CN110589368B - Control method for long cable of driving system of mining scraper conveyor - Google Patents

Control method for long cable of driving system of mining scraper conveyor Download PDF

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CN110589368B
CN110589368B CN201910327691.9A CN201910327691A CN110589368B CN 110589368 B CN110589368 B CN 110589368B CN 201910327691 A CN201910327691 A CN 201910327691A CN 110589368 B CN110589368 B CN 110589368B
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control system
voltage
cable
phase
long cable
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CN110589368A (en
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邓永红
张全柱
孙英娟
马红梅
雷旻
薛伟宁
赵立永
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North China Institute of Science and Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G19/00—Conveyors comprising an impeller or a series of impellers carried by an endless traction element and arranged to move articles or materials over a supporting surface or underlying material, e.g. endless scraper conveyors
    • B65G19/18—Details
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G23/00—Driving gear for endless conveyors; Belt- or chain-tensioning arrangements
    • B65G23/22—Arrangements or mountings of driving motors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G23/00—Driving gear for endless conveyors; Belt- or chain-tensioning arrangements
    • B65G23/24—Gearing between driving motor and belt- or chain-engaging elements
    • B65G23/30—Variable-speed gearing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G43/00—Control devices, e.g. for safety, warning or fault-correcting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G2203/00—Indexing code relating to control or detection of the articles or the load carriers during conveying
    • B65G2203/02—Control or detection
    • B65G2203/0266—Control or detection relating to the load carrier(s)

Abstract

The invention relates to a long cable control method for a driving system of a mining scraper conveyor, which is characterized by comprising the following steps of: when the scraper conveyer operates, one of the component control systems is a master control system, the master control system is used for controlling the speed of a driving motor of the scraper conveyer, the other component control system is a slave control system, the slave control system is used for controlling the torque of a driven motor of the scraper conveyer, the master control system analyzes the sampling data of the component control systems of the scraper conveyer, and controls and adjusts the operating conditions of the control systems according to the sampling data so as to achieve real-time monitoring and real-time adjustment and automatically adjust intelligent operation. The invention has the advantages that: the invention has simple circuit structure, low manufacturing cost, easy control and high cost performance, more effectively realizes various special working conditions of the driving system of the scraper conveyer and realizes the effective utilization of regenerated energy.

Description

Control method for long cable of driving system of mining scraper conveyor
Technical Field
The invention relates to a method for controlling a long cable of a driving system of a mining scraper conveyor.
Background
Along with the increase of the production quantity of mines, the mining depth is continuously increased, the transportation cost is continuously increased, and meanwhile, a large amount of automobile tail gas can be generated in the traditional automobile transportation mode to seriously pollute the underground environment. The belt conveyor system can save a large amount of conveying cost on one hand, and on the other hand, the belt conveyor system can reduce the emission of automobile exhaust, thereby improving the environment of underground operation, and accordingly, the mine conveyor is developed.
The types of conveyors include belt conveyors, plate conveyors, trolley conveyors, scraper conveyors and other conveyors. Along with the development and utilization of the motor production technology in the aspect of coal mining, the efficiency of coal mining is greatly improved. Compared with the manual mining level, the efficiency of the mechanical automatic mining is ten times or even more than one hundred times higher. Therefore, the rapid development of mechanical automation promotes the improvement of the production and life quality level of people. The belt conveyor is a high-efficiency transportation machine meeting mine transportation requirements of coal mine enterprises. Compared with other transport machines, the belt conveyor has the advantages of long distance, large capacity and continuous transport, is stable in operation, and is easy to complete automation and centralized control. For high-yield and high-efficiency mines, the belt conveyor becomes a key device of the high-efficiency coal mining electromechanical integration technology and equipment. The belt conveyer for coal mine mainly refers to a belt conveyer and a scraper conveyer for coal mining, production, transportation and processing. The belt conveyor has the advantages of strong transportation capability, adaptability to variable working environments, long-distance transportation and the like. The mine belt conveyor can be used in the coal production and processing process and can also be used for the production and processing of other minerals. In the aspect of energy consumption, the energy consumption can be effectively reduced, economic benefits are provided, and the energy is saved and the environment is protected compared with the traditional automobile transportation. In addition, the method has the characteristics of low maintenance cost, simple maintenance and the like, and is also highly popular with mine production and processing enterprises.
