The development direction of modern power electronics technology is a shift from traditional power electronics, which mainly deals with low-frequency technology, to modern power electronics, which mainly deals with high-frequency technology. Power electronics technology began with silicon rectifier devices in the late 1950s and early 1960s. Its development has successively experienced the rectifier era, the inverter era, and the variable frequency power supply era, and has promoted the application of power electronics technology in many new fields. The power semiconductor composite devices represented by power MOSFETs and IGBTs developed in the late 1980s and early 1990s, which integrate high frequency, high voltage and high current, indicate that traditional power electronics technology has entered the modern power electronics era.
1. The era of rectifiers
High-power industrial electricity is provided by a power frequency (50Hz) alternator, but about 20% of the electricity is consumed in the form of DC, the most typical of which are electrolysis (non-ferrous metals and chemical raw materials require DC electrolysis), traction (electrical Locomotives, electric drive diesel locomotives, subway locomotives, urban trolley buses, etc.) and DC drive (steel rolling, papermaking, etc.) in three major areas. High-power silicon rectifiers can efficiently convert power frequency alternating current into direct current. 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 silicon rectifier factories all over the country. At present, the large and small semiconductor manufacturers manufacturing silicon rectifiers in the country are the products of that time.
2. Inverter era
There was a worldwide energy crisis in the 1970s, 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 to alternating current of 0~100Hz. From the 1970s to the 1980s, with the popularization of variable frequency speed control devices, thyristors, giant power transistors (GTR) and gate turn-off thyristors (GT0) 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, etc. 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.
3. The era of variable frequency power supply
The variable frequency power supply transforms the alternating current in the mains from AC→DC→AC, and outputs a pure sine wave. The output frequency and voltage are adjustable within a certain range. It is different from the frequency conversion speed controller used for motor speed control, and it is also different from the ordinary AC stabilized power supply. The ideal AC power supply is characterized by stable frequency, stable voltage, zero internal resistance, and a pure sine wave (no distortion) in the voltage waveform.
Around the 1980s, electronic variable-frequency power supplies were mostly made from small Japanese instruments. The power supplies of this type of instrument were mostly made by crystal amplification. After the 1980s, they were introduced to mainland China through Taiwan. The characteristics of the power supply during this period are: low power, good accuracy, and low efficiency.
In the 1980s, mainland China embarked on the road of reform and opening up. During this stage, China's import and export equipment gradually increased, especially the export share of electrical appliances such as microwave ovens and air conditioners increased. Therefore, high-power inverter power supplies were required for testing. For the needs of this part of the market, the original product power can no longer meet, so power supply manufacturers seek new technologies to expand the power of the power supply. According to the technical conditions and electronic devices at the time, the development was mainly in two ways. On the one hand, the crystal-type method was kept unchanged, and multiple machines were connected in parallel for capacity expansion; the other method was to use power crystal modules.
