An underground coal mine continuous miner equipment power quality treatment device

Abstract

The present application belongs to the technical field of coal mine underground power supply, and discloses a coal mine underground continuous mining machine equipment electric energy quality treatment device, which comprises a dynamic reactive compensator, a first current transformer, a walking frequency converter and a second current transformer; the input end of the walking frequency converter is connected with the moving variable output end, and the output end is connected with a walking motor; the incoming line end of the dynamic reactive compensator is connected in parallel with a continuous mining machine power supply cable, the first current transformer is used for measuring the incoming line current of the continuous mining machine, and the second current transformer is used for measuring the motor load current in the continuous mining machine; the dynamic reactive compensator is used for performing reactive compensation on the continuous mining machine equipment through the motor load current in the continuous mining machine measured by the second current transformer, and the walking frequency converter is used for performing harmonic treatment on the continuous mining machine device through the incoming line current of the continuous mining machine measured by the first current transformer. The present application improves the flexible adaptation capability of the continuous mining machine equipment to the on-site power grid.

Description

Technical Field

[0001] This invention belongs to the field of underground power supply technology in coal mines, specifically relating to a power quality management device for continuous mining equipment in coal mines. It is used to perform reactive power compensation and harmonic control for the power supply operation of continuous mining equipment, including asynchronous motors and frequency converters. Background Technology

[0002] With the increasing number of continuous coal mining machines in underground coal mines, the pollution to the underground power grid from harmonic sources is also gradually increasing. Limited by the capacity of harmonic mitigation devices in existing underground power supply systems and their installation locations within the lines, the effectiveness of mitigating harmonic sources at the equipment terminals is limited. Simultaneously, due to limitations in the transformer capacity and voltage regulation range at the working face, the reactive power generated during motor startup in the continuous coal mining machine lowers the terminal voltage of the machine, making startup difficult. Current practice involves shortening the distance between the transformer and the machine, which necessitates multiple moves of the transformer, increasing the workload of coal mining and reducing mining efficiency.

[0003] To improve the efficiency of continuous mining machine operations and reduce the number of relocations, it is necessary to improve the power supply equipment of the existing continuous mining machine. Summary of the Invention

[0004] The present invention overcomes the shortcomings of the existing technology, and the technical problem to be solved is: to provide a power quality management device for a continuous mining machine in an underground coal mine, so as to improve the efficiency of continuous mining machine operation and reduce the number of relocations.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a power quality management device for a coal mine underground continuous mining machine, comprising: a dynamic reactive power compensator, a first current transformer, a traveling frequency converter, and a second current transformer.

[0006] The input terminal of the walking frequency converter is connected to the output terminal of the mobile frequency converter, and the output terminal is connected to the walking motor; the input terminal of the dynamic reactive power compensator is connected in parallel with the power supply cable of the continuous mining machine; the first current transformer is used to measure the input current of the continuous mining machine, and the second current transformer is used to measure the motor load current in the continuous mining machine.

[0007] The dynamic reactive power compensator is used to compensate for the reactive power of the continuous mining machine equipment by measuring the motor load current in the continuous mining machine through the second current transformer. The walking frequency converter is used to control the harmonics of the continuous mining machine device by measuring the incoming current of the continuous mining machine through the first current transformer.

[0008] The dynamic reactive power compensator includes a T-type three-level structure and an LCL third-order filter; the T-type three-level structure is connected to the power supply cable of the continuous mining machine through the LCL third-order filter.

[0009] The specific method for reactive power compensation by the dynamic reactive power compensator is as follows:

[0010] The reactive component of the motor load current in the continuous mining machine is detected and the output is used as the q-axis component. The current obtained by the dynamic reactive power compensator to achieve bus voltage equalization control is used as the 0-axis component. The current obtained by bus voltage stabilization control of the dynamic reactive power compensator is used as the d-axis component. Then, through the coordinate transformation from dq0 to abc, the current value in the abc coordinate system is obtained as the current command value of the dynamic reactive power compensator. According to the current command value The control duty cycle of each switching device in the dynamic reactive power compensator is obtained.

