System and method for controlling oxygen content of cooling water of converter valve of high-voltage direct-current power transmission system

Abstract

The invention relates to a high-voltage direct-current power transmission system converter valve cooling water oxygen amount control system and method, the system comprises a valve cooling water inlet pipe and a nitrogen cylinder, the valve cooling water inlet pipe is connected with a water nozzle at the upper part of a deoxidizing tank, and an oxygen content measuring meter is mounted on the valve cooling water inlet pipe and is connected with a PLC (Programmable Logic Controller); the nitrogen cylinder connects the pressure reducing valve, the electromagnetic valve and the gas flow meter in series through gas conveying pipes and is connected to a nitrogen nozzle at the bottom of the deoxidizing tank; the gas flow meter sends a signal to the PLC; and the electromagnetic valve is connected with the PLC and is controlled by the PLC. The oxygen content in the converter valve cooling water can be accurately measured, the release amount of nitrogen is adjusted according to the oxygen content, and the effect of controlling the oxygen content in the converter valve cooling water is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of maintenance of direct current power transmission equipment, and in particular relates to a control system and method for cooling water oxygen content of a converter valve of a high-voltage direct current transmission system. Background Art

[0002] With the widespread application of high-voltage direct current transmission technology in the power field, the water cooling system of the DC converter valve has become a key link to ensure the normal and stable operation of the converter valve. In the long-term operation of the water cooling system, the control of the oxygen content of the cooling water is crucial. At present, the traditional DC converter valve water cooling system has many shortcomings in oxygen content control. Most existing water cooling systems adopt a deoxygenation method and lack a multi-dimensional collaborative control strategy. Its deoxygenation efficiency is limited, and it is difficult to accurately maintain the oxygen content in the water within an ideal low level range. Once the oxygen content in the water exceeds the standard, it will cause the corrosion of the cooling pipe to intensify, reduce the service life and reliability of the pipe, and then affect the heat dissipation performance and operation stability of the entire DC converter valve, increase the risk of system failure and operation and maintenance costs, and in severe cases may even cause the converter valve to be damaged due to overheating, affecting the operation of the DC transmission project, and bringing huge challenges to the safe and stable operation of the power system. Therefore, there is an urgent need for a new, efficient and highly adaptable DC converter valve water cooling system oxygen content control method to overcome the defects of the existing technology. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a control system and method for the oxygen content of cooling water of a converter valve in a high-voltage direct current transmission system, which can accurately measure the oxygen content in the cooling water of the converter valve and adjust the release amount of nitrogen according to the oxygen content, so as to achieve the effect of controlling the oxygen content in the cooling water of the converter valve.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: A control system for the oxygen content of cooling water of a converter valve of a high-voltage direct current transmission system comprises a valve cooling water inlet pipe and a nitrogen bottle, wherein the valve cooling water inlet pipe is connected to a water nozzle on the upper part of a deaerator tank, an oxygen content measuring meter is installed on the valve cooling water inlet pipe, and the oxygen content measuring meter is connected to a PLC controller; The nitrogen cylinder connects the pressure reducing valve, solenoid valve and gas flow meter in series through the gas pipe and is connected to the nitrogen nozzle at the bottom of the deaerator; the gas flow meter sends the signal to the PLC controller; the solenoid valve is connected to the PLC controller and is controlled by the PLC controller. Preferably, a valve cooling water outlet pipe is provided at the bottom of the deaerator tank.

[0005] Preferably, an inspection valve is respectively provided at the input and output ends of the oxygen content measuring meter.

[0006] Preferably, the oxygen content measuring meter is provided with a bypass valve.

[0007] Preferably, the oxygen content measuring meter has a remote transmission function.

[0008] A control method for a cooling water oxygen control system for a converter valve in a high voltage direct current transmission system includes the following working conditions: When the oxygen content meter fails to be repaired, the bypass valve is opened and the repair valve is closed to achieve the purpose of repairing the oxygen content meter without stopping the valve cooling and deoxygenation system; the oxygen content meter sends the monitored oxygen content value in the valve cooling water to the PLC controller in real time in analog form. The PLC controller opens the solenoid valve according to the analog signal sent by the oxygen content meter to maintain the gas flow meter value within the PLC controller instruction range. When the gas flow meter flow value is too large, the PLC controller reduces the opening of the solenoid valve. When the gas flow meter flow value is too small, the PLC controller increases the opening of the solenoid valve.

