Power electronics technology has been in existence for nearly 50 years. It has greatly promoted human civilization. Now it has no field, no industry, and it has left the power electronics technology, which will make people's life eclipse. Since the development of power electronics technology aims to achieve the generation and scheduling of electric energy and the best match between the grid and the power load, the best efficiency and optimal waveform power consumption are achieved. The basis for realizing these functions is power semiconductor devices, and the means to accomplish these functions is a power electronics package. Power electronics technology is an interdisciplinary subject in many disciplines such as integrated power semiconductor devices, power conversion technology, modern electronic technology, and automatic control technology. 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 is in modern communication, electronic instruments, computers, industrial automation, power grid optimization, power engineering. The role of national defense and certain high technologies in providing high quality, high efficiency, and high reliability of electrical energy plays a key role.
The 21st century is an era of simultaneous knowledge economy and industrial economy. Human civilization will enter a higher level, and all kinds of high and new technologies will be developed rapidly. This requires that power electronics technology closely related to these technologies does not lag behind the times. Therefore, in the 21st century, power electronics technology will have more rapid development. The 21st century power electronics technology research field can be discussed from three aspects of power semiconductor devices, power electronics complete sets and control theory, and power electronics complete sets can be divided into many aspects according to different industries.
The main research fields of 221st century power semiconductor devices The research field of power semiconductor devices in the 21st century is divided into two aspects: the improvement of the performance of existing devices and the development of new devices.
2.1 The performance of existing power semiconductor devices is perfect. The first silicon controlled rectifier SCR (now called thyristor) has been invented for nearly 50 years. Nowadays, power semiconductor devices have formed a huge family of more than 40 varieties, all kinds of devices. It has occupied a place in the power electronics complete set. In the 21st century, these existing devices will achieve 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 areas can be discussed from the following aspects.
2.1.1 The development speed of GTO, thyristor and GTR is slowed down. The structure of silicon single crystal determines that the maximum capacity of devices made of silicon can only reach 10000A/10000V, which determines the device capacity of thyristor, rectifier, GTO, IGCT, etc. The expansion of the power level is slower as it approaches 10000A/10000V, and the GTR determines the contradiction between the large current and the switching frequency due to the working mechanism. People will not spend much energy. Increase its power and frequency.
2.1.2 MOS device status prominent MOS field-controlled power semiconductor devices have become the mainstream of power semiconductor device research in the 21st century. For MOSFETs, IGBTs, and IEGTs, which use MOSFETs as the control stage and have high operating frequencies, the core of their research is to increase voltage and current capacity. After efforts, it is expected that the voltage and current capacity will reach 10000V/10000A level. The deepening and breakthrough of the research will greatly improve the operating frequency of these devices, and the voltage drop will be greatly reduced to meet the power electronic equipment. The more demanding requirements, the power electronics assemblies made with these devices are more efficient and smaller.
SIT and SITH will be subject to the emphasis on frequency conversion and the improvement of performance. The frequency conversion speed control technology realizes the change of the AC motor speed by changing the frequency of the stator power supply voltage, so that a large number of fans and pumps driven by the variable frequency speed control motor achieve energy saving. Nowadays, the frequency converter with GTR as the power device has occupied at least nearly 10 billion US dollars in the market. A hot topic in the 21st century power electronics complete set is to update and modify these inverters with modern power semiconductor devices such as IGBT power integrated circuits, along with research to improve input and output waveforms, improve efficiency and reduce costs, and hope to be in control theory. And a breakthrough in the method.
Expand the application field of variable frequency power supply. Many original variable frequency power systems using 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) transmitting power supplies, and even microwave power supplies will be modern. Power semiconductor devices (such as IGBTs, MOSFETs, etc.) are replaced by new variable frequency power supplies for main power devices. Research on technologies related to these power sources (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 control strategy and EMI suppression of variable frequency power supply 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 research focuses on improving the output waveform of the inverter to make it closer to the sine wave, and can adapt to a wide range of loads. Sex, eliminate harmonics as much as possible, improve power factor, apply SPWM rectification technology, high-power resonant converter technology to reduce switching losses, and thus improve the efficiency of the whole device.