[0011] The walking inverter is a four-quadrant walking inverter, which includes a grid-side unit, a motor-side unit, and an LCL filter. One end of the motor-side unit is connected to the walking motor, and the other end is connected to the output terminal of the inverter through the grid-side unit and the LCL filter.

[0012] The specific method for harmonic mitigation of the mobile frequency converter is as follows:

[0013] The sum of the output current obtained by detecting the fundamental positive sequence active component of the continuous mining machine's incoming current and the current value obtained by the bus voltage regulation of the walking frequency converter is used as the d-axis component. The current value obtained by equalizing the bus voltage of the walking inverter is taken as the 0-axis component. The q-axis component is set to zero; then, through the coordinate transformation dq0→abc, the current value in the abc coordinate system is generated. The current value in the abc coordinate system is then subtracted from the input current of the continuous mining machine to obtain the current command value for the mobile inverter's grid-side unit. According to the current command value The control duty cycle of each switching device in the grid-side unit of the mobile inverter is obtained.

[0014] When the dynamic reactive power compensator performs reactive power compensation, it adopts dual closed-loop control of voltage and current. The voltage control is the outer loop, which realizes the equalization and stabilization control of the bus voltage. The current inner loop adopts proportional control in parallel with a repetitive controller containing the internal mode of each harmonic, forming an inner loop control strategy of proportional control and repetitive control in parallel.

[0015] When the walking frequency converter performs harmonic mitigation on the continuous mining machine, it adopts dual closed-loop control of voltage and current. The voltage control is the outer loop, which realizes the equalization and stabilization control of the bus voltage. The current inner loop adopts proportional control in parallel with a repetitive controller containing the internal modes of each harmonic, forming an inner loop control strategy of proportional control and repetitive control in parallel.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. This invention provides a power quality management device for continuous mining machines in underground coal mines. Addressing the power requirements of these machines and considering their operating conditions, it employs a distributed structure for power quality management. This reduces harmonic content in the lines, improves the power factor, indirectly extends the power supply distance for the continuous mining machine, increases the capacity utilization of mobile transformers, and reduces power line losses. Furthermore, it utilizes the existing mobile frequency converter in the continuous mining machine, representing a cost-effective upgrade to the power supply network and equipment power consumption scheme. This enhances the flexibility and adaptability of the on-site power grid for the continuous mining machine. Therefore, this invention demonstrates significant technical and economic advantages.

[0018] 2. The power quality management device of this invention is installed on the continuous mining equipment side. On the one hand, it can improve the start-up capability of the continuous mining machine; on the other hand, it can increase the power supply distance, reduce line losses and harmonic effects, and avoid protection malfunctions and transformer capacity saturation problems caused by high reactive power losses and high harmonic ratios in AC power supply lines. This improves the working efficiency of the continuous mining machine while maintaining a relatively low cost. It is applicable to other devices similar to continuous mining machines, such as power supply systems for equipment including asynchronous motors of different numbers, voltages, and capacity levels. Attached Figure Description

[0019] Figure 1 An electrical connection diagram of a power quality management device for a coal mine underground continuous mining machine provided in an embodiment of the present invention;

[0020] Figure 2 This is a topology diagram of the dynamic reactive power compensator used in the embodiments of the present invention;

[0021] Figure 3 This is a topology diagram of the four-quadrant walking frequency converter used in this embodiment of the invention;

[0022] Figure 4 This is a control block diagram of the dynamic reactive power compensator in an embodiment of the present invention;

[0023] Figure 5 This is a control block diagram of the network-side unit in an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] like Figure 1 As shown in the figure, this invention provides a power quality management device for a continuous coal mining machine, comprising: a dynamic reactive power compensator, a first current transformer 1, a traveling frequency converter, and a second current transformer 2; the input terminal of the traveling frequency converter is connected to the output terminal of the traveling frequency converter, and the output terminal is connected to the traveling motor; the input terminal of the dynamic reactive power compensator is connected in parallel with the power supply cable of the continuous coal mining machine, and the first current transformer is used to measure the input current i of the continuous coal mining machine. lcj The second current transformer is used to measure the motor load current i in the continuous mining machine. load The dynamic reactive power compensator is used to compensate for the reactive power of the continuous mining machine equipment by measuring the motor load current in the continuous mining machine through the second current transformer; the walking frequency converter is used to control the harmonics of the continuous mining machine device by measuring the incoming current of the continuous mining machine through the first current transformer.

