Frequency conversion feedback controlled emission-free SF6 two-stage compressor device and working method

Abstract

The present invention provides a variable frequency feedback controlled emission-free SF6 two-stage compressor device, comprising an inlet low-pressure filter, a pressure regulating valve, an inlet buffer tank, a pressure sensor, a first-stage compression cylinder, a first-stage safety valve, a drive motor, a first-stage compression cylinder, a frequency converter, a PLC controller, a second-stage safety valve, a two-stage cooler, a cooling fan, and an outlet combined filter. The drive motor is controlled by a frequency converter to achieve variable frequency soft starting of a high-power and high-load motor, and the speed of the compressor is steadily increased by gradually increasing the frequency. At the same time, combined with PLC control, automatic adjustment of the compressor displacement and load can be achieved. The frequency is adjusted according to demand based on the pressure signal feedback at the compressor inlet and outlet, thereby achieving adjustment of the compressor power and displacement. The required compressor displacement can also be adjusted according to the control input of the operation, thereby adapting to different working conditions and making the SF6 compressor operate in an efficient and economical efficiency range.

Description

Technical Field

[0001] The present invention belongs to the technical field of SF6 gas processing in power equipment, and specifically relates to a variable frequency feedback controlled emission-free SF6 two-stage compressor device and a working method. Background Art

[0002] In the electric power industry, SF6 gas is an important high-voltage arc extinguishing and insulating medium. It is used as arc extinguishing and insulating gas for closed, high-voltage switches and is widely used in high-voltage transmission and transformation grid projects, especially in gas-insulated combined electrical GIS, gas-insulated lines GIL, gas-insulated transformers GIT and other grid equipment in high-voltage, ultra-high-voltage and ultra-high-voltage transmission networks. However, SF6 gas is a fluorinated gas with a high global greenhouse effect. It is one of the six gases that must be monitored as stipulated in the Kyoto Protocol. Therefore, SF6 gas must be used in a closed system and emissions must be strictly controlled. In addition, under the action of arc or corona discharge in GIS or GIL, the local strong electromagnetic energy generated will cause the SF6 insulating gas to decompose and generate various low-fluorine sulfides SF x SF6 gas-insulated equipment combines with impurities such as H2O and O2, and their decomposition products further react with SF6 to produce acidic and highly toxic gases such as SO2, HF, and H2S. These characteristic decomposition components can corrode the solid insulation and metal components within the equipment, accelerating insulation degradation and leading to sudden equipment failures. Therefore, effective filtration and protection are essential for the equipment.

[0003] SF6 gas compressors used in the power engineering industry typically utilize three-phase power. Conventional SF6 gas compressor motors utilize three-phase motors that operate at a fixed frequency under specific power supply conditions. Although some higher-power motors utilize Y-△ step-down starting, the starting current remains high, and the speed fluctuations are significant. The impact of this high current during startup can affect the operational safety of the power supply system and other electrical equipment. The speed of a three-phase motor is directly proportional to the frequency, while the displacement of reciprocating compressors, such as piston compressors, is directly proportional to the speed. Therefore, when the power supply frequency is 50Hz, increasing the frequency to 60Hz theoretically increases the motor speed by 20%, and the theoretical compressor displacement by 20%. Therefore, variable frequency control is necessary to fully utilize the motor's potential, increase the compressor displacement, and improve the operating efficiency of the device.

[0004] During the SF6 gas recovery process in GIS or GIL, since SF6 gas must be recovered to a deep vacuum, the front stage of the SF6 compressor is usually equipped with an SF6 negative pressure recovery pump or a front stage booster pump with sufficient vacuum performance. When the SF6 gas pressure in the GIS or GIL reaches vacuum or high vacuum, the recovery speed mainly depends on the negative pressure recovery pump and the booster pump. Since the gas is very thin, the compressor inlet pressure at this time is still very low, and the inlet pressure is close to the minimum allowable suction pressure of the compressor. Therefore, the efficiency of the compressor running at a fixed frequency is very low, and the effective compressed gas volume is very small. It is necessary to reduce the displacement and energy consumption through frequency conversion and pressure feedback to operate under more economical and energy-saving conditions.