[0009] It also includes the following working conditions: the oxygen content of the valve cooling water in the valve cooling water inlet pipe is monitored in real time by the oxygen content measuring meter, and the data is sent to the PLC controller in real time. When the oxygen content is greater than the set value of the PLC controller, the PLC controller sends a signal to open the solenoid valve according to the calculated nitrogen intake volume, and adjusts the size of the solenoid valve opening in real time through the size change of the gas flow meter to ensure that the gas flow meter maintains the set valve opening value of the PLC controller; after the solenoid valve is opened, the nitrogen is sent to the lower part of the deaerator through the nitrogen delivery pipe, and is evenly sprayed into the valve cooling water inside the deaerator through the nitrogen nozzle; at the same time, the valve cooling water is continuously sent to the upper part of the deaerator through the valve cooling water inlet pipe by the main circulation pump pressure of the main water pipeline, and then evenly sprayed into the inside of the deaerator through the water nozzle.

[0010] It also includes the following working conditions: inside the deaerator, the valve cooling water is sprayed from top to bottom due to pressure and gravity, and at the same time, nitrogen is sprayed into the valve cooling water in the deaerator through the nitrogen nozzle. Affected by buoyancy, the nitrogen rises from bottom to top, thereby displacing the oxygen in the valve cooling water and forming an air cushion on the upper part of the deaerator. When the gas pressure is greater than the preset value of the pressure release valve, the nitrogen and oxygen mixed gas is sent into the atmosphere by the pressure release valve, and the valve cooling water with a lower oxygen content that has been replaced in the lower part of the deaerator flows back to the valve cooling water main water pipeline through the valve cooling water outlet pipe under pressure, thereby achieving the purpose of controlling the oxygen content of the converter valve cooling water.

[0011] The present invention can achieve the following beneficial effects: (1) Compared with the traditional converter valve cooling water oxygen content control device, the patent of the present invention has a simple structure, can monitor the oxygen content of the converter valve cooling water in real time and can quickly adjust it in real time according to the oxygen content.

[0012] (2) The patent of this invention uses nitrogen as the oxygen replacement medium to control the oxygen content, which has no effect on the converter valve, pipelines, electrodes and other equipment, and there is no possibility of affecting other equipment or the operating reliability of the DC converter valve; (3) The patent of the present invention only takes a branch from the main water pipe of the valve cooling water to reduce the oxygen content of the valve cooling water. The power still uses the main circulation pump of the valve cooling water. No additional power is required, and the maintenance is low.

[0013] (4) The patented method of the present invention does not emit polluting waste gas and gases such as carbon dioxide, does not require heating equipment, and does not consume energy. The waste gas generated is only nitrogen and oxygen, which can be directly discharged into the atmosphere without the need for additional waste treatment measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 This is a system structure diagram of the present invention.

[0015] In the figure: 1-valve cooling water inlet pipe, 2-valve cooling water outlet pipe, 3-oxygen meter bypass valve, 4-oxygen meter inspection valve, 5-oxygen meter, 6-pressure release valve, 7-PLC controller, 8-deoxygen tank, 9-gas flow meter, 10-solenoid valve, 11-pressure reducing valve, 12-nitrogen bottle, 13-nitrogen delivery pipe, 14-nitrogen nozzle, 15-water nozzle DETAILED DESCRIPTION The high oxygen content inside the converter valve of the DC transmission system will cause corrosion of the converter valve, pipeline, pump body, etc., and will also cause scaling of the voltage-equalizing electrode, thereby causing safety hazards such as shutdown of the DC transmission system and equipment failure. Because the converter valve cooling water is a closed circulation system, the conductivity and water temperature are required to be relatively low, so it is impossible to use chemical agents and high temperatures to reduce the oxygen content. Therefore, the patented design of this invention is a control system and method for the oxygen content of the converter valve cooling water in a high-voltage DC transmission system, as follows: like Figure 1As shown. A control system for the oxygen content of cooling water of a converter valve in a high-voltage direct current transmission system includes a nitrogen bottle, a deaerator, an oxygen content meter, a bypass valve, a valve cooling water inlet pipe, a valve cooling water outlet pipe, a pressure release valve, a nitrogen flow meter, a solenoid valve, a nitrogen pressure reducing valve, a gas nozzle, a water nozzle, and a PLC controller. The oxygen content meter is installed in series in the middle of the valve cooling water inlet pipe, the valve cooling water inlet pipe is installed on the upper part of the deaerator and connected to the water nozzle, the pressure release valve is installed directly above the deaerator, and the valve cooling water outlet is installed directly below the deaerator; the nitrogen bottle is connected in series with the pressure reducing valve and then connected to the solenoid valve, and finally connected in series with the gas flow meter and connected to the bottom of the deaerator, and connected to the gas nozzle. The first input end of the PLC controller is connected to the data of the oxygen content meter, the second input end of the PLC controller is connected to the nitrogen flow meter, and the output end of the PLC controller is connected to the solenoid valve.