Although the scraper conveyor and the belt conveyor improve the conveying efficiency in the production of mines, the scraper conveyor and the belt conveyor bring problems. Wherein, scraper conveyor is when starting or stopping, and dynamic tension is higher, and what bring thereupon is that the conveyer belt often slides, and this can increase the relative frictional force of conveyer belt and then produce more heats for scraper conveyor's security greatly reduced, scraper conveyor consequently receives serious damage. Therefore, the frequency conversion system is urgently needed to be applied to the frequency conversion system, and the speed regulation control is carried out on the frequency conversion system. After the scraper conveyor acts, the conveyor belt is forced to vibrate and easily slide, the frequency of the frequency converter is adjusted by changing the frequency of a power supply, and the frequency converter can reduce the generated reactive loss and greatly improve the conveying efficiency.
In belt conveyors, the conveyor belt is an elastomer and stores a large amount of energy when stationary or in operation. In the starting process of the belt conveyor, if a soft starting device is not added, the energy stored in the conveyor belt can be quickly released, tension waves are easily formed and are transmitted out along the conveyor belt, and the belt is torn. If soft start and soft stop are not adopted, the starting current is very large and is generally 4-7 times of the rated current of the motor. The motor machinery inside is seriously abraded and even damaged at the starting moment, which is completely not in accordance with the requirement of creating an energy-saving society. Therefore, the adoption of variable frequency speed regulation on the belt conveyor is very necessary, so that the space of a driving device can be reduced, the soft start of equipment can be realized, the transportation efficiency is improved, the power consumption is reduced, and the cost is saved. Meanwhile, a plurality of mechanical devices are used in the production process of the mine, and the coal mine conveyor must use a frequency converter to carry out step adjustment and speed change on the coal mine conveyor to realize soft start and soft stop, so that the conveying efficiency is improved, and the cost is saved.
With the continuous development of the industrial production automation of coal in China, the mining frequency converter plays an outstanding role in speed regulation function, energy conservation and loss reduction in the application of mechanical equipment under a coal mine. The mining frequency converter has a large number of active figure in a coal mine. The mining frequency converter is summarized and synthesized, and the problem that high precision is required to solve the problem that torque control of a high-power motor is disturbed; the soft start, soft stop and process control of the high-power motor can be realized; the power balance when a plurality of motors run together; the regenerative braking and energy feedback capacity is realized in the running process, so that energy conservation and emission reduction can be realized; the energy consumption is reduced, the safety is high, the service life of the equipment is long, and the like. However, most of the mining frequency converters are used for sine waveform pulse width modulation at present, and after the two-level frequency converter is converted by a rectifying circuit, a direct current circuit and an inverter circuit, the waveform output by the two-level frequency converter is not a complete sine waveform, and generally has harmonic waves of more than 3 times. Because the layout of the two-level frequency converter is 6 IGBTs, only 6 paths of PWM pulses are used, the input side of the two-level frequency converter has great electromagnetic interference on a power grid, and the monitoring system for monitoring the underground safety production of a coal mine can be possibly disturbed.
Due to the particularity of mining, a frequency converter is always arranged on the output side of the scraper conveyor to supply power to the motor through a long cable, and the length of the cable is different from hundreds of meters to thousands of meters. Because the output of the frequency converter is supplied with power by a PWM wave and a long cable, the outstanding problems exist: first, harmonic reflections. The harmonic wave is extremely serious, the frequency of the main harmonic wave and the content of the harmonic wave current are complex, an LCR loop can be formed by a long cable, the output current is easy to resonate, the higher harmonic wave generated by a power electronic device of the frequency converter causes great damage to the insulation of a motor and the cable, and when the harmonic wave generates a transmitting wave and is superposed with the long-distance motor side voltage, the power supply voltage value of the motor side voltage value has an increasing effect, so that the motor side voltage is overlarge and the insulation is damaged. The variable frequency power supply needs speed regulation, the working point of the output frequency is not fixed, and therefore, multiple harmonic waves exist corresponding to each frequency, so that the harmonic waves are distributed in a very wide frequency domain, even if a good filter cannot effectively filter the harmonic waves under all frequencies. More complicated is the fact that harmonics present a "mole" phenomenon, namely: one harmonic is suppressed and the other harmonic is emphasized. Such confusion has been a difficult problem in the field. Meanwhile, due to the existence of harmonic waves, when the long cable of the frequency converter supplies power, the supply voltage and the current are unstable, and the working condition of the load cannot be effectively controlled. Second, the transducer pulse is reflected. As a result, the motor terminal voltage is too high, and the cable and motor insulation are damaged.