[0005] In summary, there is currently a lack of research on compressors that combine variable frequency operation and pressure feedback. There is an urgent need for a simple, effective, and emission-free SF6 two-stage compressor device that can accurately control variable frequency feedback. Summary of the Invention

[0006] In order to address the deficiencies in the prior art, the purpose of the present invention is to provide a variable frequency feedback controlled emission-free SF6 two-stage compressor device and working method, so as to solve the problems that large SF6 gas compressors have a large start-up and operation impact under fixed frequency conditions, the operating conditions cannot be adjusted according to the gas pressure conditions for flow and displacement, and the problem that SF6 cannot be directly discharged and needs to be filtered during processing.

[0007] The present invention adopts the following technical solution: a variable frequency feedback controlled emission-free SF6 two-stage compressor device, comprising: a drive motor, a PLC controller, an inlet low-pressure filter, an inlet buffer tank, a pressure sensor, a first-stage compression cylinder, a first-stage safety valve, a second-stage compression cylinder, a variable frequency controller, and a second-stage safety valve;

[0008] The first-stage compression cylinder and the second-stage compression cylinder both include: a driving member, an inlet pipe and an outlet pipe;

[0009] The inlet low-pressure filter is installed at the inlet of the first-stage compression cylinder to filter the SF6 gas inhaled by the first-stage compression cylinder;

[0010] The first-stage compression cylinder is set at the outlet of the pressure regulating valve, and the air inlet end of the second-stage compression cylinder is connected to the exhaust end of the first-stage compression cylinder. Both the first-stage compression cylinder and the second-stage compression cylinder are driven by a drive motor to inhale, compress and discharge SF6 gas;

[0011] The first-level safety valve is installed on the outlet pipe of the first-level compression cylinder, and the second-level safety valve is installed on the outlet pipe of the second-level compression cylinder. Both the first-level safety valve and the second-level safety valve are used for overpressure protection of the outlet pipe;

[0012] The inlet buffer tank is installed at the inlet pipe of the first-stage compression cylinder to reduce the pulsation of the inlet airflow of the device and also to provide storage space for the SF6 released by the first-stage safety valve and the second-stage safety valve;

[0013] One pressure sensor is installed at the inlet pipe of the first-stage compression cylinder, and the other pressure sensor is installed at the outlet pipe of the second-stage compression cylinder. They are used to monitor the pressure or vacuum at the inlet pipe of the first-stage compression cylinder and the outlet pipe of the second-stage compression cylinder, and output the compressor start and stop control signal and pressure protection measurement signal to the PLC controller;

[0014] The input end of the driving motor is connected to the frequency conversion controller to receive the control signal of the frequency conversion controller, and the output end is connected to the driving parts of the first-stage compression cylinder and the second-stage compression cylinder to drive the first-stage compression cylinder and the second-stage compression cylinder;

[0015] The input end of the PLC controller receives the compressor start and stop control signal and the pressure protection measurement signal fed back by the pressure sensor, and the output end is connected to the frequency conversion controller to control the operation of the frequency conversion controller.

[0016] The input control signal end of the frequency conversion controller is connected to the PLC controller, and the output end is connected to the drive motor. The output control signal is adjusted according to the compressor pressure input signal, thereby controlling the execution of the drive motor.

[0017] Preferably, the inlet low-pressure filter uses a micron-grade large-surface-area filter material and is provided with a transparent observation window.

[0018] The two-stage compressor device also includes a pressure regulating valve installed at the inlet of the first-stage compression cylinder for regulating the suction gas pressure of the first-stage compression cylinder.

[0019] Preferably, both the first-stage compression cylinder and the second-stage compression cylinder are oil-free compression cylinders.

[0020] The two-stage compressor device also includes a two-stage cooler installed at the outlet of the second-stage compression cylinder, which is used to cool the inter-stage gas compressed by the first-stage compression cylinder and the gas compressed by the second-stage compression cylinder.

[0021] The two-stage compressor unit also includes a cooling fan that provides power for forced air cooling of the two-stage cooler.

[0022] The two-stage compressor device also includes an outlet combined filter installed at the outlet of the two-stage compressor device. The outlet combined filter is used for micron-level filtration of particulate impurities, moisture drying and adsorption filtration, and filtration of gaseous SF6 decomposition products.