[0027] like Figure 1 As shown, where i lcj The harmonic current content is extracted from the incoming current of the power supply line to the continuous mining machine; track This is the harmonic mitigation current output by the four-quadrant driving inverter, which is then connected to i. lcj Superposition eliminates harmonics on transformer power supply lines; inv This is the output current of the dynamic reactive power compensator, through which dynamic reactive power compensation is performed; i load The load current of the motor in the continuous mining machine is equal to the cutting motor current i. cut Pump station motor current i pump Transport motor current i trans and walking motor current i track The sum of these currents is obtained by measuring the current transformers in their respective circuits.

[0028] In this embodiment, the dynamic reactive power compensator is connected in parallel at the tail of the continuous mining machine, and the harmonic control function is added to the grid-side unit of the traveling frequency converter.

[0029] like Figure 2 As shown, in this embodiment, the dynamic reactive power compensator includes: a T-type three-level structure and an LCL third-order filter; the T-type three-level structure is connected to the power supply cable of the continuous mining machine through the LCL third-order filter. The bus voltage between the positive terminal P and the negative terminal N of the DC bus is u. dc u dc =u dcp +u dcn , where u dcp The voltage across the capacitor from the positive terminal P to the zero terminal O, u dcn The voltage across the capacitor from terminal O to terminal N is i. invThe output current of the dynamic reactive power compensator, u inv This is the inverter voltage of the dynamic reactive power compensator.

[0030] like Figure 3 As shown, in this embodiment, the travel inverter is a four-quadrant travel inverter, which includes a grid-side unit, a motor-side unit, and an LCL filter. One end of the motor-side unit is connected to the travel motor, and the other end is connected to the inverter output terminal through the grid-side unit and the LCL filter. The bus voltage between the positive terminal P1 and the negative terminal N1 of the DC bus is u. dc1 u dc1 =u dcp1 +u dcn1 , where u dcp1 The voltage across the capacitor from the positive terminal P1 to the zero terminal O1, u dcn1 The voltage across the capacitor from terminal O1 to terminal N1 is i. track The output current of the grid-side unit after passing through the LCL filter, u track This is the output voltage of the grid-side unit.

[0031] like Figure 4 As shown, where The figure shows the phase angle obtained by the dynamic reactive power compensator through phase-locking with the AC bus voltage. Δθ in the figure represents the phase delay caused by sampling and control of the dynamic reactive power compensator. (d-axis variable) The active current component required for the normal operation of the dynamic reactive power compensator is crucial for ensuring the establishment of the DC bus voltage; u dcn with u dcp The difference is fed into a PI controller to achieve bus voltage equalization control, and its output is the 0-axis component. To ensure the converter's line current is as small as possible while maintaining balanced DC-side capacitor voltage, the reactive power to be supplied is detected by sampling the load current, and the output is used as the q-axis component. In this embodiment, the dq0→abc coordinate transformation matrix is:

[0032]

[0033] To determine the phase angle obtained by the phase-locked loop of the AC bus voltage by the governance module, when considering the phase delay, the formula (1) is... Replaced with

[0034] like Figure 5 The diagram shown is a control block diagram of the mobile inverter on the grid side in an embodiment of the present invention. In this embodiment, the specific method for harmonic mitigation by the mobile inverter is as follows: the sum of the output current obtained by detecting the fundamental positive sequence active component of the continuous mining machine's incoming current and the current value obtained by stabilizing the bus voltage of the mobile inverter is used as the d-axis component. The current value obtained by equalizing the bus voltage of the walking inverter is taken as the 0-axis component. The q-axis component is set to zero; then, through the coordinate transformation dq0→abc, the current value in the abc coordinate system is generated. The current value in the abc coordinate system is then subtracted from the input current of the continuous mining machine to obtain the current command value for the mobile inverter's grid-side unit. According to the current command value The control duty cycle of each switching device in the grid-side unit of the mobile inverter is obtained.

