The power electronics technology has been in existence for nearly 50 years. It has played a tremendous role in promoting human civilization. Now that it has no field or no industry, it has left the power electronics technology and will make people's lives obscure. Because the development goal of power electronics technology is to realize the generation and scheduling of electric energy and the best match between the power grid and the power load, the best efficiency and the best waveform power are achieved. The basis for implementing these functions is power semiconductor devices, and the means to accomplish these functions are power electronics devices. Power electronics technology is an edge cross discipline in many disciplines such as integrated power semiconductor devices, power conversion technology, modern electronics technology, and automatic control technology. Along with the development of science and technology, power electronics technology and modern control theory, materials science, and motors Engineering, microelectronics and many other fields are closely related. 3. At present, it has gradually developed into a comprehensive technical discipline with more disciplines, and it is for modern communications, electronic instruments, computers, industrial automation, power grid optimization, and power engineering. , national defense, and some high-tech technologies play a key role in providing high-quality, high-efficiency, and high-reliability power.
The 21st century is an era of knowledge economy and industrial economy. Human civilization will enter a higher level and various high and new technologies will develop rapidly. This requires that the power electronics technology closely related to these technologies does not lag behind the times. Therefore, in the 21st century, the power electronics technology will have more rapid development. The research fields of power electronics in the 21st century can be discussed from three aspects: power semiconductor devices, power electronics and complete sets of control devices, and control theory. Power electronics devices can be divided into many aspects depending on the industry.
The main research fields of power semiconductor devices in the 221st century The research fields of the power semiconductor devices in the 21st century are divided into two aspects: the improvement of device performance and the development of new devices.
2.1 The improvement of the performance of existing power semiconductor devices The first human silicon controlled rectifier SCRs (collectively referred to as thyristors) have been invented for nearly 50 years. Today, power semiconductor devices have formed a huge family of more than 40 varieties. It has occupied a place in the power electronics package. In the 21st century, these devices will gain greater development in performance. The mainstream of development is to increase the voltage and current levels, increase the operating frequency, reduce the volume, and be highly modular and high. Work efficiency, its main research area can be discussed from the following aspects.
2.1.1 GTO, thyristor, and GTR slowed down due to the silicon single crystal structure determines the maximum capacity of silicon-based devices can only reach 10000A/10000V, thus determining the capacity of thyristors, rectifiers, GTO, IGCT and other devices With the expansion approaching 10000A/10000V, the speed of its power level increase slows down, and GTR's working mechanism determines the irreconcilable contradiction between high current and switching frequency, and people will not spend much effort on it. Increase its power and frequency.
2.1.2 Position of MOS devices The prominent MOS field-controlled power semiconductor devices have become the mainstream of research on power semiconductor devices in the 21st century. For devices such as MOSFETs, IGBTs, and IEGT, which have MOSFETs as the control stage and have a high operating frequency, the focus of their research is to increase the voltage and current capacity. After hard work is expected to make its voltage and current capacity reach the level of nearly 10000V/10000A, deep research and breakthroughs in the process will greatly increase the operating frequency of these devices, and at the same time its voltage drop will be greatly reduced to meet the power electronic complete sets of devices The more demanding requirements, the power electronic devices made using these devices are more efficient and smaller.
SIT and SITH will be paid more attention to updating and improving the performance of variable frequency speed control. The frequency conversion speed regulation technology changes the speed of the alternating current motor by changing the frequency of the stator power supply voltage, thereby enabling a large number of fans and pumps driven by the variable frequency speed regulating motor to realize energy conservation. Today, frequency converters using GTR as a power device occupy at least nearly 10 billion US dollars in the world market. A hot topic of the 21st century power electronic equipment is to use IGBT power integrated circuits and other modern power semiconductor devices to update and reconstruct these inverters, along with improving the input and output waveforms and improving efficiency and reducing costs, and is expected to be in control theory. There are breakthroughs in methods and methods.
Expand the application of variable frequency power supplies. Many variable-frequency power systems that originally used electronic tubes, such as ultrasonic power supplies, ozone ion generators, fluorescent electronic ballasts, induction heating power supplies, sonar power supplies, radio (long, medium, and short-wave) emission power supplies, and even microwave power supplies will be modernized. Power semiconductor devices (such as IGBTs, MOSFETs, etc.) are replaced by new variable-frequency power supplies for the main power devices, and studies related to these power supplies (such as driving, protection of high voltage, ultra-high frequency, etc.) will be the main research of variable frequency power supplies in the 21st century. Question.
The frequency conversion power supply control strategy and EMI suppression have become the focus of research. Various control strategies and EMI suppression to improve the performance of the variable frequency power supply will become the key research areas of the inverter. The focus of the research is to improve the output waveform of the inverter, to make it closer to a sine wave, and to have a wide range of adaptability to different loads. Sex, eliminate harmonics as much as possible, improve power factor, apply SPWM rectifier technology, high-power resonant converter technology to reduce switching losses, and then improve the efficiency of the entire device.