[0023] Example 2.

[0024] Working method of a variable frequency feedback controlled emission-free SF6 two-stage compressor device.

[0025] include:

[0026] Step 1: The inlet low-pressure filter filters the SF6 gas sucked into the first-stage compression cylinder;

[0027] Step 2: The first compression cylinder and the second compression cylinder compress the filtered SF6 gas;

[0028] Step 3: The pressure sensor detects the gas in the first and second compression cylinders, and provides compressor start and stop control signals and pressure protection measurement signals to the PLC controller;

[0029] Step 4: The PLC controller input terminal receives the compressor start / stop control signal and the pressure protection measurement signal fed back by the pressure sensor, and outputs control and adjustment instructions to the frequency conversion controller.

[0030] Step 5: The frequency converter controls the execution of the drive motor according to the control and adjustment instructions of the PLC controller;

[0031] Step 6: The driving motor drives the first-stage compression cylinder and the second-stage compression cylinder to compress the SF6 gas;

[0032] Step 7: The two-stage cooler and the cooling fan cool the interstage gas compressed by the first stage and the gas compressed by the second stage compression cylinder;

[0033] Step 8: The outlet combined filter filters the gaseous SF6 decomposition products.

[0034] Preferably, in step 2, the smoothness of gas intake by the first-stage compression cylinder is controlled by a pressure regulating valve.

[0035] Preferably, in step 6, when the first-stage compression cylinder or the second-stage compression cylinder performs pressure release and decompression, the first-stage safety valve or the second-stage safety valve is opened, and the released gas SF6 is introduced into the buffer tank.

[0036] The beneficial effect of the present invention is that, compared with the prior art,

[0037] 1. The variable frequency feedback-controlled, emission-free SF6 two-stage compressor device proposed in this invention not only uses the variable frequency controller to control the compressor's start and stop and circuit protection, but also uses the variable frequency controller to perform variable frequency soft starting of the compressor motor, gradually increasing the voltage and frequency to ensure a smooth motor startup. Because most compressors in the SF6 processing industry are small, variable frequency control has been largely unresearched, and small compressors do not suffer from the high current surge issue. Therefore, this invention, particularly for high-power SF6 compressors, avoids the high current surge caused by conventional fixed frequency hard starting, reduces circuit startup load, significantly reduces motor wear, and extends equipment life.

[0038] 2. The variable frequency feedback controlled emission-free SF6 two-stage compressor device proposed in the present invention can manually operate and adjust the compressor displacement under specific circumstances through a variable frequency controller to match the displacement with the usage requirements. For example, when used in a country or on-site power supply of 50Hz, the frequency can be adjusted to 60Hz, which significantly increases the compressor displacement, improves the compression processing speed, and adapts to working conditions more flexibly.

[0039] 3. The variable frequency feedback-controlled emission-free SF6 two-stage compressor device proposed in the present invention can adjust the operating parameters under variable frequency by feedback from the pressure sensor to adapt to pressure changes at the compressor inlet and outlet. The output parameters of the variable frequency controller are adjusted according to the feedback pressure signal input, so that the SF6 compressor operates at the most efficient or economical parameters. Adaptive adjustment is performed when the pressure parameters change. Compared with compressors operating at a fixed frequency and speed, it can save energy and reduce unnecessary wear and noise under full-speed operation.

[0040] 4. The variable frequency feedback controlled emission-free SF6 two-stage compressor device proposed in the present invention adopts two-stage compression compared with single-stage compression and single-stage cooling, which improves compression efficiency and reduces power consumption; the exhaust temperature of each stage is reduced by inter-stage cooling and after-stage cooler, which increases the service life of core components such as exhaust valves and piston rings and reduces wear.

[0041] 5. The variable frequency feedback controlled emission-free SF6 two-stage compressor device proposed in the present invention is equipped with filters at both the inlet and outlet. The inlet can filter particulate matter to prevent the invasion of larger-sized foreign matter and particulate impurities. The outlet is equipped with a combined filter to comprehensively filter moisture, SF6 decomposition products, and particles generated by wear in the compressed SF6 gas. This is suitable for treating unqualified SF6 gas, such as SF6 gas with excessive moisture and SF6 decomposition products, improving gas quality, and preventing corrosion of pipelines or storage tanks by moisture decomposition products in high-pressure and high-density SF6 gas.