[0035] Figure 5 middle The phase angle obtained by the harmonic mitigation device through phase-locking with the AC bus voltage is Δθ, which represents the phase delay caused by sampling and control of the harmonic mitigation device. (d-axis variable) The active current component required for the normal operation of the harmonic mitigation device is crucial for ensuring the DC-side voltage is established in rectification mode, and is also superimposed with i lcj The fundamental positive-sequence active component; u dcn with u dcp The difference is fed into a PI controller to achieve voltage equalization control. Its output 0-axis component Δi'0 ensures that the line current in the converter is as small as possible, while ensuring the DC-side capacitor voltage is balanced. The q-axis component is specified as zero, and then the current value in the abc coordinate system is formed under the coordinate transformation dq0→abc. Then, i is used... lcj Subtracting the generated current value yields the command value for the current control inner loop. This is the reference value for the output current of the harmonic mitigation device, dx 1～12 It is the control duty cycle of each switching device in the harmonic mitigation device.

[0036] In this embodiment, during the startup process of the continuous mining machine, the parallel dynamic reactive power compensator is activated, and its entire capacity is used to provide the reactive power required for the startup of each motor of the continuous mining machine. Then, the travel motor starts smoothly under the control of the travel frequency converter. After normal operation, the travel frequency converter continuously monitors the incoming current i in the power supply line. lcj By controlling the output voltage u of the grid-side unit track Together with the voltage output from the converter, it acts on the LCL filter to form the output current i of the grid-side unit after passing through the LCL filter. track It is used to manage the incoming line current i lcj The middle harmonic component can complete harmonic control during normal operation.

[0037] When the continuous mining machine starts, the dynamic reactive power compensator (VPC) engages. As the pump station motor starts, it provides dynamic reactive power compensation. Then, the transport motor and cutting motor start sequentially, with the VPC providing dynamic compensation for each, reducing startup difficulty and reactive power transmission losses. When the traveling motor starts, the traveling frequency converter uses a variable frequency drive to start the motor. Once it is running normally, the continuous mining machine enters a stable operating mode. At this time, the grid-side unit in the traveling frequency converter starts operating in harmonic mitigation mode, reducing the harmonic content in the line and lowering line harmonic losses.

[0038] Furthermore, in this embodiment, when the dynamic reactive power compensator performs reactive power compensation, it adopts dual closed-loop control of voltage and current, wherein the voltage control is the outer loop, realizing bus voltage equalization control and voltage stabilization control; wherein the load current i of the motor in the continuous mining machine is detected. load The reactive current component in the load current is superimposed on the q-axis component of the current command value output by the outer loop, ensuring that the reactive current component in the load current is quickly and accurately fed back to the current command value output by the outer loop, thus providing an accurate command value for the inner current loop. The inner current loop uses a proportional control parallel to a repetitive controller containing internal modes of each harmonic, forming an inner loop control strategy that combines proportional control and repetitive control in parallel. When the traveling frequency converter performs harmonic mitigation on the continuous mining machine, it adopts dual closed-loop control of voltage and current, where voltage control is the outer loop, realizing bus voltage equalization control and voltage stabilization control; wherein, by detecting the incoming current i of the continuous mining machine... lcj The fundamental positive sequence active component is superimposed onto the d-axis component of the current command value output by the outer loop, while the q-axis component is specified as zero. The result of subtracting this value from the actual load current is used as the current inner loop command value. The current inner loop adopts a proportional control parallel to a repetitive controller containing the internal modes of each harmonic, forming an inner loop control strategy of proportional control and repetitive control in parallel.

