Dynamic compensation voltage equipment for mining long-distance power supply system

Abstract

The invention relates to dynamic compensation voltage equipment for a mining long-distance power supply system. The dynamic compensation voltage equipment comprises a main control device, an energy storage converter device, a single-phase isolation conversion transformer device and a fault bypass device, the main control device is used for collecting voltage values of three-phase power grids at the input side and the output side of the dynamic compensation voltage equipment and collecting a current value flowing through the secondary side of the single-phase isolation transformer; then the collected voltage value and current value are transmitted to a processing unit in the main control device, and the processing unit calculates the magnitude of the voltage needing to be supplemented according to the difference value between the target input voltage and the voltage value of the equipment input side and the cable voltage drop condition of the power supply system. The problem of insufficient terminal voltage caused by instantaneous large current when the motor is started is solved, so that the motor is normally started; and when the voltage at the input side of the equipment drops greatly, the 100% rated voltage output capability of the inverter can still be supported. In addition, the influence of fluctuation of different amplitudes of the three-phase voltage of the power grid on the motor is solved, the motor is made to operate normally, and damage to the motor is reduced.

Description

Technical Field

[0001] The invention relates to a device for dynamic voltage compensation, and in particular to a device for dynamic voltage compensation of a long-distance power supply system for a mine. Technical Background

[0002] With the development of the domestic mining industry, the length of coal mining and tunneling working faces in coal mines has been continuously extended, which has brought considerable challenges to the power supply system. At present, the following problems are inevitable in coal mines: ① The significant voltage drop caused by the instantaneous large current when the motor starts leads to insufficient terminal voltage, which in turn affects the normal start of the motor; ② Due to the complex working conditions in coal mines, the three-phase voltage of the power grid fluctuates in different amplitudes, which may cause abnormal shutdown of the motor, affect production efficiency, and even damage the motor in serious cases.

[0003] At present, the following solutions are mainly adopted: In order to solve the above problems, the measures taken are mainly: The output voltage of the mobile transformer is increased to compensate for the voltage drop caused by the impedance of the transmission line. However, this will increase the total installed capacity of the front-stage power supply. At the same time, when the equipment is shut down or running at no load, it may cause the voltage of the equipment and cables to be too high, thereby threatening the insulation withstand voltage of the cables and equipment.

[0004] Reducing the equivalent impedance of the cable, for example, by shortening the length of the power supply cable between the mobile transformer and the load equipment, increasing the cable diameter or adopting a parallel scheme of multiple cables. However, these measures will significantly increase the workload of coal mining and tunneling operations in coal mines, reduce work efficiency and increase operating costs.

[0005] Explosion-proof SVG is added to compensate for the voltage drop caused by reactive power. However, in some mines, underground conditions are not ideal, there may be no suitable storage location, and the SVG needs to be moved multiple times to meet the needs, which results in unsatisfactory results. Summary of the invention

[0006] In order to solve the above problems, the present invention aims to provide a dynamic voltage compensation device for a long-distance power supply system for mines. The device can be connected in series to the long-distance power supply system in coal mines and can automatically detect the voltage at the end of the power grid. When the voltage at the end of a phase in the line is lower than the set value, the dynamic voltage compensation device will increase it to the set value in real time; and the energy storage converter of the device can still support the inverter's 100% rated voltage output capacity even when the voltage on the input side of the device drops significantly.

[0007] A dynamic compensation voltage device for a long-distance power supply system for a mine, which is connected in series to a long-distance power supply system in a coal mine; the device comprises a main control device, an energy storage converter device, a single-phase isolation transformer device, and a fault bypass device; The main control device is used to collect the voltage values ​​of the three-phase power grid on the input and output sides of the dynamic compensation voltage device, and collect the current value flowing through the secondary of the single-phase isolation transformer, and display the current size of the load side in real time. When the load current is too large, the power supply will be cut off to protect the load; then the collected voltage value and current value are transmitted to the processing unit inside the main control device, and the processing unit calculates the voltage size required for compensation according to the difference between the target input voltage and the voltage value on the input side of the device and the cable voltage drop of the power supply system; The energy storage and conversion device includes a rectifier, an energy storage device, an inverter, and a filter; the input voltage of the dynamic compensation voltage device is the grid voltage, the rectifier converts the AC power into DC power; the energy storage device stores electric energy; the inverter converts the DC power into a single-phase controllable AC power, and a standard sinusoidal voltage waveform is obtained after being processed by the filter; The single-phase isolation conversion transformer device includes three single-phase isolation transformers to realize energy transmission.

