable frequency speed regulation of large fans and pumps, and in the lighting power supply with huge usage, power electronics technology has a very remarkable energy-saving effect, so it is also called energy-saving technology.