Aiming at the problems of long cable power supply of the two-level frequency converter, the three-level frequency converter can perfectly solve the problems. Compared with a two-level converter, a three-level converter can cut the voltage of a switching device to be half due to the addition of one more level. Because the output has one more level, du/dtThe value of (2) can be reduced by half, so that the output voltage harmonic wave is reduced, the heat productivity of the motor is greatly reduced, and the common mode disturbance to a power grid is reduced. The advantages are very suitable for being applied to a large-capacity speed regulating system of a mine with 1140V and above.
However, the parameters (resistance, capacitance and inductance) of the long cable cannot be ignored in the high-power scraper conveyer driving system, especially heavy-load starting, load sudden change and synchronous control, so that the control method of the long cable of the scraper conveyer driving system needs to be researched.
The mining scraper is mainly used for transporting raw coal production on a coal mining working face, and belongs to bulk material conveying machinery. The conventional scraper conveyor directly starts the motor with the 1140V electric box and the soft starter, so that the motor can be started normally and run smoothly, as shown in fig. 1. However, this design has many problems: (1) when the scraper machine has more raw coal, the starting power moment is increased, manual shoveling is needed, and the efficiency is not high; (2) the cable loss exists, the mine working tunnel is long, a long cable is needed, the pipe voltage drop is large, and the starting voltage and the running voltage are insufficient. (3) Synchronous control is difficult to achieve, and the requirement of actual production is not facilitated. (4) When no load is carried, the electric energy is wasted. (5) The belt is stressed unevenly, slipping and the like are easy to occur, and the motor of the conveyor is damaged. To solve these problems, people have adopted simple speed synchronization control or power synchronization control in advance, so that the control is synchronized as much as possible. But the technical limit is compelled to solve only a part of problems, and the scraper conveyer still has the problems of high energy consumption, low efficiency, difficult heavy-load starting and the like.
From the aspects of energy conservation, flexibility, reliability, high efficiency and the like, the traditional soft start mode can not meet the actual production requirement, so the frequency conversion technology gradually replaces the direct power distribution method. At present, the mining scraper conveyor also tries to adopt a frequency conversion technology, as shown in figure 2. The scraper conveyor adopts the frequency conversion technology to weaken the defect of the traditional power distribution mode to a certain extent, solves the problem of no-load power consumption, but still has the following problems to be solved urgently. (1) The motor still can not be synchronously controlled, and the scraper conveyer is easily damaged. (2) When more raw coal exists on the conveyor, a power supply source with the rated power of a motor more than 2.5 times is needed during heavy-load starting, so that the whole power grid is unstable, and other operations are influenced. (3) The waste of electric energy is easily caused when the brake or the idle running is carried out. (4) The problem that the motor cannot be normally started when the stress is uneven is still not solved. (5) The remote control cannot be realized, the close-range control is still needed, and safety accidents are easy to happen. (6) The two-level frequency converter speed regulator has large electromagnetic interference and affects a power grid. (7) Scrape the connecting wire of trigger conveyer and converter, length varies from several hundred meters to several kilometers, is unfavorable for the converter to give the power supply of scraping the long cable of trigger conveyer, produces overvoltage, launch wave easily, damages motor and cable. (8) When the power supply grid fluctuates, the output is unstable, and unnecessary faults are easily caused. In conclusion, it is very promising to research the control method of the long cable of the scraper conveyor driving system.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for controlling a long cable of a driving system of a mining scraper conveyor, and the technical scheme of the invention is as follows:
a long cable control method for a driving system of a mining scraper conveyor comprises the following steps: when the scraper conveyer operates, one of the component control systems is a master control system which is used for controlling the speed of a driving motor of the scraper conveyer, the other component control system is a slave control system which is used for controlling the torque of a driven motor of the scraper conveyer, and the master control system analyzes the sampling data of each component control system of the scraper conveyer and controls and adjusts the operation condition of each control system according to the sampling data so as to achieve real-time monitoring and real-time adjustment and automatically adjust intelligent operation; the master control system enables the scraper conveyer to always run in the optimal state through a voltage closed-loop control algorithm; the voltage closed-loop control algorithm is realized based on a long cable model and detected data, and specifically comprises the following steps: according to the long cable model, the inductance L, the capacitance C and the resistance R are adopted to simulate the long cable parameters, and for a balanced three-phase system, the resistance value, the capacitance value and the inductance value of the three-phase cable are equal:
