At present, as the foundation of energy saving, talent saving, automation, intelligence, and electromechanical integration, power electronics is developing in the direction of high-frequency application technology, modular hardware structure, and green product performance. In the near future, power electronic technology will make power technology more mature, economical and practical, and achieve a combination of high efficiency and high quality electricity. 1. The development of power electronics technology The development direction of modern power electronics technology is a shift from traditional power electronics, which focuses on low-frequency technology to deal with problems, to modern power electronics, which focuses on high-frequency technology. Power electronics technology started from silicon rectifier devices in the late 1950s and early 1960s. Its development has successively experienced the rectifier era, the inverter era and the frequency converter era, and has promoted the application of power electronic technology in many new fields. In the late 1980s and early 1990s, the power semiconductor composite devices represented by power MOSFETs and IGBTs, which integrate high frequency, high voltage and large current, were developed in the late 1980s and early 1990s, indicating that traditional power electronics technology has entered the modern power electronics era. 1.1 High-power industrial electricity in the era of rectifiers is provided by power frequency (50Hz) AC generators, but about 20% of the electrical energy is consumed in the form of DC, the most typical of which is electrolysis (non-ferrous metals and chemical raw materials require DC electrolysis), Traction (electric locomotive, electric drive diesel locomotive, subway locomotive, urban trolleybus, etc.) and DC drive (steel rolling, paper making, etc.) are three major areas. High-power silicon rectifiers can convert power frequency alternating current into direct current with high efficiency. Therefore, in the 1960s and 1970s, the development and application of high-power silicon rectifiers and thyristors have been greatly developed. At that time, there was an upsurge of large-scale establishment of silicon rectifier factories in China. At present, the large and small semiconductor manufacturers manufacturing silicon rectifiers in the country are the products of that time. 1.2 The era of inverters In the 1970s, there was a worldwide energy crisis, and AC motors' frequency conversion speeds developed rapidly due to their remarkable energy-saving effects. The key technology of variable frequency speed regulation is to invert direct current into alternating current of 0-100Hz. In the 1970s and 1980s, with the popularization of variable frequency speed regulation devices, thyristors, giant power transistors (GTR) and gate turn-off thyristors (GT0) used for high-power inverters 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, the power electronics technology has been able to achieve rectification and inversion, but the operating frequency is low, only limited to the low frequency range. 1.3 The era of frequency converters In the 1980s, the rapid development of large-scale and very large-scale integrated circuit technology has laid the foundation for the development of modern power electronics technology. Combining the fine processing technology of integrated circuit technology and high-voltage and high-current technology organically, a new batch of fully-controlled power devices has emerged, first of all, the advent of power MOSFETs, which has led to the development of small and medium power power supplies to high frequencies, and then insulated gates. The emergence of bipolar transistors (IGBT) has brought opportunities for the development of large and medium-sized power supplies to high frequencies. The successive appearance of MOSFET and IGBT is a sign of the transformation from traditional power electronics to modern power electronics. According to statistics, by the end of 1995, power MOSFETs and GTRs had reached an equal share in the power semiconductor device market, and the use of IGBTs to replace GTRs in the field of power electronics has reached a conclusion. The development of new devices not only provides a higher frequency for AC motor frequency conversion speed regulation, making its performance more complete and reliable, but also enables modern electronic technology to continue to develop towards high frequency, which is a high-efficiency, material-saving and energy-saving for electrical equipment, and realizes small and light-weight Quantification, mechatronics and intelligence provide an important technical basis. 2. Application fields of modern power electronics 2.1 Computer high-efficiency green power supply The rapid development of computer technology has led mankind into the information society, and at the same time promoted the rapid development of power supply technology. In the 1980s, computers fully adopted switching power supplies, taking the lead in completing the replacement of computer power supplies. Then switching power supply technology has entered the field of electronics and electrical equipment one after another. With the development of computer technology, green computers and green power supplies have been proposed. Green computers generally refer to personal computers and related products that are not harmful to the environment. Green power supplies refer to high-efficiency power-saving power supplies related to green computers. According to the US Environmental Protection Agency's "Energy Star" plan on June 17, 1999, desktops If the power consumption of a type personal computer or related peripheral equipment is less than 30 watts in the sleep state, it meets the requirements of a green computer. Improving power efficiency is the fundamental way to reduce power consumption. As far as the current 200-watt switching power supply with an efficiency of 75% is concerned, the power supply itself consumes 50 watts of energy. 