[0042] 6. Since SF6 gas is a gas whose emission is strictly controlled, especially in closed areas such as closed GIL pipeline corridors and indoor substations, the leakage of SF6 gas must be avoided as much as possible. The variable frequency feedback controlled emission-free SF6 two-stage compressor device proposed in the present invention is equipped with a safety valve in the two-stage compression. The safety valve outlet is depressurized to the compressor inlet buffer tank through a conduit, thereby avoiding the discharge of SF6 gas into the environment after overpressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the variable frequency feedback controlled emission-free SF6 two-stage compressor device provided by the present invention and its component modules;

[0044] Figure 1 The description of the accompanying drawings is as follows:

[0045] 1-Inlet low-pressure filter, 2-Pressure regulating valve, 3-Inlet buffer tank, 4-Pressure sensor, 5-First-stage compression cylinder, 6-First-stage safety valve, 7-Drive motor, 8-Second-stage compression cylinder, 9-Frequency controller, 10-PLC controller, 11-Second-stage safety valve, 12-Two-stage cooler, 13-Cooling fan, 14-Outlet combination filter. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present application.

[0047] Example 1.

[0048] like Figure 1 As shown, the variable frequency feedback controlled emission-free SF6 two-stage compressor device includes: a drive motor 7, a PLC controller 10, an inlet low-pressure filter 1, a pressure regulating valve 2, an inlet buffer tank 3, a pressure sensor 4, a first-stage compression cylinder 5, a first-stage safety valve 6, a second-stage compression cylinder 8, a variable frequency controller 9, a second-stage safety valve 11, a two-stage cooler 12, a cooling fan 13, and an outlet combined filter 14.

[0049] Wherein: the first-stage compression cylinder 5 and the second-stage compression cylinder 8 both include: a driving member, an inlet pipe and an outlet pipe;

[0050] The inlet low-pressure filter 1 is located at the entrance of the first-stage compression cylinder 5. It primarily filters particulate impurities from the gas inhaled by the first-stage compression cylinder at the micron level. It can use a micron-sized filter material with a large surface area. Due to the low inlet pressure, a transparent observation window can be provided to facilitate inspection of the filter element contamination status.

[0051] The pressure regulating valve 2, installed at the inlet of the first-stage compression cylinder 5, regulates the intake gas pressure of the first-stage compression cylinder 5. This pressure can be directly reduced using a pressure reducing valve, or an electric proportional control valve can be used to adjust the valve opening based on the first-stage compression cylinder inlet pressure signal to control the intake pressure of the compression cylinder and ensure smooth regulation of the first-stage compression process. When fully opened, the electric valve has a relatively large flow path and low gas flow resistance, facilitating gas intake under low or vacuum pressures.

[0052] The inlet buffer tank 3 is located at the inlet pipe of the first-stage compression cylinder 5 and is used as a buffer container to reduce the pulsation of the inlet airflow. Since the intake air in piston compressors is pulsed rather than continuous during the compression process, the buffer tank can reduce airflow pulsation and improve the vibration of the reciprocating piston compressor's air circuit system, playing an important role. In addition, the buffer tank provides storage space for SF6 released by the safety valve.

[0053] Pressure sensors 4 are installed at the inlet pipe of the first-stage compression cylinder 5 and the outlet pipe of the second-stage compression cylinder 8. They monitor the pressure or vacuum at these locations. Within an automated control system, these sensors can monitor pressure and provide compressor start / stop control signals and pressure protection measurement signals. These measurement signals can be output to a PLC controller 10 for monitoring and control. Preferably, the sensors have combined pressure and vacuum measurement capabilities.

[0054] The first-stage compression cylinder 5 is arranged at the outlet of the pressure regulating valve 2 and is connected to the drive motor 7. It serves as the first-stage suction cylinder of the compressor to inhale, compress and discharge SF6 gas, and increase the gas pressure. The first-stage compression cylinder 5 is the actuator of the low-pressure stage compression of the compressor. Preferably, in order to avoid oil contamination of SF6 and the pipeline system, an oil-free compression cylinder is used.