Rc_u＝Rc_v＝Rc_w＝Rc (1)
Lc_u＝Lc_v＝Lc_w＝Lc (2)
Cc_u＝Cc_v＝Cc_w＝Cc (3)
make the inductance impedance as ZL＝jω1LcThe capacitance impedance is
Figure GDA0003025296530000071
The impedance per kilometer of cable in each phase is then:
Z＝Rc+ZL+Zc (4)
then, the following steps are obtained:
uc_uvw＝Z*iINV_uvw (5)
ucl_uvw＝Z*iINV_uvw*1 (6)
wherein j represents a complex number; rc-u、Rc-v、Rc-wRespectively, the resistance value of each phase of the cable is in unit omega; l isc-u、Lc-v、Lc-wRespectively, the inductance value of each phase of the cable is expressed in unit H; cc-u、Cc-v、Cc-wRespectively is the capacitance value of each phase of the cable, unit F; omega1，uc_uvw，iINV_uvwThe three-level inverter outputs each phase voltage drop and three-phase current value of the long cable;
according to the detected three-phase current value i output by the three-level inverterINV_uvwAngular frequency ω of actual output1Calculating the voltage drop u of each phase of each voltage of each kilometer of the cable according to the formula (5)c_uvw(ii) a "I" is the actual length of the cable, ucl_uvwCalculating the voltage drop of each phase voltage under the actual cable length of the scraper conveyer through a formula (6) for the voltage drop of each phase voltage under the actual cable length of the scraper conveyer;
the master control system sends out control instructions through a CAN bus, one sub-control system is a master control system, the other sub-control system is a slave control system, and the running speed and the running frequency of the scraper conveyor are controlled through the master control system; the main control system calculates the running torque, and transmits the running torque to the sub-control system through the CAN bus to further control the torque of the scraper conveyer; when the scraper conveyer actually runs, the master control system calculates the voltage required by the motor according to the rated frequency and the actual running frequency of the scraper conveyer,
Figure GDA0003025296530000081
wherein f (t) is the actual operating frequency of the scraper conveyor, UNIs the rated voltage of the motor, fNIs the rated frequency, U, of the motorSThe phase voltage for the operation of the motor of the scraper conveyor calculated by formula (7) without considering the length of the cable; considering the influence of the length of the long cable, under the actual operation frequency and the actual operation phase current, the voltage drop of the cable is calculated to be u through the formula (6)cl_uvwAnd U isSAdding up, the phase voltage actually needed by the motor of the scraper conveyer can be calculated to be
Figure GDA0003025296530000082
And uuvwThree-phase voltage values outputted for the actually detected three-level inverter,
Figure GDA0003025296530000083
and uuvwThe difference value of the three-level PWM rectifier is used as an input value of a long cable control algorithm PI of the scraper conveyor driving system, and the output value of the PI is a given value U of the output direct-current voltage of the three-level PWM rectifier*I.e. the input dc voltage value U of the three-phase inverter*(ii) a Therefore, under the condition that the length of the cable is I, different running speeds and different working conditions, the master control system calculates the given value U of the direct-current voltage through a control algorithm*Controlling the output direct-current voltage values of the three-phase PWM rectifier and the bidirectional DC/DC converter so that the driving system of the scraper conveyer always works in the optimal state; thus, the required intermediate direct current voltage U is calculated by a long cable control algorithm of a scraper conveyor driving system*The intermediate direct-current voltage is provided for the three-level PWM rectifier and the bidirectional DC/DC converter through the CAN bus to output the intermediate direct-current voltage required for stabilization, and the intermediate direct-current voltage is provided for the three-level inverter, so that the intelligent automatic adaptation to the power grid CAN be realizedFluctuations and voltage drops due to long cable outputs.
The branch control system comprises a three-level PWM rectifier, a three-level inverter and a filter which are sequentially connected, one end of the bidirectional DC/DC converter is connected with the super capacitor bank, the other end of the bidirectional DC/DC converter is connected between the three-level PWM rectifier and the three-level inverter, the filter of the master control system is connected with the driving motor through a long cable, and the filter of the slave control system is connected with the driven motor through a long cable; the quasi sine wave output of the three-level inverter is three-phase sine wave voltage output after passing through the filter, and the power is supplied to the scraper conveyer through the long cable, so that the synchronous control of the scraper conveyer is realized, and meanwhile, the power supply of the long cable is realized.
The quasi sine wave output of the three-level inverter is three-phase sine wave voltage output after passing through the filter, wherein the synchronous control of the scraper conveyer is realized by the control of the master control system and the slave control system.
