The application and research of inverter energy-saving technology, see the model paper 1.
According to the characteristic that the shaft power of water pump and fan is proportional to the square of rotating speed, this paper expounds the energy-saving principle of variable frequency speed regulation, and puts forward that water pump and fan should adopt variable frequency technology, which reduces the cost, prolongs the service life of equipment and improves the economic benefit.
Frequency converter; Frequency converter; Energy saving; Water pump; fan
Introduction to 0
Boiler is a common equipment for central heating. Usually, due to the change of air temperature and load, it is necessary to adjust the boiler combustion. The principle of traditional regulation mode is to increase the system resistance, the water pump uses the regulating valve to control the flow, and the fan uses the throttle opening to control the air volume. However, in the way of adjusting valves and baffles in operation, no matter what the heating demand is, the water pump and fan should run at full load, the shaft power of the motor driving the water pump and fan will not change, and the energy consumed by the motor will not decrease. The flow required for actual production is generally far less than the designed maximum flow, so it is widespread. Big horse-drawn car? Phenomenon. This operation mode of boiler not only loses energy, but also increases equipment loss, resulting in shortened service life of equipment and high maintenance cost. Applying frequency conversion speed regulation technology to the control of water pump (or fan) instead of valve (or baffle) control can improve the efficiency of the system without increasing pipeline resistance in the control process. Variable frequency speed regulation can make the motor automatically increase or decrease smoothly according to the change of load, and realize stepless speed change of the motor. Variable frequency speed regulation has a wide range and high precision, which is the most ideal speed regulation method for motors. If the non-adjustable-speed motors of water pumps and fans are transformed into frequency conversion motor, their power consumption can change with the load, thus saving a lot of electric energy.
Energy-saving principle of 1 frequency converter applied to water pump and fan
Figure 1 shows the H-Q relation curve of water pump (fan). In figure 1, curve R2 is the resistance characteristic curve when the water pump (fan) is fully loaded at a given speed and the valve (baffle) is fully opened; Curve R 1 is the resistance characteristic curve of the valve (baffle) when it is partially opened under partial load; Curves H(n 1) and H(n2) represent Q=f(H) curves at different rotational speeds. When the valve (baffle) is used for control, the flow (wind) decreases from Q2 to Q 1, the resistance curve moves from R2 to R 1, and the lift (wind pressure) moves from HA to HB. When speed control is adopted, H(n2) moves to H(n 1), flow (wind) decreases from Q2 to Q 1, and lift (wind pressure) moves from HA to HC.
Figure 1 H-Q relation curve of water pump (fan)
Fig. 2 is the P-Q relation curve of water pump (fan). As can be seen from Figure 2, when the flow (wind) is Q 1, the power controlled by the valve (baffle) is PB. The power of frequency conversion speed regulation control is PC. ? P=PB-PC is the power saved.
Fig. 2 is the P-Q relation curve of water pump (fan).
If you don't count the fan efficiency? In the figure, the area of OHBBQ 1 is used to represent the power consumption when the valve (baffle) is used, and the area of OHCCQ 1 is used to represent the power consumption when the speed regulation is used. The area difference between the latter and the former is HCHBBC, that is, the flow (wind) controlled by speed regulation is more energy-saving than that controlled by the valve (baffle).
2 Energy-saving calculation and analysis of pumps and fans
Usually, the speed n is proportional to the frequency f. If the operating frequency of the motor is reduced from 50Hz to 40Hz, its actual speed will be reduced to 80% of the rated speed, that is, the actual speed nsn and the rated speed NN: NSN = (■) NN = 0.4NN ... Let K be the overload coefficient of the motor, and the rated power of the motor Pn=Kn■■. Therefore, when the motor runs at 40Hz, the actual power is:
psn = Kn■■= K(0.4 nn)3 = 0.064 Kn■■= 0.064 pn
Energy saving rate = ■ = ■ = 93.6%
Table 1 motor energy saving rate
Shengli Boiler Room of Thermal Power Company changed the motor to variable frequency speed regulation, among which:
Table 2 Data measured by water pump motor under different conditions of constant speed and variable speed
According to the data in Table 2, it is calculated that a heating period is 190 days, and the unit price of industrial electricity is 0.37 yuan/kWh. Adding frequency converter to water pump motor to save electricity fee;
( 1 1- 1.73)? 24? 190? 0.37= 15640.344 yuan
Table 3 Data measured by fan motor under different constant speed and variable speed conditions
According to the data in Table 3, there are five blower motors in Shengli Workshop. A heating period is calculated as 190 days, and the unit price of industrial electricity is 0.37 yuan/kwh. After installing the frequency converter, the fan motor saves electricity;
( 18.5-3.95)? 24? 190? 0.37? 5= 122743.8 yuan
Table 4 Measurement data of induced draft fan motor under different constant speed and variable speed conditions.