[0055] The first-level safety valve 6 is installed on the outlet pipe of the first-level compression cylinder 5 to prevent overpressure protection of the pipeline pressure at this position under extreme or fault conditions (such as fault or failure of the second-level compression cylinder) and to perform pressure release and pressure relief. Since SF6 emissions should be controlled, the released gas SF6 is introduced into the inlet buffer tank through the pressure relief conduit, so that no SF6 is discharged into the air.

[0056] The drive motor 7 has its input connected to a variable frequency controller 9 and its output connected to the drive components (e.g., drive shafts) of the primary and secondary compression cylinders. This motor is used to drive the primary and secondary compression cylinders, providing power for compressing the SF6 gas and adapting to the frequency range of the variable frequency controller. Preferably, the motor should be compatible with the world's main AC power frequencies of 50 Hz and 60 Hz.

[0057] The inlet end of the secondary compression cylinder 8 is connected to the exhaust end of the primary compression cylinder 5. Its drive is connected to the drive motor 7. Serving as the compressor's second-stage booster, the secondary compression cylinder 8 draws in the exhaust gas from the primary compression cylinder 5, compresses and discharges the SF6 gas, and further increases the gas pressure. The secondary compression cylinder 8 is the actuator for the high-pressure stage of the compressor. To prevent backflow of high-pressure gas, a check valve is integrated at the outlet of the secondary compression cylinder 8. To prevent oil contamination of the SF6 and piping system, an oil-free compression cylinder is preferably used. Based on thermodynamic theory, a two-stage compression with equal compression ratios is preferred for maximum efficiency. Therefore, the secondary compression cylinder 8 uses the same compression ratio as the primary compression cylinder 5.

[0058] The variable frequency controller 9 has a frequency conversion function that converts fixed-frequency AC power into variable-frequency, variable-voltage AC power. Its input control signal terminal is connected to the PLC controller, and its output terminal is connected to the motor. It can also issue start and stop commands and adjust its output based on feedback from the compressor pressure input signal, thereby controlling the execution of the drive motor 7 and ultimately controlling and regulating the compressor. Preferably, the variable frequency controller has a manual adjustment function that allows manual adjustment of the output to facilitate manual operation and maintenance testing required for capacity adjustment in specific situations.

[0059] The PLC controller 10 receives the compressor start / stop control signal and pressure protection measurement signal fed back by the pressure sensor 4 at its input, and is connected to the frequency converter 9 at its output. It uses a digital logic controller for automated control, allowing control instructions to be loaded into memory for storage and execution at any time, controlling the operation of the frequency converter 9 and the cooling fan 13. The system PLC consists of a central processing unit (CPU), external I / O ports, extended I / O interface addresses, and memory. The core of the CPU is composed of one or more accumulators, which have logical mathematical operation capabilities and can read the contents of the program memory. After calculation, they drive the corresponding memory and I / O ports. The I / O ports connect the internal accumulators to the external input and output systems and store relevant data in the program memory or data memory. The memory can store data input from the I / O ports. Based on the operating conditions of the compressor, typically the compressor inlet and outlet pressures, the compressor speed is adjusted to control the displacement. The motor power is also adjusted. Combined with the SF6 pumping conditions of the upstream and downstream stages, the control instruction program for input feedback and variable frequency output is set to enable the compressor to operate at the highest exhaust volume or in the most economical range. For example, when the fastest compression pumping speed is required, the maximum rated speed or power of the motor and compressor can be used as the adjustment target to maintain the motor speed at the maximum value under the current pressure conditions. When optimal economic adjustment is required, the optimal compression power consumption corresponding to the compressor inlet and outlet pressure conditions can be used as the adjustment target, thereby achieving higher economic efficiency while processing the same amount of gas.

[0060] The secondary safety valve 11 is installed on the outlet pipe of the secondary compression cylinder 8 to prevent overpressure protection of the pipeline pressure at this position under extreme or fault conditions (such as blockage of the secondary cylinder outlet filter) and to perform pressure release and pressure relief. Since SF6 emissions should be controlled, the released gas SF6 is introduced into the inlet buffer tank through the pressure relief conduit, so that no SF6 is discharged into the air.