[0008] Fault bypass device, used to seamlessly switch the load to the grid power supply when the dynamic compensation voltage equipment fails.

[0009] Furthermore, the main control device includes 6 voltage sensors, 3 current sensors and a processing unit. The 6 voltage sensors are used to collect the voltage values ​​of the three phases on the input side and the three phases on the output side of the dynamic compensation voltage device; the 3 current sensors are used to collect the current values ​​flowing through the secondary of the three single-phase isolation transformers, and the voltage and current values ​​are transmitted to the processing unit; the processing unit calculates the required compensation voltage according to the difference between the target input voltage and the voltage value on the input side of the dynamic compensation voltage device and the cable voltage drop of the power supply system, and controls the energy storage converter to output different voltages. The processing unit achieves the purpose of controlling the energy storage converter to output different voltages by adjusting the duty cycle of the PWM wave. Even when the voltage on the input side of the dynamic compensation voltage device drops significantly, the energy storage converter can still support the inverter's 100% rated voltage output capacity.

[0010] Furthermore, the energy storage device includes a supercapacitor for storing electrical energy. Even if the voltage on the input side of the dynamic compensation voltage device drops to 0V, it can still support 100% of the rated voltage output capacity of the inverter, which can be maintained for about 5 seconds, which is enough to support the device to survive the large voltage drop caused by the motor starting moment.

[0011] Furthermore, the single-phase isolation transformer is used for electrical isolation between the inverter and the power grid, and the turns ratio of its primary coil to the secondary coil is n:1. The specific turns ratio can be determined based on the difference between the target output voltage and the input voltage of the dynamic compensation voltage device in actual working conditions.

[0012] When a phase voltage on the output side of the dynamic compensation voltage device differs from the target output voltage, the processing unit will adjust the output capacity of the inverter by changing the duty cycle of the PWM wave so that the phase voltage reaches the target output voltage. When a phase voltage is lower than the target voltage, the processing unit will control the IGBT to turn off to increase the duty cycle, thereby increasing the output capacity of the inverter.

[0013] Furthermore, the fault bypass device includes a thyristor bypass and a contactor bypass, and has the function of instantaneous fault response; when the dynamic compensation voltage device fails, the dynamic compensation voltage device will first perform the thyristor conduction action, and the input and output of the dynamic compensation voltage device will be directly connected to realize the conversion to industrial frequency, and then the contactor closing action will be performed. After the preset time, the thyristor performs the shutdown action. The preset time is generally 500ms. The advantage of this logic is that the thyristor acts quickly and can realize the seamless conversion to industrial frequency. . The fault bypass device can realize automatic and seamless switching to grid power supply when the dynamic compensation voltage device fails. The fault response speed is fast, which effectively protects the load equipment and avoids the loss caused by unstable power supply, greatly improving the reliability and stability of the system.

[0014] Furthermore, in order to meet the explosion-proof requirements for mining, the dynamic compensation voltage equipment is of flameproof and intrinsically safe type, meets the national standard GB3836, and the equipment casing uses an explosion-proof shell, and the external signals are all intrinsically safe signals.

[0015] Compared with the prior art, the advantages of the present invention are as follows: ① Solve the problem of insufficient terminal voltage caused by instantaneous large current when the motor starts, so that the motor can start normally; and the energy storage converter of the equipment can still support the inverter's 100% rated voltage output capacity even when the voltage on the input side of the equipment drops sharply.

[0016] ② The present invention is provided with a single-phase isolation conversion transformer device, which can perform single-phase compensation, and can solve the influence of fluctuations of different amplitudes of the three-phase voltage of the power grid on the motor, so that the motor can run normally and reduce damage to the motor.