According to the data in Table 4, there are five blower motors in Shengli Workshop. A heating period is calculated as 190 days, and the unit price of industrial electricity is 0.37 yuan/kwh. Saving electricity fee after adding frequency converter to induced draft fan motor;
(37-32.9)? 24? 190? 0.37? 5 = 34,587.6 yuan
To sum up, after the installation of frequency conversion in Shengli workshop, a heat preservation period will save the total electricity fee:
15640.344+122743.8+34587.6 =172971.744 yuan.
The energy-saving effect is obvious.
Through the above analysis and practical application, the boiler water pump and fan have the following advantages after adopting frequency conversion speed regulation.
(1) The working current of water pump and fan motor decreases, and the temperature rise obviously decreases. At the same time, the mechanical wear is reduced, and the maintenance workload is greatly reduced.
(2) The protection function is reliable, which eliminates the burning phenomenon of the motor due to overload or single-phase operation, prolongs the service life and can run stably for a long time.
(3) The motor realizes soft start and smooth stepless speed regulation with high precision and wide speed regulation range (0- 100%). Wide frequency range (0-50Hz). The efficiency can be as high as 90%-95%. And the influence on the power grid is reduced.
(4) Easy installation, convenient debugging, simple operation and less maintenance.
(5) Save energy and electricity, and improve the efficiency of coal burning.
(6) The frequency converter can be controlled online by software and computer programmable controller, which is easy to realize automatic control of the production process.
3 Conclusion
The introduction of frequency converter can realize the effective utilization of energy and avoid excessive consumption of energy. Using frequency converter to save energy is mainly to control the flow and pressure by changing the speed of motor, so as to reduce the pipeline resistance and reduce the energy loss of half-open valve. Secondly, the running speed of water pump (fan) under frequency conversion is obviously lower than that under power frequency supply, which can minimize the power loss caused by friction. Finally, frequency conversion technology is an advanced modern automation technology, and automatic operation can increase the reliability of electric power operation and save manpower input, thus achieving the purpose of saving costs.
refer to
[1] Zhao Bin, Mo Guiqiang. Application of frequency conversion governor in energy-saving transformation of boiler fan [J]. Guangxi Electric Power.
[2] Wu Minqiang. Questions and answers on energy-saving technology of pumps and fans [M]. Beijing: China Electric Power Press, 1998.
[3] Liang Xuezao, Cai Zefa. Energy-saving method of asynchronous motor [Z]. Hunan Electric Power Industry Bureau.
Application technology paper of frequency converter: See model 2 for the practice and application of frequency converter technical transformation.
This paper introduces the examples and applications of the technical transformation of boiler fan motor, make-up pump, circulating pump motor and other equipment, and probes into some technical problems that should be paid attention to in the speed regulation transformation of the frequency converter.