[0061] The two-stage cooler 12, installed at the outlet of the second-stage compression cylinder 8, is used to cool the interstage gas compressed by the first-stage compression cylinder 5 and the gas compressed by the second-stage compression cylinder 8. This enhances the heat dissipation of the compressor during operation. By reducing interstage cooling and post-stage cooling on the high-pressure side during the two-stage compression process, the SF6 temperature is lowered, reducing the work performed by the compressor during compression, thereby saving power. Preferably, to prevent SF6 gas contamination by moisture infiltration and high-temperature corrosion of the compressor, an air-cooled cooler is used instead of water cooling, using heat dissipation coils and fins to increase the heat dissipation area.

[0062] The cooling fan 13 is combined with the double-stage cooler to provide forced air cooling power for the double-stage cooler 12 through the fan blades. A suitable cooling air source is provided according to the type of cooler.

[0063] The outlet filter assembly 14, installed at the outlet of the device, includes micron-level filtration for particulate impurities, dry moisture adsorption filtration, and filtration for gaseous SF6 decomposition products. It uses micron-level filtration materials for particulate impurities, dry moisture adsorption materials, and gaseous SF6 decomposition adsorption materials. Dry adsorption materials such as aluminum oxide or molecular sieves are used to absorb moisture, while activated molecular sieves and activated carbon are used as adsorption materials to absorb gaseous SF6 decomposition products.

[0064] Example 2.

[0065] The invention discloses an operating method of a variable frequency feedback controlled emission-free SF6 two-stage compressor device.

[0066] The following steps are involved:

[0067] Step 1: The inlet low-pressure filter filters the SF6 gas sucked into the first-stage compression cylinder;

[0068] Step 2: The first-stage compression cylinder and the second-stage compression cylinder compress the filtered SF6 gas; the first-stage compression cylinder is controlled to inhale the gas stably through the pressure regulating valve;

[0069] Step 3: The pressure sensor detects the gas in the first and second compression cylinders, and provides compressor start and stop control signals and pressure protection measurement signals to the PLC controller;

[0070] Step 4: The PLC controller input terminal receives the compressor start / stop control signal and pressure protection measurement signal fed back by the pressure sensor, and outputs control and adjustment instructions to the frequency conversion controller;

[0071] Step 5: The frequency converter controls the execution of the drive motor according to the control and adjustment instructions of the PLC controller;

[0072] Step 6: The driving motor drives the first-stage compression cylinder and the second-stage compression cylinder to compress the SF6 gas; when the first-stage compression cylinder or the second-stage compression cylinder releases and relieves pressure, the first-stage safety valve or the second-stage safety valve is opened, and the released SF6 gas is introduced into the buffer tank.

[0073] Step 7: The two-stage cooler and the cooling fan cool the interstage gas compressed by the first stage and the gas compressed by the second stage compression cylinder;

[0074] Step 8: The outlet combined filter filters the gaseous SF6 decomposition products.

[0075] The beneficial effect of the present invention is that, compared with the prior art,

[0076] 1. The variable frequency feedback-controlled, emission-free SF6 two-stage compressor device proposed in this invention not only uses the variable frequency controller to control the compressor's start and stop and circuit protection, but also uses the variable frequency controller to perform variable frequency soft starting of the compressor motor, gradually increasing the voltage and frequency to ensure a smooth motor startup. Because most compressors in the SF6 treatment industry are small, variable frequency control has been largely unresearched. Small compressors do not suffer from the high current surge issue. Therefore, this invention, particularly for high-power SF6 compressors, avoids the high current surge associated with conventional fixed frequency hard starting, reduces circuit startup load, significantly reduces motor wear, and extends equipment life.

[0077] 2. The variable frequency feedback controlled emission-free SF6 two-stage compressor device proposed in the present invention can manually operate and adjust the compressor displacement under specific circumstances through a variable frequency controller to match the displacement with the usage requirements. For example, when used in a country or on-site power supply of 50Hz, the frequency can be adjusted to 60Hz, which significantly increases the compressor displacement, improves the compression processing speed, and adapts to working conditions more flexibly.

