Natural gas long-distance pipeline compressor start-up and shutdown process protection control method and device

Abstract

The application discloses a natural gas long-distance pipeline compressor start-up and shutdown process protection control method and device, and the method comprises the following steps: monitoring the motor operating point of the running unit during the compressor unit shutdown / start-up process, executing corresponding protection schemes for the running unit and the shutdown unit / the running unit and the start-up unit according to the distribution position of the motor operating point in the pre-control diagram; or controlling the motor speed reduction rate of the shutdown unit / the motor speed increase rate of the start-up unit and the anti-surge valve opening / closing valve rate according to the size relationship between the motor speed of the shutdown / start-up unit and the preset speed. The application can judge the abnormal condition in the compressor start-up and shutdown process in advance, and protection is performed in advance, so that the abnormal condition of the compressor unit is prevented from further expanding, the emergency shutdown of the compressor unit is avoided, and the safe and stable operation of the compressor and the pipeline network is ensured.

Description

Technical Field

[0001] This invention relates to the field of natural gas pipeline technology, and in particular to a method and device for protecting and controlling the start-up, shutdown, and acceleration / deceleration processes of a compressor in a long-distance natural gas pipeline. Background Technology

[0002] Natural gas long-distance pipeline compressor stations typically have multiple compressor units to pressurize the pipeline natural gas. With dynamic changes in operating conditions, compressor units need to be started, stopped, and increased in real time to ensure the number of operating compressor units meets the pipeline network's operational needs. However, currently, only two types of protection and control methods are implemented for the compressor units: pressure-holding ESD (Emergency Shutdown) and pressure-relief ESD. These methods enable timely shutdown of the compressors in abnormal situations, thus protecting them. However, emergency shutdown of compressor units can easily cause mechanical damage to the compressors and also cause significant pressure fluctuations in the pipeline network, affecting its operation. Therefore, emergency shutdowns should be avoided as much as possible in actual operation. How to proactively identify and protect against abnormal situations during compressor start-up and shutdown, preventing emergency shutdowns and ensuring the safe and stable operation of both the compressor units and the pipeline network, is a pressing issue that needs to be addressed. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and device for protection and control of the start-up and shutdown process of a natural gas long-distance pipeline compressor, which addresses the problems existing in the prior art.

[0004] To address the aforementioned technical problems, embodiments of the present invention provide a protection and control method for the start-up, shutdown, and acceleration / deceleration processes of a natural gas long-distance pipeline compressor, comprising:

[0005] During the compressor unit's shutdown / start-up process, the operating point of the motor of the operating unit is monitored. Based on the distribution of the motor operating point in the pre-made control diagram, corresponding protection schemes are implemented for the operating unit and the shutdown / start-up unit; or, based on the relationship between the motor speed of the shutdown / start-up unit and the preset speed, the speed reduction rate of the motor speed of the shutdown unit / speed increase rate of the motor speed of the start-up unit, as well as the opening / closing rate of the anti-surge valve are controlled.

[0006] During the compressor unit's reduction and shutdown process, the operating point of the running unit's motor is recorded as the first motor operating point, and the pre-made control diagram is recorded as the first control diagram; the horizontal axis of the first motor operating point is the motor speed of the running unit, and the vertical axis is the motor current of the running unit; the horizontal axis of the first control diagram is the motor speed, and the vertical axis is the motor current, including multiple load distribution lines and multiple current distribution lines;

[0007] During the compressor unit start-up process, the operating point of the motor of the running unit is recorded as the second motor operating point, and the pre-made control diagram is recorded as the second control diagram. The horizontal axis of the second motor operating point is the motor speed of the running unit, and the vertical axis is the compressor outlet manifold pressure. The horizontal axis of the second control diagram is the motor speed, and the vertical axis is the compressor outlet manifold pressure, including multiple pressure distribution lines.