Automatic control; Frequency converter; Technical reform
1 The fan motor of the boiler is controlled by frequency converter.
Take DHL141.57150/90aii hot water boiler as an example. Each boiler is equipped with 6 induced draft fans and 6 blowers. The main technical parameters of each motor are as follows:
Model capacity (KW) Voltage (V) Rated current (A)
Induced draft fan Y280S4 75 380 139.7
Blower Y200L4 30 380 57
Before the transformation of the frequency converter, under normal circumstances, the operation data statistics of each fan are as follows:
Average current maximum current minimum current
Induced draft fan 142 145 139
Blower 59 63 57
Firstly, the drum and induced draft fan of 1#5# boiler are selected for reconstruction. Considering the configuration of fan motor power design, the inverter with matching power is selected to control the motor. The frequency converters are abbacs51001157a4 (induced draft fan) and ZXBP30 (blower), and the voltage level is 380V. The power frequency current of induced draft fan dropped from the original average value of 140(A) to the current average value of 95- 1 10 (a), and the power frequency current of blower dropped from the original average value of 57(A) to the current average value of 30(A). The energy-saving effect is quite remarkable. The technical performance of the frequency converter fully meets the requirements of boiler operation technology (mainly wind pressure, air volume, positive and negative air). The frequency conversion speed regulation is remotely controlled by the start, stop and speed regulation switches installed on the boiler operation platform, and can be interfaced with DCS system, so that the speed control of the frequency converter can be realized through DCS. The frequency conversion speed regulating device also provides protection information such as alarm indication, fault indication, standby state, operation state and interlock protection, as well as necessary indications such as given speed value and actual speed value of the fan, which is convenient for operators to operate and control.
2. The motors of makeup pump and circulating pump should be regulated and controlled by frequency converter.
Taking the practical application of two makeup pumps and four circulating pumps as an example, the technical parameters of their motors are as follows:
Serial number model power rated current
Makeup pump 1# pump Y 180M4 18.5 35.9 25
2# pump Y 180M4 18.5 35.9 25
Circulating pump 1# pump y 315m14132 237 630
2# pump y 315m14132 237 630
3# pump y 315m14132 237 630
4# pump Y2315m4132 240.4630
The output of the pump is too large during normal water replenishment, and one pump cannot meet the water demand during emergency water replenishment. At the same time, the output is too large when starting, so the continuous water supply has high efficiency and good effect. We should not only consider its energy-saving benefits for motors, but also consider the safety of production equipment. The inverter is Fuji FRN132 P11S-4Cx, and the voltage level is 380V.
In order to make full use of the frequency converter, 1 frequency converter is used to realize the speed control of two motors; The two make-up pumps can operate in variable speed and constant speed modes, and the frequency converter can only be used as the frequency conversion power supply of one motor at the same time, so the start and stop of each motor must be locked with each other, controlled by a logic circuit to ensure reliable switching, and the outlet adopts double-throwing switch; When two make-up pumps are working, one is powered by power frequency and runs at constant speed, and the other is powered by frequency converter and runs at variable speed. The variable speed and constant speed operation of the same motor are locked by the AC contactor, that is, the constant speed cannot be closed during variable speed operation, as shown in the following figure, 1c 1c2 and 2c 1c2 are not allowed to be closed at the same time; In order to ensure the safety and reliability of process control, the control, protection and measurement units of frequency converter and two motors are all concentrated in the local control cabinet, and the control and adjustment are connected to the control room through shielded signal cables;
Figure 1 Connection of inverter of makeup water pump motor, some technical problems that should be paid attention to in speed regulation transformation of three inverters are added in the virtual box.
The safe operation of the boiler is the fundamental guarantee of the team's power. Although the frequency conversion speed regulating device is reliable, once there is a problem, it is necessary to ensure the safe heating of the boiler. Therefore, it is necessary to realize the switching system (bypass system) with power frequency-frequency conversion operation. In the production process, if manual switching can meet the technical requirements of equipment operation, it is recommended not to choose automatic bypass as far as possible. For ordinary low-power motors, it is also an ideal method to use double flying knives as manual and automatic switching means.
For motors with large inertia load (such as boiler induced draft fan), after frequency conversion transformation, attention should be paid to the possibility of twisted vibration of the fan. In operation, once * * * vibration occurs, the fan and driving motor will be seriously damaged. Therefore, it is necessary to calculate or measure the critical speed of torsional vibration of the connecting shafting of fan motor, and take corresponding technical measures (such as setting frequency hopping function, avoiding vibration points, soft connection, adding damping rubber on the frame, etc.). ).
After adopting variable frequency speed regulation, if the frequency converter runs below 1/2 power frequency for a long time, with the decrease of motor speed, the heat dissipation capacity of the motor will also decrease, and the heat generation of the motor will also decrease. Therefore, the temperature of the motor itself actually drops, and it can still run normally without overheating.