3.1.3 Application of power electronics technology to achieve energy conservation is an important research direction Energy conservation in motion control. According to statistics, about 60% of the world's power generation is consumed by the electric motor. The electric motor has the highest efficiency only in the vicinity of the rated load. However, due to the consideration of overload and safety factor, the electric motor often operates in low efficiency. In order to solve the human energy crisis and achieve large-scale energy conservation, the 21st century will use computers and power electronics technology to achieve optimal operation of the motor, and realize variable voltage and energy-saving speed regulation for variable-load motors such as lathes, punches, shears, etc. A wide range of general-purpose mechanically driven motors such as fans, pumps, and compressors (which accounts for about half of the motor's power consumption) are used for frequency conversion and speed control, and for rolling and non-ferrous metal rolling, papermaking, sugar pressing, and large-scale machine tools, etc. Implementation of variable frequency speed regulation, transformation and transformation of electric locomotives, internal combustion engines, underground railways, light rail locomotives, trolleybuses, maglev trains and electric vehicles, as well as elevators, escalators, mine hoists and gantry cranes. The supporting AC speed regulation and the development of research related to these fields are another important research area for the 21st century power electronics assembly.
Lighting Fixtures and Energy Saving Research. According to reports, lighting power consumption accounts for about 20% of the total human power generation, so in the 21st century, great efforts will be invested in the transformation of lighting fixtures for energy conservation, which will be reflected in the development and upgrading of electronic ballasts and the transformation of past traditions. Ballast.
3.1.4 Renewal of the use of power electronics systems for power systems The power electronics system in power systems is used in power generation, power distribution, and power transmission and transformation in all areas. In the 21st century, new research and exploration are carried out in the following areas.
Transformation of traditional excitation methods. The traditional generator DC excitation is changed to frequency excitation to obtain higher reliability and greater benefits. The use of variable-frequency excitation for hydro-generators ensures that the voltage emitted from the turbines in the dry and rich periods can be kept constant. This technology can also be used in wind power generation.
(eg cross-sea power transmission), HVDC transmission is superior to AC transmission in the realization of non-periodic (non-synchronous) power system networking. At the same time, HVDC transmission saves the amount of metal materials (less one transmission line), and HVDC transmission needs to constitute an extremely high power. The rectifier and inverter devices require high reliability. In the 21st century, further research will be conducted on the basis of existing technologies to improve reliability. Humans will have more DC transmission lines in operation.
Dynamic reactive power compensation (SVC) technology. The existence of reactive power reduces the power factor of the generator, harmonics pollute the power grid, causes grid voltage fluctuations, and heats the generator and other equipment. Reactive power compensation using power electronics is still a hot topic in the 21st century power system. The focus of research is to achieve optimal results, and to make the power factor as close as possible to 1. Eliminating harmonics improves grid quality. Power electronic technology is used to suppress the EMI of the by-products in the operation of various power electronic equipments. The main research topic is that the active filter technology will suppress the occurrence of harmonics and realize the greening of the power grid.
3.2 The power electronics package will open up new areas of research 3.2.1 The energy storage sector is eager for new types of power electronics. As the load of the grid changes with the season and day and night, peaks and troughs occur. When electricity is used in the trough, the current method is to turn off one or several generators, and the energy waste is quite serious. The use of power electronic equipment to store surplus power generated by generators during peak power usage and to feed power to the grid at peak power usage is equivalent to covering at least one third of power plants. The value is obvious. Research in this area focuses on the power electronics assembly that implements the following three energy storage methods.
Pumped water storage power generation. During the day, the upstream reservoir discharges water to generate electricity. In the evening, excess electric grid power is used to drive the electric motor to drive the pump to pump water from the downstream reservoir into the upstream reservoir, and the reservoir fills the reservoir so that more electricity can be generated during the day. Of course, this electrical energy becomes mechanical energy, and then it becomes the energy conversion process of electrical energy, and the efficiency is relatively low.
Storage batteries and capacitor banks in the basement store energy. To rectify the excess AC power provided by the night power grid into DC power and store it in the â€œstorage battery-capacitor bankâ€ of the buildingâ€™s basement; during the day, this stored power is converted into AC power to supply electricity to the entire building. Power electronics equipment is also an important research area in the 21st century.
Superconducting coil magnetic field energy storage. In a superconductor coil, hundreds of thousands of ampere-amperes of DC current flow therethrough without loss. This type of energy storage device is greatly reduced in size and has high conversion efficiency. However, how to achieve the mutual conversion of conventional AC power and such low-voltage ultra-high-current DC power supplies presents a new topic for power electronics technology.
2 New energy utilization New research topics have been proposed for power electronics devices. The research on the use of power electronic equipment for sewage treatment, control of toxic and hazardous gas emissions, and control of human warming is also an important research area.
4 Concluding remarks The 21st century will be an era of vigorous development of power electronics technology. Research in these areas will make the human civilization more brilliant and splendid. Let us expand our arms and greet this day with joy and joy.
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