2.2 High-frequency switching power supplies for communications The rapid development of the communications industry has greatly promoted the development of communications power supplies. High-frequency miniaturized switching power supply and its technology have become the mainstream of modern communication power supply systems. In the communication field, the rectifier is usually called the primary power supply, and the DC-DC (DC/DC) converter is called the secondary power supply. The function of the primary power supply is to transform a single-phase or three-phase AC power grid into a DC power supply with a nominal value of 48V. At present, in the primary power supply for program-controlled switches, the traditional phase-controlled regulated power supply has been replaced by a high-frequency switching power supply. The high-frequency switching power supply (also known as the switching rectifier SMR) works through the high frequency of MOSFET or IGBT, and the switching frequency It is generally controlled in the range of 50-100kHz to achieve high efficiency and miniaturization. In recent years, the power capacity of switching rectifiers has continued to expand, and the capacity of a single unit has expanded from 48V/12.5A, 48V/20A to 48V/200A, 48V/400A. Due to the various types of integrated circuits used in communication equipment, their power supply voltages are also different. In the communication power supply system, a high-power density high-frequency DC-DC isolated power supply module is used to transform the intermediate bus voltage (usually 48V DC) into The various DC voltages required can greatly reduce losses, facilitate maintenance, and are very convenient to install and increase. Generally, it can be directly installed on the standard control board, and the requirement for the secondary power supply is high power density. As the communication capacity continues to increase, the communication power supply capacity will also continue to increase. 2.3 DC-DC (DC/DC) converter The DC/DC converter transforms a fixed DC voltage into a variable DC voltage. This technology is widely used in the stepless speed change of trolleybuses, subway trains, and electric vehicles. Control, at the same time, the above-mentioned control obtains the performance of accelerating smoothly, fast response, and at the same time receiving the effect of saving energy. Replacing the varistor with a DC chopper can save power (20-30)%. The DC chopper can not only regulate the voltage (switching power supply), but also effectively suppress the harmonic current noise on the grid side. The secondary power DC/DC converter of the communication power supply has been commercialized. The module adopts high-frequency PWM technology, the switching frequency is about 500kHz, and the power density is 5W～20W/in3. With the development of large-scale integrated circuits, the power supply module is required to be miniaturized, so it is necessary to continuously increase the switching frequency and adopt new circuit topologies. At present, some companies have developed and produced two types of zero-current switching and zero-voltage switching technologies. The power density of the secondary power supply module has been greatly improved. 2.4 Uninterruptible power supply (UPS) Uninterruptible power supply (UPS) is a high-reliability and high-performance power supply necessary for computers, communication systems, and occasions requiring uninterrupted provision. The AC mains input is converted into DC by the rectifier, part of the energy is charged to the battery pack, and the other part of the energy is converted into AC by the inverter, and sent to the load through the transfer switch. In order to still provide energy to the load when the inverter fails, another backup power source is realized through a power transfer switch. Modern UPS generally adopts pulse width modulation technology and modern power electronic devices such as power MOSFETs and IGBTs. The noise of the power supply can be reduced, and the efficiency and reliability can be improved. The introduction of microprocessor software and hardware technology can realize the intelligent management of UPS, remote maintenance and remote diagnosis. At present, the maximum capacity of online UPS can reach 600kVA. The development of ultra-small UPS is also very rapid, and there are products with various specifications such as 0.5kVA, lVA, 2kVA, and 3kVA. 2.5 Inverter power supply Inverter power supply is mainly used for frequency conversion and speed regulation of AC motors, and its position in the electric drive system is becoming more and more important, and it has achieved huge energy-saving effects. The main circuit of the inverter power supply adopts AC-DC-AC scheme. The industrial frequency power supply is converted into a fixed DC voltage through a rectifier, and then a PWM high-frequency converter composed of high-power transistors or IGBTs inverts the DC voltage into a voltage and frequency variable AC output. The output waveform of the power supply is similar to a sine wave. Used to drive AC asynchronous motors to achieve stepless speed regulation. The inverter power supply series