[0017] ③ The present invention is provided with a bypass fault device, which can perform seamless switching when the machine is shut down due to a fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The topological diagram of the dynamic compensation voltage device involved in the present invention is Figure 2 This is the topological diagram of the energy storage converter of the present invention. Figure 3 The topological diagram of the three single-phase isolation conversion transformer devices involved in the present invention is Figure 4 This is a topological diagram of the fault bypass device of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be described clearly, systematically and completely below in conjunction with the accompanying drawings of the present invention.

[0020] like Figure 1 The topology diagram of the dynamic compensation voltage device is given, a dynamic compensation voltage device for a long-distance power supply system for a mine, the dynamic compensation voltage device is connected in series to the long-distance power supply system in the coal mine; the device includes a main control device, an energy storage converter device, a single-phase isolation transformer device, and a fault bypass device; The main control device includes 6 voltage sensors, 3 current sensors and a processing unit. The 6 voltage sensors are respectively used to collect the voltage values ​​of the three phases on the input side of the dynamic compensation voltage device (UR, US, UT) and the voltage values ​​of the three phases on the output side (UU, UV, UW); the 3 current sensors are respectively used to collect the current values ​​(IU, IV, IW) flowing through the secondaries of three single-phase isolation transformers, and the voltage and current values ​​are transmitted to the processing unit; when the equipment is powered on, the voltage sensor, current sensor and processing unit start working, and the processing unit automatically compares the target input voltage with the voltage value on the input side of the dynamic compensation voltage device and calculates the required compensation voltage according to the cable voltage drop of the power supply system, and controls the energy storage converter to output PWM waves with different duty cycles.

[0021] like Figure 2 As shown, the energy storage and current conversion device includes a rectifier, an energy storage device, an inverter, and a filter; the input voltage of the dynamic compensation voltage device is the grid voltage, and the rectifier converts the alternating current into direct current; the energy storage device stores electric energy, and the energy storage device includes a super capacitor for storing electric energy, and the inverter converts the direct current into a single-phase controllable alternating current, and a standard sinusoidal voltage waveform is obtained after being processed by the filter. When the load voltage of a certain phase in the line suddenly decreases, the super capacitor provides energy for the inverter to output voltages of different sizes, and the electric energy stored in the super capacitor can make the inverter work for about 5s. The purpose is that at the moment of motor starting, the large current impact brought by the motor will cause a large voltage drop on the entire transmission line, and the input voltage of the dynamic compensation voltage device will also be greatly reduced. Without the energy storage device, the output capacity of the latter stage of the present invention is limited, and under the maximum compensation capacity of the equipment, there will still be a situation where the load voltage decreases with the decrease of the input voltage. After adding the supercapacitor, even if the voltage on the input side of the device drops to 0V, it can still support 100% of the rated voltage output capacity of the inverter. This period can be maintained for about 5s, which is enough to support the device to survive the large voltage drop caused by the motor starting.

[0022] like Figure 3As shown, the single-phase isolation conversion transformer device includes three single-phase isolation transformers, which are used for electrical isolation between the inverter and the power grid to achieve energy transmission; and have the ability to compensate for single-phase voltage. The turns ratio of its primary coil to the secondary coil is n:1; when a phase voltage on the output side of the dynamic compensation voltage device differs from the target output voltage, the processing unit will adjust the output capacity of the inverter to make the phase voltage reach the target output voltage. Due to the complex working conditions underground in coal mines, three-phase voltages are prone to voltage fluctuations. When there are fluctuations in the underground power supply system, there will be a large difference in the three-phase voltages. When a phase voltage differs from the target output voltage, the processing unit will adjust the output capacity of the inverter to make the phase voltage reach the target output voltage.