[0008] To address the aforementioned technical problems, embodiments of the present invention also provide a protection and control device for the start-up, shutdown, and acceleration / deceleration processes of a natural gas long-distance pipeline compressor, comprising:

[0009] The monitoring module is used to monitor the operating point of the motor of the operating unit during the compressor unit's shutdown / start-up process;

[0010] The control module is used to implement corresponding protection schemes for operating units and units that are reduced or stopped, or for operating units and units that are increased or stopped, based on the distribution of the motor operating points in the pre-made control diagram; or, based on the relationship between the motor speed of the units that are reduced or stopped / increased or stopped and the preset speed, to control the rate of decrease of the motor speed of the units that are reduced or stopped / increased or stopped / increased or stopped / increased or stopped, as well as the rate of opening / closing of the anti-surge valve.

[0011] During the compressor unit's reduction and shutdown process, the operating point of the running unit's motor is recorded as the first motor operating point, and the pre-made control diagram is recorded as the first control diagram; the horizontal axis of the first motor operating point is the motor speed of the running unit, and the vertical axis is the motor current of the running unit; the horizontal axis of the first control diagram is the motor speed, and the vertical axis is the motor current, including multiple load distribution lines and multiple current distribution lines;

[0012] During the compressor unit start-up process, the operating point of the motor of the running unit is recorded as the second motor operating point, and the pre-made control diagram is recorded as the second control diagram. The horizontal axis of the second motor operating point is the motor speed of the running unit, and the vertical axis is the compressor outlet manifold pressure. The horizontal axis of the second control diagram is the motor speed, and the vertical axis is the compressor outlet manifold pressure, including multiple pressure distribution lines.

[0013] A natural gas long-distance pipeline compressor start-up, de-start-up, and shutdown process protection and control device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the natural gas long-distance pipeline compressor start-up, de-start-up, and shutdown process protection and control method provided by the above-mentioned technical solution.

[0014] The beneficial effects of this invention are as follows: During the compressor unit's shutdown and restart process, this invention monitors and judges the motor current of the operating unit and provides early protection against abnormal situations; during the compressor unit's restart process, it monitors and judges the outlet pressure and provides early protection against abnormal situations; by judging abnormal situations during the compressor's restart and shutdown process in advance and providing early protection, this invention prevents the abnormal situation of the compressor unit from further escalating, avoids emergency shutdown of the compressor unit, and ensures the safe and stable operation of the compressor and pipeline network.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0016] Figure 1 A flowchart of the protection and control method for the start-up and shutdown process of a natural gas long-distance pipeline compressor provided in an embodiment of the present invention;

[0017] Figure 2 First control diagram provided for embodiments of the present invention

[0018] Figure 3 The second control diagram is provided for an embodiment of the present invention. Detailed Implementation

[0019] The following specific examples illustrate the implementation of this disclosure. Those skilled in the art can easily understand other advantages and effects of this disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. This disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this disclosure. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0020] It should be noted that various aspects of the embodiments described below are within the scope of the appended claims. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using other structures and / or functionalities besides one or more of the aspects set forth herein.

[0021] Figure 1 This is a flowchart illustrating the protection and control method for the start-up, shutdown, and restart processes of a natural gas long-distance pipeline compressor, as provided in an embodiment of the present invention. Figure 1 As shown, the method includes:

[0022] S1 monitors the operating point of the motor of the operating unit during the compressor unit's shutdown / start-up process.

[0023] During the compressor unit's deceleration and shutdown process, the operating point of the running unit's motor is recorded as the first motor operating point. The horizontal axis of the first motor operating point is the motor speed of the running unit, and the vertical axis is the motor current of the running unit.

[0024] During the compressor unit start-up process, the operating point of the motor of the running unit is recorded as the second motor operating point. The horizontal axis of the second motor operating point is the motor speed of the running unit, and the vertical axis is the compressor outlet manifold pressure.

[0025] S2, based on the distribution of the motor operating points in the pre-made control diagram, executes corresponding protection schemes for the operating units and the reduced / stopped units / operating units and the increased / increased units.

[0026] During the compressor unit's deceleration and shutdown process, the pre-made control diagram is denoted as the first control diagram. The horizontal axis of the first control diagram represents the motor speed, and the vertical axis represents the motor current. It includes multiple load distribution lines and multiple current distribution lines.

