Power Supply Status Analysis and Scheme Design of High Efficiency and Rapid Driving Equipment

In the view of the problems of frequent movement and change in the practical application of complete sets of high efficient and rapid driving equipment, a scheme of extending the power supply distance is designed. In this scheme, an intelligent comprehensive regulation device is arranged in the shifting area and a power quality parameter monitoring device is arranged in the combination switch of the device. Real-time and accurate monitoring of the three-phase line voltage and phase Angle during the operation of the equipment and feedback to the intelligent integrated regulation device through optical fiber communication mode. The PLC controller in the intelligent integrated regulation device implements different voltage and phase regulation control strategies according to the voltage and phase Angle values monitored at the head and end. The test results in the plant show that the scheme can improve the terminal voltage of the equipment and achieve the purpose of “shift and change, long distance power supply.


Introduction
The underground excavation face of the coal mine is a separate single-headed roadway based on excavation, which needs to be supported by the top of the roadway and the two gangs, and there are two ways of mechanical excavation and artillery excavation.At present, the underground excavation face of coal mine with good geological conditions is mainly boring machine, windlass digging machine and continuous mining machine.With the continuous advancement of the intelligent process of coal mine underground [1], the complete set of efficient and rapid tunneling equipment is gradually applied to the underground excavation face of coal mine, which realizes the parallel and continuous operation of excavation, support and transportation, and effectively improves the excavation efficiency and automation degree of the excavation face.
The complete set of efficient and rapid tunneling equipment has continuously extended the whole length of the underground excavation face of the coal mine, which brings challenges to the safe and efficient power supply of the equipment.In order to extend the power supply distance of the coal mine underground tunneling face, the commonly used solutions are: 1) Increase the cross-sectional area of the power supply cable, and combine it with the model power supply cable, as described in the bibliographic [2].2) According to the actual industrial and mining of the comprehensive excavation roadway, arrange the load center, as described in the bibliographic [3]. 3) Add reactive power compensation devices, as shown in the bibliographic [4][5][6][7][8][9].4) Increase the power supply voltage at the first end of the power supply.When applied to engineering practice, scheme 1 has the disadvantages of large maintenance workload and high work intensity; Solution 2 has the disadvantages of limited extended power supply distance and poor economy; Option 3 has the disadvantage of complex engineering implementation and the introduction of new reactive/harmonic interference.There are two ways to implement the engineering of scheme 4, mode 1 is to move and shift according to the actual working conditions; Method 2 is to arrange an intelligent comprehensive adjustment device at the shift place, and dynamically adjust the voltage at the first end of the shift according to the voltage value at the end of the equipment, so that the voltage fluctuation range at the end of the equipment meets the requirements of 75%-110% of the rated power supply voltage.
This paper takes the complete set of efficient and rapid tunneling equipment applied to the underground excavation face of coal mine as an example, and on the basis of analyzing its power supply status, the scheme of extending the power supply distance is designed to achieve the purpose of increasing the voltage at the end of the equipment.According to the test conditions in the factory, the test was carried out under the heavy load starting condition of a certain type of windlass cutting motor, and the terminal voltage fluctuation law was recorded and analyzed to verify the correctness and effectiveness of the designed scheme to extend the power supply distance.