Inverter can't send power from the output port in the opposite direction. Attention must be paid when designing the circuit. For example, 1c 1c2 and 2c 1c2 are not allowed to be closed at the same time in the wiring diagram of the inverter of the make-up pump and circulating pump, which requires not only electrical interlocking in the electrical secondary circuit, but also mechanical interlocking to ensure the safe operation of the inverter.
Low-voltage inverter, because of its small size, is easier to choose the installation location in the transformation. When choosing the location of the inverter room, we should not only consider the distance from the motor equipment, but also consider the possible influence of the surrounding environment on the operation of the inverter. The installation and operation environment of frequency converter is very demanding. In order to make the inverter run stably and reliably for a long time, the indoor ambient temperature in the inverter installation room should be controlled between 0-40℃. If the temperature exceeds the allowable value, the corresponding air conditioning equipment should be considered. At the same time, there should be no large dust, corrosive or explosive gas, conductive dust, etc. Indoor.
It is necessary to ensure the reliable connection between inverter cabinet and workshop floor, and ensure the safety of personnel and equipment. In order to prevent signal interference, it is best to bury an independent grounding system in the control system, and the grounding resistance is not more than 4? . The signal line to the frequency converter must be a shielded cable, and one end of the shielded cable should be reliably grounded.
With the development of power electronics technology, the technical performance of frequency converter has been broadened and improved. In the thermoelectric industry, the load of fans and pumps is more, and it has been gradually accepted by everyone to make full use of frequency converters for energy-saving transformation. For the current low-voltage inverter, the investment is low and the benefit is high, and the investment can be recovered in about one year, so it is widely used. With the rapid development of domestic frequency converters, the cost performance of frequency converters has been greatly improved, which provides a broader prospect for energy-saving technological transformation using frequency converters.
References:
[1] Wang Zhankui. Hundreds of examples of variable frequency speed regulation. Beijing: Science Press, 1999.4.
[2] Wu Zhongzhi, from Wu Jialin. Inverter application manual. Beijing: Machinery Industry Press, July 2002.
For the paper on the application technology of frequency converter, see model article 3: application of frequency conversion speed regulation technology.
It has the advantages of good speed regulation and braking performance, high efficiency, high power factor, good energy saving effect and wide application range, and is considered as the most promising speed regulation mode at home and abroad. With the continuous improvement of industrial automation and global energy shortage, frequency converters are more and more widely used in metallurgy, machinery, petroleum, chemical industry, textile, paper making, food and other industries as well as energy-saving occasions such as fans and pumps, and have achieved remarkable economic benefits. In recent years, the production of high-voltage and high-current devices such as SCR, GTO, IGBT, IG-GT, IPM(IntelligentPowerModule) and the development and application of parallel and series technology have made the production and application of high-voltage and high-power inverter products a reality.
Keywords: frequency converter, control technology, application
Power electronic technology has been born for nearly 50 years, which has played a great role in human civilization. In recent 10 years, with the rapid development of power electronics technology, computer technology and automatic control technology, electric drive technology is facing a historic revolution, that is, AC speed regulation replaces DC speed regulation, and computer digital control technology replaces analog control technology has become a development trend. Frequency conversion speed regulation technology of AC motor is the main means to save electric energy, improve technological process, improve product quality, improve environment and promote technological progress. Variable frequency speed regulation is beneficial to it.
Good speed regulation and braking performance, high efficiency, high power factor, good energy saving effect and wide application range. It is considered to be the most promising speed regulation method at home and abroad.
1. Current situation of variable frequency speed regulation technology
Electric drive control system usually consists of three parts: motor, control device and information device. Electric drive can be divided into two categories: speed regulation and non-speed regulation, and speed regulation can be divided into AC speed regulation and DC speed regulation. Non-adjustable speed motors are directly powered by the power grid. However, with the development of power electronics technology, more and more machines without speed regulation are driven by speed regulation to save electricity, improve product quality and increase output. For example, in China, 60% of electricity generation is consumed by electric motors. Therefore, speed regulation drive has great energy-saving potential, and frequency conversion speed regulation is the basis and main content of AC speed regulation. The appearance of variable frequency speed regulation technology makes frequency a resource that can be fully utilized. In recent years. Frequency conversion speed regulation technology has become the most active and fastest developing technology in AC speed regulation.