[0016] The present invention uses a PLC controller to retrieve the oxygen content in the valve cooling water in real time through an oxygen content measuring meter, and determines the opening of the output regulating solenoid valve by measuring the size of the oxygen content data, thereby achieving the purpose of regulating the flow control of nitrogen entering the deaerator. Nitrogen enters from the bottom of the deaerator and is in the deaerator, and valve cooling water enters from the top of the deaerator. Nitrogen replaces oxygen in the cooling water of the converter valve in the deaerator. When the internal pressure of the deaerator is high, the pressure release valve installed above the deaerator is activated to release the replaced oxygen and excess nitrogen, thereby achieving the purpose of controlling the oxygen content in the valve cooling water.

[0017] The operation method of this system is: The valve cooling water inlet pipe 1 is connected to the water nozzle on the upper part of the deaerator tank 8, and an oxygen content measuring meter 5 with a remote transmission function is installed on the valve cooling water inlet pipe 1, and the oxygen content measuring meter 5 is connected to the PLC controller 7; when the oxygen content measuring meter 5 fails to be repaired, the bypass valve 3 can be opened and the repair valve 4 can be closed to achieve the purpose of repairing the oxygen content meter without stopping the valve cooling and deaerator system; the nitrogen cylinder 12 connects the pressure reducing valve 11, the solenoid valve 10, and the gas flow meter 9 in series through the gas transmission pipe 13, and is connected to the nitrogen nozzle 14 at the bottom of the deaerator tank 8; the gas flow meter 9 sends a signal to the PLC controller 7, the solenoid valve 10 is connected to the PLC controller 7, and the solenoid valve 7 is controlled by the PLC controller. The oxygen content measuring meter 5 sends the monitored oxygen content value in the valve cooling water to the PLC controller 7 in real time in analog form. The PLC controller 7 opens the solenoid valve 10 according to the analog signal sent by the oxygen content measuring meter 5 to maintain the value of the gas flow meter 9 within the command range of the PLC controller 7. When the flow value of the gas flow meter 9 is too large, the PLC controller reduces the opening of the solenoid valve 10. When the flow value of the gas flow meter 9 is too small, the PLC controller 7 increases the opening of the solenoid valve 10.

[0018] The oxygen content of the valve cooling water in the valve cooling water inlet pipe 1 is monitored in real time by the oxygen content measuring meter 5, and the data is sent to the PLC controller 7 in real time. When the oxygen content is greater than the set value of the PLC controller 7, the PLC controller 7 sends a signal to open the solenoid valve 10 according to the calculated nitrogen intake, and adjusts the size of the solenoid valve 10 through the size change of the gas flow meter 9 in real time to ensure that the gas flow meter 9 maintains the set valve opening value of the PLC controller 7. After the solenoid valve 10 is opened, the nitrogen is sent to the lower part of the deaerator tank 8 through the nitrogen delivery pipe 13, and is evenly sprayed into the valve cooling water inside the deaerator tank 8 through the nitrogen nozzle 14; at the same time, the valve cooling water is continuously sent to the upper part of the deaerator tank 8 through the valve cooling water inlet pipe 1 by the pressure of the main circulation pump of the main water pipeline, and then evenly sprayed into the inside of the deaerator tank 8 through the water nozzle 15. Inside the deaerator 8, the valve cooling water is sprayed from top to bottom due to pressure and gravity, and at the same time, nitrogen is sprayed into the valve cooling water in the deaerator 8 through the nitrogen nozzle 14. Affected by buoyancy, the nitrogen rises from bottom to top, thereby replacing the oxygen in the valve cooling water and forming an air cushion on the upper part of the deaerator 8. When the gas pressure is greater than the preset value of the pressure release valve 6, the nitrogen and oxygen mixed gas is sent into the atmosphere by the pressure release valve 6, and the valve cooling water with a lower oxygen content that has been replaced in the lower part of the deaerator 8 flows back to the valve cooling water main water pipeline through the valve cooling water outlet pipe 2 under pressure, thereby achieving the purpose of controlling the oxygen content of the converter valve cooling water.