[0023] like Figure 3 The topology diagram of the single-phase isolation conversion transformer is shown. The dynamic compensation voltage device side leads to 6 taps of three phases AX, BY, CZ, and the grid side leads to 6 taps of three phases ax, by, cz. Figure 2 The output U1 of the energy storage inverter device is connected to A of the U-phase isolation conversion transformer, and the output U2 of the energy storage inverter device is connected to X of the U-phase isolation conversion transformer; the output W1 of the energy storage inverter device is connected to B of the W-phase isolation conversion transformer, and the output W2 of the energy storage inverter device is connected to Y of the W-phase isolation conversion transformer; the output V1 of the energy storage inverter device is connected to C of the V-phase isolation conversion transformer, and the output V2 of the energy storage inverter device is connected to Z of the V-phase isolation conversion transformer.

[0024] like Figure 4 As shown, the fault bypass device includes a thyristor bypass and a contactor bypass. When the dynamic compensation voltage device fails, the dynamic compensation voltage device will first execute the thyristor conduction, and then execute the contactor closure. After a preset time of 500ms, the thyristor performs the shutdown action. The fault bypass device can automatically and seamlessly switch to the grid power supply when the dynamic compensation voltage device fails. The fault response speed is fast, which effectively protects the load equipment, avoids the loss caused by unstable power supply, and greatly improves the reliability and stability of the system.

[0025] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention or any person skilled in the art who is familiar with the present invention may easily think of changes or substitutions within the technical scope disclosed by the present invention, and shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A dynamic compensation voltage device for a long-distance power supply system for a mine, which is connected in series to a long-distance power supply system in a coal mine; characterized in that: The equipment includes a main control device, an energy storage converter device, a single-phase isolation transformer device, and a fault bypass device; The main control device is used to collect the voltage values ​​of the three-phase power grid on the input and output sides of the dynamic compensation voltage device, and collect the current value flowing through the secondary of the single-phase isolation transformer; then the collected voltage value and current value are transmitted to the processing unit inside the main control device, and the processing unit calculates the required compensation voltage according to the difference between the target input voltage and the voltage value on the input side of the device and the cable voltage drop of the power supply system; The energy storage and conversion device includes a rectifier, an energy storage device, an inverter, and a filter; the input voltage of the dynamic compensation voltage device is the grid voltage, the rectifier converts the AC power into DC power; the energy storage device stores electric energy; the inverter converts the DC power into a single-phase controllable AC power, and a standard sinusoidal voltage waveform is obtained after being processed by the filter; A single-phase isolation transformer device, including three single-phase isolation transformers, realizes energy transmission; Fault bypass device, used to seamlessly switch the load to the grid power supply when the dynamic compensation voltage equipment fails.

2. The dynamic compensation voltage device for a long-distance power supply system for a mine according to claim 1 is characterized in that: The main control device includes 6 voltage sensors, 3 current sensors and a processing unit. The 6 voltage sensors are used to collect the voltage values ​​of the three phases on the input side and the three phases on the output side of the dynamic compensation voltage device; the 3 current sensors are used to collect the current values ​​flowing through the secondary of the three single-phase isolation transformers, and the voltage and current values ​​are transmitted to the processing unit. The processing unit calculates the required compensation voltage according to the difference between the target input voltage and the voltage value on the input side of the dynamic compensation voltage device and the cable voltage drop of the power supply system, and controls the energy storage converter to output voltages of different magnitudes.

3. The dynamic compensation voltage device for a long-distance power supply system for a mine according to claim 1 is characterized in that: The energy storage device includes a super capacitor for storing electrical energy.

4. The dynamic compensation voltage device for a long-distance power supply system for a mine according to claim 1 is characterized in that: The single-phase isolation transformer is used for electrical isolation between the inverter and the power grid, and the turns ratio of its primary coil to the secondary coil is n:1; when a phase voltage on the output side of the dynamic compensation voltage device differs from the target output voltage, the processing unit will adjust the output capacity of the inverter to make the phase voltage reach the target output voltage.

5. The dynamic compensation voltage device for a long-distance power supply system for a mine according to claim 1 is characterized in that: The fault bypass device includes a thyristor bypass and a contactor bypass, and has the function of instantaneous fault response; when a dynamic compensation voltage device fails, the dynamic compensation voltage device will first execute the thyristor conduction action, then execute the contactor closing action, and the thyristor will be turned off after a preset time.

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