Application of the hottest variable frequency driv

2022-07-24
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Application of variable frequency drive technology in urban traffic vehicles Abstract: This paper introduces the application of variable frequency drive technology in urban traffic vehicles, the social and economic benefits, and expounds the development trend of variable frequency drive technology

I. overview:

with the advent of modern power electronic devices and intelligent power integration modules, the development of control theory and microelectronics technology has enabled the smooth realization of voltage regulation, frequency conversion and speed regulation of asynchronous motors, so that AC variable frequency drives are widely used in all sectors of the national economy and are gradually replacing DC drive systems, At the same time, with the improvement of high-power self turning off devices and the development of digital control technology with microprocessor as the core, the application of AC variable frequency drive system in urban traffic vehicles is promoted

II. Application of variable frequency drive technology in foreign countries

urban rail locomotives have been developed in foreign countries for more than 100 years. With the application and development of modern technology, their electric drive system has undergone great changes. Their drive and speed regulation system has developed from the initial variable resistance speed regulation to chopper speed regulation, and then to the application of AC three-phase asynchronous traction motor using voltage variable frequency speed regulation (VVVF) drive technology. Due to the excellence of this variable frequency drive technology, almost all metro and light rail vehicles recently developed by Germany, Japan and other developed countries in the world adopt AC variable frequency drive technology. Moreover, with the increasingly close relationship between energy, environmental protection and human beings, the locomotive adopting this speed regulation technology will be accepted by a broader market and society

for example, according to the test results of BR120 AC variable frequency drive electric locomotive in Germany recorded in relevant documents, this kind of locomotive has the following significant advantages over DC drive vehicles:

① At the same adhesion weight, the traction force is increased by 30%

②. High power factor (COS φ It can reach 1), and the power utilization rate can be increased by 30%

③. Because it uses power electronic devices instead of contact devices, the maintenance cost can be reduced by 50%

④. Fault free operation exceeds 400000km

⑤. Energy saving is remarkable. The efficiency of AC drive with GTO frequency converter can be increased by 6 ~ 7% compared with DC drive with chopper speed regulation of the same capacity. According to relevant information, a 5600kW locomotive can save 392 kwh per hour. If it runs 3000 hours per year, it can save 1176000 kwh per year. Its remarkable energy-saving effect will bring remarkable social and economic benefits

at present, Japan and Germany, which are at the leading level of AC drive vehicles in the world, basically adopt PWM (AC-DC-AC) gto-vvv inverter (GTO inverter for short) and asynchronous traction motor to form a frequency conversion drive system

the capacity of GTO frequency converter produced in Japan after 1990 has reached 4500V and 3000A. The main parameters of all Japanese AC variable frequency speed regulation vehicles published by Japan in november1991. The GTO frequency converters manufactured by Hitachi, Toshiba, Mitsubishi Electric, Fuji electric and Toyo electric are used in this design. From 1986 to the end of 1990, Toyo has provided GTO frequency converters for 23 models. According to relevant information, the number of small and medium power frequency converters below 100kW produced in Japan in 1994 has reached 1million. In addition to Japan, developed countries such as Europe and the United States have formed a relatively complete inverter technology industry system

at present, almost all metro and light rail trains newly developed by Germany, Japan and other developed countries in the world in recent years adopt AC variable frequency transmission technology; The three-point inverter is used in the AC drive system, which has been applied in Germany and Japan. In 1993, thousands of IGBT three-point inverters formed through the cooperation scheme with Siemens were used in light rail cars in Germany

III. characteristics and benefits of the application of variable frequency drive technology in urban traffic vehicles in China

1) Advantages of AC variable frequency drive vehicles:

AC variable frequency drive system is generally composed of three-phase AC asynchronous motor, frequency converter and its control device. Compared with DC drive system, it has the following remarkable advantages:

compared with DC motor, asynchronous motor has simple structure, no commutator, reliable operation, light weight, high efficiency and low price. It has hard mechanical characteristics and excellent traction performance. The control circuit is simpler than the DC drive system, and the maintenance is very easy

2) at present, the energy-saving situation of new-type variable-frequency energy-saving trolleybuses in China:

for example, Guangzhou Honda company replaced 152 old resistance controlled trolleybuses and 48 chopper controlled trolleybuses with 200 variable-frequency trolleybuses. On the actual operation route, they measured the power consumption of various trams, and their measurement results showed that the power consumption of the new type of trams was 72.6% of that of the resistance control vehicles. The measurement results are shown in the following table:

according to their comparison and calculation of the power consumption of 200 new frequency conversion vehicles and 200 old vehicles in one year, the power consumption of the new vehicle is reduced by about 24%, which shows that the power saving effect of the new frequency conversion drive control vehicle is very obvious. According to the introduction of relevant data, the efficiency of the device driven by GTO frequency converter is 6 ~ 7% higher than that of the DC drive device with the same capacity. As mentioned above, the application of variable frequency drive technology in urban traffic vehicles has achieved obvious technical and economic benefits. Therefore, the Ministry of electronic industry of China has listed the energy-saving technology represented by the frequency converter drive as one of the development priorities in the "Ninth Five Year Plan" of the electronic industry