Analysis of the Power Supply Status of Efficient and Fast Boring Complete Equipment
Efficient and rapid boring complete sets of equipment are used in coal mine underground excavation face, and their characteristics are: 1) There are many electrical equipment, including roadheader bolter, bolting-loading machine bendable belt transfer machine, step self-moving tail and other equipment.2) There are many power levels of electrical equipment, and the motor power level distribution involved is 22KW-170KW.3) There is a strict start-stop sequence between the electrical equipment and the motor of the equipment itself.4) Power frequency and frequency conversion control mode of electrical equipment coexist.
The distribution of equipment in typical operation scenarios of efficient and rapid boring equipment is shown in figure 1, with the coal wall as the front end, the electrical equipment arranged are roadheader bolter, bolting-loading machine (crusher), bendable belt loader and step-type self-moving tail, the total length is L2, and the L2 value is generally 100-150 m.A combination switch is arranged at the tail of the self-moving machine, and the power supply of the combination switch is provided by the shifter.The distance between the shift and the combination switch is L1, and according to the actual working conditions of the boring face, the value of L1 is generally 1000 m, and it is generally connected by a power supply cable of 75 mm 2 -120 mm 2 .In the actual working process, with the increasing number of windlass boring feet, the efficient and fast boring equipment as a whole moves slowly along the boring direction, and the power supply cables stored between the shifting and efficient and fast boring equipment are gradually deployed.When the power supply cable with length L1 is transmitted to the power equipment at the excavation face, the instantaneous value of the voltage at the end of the equipment drops sharply due to nonlinear loads, high-power switchgear, passive devices, etc. Taking the windlass digging machine equipped with dual power rating 170 kW cutting motor as an example, when the cutting motor is started without load, the terminal voltage can drop to 700 V instantaneously.With the continuous movement of highefficiency and rapid boring equipment, the terminal voltage drop phenomenon becomes more and more serious, which will lead to safety accidents such as difficult start-up of electrical equipment, motor stalling, overheating and burning.The above phenomenon is caused by the reactive power of the power supply system of the tunneling face, which causes power quality problems such as voltage fluctuations, voltage flicker and even voltage dip at the power supply end.For example, taking L1 length of 1000 m as an example, it is necessary to arrange a chamber every 1000 m, and then disassemble, handle, and install the transfer equipment into the chamber, which generally requires two maintenance shifts, which seriously affects the efficiency of efficient and rapid boring equipment.
At present, the power supply scheme of the efficient and fast boring equipment of the boring face is to store the fixed-length L1 power supply cable according to the actual situation of the boring roadway and according to the terminal voltage drop.When the slow movement distance of the efficient and fast boring kit is greater than L1, the shift is moved to the new chamber, and so on.Taking an excavation roadway of 5000m as an example, at least 5 shifts are required.Due to the large number of underground shifting equipment, large volume and self-weight weight of coal mines, trackless auxiliary transportation equipment or winches are used in the moving process, which has a large workload, high intensity and long time [10][11][12][13], which seriously affects the work efficiency of efficient and rapid boring equipment.
Therefore, according to the actual working conditions of high-efficiency and rapid tunneling equipment, it is of great social and economic significance to design a long-distance power supply scheme to extend the power supply distance between the shifting and efficient rapid boring equipment, reduce the number of shifting movements, and improve the tunneling efficiency.

Theoretical Analysis
Taking a certain type of high-efficiency and rapid boring complete set of equipment as an example, the main parameter statistics are shown in table 1, the total installed power is 1 199 kW, of which the installed power of roadheader bolter is 742 kW, and the maximum power of cutting motor is 170*2 kW.When the complete set of equipment is operated efficiently and quickly, the roadheader bolter cutting motor has the most complex operating conditions and the longest power supply distance.Under the existing long-distance power supply conditions, it is difficult to start, and problems such as motor heating are more prominent.When the complete set of equipment is carried out efficiently and quickly, the main factors of the voltage drop at the end of the equipment are the moving voltage drop and the cable voltage drop.
(1) Shift voltage drop According to the transmutation parameters of a certain type of high-efficiency and rapid boring complete set of equipment, the transfer voltage drop calculation formula is [14]: ) as shown in equation ( 1),  is the variable load coefficient, the value is constant 0.906; r U is the voltage drop coefficient of the shift resistor, the value is constant 0.635; x U is the shift reactance voltage drop coefficient, the value is constant 4.959; cos is the weighted average power factor, the value is constant 0. (2) Cable voltage drop The roadheader bolter is located at the forefront of the efficient and fast boring package, and the voltage drop calculation formula is: as shown in equation ( 1), e P  is the sum of the power of the electrical equipment in the power supply cable, which is 742 kW.g L is the length of the power supply cable, which is 1000m.r K is the demand coefficient of the power supply cable, taking the constant 0.52. is the conductivity of the power supply cable, take the constant 42.5mm/(Ω.mm2).N U is the rated voltage of the power supply, which is 1140 V. g A is the cross-sectional area of the power supply cable, which is 25 mm 2 .Bringing the above data into equation (1) calculates that the cable voltage drop is 167.66V.

Scheme Implementation
The long-distance power supply scheme suitable for efficient and fast boring equipment is shown in figure 2, and the output of the 1140 V three-phase power supply at the shift is connected to the combined switch input of the high-efficiency and rapid boring complete set of equipment step self-moving tail equipment train through an intelligent integrated adjustment device.The combination switch is located on the equipment train of the step-type self-moving tail, and independently outputs four 1140 V power supplies, which are respectively powered by the roadheader bolter, the bolting-loading machine, the bendable belt loader and the step-type self-moving tail.The power quality parameter monitoring device monitors the three-phase voltage and phase angle at the input of the combined switch in real time.