[0039] In summary, this invention provides a newly added dynamic reactive power compensator to compensate for reactive power in continuous mining machines, and utilizes the grid-side terminal of a four-quadrant walking frequency converter to add harmonic mitigation function to the continuous mining machine, thus forming a distributed power quality management function. Among them, the reactive power compensation function, when the pump station motor, cutting motor and transport motor in the continuous mining machine are started and during normal operation after start-up, detects the reactive power component in the incoming current of the continuous mining machine equipment and performs reactive power exchange with the compensation device nearby. The purpose is to compensate for the reactive power absorbed from the transfer terminal when the motor starts, thereby improving the power factor and the voltage at the continuous mining machine terminal during startup, indirectly increasing the power supply distance and reducing the losses caused by reactive current on the line. The harmonic control function uses the grid-side unit and LCL filter in the four-quadrant walking frequency converter to control the harmonic components in the power supply line by detecting the fundamental positive sequence active component in the incoming current on the continuous mining machine side. This reduces the harmonic loss in the power supply line and lowers the harmonic content in the power supply line of the continuous mining machine equipment, thus controlling the power quality in the underground power supply line from the source of the power load.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power quality management device for a coal mine underground continuous mining machine, characterized in that, include: Dynamic reactive power compensator, first current transformer, mobile frequency converter and second current transformer; The input terminal of the walking frequency converter is connected to the output terminal of the moving frequency converter, and the output terminal is connected to the walking motor; The input terminal of the dynamic reactive power compensator is connected in parallel with the power supply cable of the continuous mining machine. The first current transformer is used to measure the input current of the continuous mining machine, and the second current transformer is used to measure the motor load current in the continuous mining machine. The dynamic reactive power compensator is used to compensate for the reactive power of the continuous mining machine equipment by measuring the motor load current in the continuous mining machine through the second current transformer. The walking frequency converter is used to control the harmonics of the continuous mining machine device by measuring the incoming current of the continuous mining machine through the first current transformer. The specific method for reactive power compensation by the dynamic reactive power compensator is as follows: The reactive component of the motor load current in the continuous mining machine is detected and the output is used as the q-axis component. The current obtained by the dynamic reactive power compensator to achieve bus voltage equalization control is used as the 0-axis component. The current obtained by using the dynamic reactive power compensator for bus voltage stabilization control is taken as the d-axis component. Then through The coordinate transformation is used to obtain the current value in the abc coordinate system, which is then used as the current command value for the dynamic reactive power compensator. According to the current command value The control duty cycle of each switching device of the dynamic reactive power compensator is obtained. The specific method for harmonic mitigation of the mobile frequency converter is as follows: The sum of the output current obtained by detecting the fundamental positive sequence active component of the continuous mining machine's incoming current and the current value obtained by the bus voltage regulation of the walking frequency converter is used as the d-axis component. The current value obtained by equalizing the bus voltage of the walking inverter is taken as the 0-axis component. Specify the q-axis component as zero; then through The coordinate transformation generates the current value in the abc coordinate system. Then, the current value in the abc coordinate system is subtracted from the current value in the continuous mining machine's input current to obtain the current command value for the mobile inverter's grid-side unit. According to the current command value The control duty cycle of each switching device in the grid-side unit of the walking frequency converter is obtained.

2. The power quality management device for a coal mine underground continuous mining machine according to claim 1, characterized in that, The dynamic reactive power compensator includes a T-type three-level structure and an LCL third-order filter; the T-type three-level structure is connected to the power supply cable of the continuous mining machine through the LCL third-order filter.

3. The power quality management device for a coal mine underground continuous mining machine according to claim 1, characterized in that, The walking inverter is a four-quadrant walking inverter, which includes a grid-side unit, a motor-side unit, and an LCL filter. One end of the motor-side unit is connected to the walking motor, and the other end is connected to the output terminal of the inverter through the grid-side unit and the LCL filter.

4. The power quality management device for a coal mine underground continuous mining machine according to claim 1, characterized in that, When the dynamic reactive power compensator performs reactive power compensation, it adopts dual closed-loop control of voltage and current. The voltage control is the outer loop, which realizes the equalization and stabilization control of the bus voltage. The current inner loop adopts proportional control in parallel with a repetitive controller containing the internal mode of each harmonic, forming an inner loop control strategy of proportional control and repetitive control in parallel.

5. The power quality management device for a coal mine underground continuous mining machine according to claim 1, characterized in that, When the walking frequency converter performs harmonic mitigation on the continuous mining machine, it adopts dual closed-loop control of voltage and current. The voltage control is the outer loop, which realizes the equalization and stabilization control of the bus voltage. The current inner loop adopts proportional control in parallel with a repetitive controller containing the internal modes of each harmonic, forming an inner loop control strategy of proportional control and repetitive control in parallel.

Images