The three-level PWM rectifier outputs stable and adjustable intermediate direct-current voltage to be supplied to the three-level inverter, wherein the three-level PWM rectifier is combined with a bidirectional DC/DC converter connected with the super capacitor bank to adapt to sudden change and heavy load starting of a load, and can continuously control and adjust the scraper conveyor to synchronously run.
The two three-level inverters, the two three-level PWM rectifiers and the two bidirectional DC/DC converters are connected with a master control system through a CAN bus to exchange data.
The three-level PWM rectifier is combined with the bidirectional DC/DC converter to charge the super capacitor bank instantly, and after charging is finished, the three-level PWM rectifier is coordinated with a power supply formed by the bidirectional DC/DC converter and the super capacitor bank to operate, and the three-level PWM rectifier is controlled to work under a constant-voltage current-limiting working condition.
Regenerative braking energy generated by the driving motor and the driven motor is stored in the super capacitor bank through the bidirectional DC/DC converter, and energy storage is achieved or the regenerative braking energy is fed back to a power grid through the three-level PWM rectifier.
The master control system and the slave control system can be in master-slave control with each other.
The invention has the advantages that: the invention has simple circuit structure, low manufacturing cost, easy control and high cost performance, utilizes the power electronic technology and the full-digital intelligent technology to realize the high-efficiency utilization of the motor and the electric energy thereof, can more effectively realize various special working conditions and long cable operation of the scraper conveyor by organically combining the super capacitor bank and the bidirectional DC/DC converter, realizes the effective utilization of the regenerated energy, supplements the energy in time at the moment of starting the motor and under the heavy load condition, prolongs the service life and the service efficiency of the motor, and avoids the instability of a power supply grid. The super capacitor bank has an energy storage function and an instant heavy current discharge function, so that energy waste is avoided, energy conservation and environmental protection are realized, and the explosion-proof performance and the use safety performance of the whole product are improved. And meanwhile, the remote control is adopted, so that personal risks are avoided to a great extent.
Drawings
Fig. 1 is a schematic view of a conventional mining face conveyor drive system.
Fig. 2 is a schematic diagram of a conventional mining face conveyor frequency converter drive system.
FIG. 3 is a schematic flow diagram of the present invention.
Fig. 4 is a diagram of a model of the long cable of fig. 3.
Detailed Description
The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. These examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.
Referring to fig. 3 to 4, the invention relates to a long cable control method for a driving system of a mining scraper conveyor, which comprises the following steps: when the scraper conveyer operates, one of the component control systems is a master control system which is used for controlling the speed of a driving motor of the scraper conveyer, the other component control system is a slave control system which is used for controlling the torque of a driven motor of the scraper conveyer, and the master control system analyzes the sampling data of the component control systems of the scraper conveyer and controls and adjusts the operation conditions of each control system according to the sampling data so as to achieve real-time monitoring and real-time adjustment and automatically adjust intelligent operation; the master control system enables the scraper conveyer to always run in the optimal state through a voltage closed-loop control algorithm; the voltage closed-loop control algorithm is realized based on a long cable model and detected data, and specifically comprises the following steps: according to the long cable model, the inductance L, the capacitance C and the resistance R are adopted to simulate the long cable parameters, and for a balanced three-phase system, the resistance value, the capacitance value and the inductance value of the three-phase cable are equal:
Rc_u＝Rc_v＝Rc_w＝Rc (1)
Lc_u＝Lc_v＝Lc_w＝Lc (2)
Cc_u＝Cc_v＝Cc_w＝Cc (3)
make the inductance impedance as ZL＝jω1LcThe capacitance impedance is
Figure GDA0003025296530000111
The impedance per kilometer of cable in each phase is then:
Z＝Rc+ZL+Zc (4)
uc_uvw＝Z*iINV_uvw (5)
ucl_uvw＝Z*iINV_uvw*l (6)
wherein j represents a complex number; rc-u、Rc-v、Rc-wRespectively, the resistance value of each phase of the cable is in unit omega; l isc-u、Lc-v、Lc-wRespectively, the inductance value of each phase of the cable is expressed in unit H; cc-u、Cc-v、Cc-wRespectively is the capacitance value of each phase of the cable, unit F; omega1，uc_uvw，iINV_uvwThe three-level inverter outputs each phase voltage drop and three-phase current value of the long cable;
according to the detected three-phase current value i output by the three-level inverterINV_uvwAngular frequency ω of actual output1Calculating the voltage drop u of each phase of each voltage of each kilometer of the cable according to the formula (5)c_uvw(ii) a "I" is the actual length of the cable, ucl_uvwCalculating the voltage drop of each phase voltage under the actual cable length of the scraper conveyer through a formula (6) for the voltage drop of each phase voltage under the actual cable length of the scraper conveyer;