products below 400kVA have come out internationally. In the early 1980s, Toshiba of Japan first applied AC frequency conversion speed regulation technology to air conditioners. By 1997, its share has reached more than 70% of household air conditioners in Japan. Inverter air conditioners have the advantages of comfort and energy saving. Domestic research on inverter air conditioners began in the early 1990s. In 1996, the production line was introduced to produce inverter air conditioners, which gradually formed a hot spot for the development and production of inverter air conditioners. It is expected that the climax will be formed around 2000. In addition to the inverter power supply, inverter air conditioners also require a compressor motor suitable for inverter speed regulation. Optimizing the control strategy and selecting functional components are the further development direction of the air conditioner inverter power supply. 2.6 High-frequency inverter rectifier welding machine power supply High-frequency inverter rectification welding machine power supply is a high-performance, efficient, and material-saving new welding machine power supply, which represents the development direction of today's welding machine power supply. Due to the commercialization of IGBT high-capacity modules, this kind of power supply has broader application prospects. Inverter welding machine power supply mostly adopts AC-DC-AC-DC (AC-DC-AC-DC) conversion method. The 50Hz alternating current is converted into direct current through full bridge rectification, and the PWM high-frequency conversion part composed of IGBTs inverts the direct current into a high frequency rectangular wave of 20kHz, coupled by a high-frequency transformer, rectified and filtered, and becomes a stable direct current, which is used for arc power supply. Due to the poor working conditions of the welding machine power supply, and frequent short-circuit, arcing, and open-circuit alternate changes, the working reliability of the high-frequency inverter rectifier welding machine power supply has become the most critical issue, and it is also the most concerned issue of users. . Using a microprocessor as a pulse width modulation (PWM) related controller, through the extraction and analysis of multiple parameters and multiple information, the purpose of predicting the various working conditions of the system is achieved, and the system can be adjusted and processed in advance to solve the problem. Improve the reliability of current high-power IGBT inverter power supplies. Foreign inverter welding machines can achieve a rated welding current of 300A, a load duration of 60%, a full load voltage of 60 to 75V, a current adjustment range of 5 to 300A, and a weight of 29kg. 2.7 High-power switching high-voltage DC power supplies High-power switching high-voltage DC power supplies are widely used in large equipment such as electrostatic dust removal, water quality improvement, medical X-ray machines and CT machines. The voltage is as high as 50～l59kV, the current is above 0.5A, and the power is up to 100kW. Since the 1970s, some companies in Japan have adopted inverter technology, which converts the mains power to an intermediate frequency of about 3kHz after rectification, and then boosts it. In the 1980s, high-frequency switching power supply technology developed rapidly. Germany's Siemens uses power transistors as the main switching element to increase the switching frequency of the power supply to more than 20kHz. The dry-type transformer technology is successfully applied to high-frequency and high-voltage power supplies, and the high-voltage transformer oil tank is eliminated, which further reduces the volume of the transformer system. Domestically, the electrostatic precipitator high-voltage DC power supply has been developed. The mains is rectified into DC, and the full-bridge zero-current switch series resonant inverter circuit is used to invert the DC voltage into high-frequency voltage, and then the high-frequency transformer is boosted, and finally rectified It is DC high voltage. Under resistive load conditions, the output DC voltage reaches 55kV, the current reaches 15mA, and the operating frequency is 25.6kHz. 2.8 When the traditional AC-DC (AC-DC) converter of the active power filter is put into operation, it will inject a large amount of harmonic current into the power grid, causing harmonic loss and interference, and at the same time, the power factor of the device will deteriorate on the grid side. Phenomenon, the so-called "power pollution", for example, when uncontrollable rectification and capacitor filtering, the third harmonic content on the grid side can reach (70～80)%, and the power factor on the grid side is only 0.5～0.6. Active power filter is a new type of power electronic device that can dynamically suppress harmonics. It can overcome the shortcomings of traditional LC filters and is a promising harmonic suppression method. The filter is composed of a bridge switching power converter and a specific control circuit. Not only the output voltage is fed back, but also the average input current is fed back; (2) The current loop reference signal is the product of the voltage loop error signal and the full-wave rectified voltage sampling signal. 