China successfully developed AC4000 AC drive electric machine in 1996. At present, the power of each traction motor of metro vehicles under 750vdc system is about 90 ~ 160kW, so the three-point inverter drive system composed of 600 ~ 1000a/1200v IBGT can reach the required capacity. In order to consider the development trend consistent with the international advanced level, energy conservation and economic rationality, the drive scheme of variable frequency speed regulation for three-phase AC asynchronous motor was finally determined

at present, in order to save energy in various fields of industrial production in China, frequency conversion drive technology has also been used to transform equipment

IV. development of variable frequency drive technology

DC rotating motors have been widely used in traction motors of urban rail transit vehicles for a long time. Only by deeply understanding the product can we better use this machine. Its transmission modes include variable resistance control and chopper voltage regulation control. Variable resistance control is commonly used on old urban rail vehicles. Although the structure is simple, 20% of the electric energy is consumed on the resistance due to the frequent starting and braking of the vehicle. Most of this method has been eliminated

with the rapid development of power electronic devices, from non controlled rectifier to semi controlled thyristor (SCR), 8 so the gate turn off fully controlled thyristor (GTO), giant transistor GTR to insulated gate bipolar transistor IGBT have been successfully developed since the middle and late 1990s, which has led to the development of variable-frequency speed regulation products with different power levels that integrate drive, protection, self-detection and power output. As soon as the AC variable frequency speed regulation device appeared, it developed rapidly with its excellent speed regulation performance and obvious power saving effect, and gradually replaced the past slip speed regulation, commutator motor speed regulation, cascade speed regulation, medium frequency generator set and DC speed regulation device. Therefore, all countries in the world attach great importance to its development

in the late 1980s, urban rail vehicles developed using the latest VVVF frequency conversion control technology have entered the practical stage. VVVF drive system is to obtain a three-phase AC power supply with controllable frequency and voltage through GTO inverter and microcomputer, so that the speed of AC asynchronous traction motor can be smoothly adjusted. Due to the use of microcomputer control, the system can be more reliable, and can also realize the automatic detection and fault diagnosis of the system, which provides great convenience for the safe operation, repair and maintenance of vehicles

the application prospect of GTO is controversial because of its low turn-off gain, large turn-off loss and the risk of secondary breakdown. In recent years, IGBT, which has the advantages of both GTR and MOS-FET, has developed rapidly. At present, it has entered the fourth generation of products. The withstand voltage has also been increased to 3300 ~ 4500V, and the current can reach more than 1000A. IGBT devices have more advantages than turn off thyristor GTO. IGBT is voltage driven, with high switching frequency and strong anti-interference and through short-circuit protection ability, so it has small loss, good performance and reliable operation. In addition, the high-power IGBT module is insulated, the shell is not charged, easy to cool, and the system structure is simple. Although the withstand voltage of IGBT is not as high as that of GTO at present, a new three-point voltage type inverter can be used. Its voltage can not only use devices with a half of the withstand voltage level, but also effectively reduce harmonic current and suppress electromagnetic noise. The switching time of IGBT is only 1/6 of that of GTO, and the switching frequency can be increased to about 3 times of 1500hz, reducing the noise of three-point IGBT inverter by 15dB, and the gate control power of IGBT is less than 1/1000 of that of GTO The safe working area of voltage is wide, and the required absorption capacitor is small. Therefore, the volume and weight of GTO inverter are reduced by about 40%

at present, great progress has been made in the application of variable voltage and frequency converter and microcomputer technology in vehicles, which are composed of GTO and IGBT modules with high voltage and large current

since AC variable frequency drive has a series of advantages over DC drive, such as high adhesion utilization, almost no maintenance, reliable operation and energy saving, it is an inevitable trend to develop AC variable frequency drive for Metro and light rail trains for urban rail transit, except for trunk railways

as mentioned above, the three-point inverter composed of mature mass-produced and inexpensive voltage withstand 1200V tgbt is used in the metro running under 750vdc system to realize the AC drive scheme of metro vehicles. The cost is not expensive, and it is also in line with the development trend of urban rail locomotives

v. conclusion

the electric drive system of metro vehicles in China has developed from DC to AC, from variable resistance speed regulation to chopper speed regulation, and then to the variable frequency drive technology using three-phase asynchronous motor. Moreover, for the electrical equipment required for AC transmission on Metro or light rail vehicles in urban rail transit 750vdc system, this compact machine can use various plastic materials to produce particles and fragments, and China has been able to design and manufacture it by itself. At present, the planned Shanghai Metro Line 2 and the newly-built Guangzhou Metro Line 1 both choose the three-phase asynchronous motor AC variable frequency drive scheme. Thus, China's railway locomotive industry has stepped into the international advanced ranks of developing green transportation

the newly developed AC traction motor adopts variable frequency variable voltage control (VVVF) speed regulation mode. It uses inverter to convert DC into AC, and the speed regulation system that controls AC motor by voltage and frequency changes has been recognized as the most advanced speed regulation mode in terms of speed regulation performance and energy saving. It cooperates with AC motor, has no commutation part, reliable operation, strong overload capacity, simple structure, light weight and almost no maintenance, It has been applied in Germany, Japan and other countries. It is also the development trend of urban rail transit vehicles in the future. (end)

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