Research on expanding the application field of series superposition high-voltage inverters

1 Introduction

众所周知，高压大 功率 风机、水泵采用变频调速的方法，在方便的调整工况的同时，还可以收到显著的节能效果，其直接经济效益很明显，宏观经济效益及社会效益则更加巨大。可以预计，在当前国家大力倡导建设节约型社会、实现和谐发展的形势下，高压大功率变频调速新技术的发展将成为我国节电事业的重要方向之一。据统计，我国每年高压电机用电量估计在3600~4200亿kw& mid dot;h，这个数字还在随着经济的增长而不断的增加。

2 TS-HVAF1.5, TS-HVAF1.5R High-voltage inverter Research and development background

At present, there are some solutions for high-voltage frequency conversion speed regulation and energy-saving technology at home and abroad, but none of them are very ideal. Early foreign products flooded the Chinese market. These devices have high requirements for the use environment, limited service life, complex equipment, poor stability and reliability, and are not easy to maintain and transport. They cannot be used safely in high temperature, high humidity, highly corrosive gas, high dust, explosion-proof and other environments.

In fact, the application areas of high-voltage inverters cover all walks of life in the field of industrial production. However, due to the complex application environment and the various defects mentioned above, traditional high-voltage inverters cannot fully meet the needs of users, which limits the promotion and application of high-voltage inverters.

After Beijing Xianxing New Electromechanical Technology Co., Ltd. successfully developed a high-voltage inverter based on the "series superposition" principle, Shandong Dianshi Energy Saving Technology Development Co., Ltd., based on the introduction and absorption, independently developed and successfully manufactured the TS-HVAF1.5 and TS-HVAF1.5R "series superposition" high-voltage inverters, achieving a major technological breakthrough in high-voltage inverter products and solving major problems existing in traditional high-voltage inverters.

3 Major technological breakthroughs achieved by TS-HVAF1.5 and TS-HVAF1.5R high-voltage inverters

3.1 Reduced restrictions on the use environment

High-voltage and high-power electromechanical equipment has a large current and a high temperature rise, so the power components must be well ventilated and cooled. However, ventilation and dust prevention are a pair of contradictions that are difficult to resolve, so traditional high-voltage inverters cannot be used safely in environments with high dust, high humidity, high temperature and corrosive gases. The TS-HVAF1.5R high-voltage inverter adopts the technology of a fully enclosed built-in heat exchanger, which does not directly exchange air with the external environment, completely overcomes the defects of traditional high-voltage inverters, and greatly expands the application field of high-voltage inverters. Since the volume of the power unit cabinet of the TS-HVAF1.5 high-voltage inverter is less than 3m3, although a central air conditioner consisting of 6 industrial air conditioners is designed for safe operation, in fact, the long-term power consumption of the central air conditioner is only about 2kw.

3.2 Cleaner electricity output and no pollution to the power grid

The TS-HVAF1.5 series superposition high-voltage inverter uses the pulsating DC superposition principle (maximum frequency 50 Hz) to replace the traditional PWM (generally with a base frequency of about 4 kHz) technology. The output line voltage waveform and current waveform are both very good sine waves, which not only greatly reduces the output harmonics and pollution to the power grid, but also greatly prolongs the service life of the switch device ( IGBT ).

3.3 Anti-interference ability is greatly improved

In the central control system of the TS-HVAF1.5 high-voltage inverter, large-scale integrated circuits are used to replace the single-chip microcomputer in the traditional high-voltage inverter, realizing "hardware processing of software problems", greatly improving the anti-interference ability, and no longer causing program disorder, crashes, etc., making the operation of the equipment safer, more stable and reliable.

3.4 Safer and more reliable operation

Due to the simpler and more reliable control program, the TS-HVAF1.5 and TS-HVAF1.5R high-voltage inverters can increase the number of splitting and superposition units on the basis of traditional high-voltage inverters, and are equipped with "continuous waveform conversion" technology. Once an individual power unit fails, the output voltage loss is relatively small, and it can still maintain higher power operation, that is, it can continue to operate safely at a frequency of 45 Hz and below; while the traditional high-voltage inverter must significantly reduce the power used by the controlled motor as long as one power unit is damaged.

3.5 Product factory inspection is more effective

Since the volume of the TS-HVAF1.5 high-voltage inverter is only about one-third of that of the traditional high-voltage inverter, the whole machine can be transported, which not only greatly shortens the time of on-site installation and commissioning, but also minimizes the production losses caused by installation and commissioning; more importantly, all the inspections of the high-voltage inverter in the factory are more real, reliable and effective.

3.6 Greatly improve the reliability of high voltage inverter

In the structure of the entire TS-HVAF1.5 high-voltage inverter, except for the incoming and outgoing cables and the control circuit, no other wires are used, which greatly reduces the wiring resistance and possible fault points. The overall layout is simple and clear, which greatly improves the reliability of the high-voltage inverter. In addition, the unitization of the whole machine allows users to perform maintenance and repairs on site by themselves.

3.7 A relatively complete system to prevent misoperation can be set up

If the user requests, the TS-HVAF1.5 and TS-HVAF1.5R high-voltage inverters can also be equipped with a relatively complete system to prevent misoperation, thereby avoiding the possibility of failure due to operator misoperation.

3.8 Solved the technical difficulties of domestic synchronous motor variable frequency speed regulation transformation

Since synchronous motors are equipped with rotor excitation current, and the control of excitation current is very difficult, at present, only Shandong Dianshi Energy Saving Technology Development Co., Ltd. can produce high-voltage inverters for synchronous motors in China. The company can undertake high-voltage frequency conversion projects for synchronous motors when the user can meet the following conditions:

(1) The excitation cabinet used by the user is controllable, that is, the excitation current and excitation voltage can be adjusted;

(2) The user allows the excitation cabinet to be modified;

(3) The debugging time at the installation site needs to be extended by 10 to 15 days.

4 Conclusion

The successful development of TS-HVAF1.5 and TS-HVAF1.5R high-voltage inverters can be said to be a revolution in the field of high-voltage variable-frequency speed regulation. It has greatly improved the reliability, safety, and applicability of high-voltage inverters, met the needs of users to the greatest extent, and enabled high-voltage inverters to be used in a wider range of fields. It will definitely play a positive role in promoting the variable-frequency speed regulation transformation of high-voltage and high-power motors.