2.9 Distributed switching power supply system The distributed power supply system uses low-power modules and large-scale control integrated circuits as basic components, and uses the latest theories and technical achievements to form a building block-style, intelligent high-power power supply, so as to make the strong current and The tight integration of weak current reduces the pressure on the development of high-power components and high-power devices (centralized) and improves production efficiency. In the early 1980s, the research on distributed high-frequency switching power supply systems basically focused on the research of converter parallel technology. In the middle and late 1980s, with the rapid development of high-frequency power conversion technology, various converter topologies appeared one after another. Combining large-scale integrated circuit and power component technology, the integration of small and medium power devices became possible, thereby rapidly Promote the development of distributed high-frequency switching power supply system research. Since the late 1980s, this direction has become a research hotspot in the international power electronics circle. The number of papers has increased year by year, and the field of application has continued to expand. The distributed power supply method has the advantages of energy saving, reliability, high efficiency, economy and convenient maintenance. It has been gradually adopted by large-scale computers, communication equipment, aerospace, industrial control and other systems. It is also the most ideal power supply method for low-voltage power (3.3V) of ultra-high-speed integrated circuits. In high-power applications, such as electroplating, electrolysis power supply, electric locomotive traction power supply, intermediate frequency induction heating power supply, motor drive power supply and other fields, there are also broad application prospects. 3. The development trend of high-frequency switching power supply In the application of power electronic technology and various power supply systems, switching power supply technology is at the core. For large electrolytic plating power supplies, the traditional circuits are very bulky and heavy. If Gordon switching power supply technology is used, its volume and weight will be greatly reduced, and the power utilization efficiency can be greatly improved, material savings, and costs can be reduced. In electric vehicles and variable frequency drives, it is inseparable from the switching power supply technology. The switching power supply changes the power frequency to achieve near-ideal load matching and drive control. High-frequency switching power supply technology is the core technology of various high-power switching power supplies (inverter welding machine, communication power supply, high-frequency heating power supply, laser power supply, electric power operation power supply, etc.). 3.1 High frequency Theoretical analysis and practical experience show that the volumetric weight of transformers, inductors and capacitors of electrical products is inversely proportional to the square root of the power supply frequency. So when we increase the frequency from 50Hz to 20kHz, 400 times, the volume and weight of electrical equipment will be reduced to 5~l0% of the power frequency design. Whether it is an inverter rectifier welding machine or a switching rectifier for communication power supply, both It is based on this principle. Similarly, various DC power supplies such as electroplating, electrolysis, electrical processing, charging, floating charging, and power closing in the traditional "rectifier industry" can also be transformed according to this principle to become a "switching conversion power supply". The main materials can be It can save 90% or more, and can save electricity by 30% or more. Due to the gradual increase in the upper limit of the working frequency of power electronic devices, many traditional high-frequency equipment that originally used electronic tubes are solidified, which brings significant economic benefits of energy saving, water saving, and material saving, and can reflect the value of technical content. 3.2 Modularity Modularization has two meanings, one is the modularization of power devices, and the other is the modularization of power supply units. Our common device modules, including one unit, two units, six units to seven elements, including switching devices and freewheeling diodes in anti-parallel with them, are essentially "standard" power modules (SPM). In recent years, some companies have installed the drive protection circuit of the switching device into the power module to form an "intelligent" power module (IPM), which not only reduces the size of the whole machine, but also facilitates the design and manufacture of the whole machine. In fact, due to the continuous increase of frequency, the influence of lead parasitic inductance and parasitic capacitance has become more serious, causing greater electrical stress on the device (in the form of overvoltage and overcurrent burrs). In order to improve the reliability of the system, some manufacturers have developed a "user-specific" power module (ASPM), which installs almost all hardware of a complete machine into a module in the form of a chip, so that the components are no longer between With traditional lead connections, such modules have undergone strict and reasonable thermal, electrical, and mechanical design to achieve a perfect state of optimization. It is similar to the user-specific integrated circuit (ASIC) in microelectronics. As long as the control software is written into the microprocessor chip in the module, and then the whole module is fixed on the corresponding radiator, a new type of switching power supply device is formed. It can be seen that the purpose of modularization is not only to facilitate use and reduce the