the master control system sends out control instructions through a CAN bus, one sub-control system is a master control system, the other sub-control system is a slave control system, and the running speed frequency of the scraper conveyor is controlled through the master control system; the running torque signal is controlled by a sub-control system, and the torque of the scraper conveyer is further controlled; when the scraper conveyer actually runs, the master control system calculates the voltage required by the motor according to the rated frequency and the actual running frequency of the scraper conveyer,
Figure GDA0003025296530000121
wherein f (t) is the actual operating frequency of the scraper conveyor, UNIs the rated voltage of the motor, fNIs the rated frequency, U, of the motorSThe phase voltage for the operation of the motor of the scraper conveyor calculated by formula (7) without considering the length of the cable; considering the influence of the length of the long cable, under the actual operation frequency and the actual operation phase current, the voltage drop of the cable is calculated to be u through the formula (6)cl_uvwAnd U isSAdding up, the phase voltage actually needed by the motor of the scraper conveyer can be calculated to be
Figure GDA0003025296530000131
And uuvwThree-phase voltage values outputted for the actually detected three-level inverter,
Figure GDA0003025296530000132
and uuvwAs long cable control of the scraper conveyor drive systemThe input value of the algorithm PI and the output value of the algorithm PI are given values U of the output direct-current voltage of the three-level PWM rectifier*I.e. the input dc voltage value U of the three-phase inverter*(ii) a Therefore, under the condition that the length of the cable is I, different running speeds and different working conditions, the master control system calculates the given value U of the direct-current voltage through a control algorithm*Controlling the output direct-current voltage values of the three-phase PWM rectifier and the bidirectional DC/DC converter so that the driving system of the scraper conveyer always works in the optimal state; thus, the required intermediate direct current voltage U is calculated by a long cable control algorithm of a scraper conveyor driving system*The intermediate direct-current voltage is provided for the three-level PWM rectifier and the bidirectional DC/DC converter through the bus to output the stable required intermediate direct-current voltage, and the intermediate direct-current voltage is provided for the three-level inverter, so that the fluctuation of a power grid and the voltage drop caused by the output of a long cable can be intelligently and automatically adapted.
The branch control system comprises a three-level PWM rectifier 1, a three-level inverter 2 and a filter 3 which are sequentially connected, one end of a bidirectional DC/DC converter 5 is connected with a super capacitor bank 6, the other end of the bidirectional DC/DC converter is connected between the three-level PWM rectifier and the three-level inverter, the filter of the master control system is connected with a driving motor M1 through a long cable, and the filter of the slave control system is connected with a driven motor M2 through a long cable; the quasi sine wave output of the three-level inverter is three-phase sine wave voltage output after passing through the filter, and the power is supplied to the scraper conveyer through the long cable, so that the synchronous control of the scraper conveyer is realized, and meanwhile, the power supply of the long cable is realized.
The quasi sine wave output of the three-level inverter is three-phase sine wave voltage output after passing through the filter, wherein the synchronous control of the scraper conveyer is realized by the control of the master control system and the slave control system.
The three-level PWM rectifier outputs stable and adjustable intermediate direct-current voltage to be supplied to the three-level inverter, wherein the three-level PWM rectifier is combined with a bidirectional DC/DC converter connected with the super capacitor bank to adapt to sudden change and heavy load starting of a load, and can continuously control and adjust the scraper conveyor to synchronously run.
The two three-level inverters, the two three-level PWM rectifiers and the two bidirectional DC/DC converters are connected with a master control system through a CAN bus to exchange data.
The three-level PWM rectifier is combined with the bidirectional DC/DC converter to charge the super capacitor bank instantly, and after charging is finished, the three-level PWM rectifier is coordinated with a power supply formed by the bidirectional DC/DC converter and the super capacitor bank to operate, and the three-level PWM rectifier is controlled to work under a constant-voltage current-limiting working condition.
Regenerative braking energy generated by the driving motor and the driven motor is stored in the super capacitor bank through the bidirectional DC/DC converter, and energy storage is achieved or the regenerative braking energy is fed back to a power grid through the three-level PWM rectifier. The intelligent high-efficiency variable-frequency driving system of the mining scraper conveyor has the advantages that a charging resistance unit and a braking resistance unit are not required to be additionally arranged, the control performance, the explosion-proof performance and the reliability of the intelligent high-efficiency variable-frequency driving system of the mining scraper conveyor are improved, and the efficiency of the driving system is improved.