[0019] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A control system for cooling water oxygen content of converter valves in a high-voltage direct current transmission system, characterized in that: It comprises a valve cooling water inlet pipe (1) and a nitrogen bottle (12), the valve cooling water inlet pipe (1) is connected to a water nozzle on the upper part of a deaerator (8), an oxygen content measuring meter (5) is installed on the valve cooling water inlet pipe (1), and the oxygen content measuring meter (5) is connected to a PLC controller (7); The nitrogen cylinder (12) is connected in series to the pressure reducing valve (11), the solenoid valve (10), and the gas flow meter (9) through the gas transmission pipe (13), and is connected to the nitrogen nozzle (14) at the bottom of the deoxygenation tank (8); the gas flow meter (9) sends a signal to the PLC controller (7); the solenoid valve (10) is connected to the PLC controller (7), and the solenoid valve (7) is controlled by the PLC controller.

2. A high voltage direct current transmission system converter valve cooling water oxygen control system according to claim 1, characterized in that: A valve cooling water outlet pipe (2) is provided at the bottom of the deaerator tank (8).

3. A high voltage direct current transmission system converter valve cooling water oxygen control system according to claim 1, characterized in that: An inspection valve (4) is respectively provided at the input and output ends of the oxygen content measuring meter (5).

4. A high voltage direct current transmission system converter valve cooling water oxygen control system according to claim 1, characterized in that: The oxygen content measuring meter (5) is provided with a bypass valve (3).

5. A high voltage direct current transmission system converter valve cooling water oxygen control system according to claim 1, characterized in that: The oxygen content measuring meter (5) has a remote transmission function.

6. A control method for a cooling water oxygen control system for a high voltage direct current power transmission system according to any one of claims 1 to 5, characterized in that The following conditions are included: When the oxygen content measuring meter (5) fails and needs to be repaired, the bypass valve (3) is opened and the repair valve (4) is closed to achieve the purpose of repairing the oxygen content meter without stopping the valve cooling and deoxygenation system; the oxygen content measuring meter (5) sends the oxygen content value of the valve cooling water monitored in real time in the form of analog quantity to the PLC controller (7), and the PLC controller (7) opens the solenoid valve (10) according to the analog signal sent by the oxygen content measuring meter (5) to maintain the value of the gas flow meter (9) within the command range of the PLC controller (7). When the flow value of the gas flow meter (9) is too large, the PLC controller reduces the opening of the solenoid valve (10), and when the flow value of the gas flow meter (9) is too small, the PLC controller (7) increases the opening of the solenoid valve (10).

7. The control method of the cooling water oxygen content control system of the high voltage direct current transmission system according to claim 6 is characterized in that The invention also includes the following working conditions: the oxygen content of the valve cooling water in the valve cooling water inlet pipe (1) is monitored in real time by the oxygen content measuring meter (5), and the data is sent to the PLC controller (7) in real time; when the oxygen content is greater than the set value of the PLC controller (7), the PLC controller (7) sends a signal to open the solenoid valve (10) according to the calculated nitrogen intake volume, and adjusts the opening size of the solenoid valve (10) in real time through the size change of the gas flow meter (9), so as to ensure that the gas flow meter (9) maintains the set opening value of the PLC controller (7); after the solenoid valve (10) is opened, the nitrogen is sent to the lower part of the deaerator (8) through the nitrogen delivery pipe (13), and is uniformly sprayed into the valve cooling water inside the deaerator (8) through the nitrogen nozzle (14); at the same time, the valve cooling water is continuously sent to the upper part of the deaerator (8) through the valve cooling water inlet pipe (1) by the pressure of the main circulation pump of the main water pipeline, and then is uniformly sprayed into the inside of the deaerator (8) through the water nozzle (15).

8. The control method of a cooling water oxygen content control system for a converter valve in a high-voltage direct current transmission system according to claim 6 is characterized in that The invention also includes the following working conditions: inside the deaerator (8), valve cooling water is sprayed from top to bottom due to pressure and gravity, and at the same time, nitrogen is sprayed into the valve cooling water in the deaerator (8) through the nitrogen nozzle (14). The nitrogen rises from bottom to top due to buoyancy, thereby displacing oxygen in the valve cooling water and forming an air cushion on the upper part of the deaerator (8). When the gas pressure is greater than the preset value of the pressure release valve (6), the nitrogen and oxygen mixed gas is discharged into the atmosphere by the pressure release valve (6). The valve cooling water with a lower oxygen content that has been displaced in the lower part of the deaerator (8) flows back to the valve cooling water main water pipeline through the valve cooling water outlet pipe (2) under the action of pressure, thereby achieving the purpose of controlling the oxygen content of the converter valve cooling water.

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