size of the whole machine, but more importantly, to cancel the traditional connection and minimize the parasitic parameters, so as to minimize the electrical stress on the device and improve the reliability of the system. . In addition, high-power switching power supplies, due to the limitation of device capacity and increased redundancy to improve reliability, generally use multiple independent module units to work in parallel, using current sharing technology, and all modules share the load current. If one module fails, the other modules share the load current equally. In this way, not only the power capacity is increased, but the requirement of large current output is met under the condition of limited device capacity, and the system reliability is greatly improved by adding redundant power supply modules with low power relative to the entire system. In case of a single module failure, it will not affect the normal operation of the system and provide sufficient time for repair. 3.3 Digitization In traditional power electronic technology, the control part is designed and worked according to analog signals. In the 1960s and 1970s, power electronics technology was completely based on analog circuits. However, now that digital signals and digital circuits are becoming more and more important, digital signal processing technology is becoming more and more mature, showing more and more advantages: convenient for computer processing and control, avoiding distortion and distortion of analog signals, and reducing spurious signals. Interference (improvement of anti-interference ability), convenient for software package debugging and remote sensing, telemetry and remote adjustment, and also for the implantation of self-diagnosis, fault tolerance and other technologies. Therefore, in the 1980s and 1990s, analog technology was still useful for the design of various circuits and systems, especially: such as the layout of printed plates, electromagnetic compatibility (EMC) issues, and power factor correction (PFC) The solution to other problems is inseparable from the knowledge of analog technology, but for intelligent switching power supplies, when computer control is required, digital technology is inseparable. 3.4 Greening The greening of the power supply system has two meanings: the first is significant power saving, which means the saving of power generation capacity, and power generation is an important cause of environmental pollution, so power saving can reduce environmental pollution; secondly, these The power supply can not (or less) cause pollution to the power grid. The International Electrotechnical Commission (IEC) has formulated a series of standards for this, such as IEC555, IEC917, IEC1000 and so on. In fact, many power electronic energy-saving devices tend to become a source of pollution to the power grid: inject serious high-order harmonic currents into the power grid, which reduces the total power factor, couples many burr spikes to the grid voltage, and even has missing angles and distortions. . At the end of the 20th century, various active filters and active compensator schemes were born, and there were many ways to correct the power factor. These laid the foundation for mass production of various green switching power supplies in the 21st century. Modern power electronic technology is the basis for the development of switching power supply technology. With the continuous emergence of new power electronic devices and circuit topologies suitable for higher switching frequencies, modern power supply technology will develop rapidly under the impetus of actual needs. Under the traditional application technology, the performance of the switching power supply is affected due to the limitation of the performance of power devices. In order to maximize the characteristics of various power devices and minimize the impact of device performance on the performance of the switching power supply, the new power circuit topology and new control technology can make the power switch work in a zero voltage or zero current state, which can be Greatly improve the operating frequency, improve the efficiency of the switching power supply, and design a switching power supply with excellent performance. All in all, power electronics and switching power supply technology continue to develop due to application requirements, and the emergence of new technologies will update many application products and open up more updated application fields. The realization of switching power supply's high frequency, modularization, digitization, greenization, etc. will mark the maturity of these technologies and realize the combination of high-efficiency and high-quality electricity. In recent years, with the development of the communication industry, the switching power supply for communication with switching power supply technology as the core has a domestic market demand of more than 2 billion yuan, which has attracted a large number of scientific and technological personnel at home and abroad to conduct development and research. It is a general trend that switching power supplies replace linear power supplies and phase-controlled power supplies. Therefore, the domestic market for power-operated power supply systems that also has a demand for billions of output value is starting and will soon develop. There are many other special power supplies and industrial power supplies with switching power supply technology as the core are waiting for people to develop.
The development of modern power electronics and power technology
Jun 21, 2021
Leave a message