The master control system and the slave control system can be in master-slave control with each other.
The master control system can carry out intelligent identification and fault diagnosis. The controller exchanges data with the three-level PWM rectifier, the bidirectional DC/DC converter, the three-level inverter and the super capacitor bank through the CAN bus, reasonably controls the operation of the scraper conveyer, CAN effectively deal with different working conditions and severe environments, enables the scraper conveyer to always work at the highest operation efficiency, and prolongs the service life of the scraper conveyer. Particularly, in the process of regenerative braking, regenerative braking energy is stored quickly or fed back quickly, energy is supplemented quickly at the moment of starting, the scraper conveyor can be started in a heavy load mode, the instability of a power supply grid cannot be caused, the service life of an intelligent high-efficiency frequency converter driving system of the scraper conveyor is prolonged, and the energy-saving and environment-friendly effects are achieved. The voltage-stabilizing and current-limiting functions of the three-level PWM rectifier are combined with the instantaneous heavy-current discharge of the super capacitor bank and the constant-voltage working mode of the bidirectional DC/DC, so that the three-level PWM rectifier can adapt to the large fluctuation of a power grid, the sudden change of load, the power supply of a long cable and synchronous control, and the reliable operation of the scraper conveyor is ensured.

Claims (8)

1. A long cable control method for a driving system of a mining scraper conveyor is characterized by comprising the following steps: when the scraper conveyer operates, one of the component control systems is a master control system which is used for controlling the speed of a driving motor of the scraper conveyer, the other component control system is a slave control system which is used for controlling the torque of a driven motor of the scraper conveyer, and the master control system analyzes the sampling data of each component control system of the scraper conveyer and controls and adjusts the operation condition of each control system according to the sampling data so as to achieve real-time monitoring and real-time adjustment and automatically adjust intelligent operation; the master control system enables the scraper conveyer to always run in the optimal state through a voltage closed-loop control algorithm; the voltage closed-loop control algorithm is realized based on a long cable model and detected data, and specifically comprises the following steps: according to the long cable model, the inductance L, the capacitance C and the resistance R are adopted to simulate the long cable parameters, and for a balanced three-phase system, the resistance value, the capacitance value and the inductance value of the three-phase cable are equal:
Rc_u＝Rc_v＝Rc_w＝Rc (1)
Lc_u＝Lc_v＝Lc_w＝Lc (2)
Cc_u＝Cc_v＝Cc_w＝Cc (3)
make the inductance impedance as ZL＝jω1LcThe capacitance impedance is
Figure FDA0003025296520000011
The impedance per kilometer of cable in each phase is then:
Z＝RC+ZL+Zc (4)
then, the following steps are obtained:
uC_uvw＝Z*iINV_uvw (5)
ucl_uvw＝Z*iINV_uvw*l (6)
wherein j represents a complex number; rc-u、Rc-v、Rc-wRespectively, the resistance value of each phase of the cable is in unit omega; l isc-u、Cc-v、Cc-wAre respectively provided withThe inductance value of each phase of the cable is expressed in H; cc-u、Cc-v、Cc-wRespectively is the capacitance value of each phase of the cable, unit F; omega1，uc_uvw，iINV_uvwThe three-level inverter outputs each phase voltage drop and three-phase current value of the long cable;
according to the detected three-phase current value i output by the three-level inverterINV_uvwAngular frequency ω of actual output1Calculating the voltage drop u of each phase of each voltage of each kilometer of the cable according to the formula (5)c_uvw(ii) a "l" is the actual length of the cable, ucl_uvwCalculating the voltage drop of each phase voltage under the actual cable length of the scraper conveyer through a formula (6) for the voltage drop of each phase voltage under the actual cable length of the scraper conveyer;
the master control system sends out control instructions through a CAN bus, one sub-control system is a master control system, the other sub-control system is a slave control system, and the running speed and the running frequency of the scraper conveyor are controlled through the master control system; the main control system calculates the running torque, and transmits the running torque to the sub-control system through the CAN bus to further control the torque of the scraper conveyer; when the scraper conveyer actually runs, the master control system calculates the voltage required by the motor according to the rated frequency and the actual running frequency of the scraper conveyer,
Figure FDA0003025296520000021
wherein f (t) is the actual operating frequency of the scraper conveyor, UNIs the rated voltage of the motor, fNIs the rated frequency, U, of the motorSThe phase voltage for the operation of the motor of the scraper conveyor calculated by formula (7) without considering the length of the cable; considering the influence of the length of the long cable, under the actual operation frequency and the actual operation phase current, the voltage drop of the cable is calculated to be u through the formula (6)cl_uvwAnd U isSAdding up, the phase voltage actually needed by the motor of the scraper conveyer can be calculated to be