Combination switch
Fiber optic transmission


Step-type self-moving tail According to the power supply characteristics of high-efficiency and rapid boring complete equipment, the power supply scheme of extended high-efficiency and rapid boring complete sets of equipment designed is: 1) An intelligent integrated adjustment device was added and placed in the faceshifting chamber.2) The intelligent integrated regulation device collects the three-phase line voltage and phase of the output side of the device with the sampling period T1, which are  , and 1 ca  , respectively. 3)Design power quality parameter monitoring device, adjacent to the combination switch, as for the step-type self-moving tail equipment train.4) The power quality parameter monitoring device collects the three-phase line voltage and phase of the input side of the combined switch with the sampling period T2, which are  , and 2 ca  , respectively.The collected power quality parameters are transmitted to the intelligent integrated regulation device through optical fiber communication.5) The PLC controller inside the intelligent comprehensive regulation device analyzes and calculates  , and determines the voltage regulation strategy. 6)The execution unit inside the intelligent integrated regulation device generates an action signal according to the voltage regulation strategy.7) The multi-tap three-phase dry-type transformer inside the intelligent integrated regulation device outputs the corresponding three-phase line voltage and phase according to the action signal.Through the above scheme, the safe, stable and efficient operation of the complete set of efficient and rapid equipment is guaranteed.
According to the "Coal Mine Safety Regulations", the power supply voltage range of the underground motor in the coal mine is 75%-110% when it works normally.The rated voltage on the input side of the combination switch is 1140 V, and the voltage range to ensure the normal operation of efficient and fast boring equipment is 855 V-1254 V.
(1) Line voltage value adjustment strategy Enable

Experiment
According to the test conditions in the factory, EJM270/4-2 roadheader bolter was used as the test object to verify the correctness and applicability of the provided electrical scheme.The basic parameters of the roadheader bolter are: (1) total motor power, 542 kW (cut-off motor: 270 kW; Transport motor: 2*36 kW; Oil pump motor: 200 kW).(2) Weight: 96 T. (3) Mining height range: 3800~5500 mm.(4) Voltage level: 1140 V.The same driver completes the test 1-6 respectively, the parameter settings of the test scene are shown in table 2, the length of the power supply cable is selected as 200 m, 500 m and 1000 m respectively, the cutting motor, transport motor and oil pump motor are running during the test, and the power supply voltage data of the windlass roadheader bolter end within 30min is recorded and the power supply voltage curve is drawn.The change curve of the supply voltage value of the EJM270/4-2 roadheader bolter at the inlet end of test 1-test 6 is shown in figure 3. It can be seen from figure 3 that the longer the power supply cable, the greater the voltage drop of the power supply at the inlet end of the roadheader bolter.After applying the intelligent integrated adjustment device, the power supply voltage at the inlet end of the roadheader bolter.can be raised from 930 V (the length of the power supply cable is 1000 m) and 950 V (the length of the power supply cable is 500 m) to about 1140 V, achieved the purpose of extending the power supply distance of roadheader bolter, and verifies the correctness and applicability of the proposed longdistance power supply scheme.

Conclusion
(1) The long-distance power supply method and existing problems of the coal mine underground excavation face were analyzed, and it was pointed out that the method of increasing the power supply voltage at the first end of the power supply was easy to implement.
(2) The current situation of power supply for complete sets of high-efficiency and rapid tunneling equipment was expounded, and the boring scale needed to be moved and shifted after it was greater than 1000m, which seriously affected the tunneling efficiency.
(3) The intelligent comprehensive regulation device + power quality parameter monitoring device extended the power supply distance scheme was designed, and the test was completed based on the test conditions in the plant, and the power supply voltage change law of the electric drive windlass before and after the application of the extended power supply distance scheme was compared, and the correctness and effectiveness of the long-distance power supply scheme were verified.

Figure 1 .
Figure 1.Efficient and fast boring complete equipment operation scene equipment layout.

7 .
The values of  , cos are directly given based on the empirical value of voltage loss calculation at transformer station in coal mine.Taking the above data band equation (1) gives B U  as 3.548%.The rated output voltage of the shift is 1140 V, and the voltage drop at the shift of this high-efficiency and fast boring plant is 40.45V.

Figure 2 .
Figure 2. Block diagram of a long-distance power supply scheme for efficient and fast boring packages.

Uand 2 k
be the rated input voltage of the combined switch, and let voltage adjusted by the intelligent comprehensive regulation device.①When the three-Generate a voltage reduction command) ② When the three-phase line voltage Generate a voltage raise command) ③where 1 k are correction coefficients, according to the actual working conditions, the values in the voltage comprehensive control center device analyzes and calculates the three-phase line voltage and phase signal of the power supply end collected by the multi-tap threecoherent transformer and the power quality parameter monitoring device, compares and analyzes the PLC controller, and outputs the voltage regulation strategy (raise voltage or reduce voltage) to the voltage regulation execution unit.The voltage regulator executing unit sends an action signal to the multi-tap tri-coherent transformer for voltage regulation, and finally executes the voltage regulation strategy.

Table 1 .
Statistics of the main parameters of a certain type of efficient and rapid boring complete set of equipment.

Table 2 .
Power supply scheme test scenario parameters.