[0078] 3. The variable frequency feedback-controlled emission-free SF6 two-stage compressor device proposed in the present invention can adjust the operating parameters under variable frequency by feedback from the pressure sensor to adapt to pressure changes at the compressor inlet and outlet. The output parameters of the variable frequency controller are adjusted according to the feedback pressure signal input, so that the SF6 compressor operates at the most efficient or economical parameters. Adaptive adjustment is performed when the pressure parameters change. Compared with compressors operating at a fixed frequency and speed, it can save energy and reduce unnecessary wear and noise under full-speed operation.

[0079] 4. The variable frequency feedback controlled emission-free SF6 two-stage compressor device proposed in the present invention adopts two-stage compression compared with single-stage compression and single-stage cooling, which improves compression efficiency and reduces power consumption; the exhaust temperature of each stage is reduced by inter-stage cooling and after-stage cooler, which increases the service life of core components such as exhaust valves and piston rings and reduces wear.

[0080] 5. The variable frequency feedback controlled emission-free SF6 two-stage compressor device proposed in the present invention is equipped with filters at both the inlet and outlet. The inlet can filter particulate matter to prevent the invasion of larger-sized foreign matter and particulate impurities. The outlet is equipped with a combined filter to comprehensively filter moisture, SF6 decomposition products, and particles generated by wear in the compressed SF6 gas. This is suitable for treating unqualified SF6 gas, such as SF6 gas with excessive moisture and SF6 decomposition products, improving gas quality, and preventing corrosion of pipelines or storage tanks by moisture decomposition products in high-pressure and high-density SF6 gas.

[0081] 6. Since SF6 gas is a gas whose emission is strictly controlled, especially in closed areas such as closed GIL pipeline corridors and indoor substations, the leakage of SF6 gas must be avoided as much as possible. The variable frequency feedback controlled emission-free SF6 two-stage compressor device proposed in the present invention is equipped with a safety valve in the two-stage compression. The safety valve outlet is depressurized to the compressor inlet buffer tank through a conduit, thereby avoiding the discharge of SF6 gas into the environment after overpressure.

[0082] The applicant of the present invention has made a detailed explanation and description of the implementation examples of the present invention in conjunction with the drawings in the specification. However, those skilled in the art should understand that the above implementation examples are only preferred implementation plans of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, and is not a limitation on the scope of protection of the present invention. On the contrary, any improvements or modifications based on the inventive spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. Frequency conversion feedback controlled emission-free SF6 two-stage compressor device, including: A drive motor (7), a PLC controller (10), wherein the device further comprises: a pressure sensor (4), a first-stage compression cylinder (5), a first-stage safety valve (6), a second-stage compression cylinder (8), a frequency conversion controller (9), and a second-stage safety valve (11); The first-stage compression cylinder (5) and the second-stage compression cylinder (8) both include: a driving member, an inlet pipe and an outlet pipe; The first compression cylinder (5) is arranged at the outlet of the pressure regulating valve (2), the air inlet end of the second compression cylinder (8) is connected to the air outlet end of the first compression cylinder (5), and both the first compression cylinder (5) and the second compression cylinder (8) are driven by a drive motor (7) for sucking, compressing and discharging SF6 gas. A one-way valve is integrated at the outlet of the second compression cylinder (8); The first-stage safety valve (6) is installed on the outlet pipe of the first-stage compression cylinder (5), and the second-stage safety valve (11) is installed on the outlet pipe of the second-stage compression cylinder (8). Both the first-stage safety valve (6) and the second-stage safety valve (11) are used for overpressure protection of the outlet pipe; A pressure sensor (4) is installed at the inlet pipe of the first compression cylinder (5), and another pressure sensor (4) is installed at the outlet pipe of the second compression cylinder (8), for monitoring the pressure or vacuum at the inlet pipe of the first compression cylinder (5) and the outlet pipe of the second compression cylinder (8), and outputting a compressor start / stop control signal and a pressure protection measurement signal to a PLC controller (10); The input end of the driving motor (7) is connected to the frequency conversion controller (9) for receiving a control signal from the frequency conversion controller (9), and the output end is connected to the driving parts of the first compression cylinder (5) and the second compression cylinder (8) to drive the first compression cylinder (5) and the second compression cylinder (8); The input end of the PLC controller (10) receives the compressor start / stop control signal and the pressure protection measurement signal fed back by the pressure sensor (4), and the output end is connected to the frequency conversion controller (9) for controlling the operation of the frequency conversion controller (9); The input control signal terminal of the frequency conversion controller (9) is connected to the PLC controller (10), and the output terminal is connected to the drive motor (7). The output control signal is adjusted according to the compressor pressure input signal, thereby controlling the execution of the drive motor (7); The two-stage compressor device also includes an inlet buffer tank (3), which is arranged at the inlet pipe of the first-stage compression cylinder (5) and is used to reduce the pulsation of the air flow at the inlet of the device and is also used to provide storage space for SF6 released by the first-stage safety valve (6) and the second-stage safety valve (11).