3.1.3 Application of power electronics technology to achieve energy conservation is an important direction of research and energy saving for motion control. According to statistics, about 60% of the world's power generation is consumed by electric motors. The electric motor only has the highest operating efficiency near the rated load. However, due to the consideration of overload and safety factor, the electric motor is often inefficient operation. In order to solve the human energy crisis and achieve large-area energy conservation, the 21st century will use computer and power electronics technology to achieve optimal operation of the motor, and realize voltage-regulating and energy-saving speed regulation for variable-load motors such as lathes, punching machines and shearing machines. Extensively realize general-purpose mechanical drive motors such as fans, pumps, compressors, etc. (accounting for about half of the motor power consumption), variable frequency speed regulation, and the process of dragging motors for rolling steel, non-ferrous metal rolling, paper making, sugar extraction, large machine tools, etc. Implementing variable frequency speed regulation, implementing electric current locomotives, internal combustion engines, underground railways, light rail locomotives, trolley buses, maglev trains and electric vehicles, as well as elevators, escalators, mine winches and gantry cranes, etc. The supporting AC speed regulation and research related to these fields are another important research field of the 21st century power electronics complete sets.
Lighting fixture renovation and energy conservation research. According to reports, lighting power consumption accounts for about 20% of total human power generation. Therefore, in the 21st century, energy conservation will put a lot of energy into the renovation of lighting fixtures, which is reflected in the development and upgrading of electronic ballasts, transforming the past tradition. Ballast.
3.1.4 Power system use of power electronics complete sets of equipment research and development of power systems in the power system complete sets of power electronics, power supply and transmission and power transformation in the 21st century in the following aspects of new research and exploration.
The transformation of the traditional excitation method. The traditional generator DC excitation is changed to variable frequency excitation for higher reliability and greater efficiency. The frequency converter is used for the hydro-generator to ensure that the voltage of the turbine is constant for the change of the turbine speed during the dry season and the rich period. This technology can also be used in wind power generation.
(such as trans-ocean transmission), non-periodic (non-synchronous) power systems to achieve networking, high-voltage direct current transmission is better than AC transmission, while direct current transmission saves the amount of metal materials (less than one transmission line), DC transmission needs to constitute extra power The rectification and inverter devices require high reliability. In the 21st century, further research will be carried out on the basis of the existing technology to improve reliability, and humans will have more DC transmission lines put into operation.
Dynamic Reactive Power Compensation (SVC) technology. The existence of reactive power reduces the power factor of the generator, and the harmonics pollute the power grid, causing voltage fluctuations in the power grid and adding heat to the generator and other equipment. The use of power electronics complete sets of reactive power compensation will continue to be a hot topic in the 21st century power system. The focus of research is to achieve optimal results, and to make the power factor close to 1. Eliminate harmonics and improve grid quality. The power electronics technology is used to suppress the EMI of by-products in the operation of various power electronic equipments. The main research topic is that active filtering technology suppresses harmonic generation and realizes green grid.
3.2 Power electronics complete sets of equipment will open up new research areas 3.2.1 Energy storage field eager for new power electronic complete sets of equipment Because the load of the power grid changes with the influence of seasons and day and night, resulting in peaks and valleys of power consumption. When using electricity, the current method is to turn off one to several generators, and the energy waste is quite serious. The power electronic equipment is used to store the excess electric energy generated by the generator when the electricity is low, and then to the power grid when the electricity is at a peak. This method is equivalent to covering at least one third of the power plant, and its economy. The value is obvious, and research in this area focuses on power electronics packages that implement the three energy storage methods described below.
Pumped water storage for power generation. During the day, the upstream reservoir discharges water to generate electricity; in the evening, the excess grid power is used to drive the electric motor to drive the water pump to pump the water from the downstream reservoir into the upstream reservoir, and the upstream reservoir to store water, so that more electricity can be generated during the day. Of course, this kind of electric energy becomes mechanical energy, and then it becomes the energy conversion process of electric energy, and the efficiency is relatively low.
The battery and capacitor bank in the basement store energy. The excess AC power provided by the night power grid is rectified into direct current and stored in the "battery-capacitor bank" in the basement of the building; during the day, the stored electrical energy is inverted into alternating current to supply power to the entire building, and the process is studied. The power electronics package is also an important research area in the 21st century.
The magnetic field energy storage of the superconducting coil. In a superconductor coil, hundreds of thousands of amps of direct current flow therethrough without loss, and the accumulator is greatly reduced in size and high in conversion efficiency. However, how to realize the mutual conversion between conventional AC power and such low-voltage super-current DC power has brought about an updated issue for power electronics technology.
2 New energy utilization proposes new research topics for power electronics complete sets of equipment. The use of power electronics complete sets of equipment for wastewater treatment, control of toxic and harmful gas emissions, and control of human climate warming is also an important research area.
4 Conclusion The 21st century will be an era of vigorous development of power electronics technology. The research in the above-mentioned fields will make the human civilization more brilliant and splendid. Let us expand our arms and welcome them with joy.
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