Figure FDA0003025296520000031
And uuvwThree-phase voltage values outputted for the actually detected three-level inverter,
Figure FDA0003025296520000032
and uuvwThe difference value of the three-level PWM rectifier is used as an input value of a long cable control algorithm PI of the scraper conveyor driving system, and the output value of the PI is a given value U of the output direct-current voltage of the three-level PWM rectifier*I.e. the input dc voltage value U of the three-phase inverter*(ii) a Therefore, under the condition that the length of the cable is I, different running speeds and different working conditions, the master control system calculates the given value U of the direct-current voltage through a control algorithm*Controlling the output direct-current voltage values of the three-phase PWM rectifier and the bidirectional DC/DC converter so that the driving system of the scraper conveyer always works in the optimal state; thus, the required intermediate direct current voltage U is calculated by a long cable control algorithm of a scraper conveyor driving system*The intermediate direct-current voltage is provided for the three-level PWM rectifier and the bidirectional DC/DC converter through the CAN bus to output the stable required intermediate direct-current voltage, and the intermediate direct-current voltage is provided for the three-level inverter, so that the fluctuation of a power grid and the voltage drop caused by the output of a long cable CAN be intelligently and automatically adapted.
2. The long cable control method for the driving system of the mining scraper conveyor according to claim 1, characterized in that the branch control system comprises a three-level PWM rectifier, a three-level inverter and a filter which are sequentially connected, one end of a bidirectional DC/DC converter is connected with a super capacitor bank, the other end of the bidirectional DC/DC converter is connected between the three-level PWM rectifier and the three-level inverter, the filter of the master control system is connected with the driving motor through a long cable, and the filter of the slave control system is connected with the slave motor through a long cable; the quasi sine wave output of the three-level inverter is three-phase sine wave voltage output after passing through the filter, and the power is supplied to the scraper conveyer through the long cable, so that the synchronous control of the scraper conveyer is realized, and meanwhile, the power supply of the long cable is realized.
3. The method for controlling the long cable of the driving system of the mining scraper conveyor according to claim 1 or 2, wherein the quasi-sine wave output of the three-level inverter is a three-phase sine wave voltage output after passing through a filter, and the synchronous control of the scraper conveyor is realized by the control of the master control system and the slave control system.
4. The method for controlling the long cable of the driving system of the mining scraper conveyor according to claim 3, wherein the three-level PWM rectifier outputs a stable and adjustable intermediate DC voltage to be supplied to the three-level inverter, wherein the three-level PWM rectifier can continuously control and adjust the scraper conveyor to run synchronously in combination with the bidirectional DC/DC converter connected with the super capacitor bank to adapt to sudden load change and heavy load starting.
5. The method for controlling the long cable of the driving system of the mining scraper conveyor according to claim 3, wherein the two three-level inverters, the two three-level PWM rectifiers and the two bidirectional DC/DC converters are connected with a master control system through CAN buses for data exchange.
6. The method for controlling the long cable of the driving system of the mining scraper conveyor according to claim 2, wherein the three-level PWM rectifier is combined with the bidirectional DC/DC converter to charge the super capacitor bank instantly, and after the charging is finished, the three-level PWM rectifier is coordinated with a power supply formed by the bidirectional DC/DC converter and the super capacitor bank to operate, and the three-level PWM rectifier is controlled to work under a constant-voltage current-limiting working condition.
7. The method for controlling the long cable of the driving system of the mining scraper conveyor according to claim 4, wherein regenerative braking energy generated by the driving motor and the driven motor is stored in the super capacitor bank through the bidirectional DC/DC converter, so that energy storage is realized or the regenerative braking energy is fed back to a power grid through the three-level PWM rectifier.
8. The method for controlling the long cable of the driving system of the mining scraper conveyor according to claim 1, characterized in that the master control system and the slave control system are master-slave controlled.
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US1437549A (en) * 1922-05-15 1922-12-05 Henry S Putnam Electrically-operated transportation apparatus
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