2. The variable frequency feedback controlled emission-free SF6 two-stage compressor device according to claim 1 is characterized in that: The two-stage compressor device further comprises an inlet low-pressure filter (1), which is arranged at the inlet of the first-stage compression cylinder (5) and is used to filter the SF6 gas sucked into the first-stage compression cylinder (5); The inlet low-pressure filter (1) adopts a micron-grade large-surface-area filter material and is provided with a transparent observation window.

3. The variable frequency feedback controlled emission-free SF6 two-stage compressor device according to claim 1 is characterized in that: The two-stage compressor device further comprises a pressure regulating valve (2) which is installed at the inlet of the first-stage compression cylinder (5) and is used for regulating the suction gas pressure of the first-stage compression cylinder (5).

4. The variable frequency feedback controlled emission-free SF6 two-stage compressor device according to claim 1 is characterized in that: The first-stage compression cylinder (5) and the second-stage compression cylinder (8) are both oil-free compression cylinders.

5. The variable frequency feedback controlled emission-free SF6 two-stage compressor device according to claim 1 is characterized in that: The two-stage compressor device also includes a two-stage cooler (12) installed at the outlet of the second-stage compression cylinder (8) for cooling the inter-stage gas compressed by the first-stage compression cylinder (5) and the gas compressed by the second-stage compression cylinder (8).

6. The variable frequency feedback controlled emission-free SF6 two-stage compressor device according to claim 5, characterized in that: The two-stage compressor device also includes a cooling fan (13) for providing power for forced air cooling of the two-stage cooler (12).

7. The variable frequency feedback controlled emission-free SF6 two-stage compressor device according to claim 6, characterized in that: The two-stage compressor device also includes an outlet combined filter (14) installed at the outlet of the two-stage compressor device. The outlet combined filter (14) is used for micron-level filtration of particulate impurities, moisture drying adsorption filtration and gaseous SF6 decomposition product filtration.

8. An operating method of a variable frequency feedback controlled emission-free SF6 two-stage compressor device, implemented based on the variable frequency feedback controlled emission-free SF6 two-stage compressor device according to any one of claims 1 to 7, characterized in that: The working method comprises: Step 1: The inlet low-pressure filter filters the SF6 gas sucked into the first-stage compression cylinder; Step 2: The first compression cylinder and the second compression cylinder compress the filtered SF6 gas; Step 3: The pressure sensor detects the gas in the first and second compression cylinders, and provides compressor start and stop control signals and pressure protection measurement signals to the PLC controller; Step 4: The PLC controller input terminal receives the compressor start / stop control signal and pressure protection measurement signal fed back by the pressure sensor, and outputs control and adjustment instructions to the frequency conversion controller; Step 5: The frequency converter controls the execution of the drive motor according to the control and adjustment instructions of the PLC controller; Step 6: The driving motor drives the first-stage compression cylinder and the second-stage compression cylinder to compress the SF6 gas; Step 7: The two-stage cooler and the cooling fan cool the interstage gas compressed by the first stage and the gas compressed by the second stage compression cylinder; Step 8: The outlet combined filter filters the gaseous SF6 decomposition products.

9. The operating method of the variable frequency feedback controlled emission-free SF6 two-stage compressor device according to claim 8, characterized in that: In step 2, the pressure regulating valve is used to control the smoothness of the gas intake by the first-stage compression cylinder.

10. The operating method of the variable frequency feedback controlled emission-free SF6 two-stage compressor device according to claim 8, characterized in that: In step 6, when the first-stage compression cylinder or the second-stage compression cylinder performs pressure release and decompression, the first-stage safety valve or the second-stage safety valve is opened, and the released gas SF6 is introduced into the buffer tank.

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