1. 1 current situation abroad
It has been about 40 years since frequency conversion was used to control motor speed. However, the rapid development of variable frequency speed regulation technology is in the last decade, which is mainly determined by the following factors:
1. 1 has a great market demand.
With the continuous improvement of industrial automation and global energy shortage, frequency converters are more and more widely used in metallurgy, machinery, petroleum, chemical industry, textile, paper making, food and other industries as well as energy-saving occasions such as fans and pumps, and have achieved remarkable economic benefits.
1. 1.2 power devices have developed rapidly.
Frequency conversion speed regulation technology is based on power electronics technology. In recent years, the production of high-voltage and high-current devices such as SCR, GTO, IGBT, IG-GT, intelligent module IPM (intelligent power module) and the development and application of parallel and series technology have made the production and application of high-voltage and high-power inverter products a reality. Under high-power alternating current? In the aspect of AC frequency conversion (AC-AC frequency conversion) speed regulation technology, Alstom of France has been able to provide a single electric drive device with a capacity of 30000kW for the ship propulsion system. In the aspect of frequency conversion speed regulation technology of high-power commutatorless motor, ABB company of Italy provided equipment with a single unit capacity of 60000kW for pumped storage power station; In terms of medium-power frequency conversion speed regulation technology, the single-machine capacity of Simovert A current-mode thyristor frequency conversion speed regulation equipment of Siemens Company of Germany is10-2,600 kva, and the single-machine capacity of Simovert PGTOPWM frequency conversion speed regulation equipment is 100-900kVA, and its control system has been completely digitized, which is used to drive motor windmills, fans and pumps. In terms of low-power frequency conversion speed regulation technology, the maximum single machine capacity of Fuji BJT inverter in Japan can reach 700kVA, IGBT inverter has formed a series of products, and its control system has been completely digitized.
IPM is put into application about two years later than IGBT, because IPM includes 1GBT chip, peripheral drive and protection circuits, and some even integrate optocouplers, so it is a more suitable integrated power device. At present, in the range of module rated current 10-600A, there is a tendency to adopt IPM in general frequency converters. Economical IPM is not only widely used in industrial frequency converters, but also in some civilian products in recent years, such as household air conditioner frequency converters, refrigerator frequency converters, washing machine frequency converters and so on. IPM is also developing to a higher level. ASIPM, a special intelligent module newly developed by mitsubishi electric, Japan, will not need an external optical coupler, but can be powered by a single power supply through an internal bootstrap circuit, and adopts low inductance packaging technology, which is a step closer to realizing miniaturization, specialization, high performance and low cost of the system.
1. 1.3 control theory and microelectronics technical support
In the field of modern automation control, based on modern cybernetics, new control theories such as fuzzy control, expert control and neural control are integrated, which provides a theoretical basis for high-performance variable frequency speed regulation. The rapid development of 16-bit and 32-bit high-speed microprocessors, signal processors (DSP) and application-specific integrated circuits (ASIC) provides hardware means for realizing high precision and multifunction of variable frequency speed regulation.
1.2 domestic status
Generally speaking, the manufacturing technology level of electric drive system in China lags behind the international advanced level 10- 15 years. Only a few scientific research institutes in China have the ability to manufacture high-power AC-AC, commutatorless motors and other frequency conversion technologies, but there is still a considerable gap with foreign countries in digitalization and system reliability. However, there is a great demand for products in this field, such as the start-up and operation of pumped storage power stations, large-capacity fans, compressors and rolling mill drives and mine hoists. In the medium and small frequency technology, domestic scholars have done a lot of basic research on frequency conversion theory. As early as 1980s, vector control theory has been successfully introduced. Aiming at the multivariable, strong coupling and nonlinear characteristics of AC motor, the control strategy of variable frequency speed regulation of AC motor is discussed by using linear decoupling and nonlinear decoupling methods.
In 1990s, with the use of high-performance single-chip microcomputer and digital signal processing technology, domestic scholars followed the latest foreign control strategies and adopted high-order harmonic injection SPWM and space flux vector PWM according to the induction characteristics of AC motors. Fuzzy control is used in the control algorithm, and the rotor resistance, flux linkage and torque of induction motor are observed online by using neural network theory, which makes a beneficial basic research for realizing speed sensorless AC variable frequency speed regulation system. In the application of new power electronic devices, due to the use of fully controlled devices such as GTR, GTO, IGBT and IPM, the main converter circuit of medium and small power is greatly simplified, and the parallel and series technology of high power SCR, GTO, IGBT and IGCT makes the production and application of high voltage and high current inverter products become a reality. In the aspect of control devices, the application from 16-bit single chip microcomputer to 32-bit DSP is realized. Domestic scholars have been committed to the research of new control strategy of variable frequency speed regulation, but because semiconductor power devices and DSP devices rely on imports, the manufacturing cost of inverters is high, and they cannot be industrialized and compete with foreign famous brands. Almost all domestic products are controlled by ordinary V/f, and only a few prototypes adopt vector control. Variety and quality can't meet the market demand, and a large number of high-performance inverters need to be imported every year.
Therefore, the domestic industrial situation of AC variable frequency speed regulation technology is as follows: (1) The basic research of inverter control strategy is not far from that of foreign countries. (2) The technology of inverter is backward. Although many domestic units have invested a certain amount of manpower and material resources, they have not formed a certain technology and production scale because of the scattered strength. (3) The manufacture of semiconductor power devices for inverter products is almost blank. (4) Related supporting industries and industries are backward. (5) Less production and sales, low reliability and low technological level.
2. Future development direction of variable frequency speed regulation technology.
Frequency conversion speed regulation technology mainly develops in two directions: first, it realizes high power factor, high efficiency, no harmonic interference and develops high electromagnetic compatibility? Green appliances? ; The second is to develop the depth and breadth of inverter application. With the continuous development of inverter application field, the importance of variable frequency speed regulation technology in a country's national economy will become more and more obvious. It can be expected that the application and popularization of modern control theory and artificial intelligence technology in variable frequency speed regulation technology will give it stronger vitality and higher technical content. Its development direction is as follows: (1) realizing high-level control; (2) Developing clean electric energy converter; (3) reducing the size of the equipment; (4) high-speed digital control; (5) Simulation and computer aided design technology. Paper test.
Application of frequency conversion speed regulation technology
Generally speaking, the application of variable frequency speed regulation technology in China is a process from experiment to practice, from sporadic to large-scale, from auxiliary system to production device, from simply considering energy saving to comprehensively improving process level, from manual control to automatic control, from low-voltage medium-small capacity to high-voltage large capacity, in a word, from low-level to high-level paper testing. China is a big country of energy consumption, and 60% of power generation is consumed by motors. According to relevant statistics, there are about 42 million fans, pumps and air compressors in China, and the installed capacity is about1.1000 million kilowatts. But the actual work efficiency is only 40%-60%, and the power loss accounts for 40% of the total power generation. Experience shows that the application of frequency conversion speed regulation technology can save electricity.
Relevant data show that there are eight kinds of pumps and fans in thermal power plants in China, with a total capacity of 12829MW and an annual total power consumption of 450. 200 million kwh. There are also pumps and fans with a total capacity of about 39 1.3 MW that need energy-saving transformation. After the transformation, it is estimated that the annual power saving can reach 25. Paper test. 6.9 billion kWh; Metallurgical enterprises are also big consumers of energy in China, and the energy consumption per unit product is 3 times higher than that of Japanese and 4.5 times higher than that of French. 9 times, India 1. 9 times, metallurgical enterprises use a large number of fans and pumps, and the implementation of frequency conversion reform can not only greatly save electricity, but also improve product quality.
refer to
[1] He Qinghua, Chen Daobing. Treatment and Daily Maintenance of Common Faults of Inverter [J]. Inverter World, 2009, (04).
Long Zhuomin, Luo Xuelian. Anti-interference design of matrix variable frequency speed regulation system [J]. Inverter World, 2009, (04).
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