[0027] During the compressor unit start-up process, the pre-made control chart is denoted as the second control chart. The horizontal axis of the second control chart represents the motor speed, and the vertical axis represents the compressor outlet manifold pressure, including multiple pressure distribution lines.

[0028] It should be noted that during the compressor unit's deceleration and shutdown process, the decelerating unit gradually reduces its speed, and the anti-surge valve gradually opens. To meet the set pressure requirements, the operating unit gradually increases its speed under the action of the pressure controller. During this process, the load on the operating unit increases, and the speed rises, which can easily cause excessive motor current. This embodiment of the invention monitors and judges the motor current of the operating unit and provides early protection against abnormal situations. Specifically, during the compressor unit's deceleration and shutdown process, the operating point of the operating unit's motor is monitored, and corresponding protection schemes are implemented for the operating unit and the decelerating unit based on the distribution of the motor operating point in the pre-designed control diagram.

[0029] It should be noted that during the compressor unit start-up process, the start-up unit gradually increases its speed, and the anti-surge valve gradually closes. During this process, as the speed of the start-up unit increases, the pipeline pressure gradually increases, which can easily lead to excessively high outlet pressure. This embodiment of the invention monitors and judges the outlet pressure situation and provides early protection against abnormal situations. Specifically, during the compressor unit start-up process, the operating point of the motor of the operating unit is monitored, and according to the distribution of the motor operating point in the pre-designed control diagram, corresponding protection schemes are implemented for both the operating unit and the start-up unit.

[0030] This invention, by predicting abnormal situations during the compressor's start-up, shutdown, and reactivation processes in advance and taking preventative measures, avoids further escalation of compressor unit abnormalities, prevents emergency shutdown of the compressor unit, and ensures the safe and stable operation of the compressor and pipeline network.

[0031] The following sections will introduce the process control for reducing shutdown and increasing startup.

[0032] 1) Overcurrent protection during the reduction and shutdown process.

[0033] During the compressor unit's shutdown process, based on the distribution of the motor's operating point in the pre-designed control diagram, corresponding protection schemes are implemented for the operating and shut-down units. These schemes include: when the motor's operating point is located within the control area of ​​multiple load distribution lines / current distribution lines in the pre-designed control diagram, controlling the motor speed and / or compressor inlet valve position of the operating unit until the motor's operating point is located to the lower right of the protected load line / below the protected current line in the pre-designed control diagram.

[0034] Taking a certain compressor station as an example, the first control diagram is as follows: Figure 2 As shown in the figure, the multiple load distribution lines include the ultimate load line LLL, the protective load line PLL, and the control load line CLL, which are distributed from left to right; the multiple current distribution lines include the ultimate current line LCL, the protective current line PCL, and the control current line CCL, which are distributed from top to bottom.

[0035] Limit load line (LLL).

[0036] In this embodiment of the invention, a limit load test is performed on the centrifugal compressor. Multiple sets of motor current values ​​are tested at the lower limit of motor operating speed, the upper limit of motor operating speed, and the range of motor operating speed. The measured data points are plotted on a coordinate system with motor speed as the abscissa and motor current as the ordinate. The plotted data points are connected to obtain the limit load line of the centrifugal compressor.

[0037] The centrifugal compressor ultimate load test mainly consists of two parts. First, using the compressor's maximum operating flow rate as the ultimate load, the corresponding motor current values ​​are measured at different speeds. Second, using the compressor's maximum pressure ratio as the ultimate load, the corresponding motor current values ​​are measured at different speeds. The minimum value of the two current values ​​measured at the same speed is used as the current value for plotting the ultimate load line.

[0038] Maximum operating flow rate of the compressor: Based on the compressor's performance curve (efficiency curve), since the compressor's efficiency drops significantly at high flow rates, compressor stations typically do not allow the compressor to operate at high or maximum flow rates with very low efficiency. To save energy, the maximum operating flow rate of the compressor is determined based on the acceptable operating efficiency set by the compressor station.

[0039] The compressor's maximum pressure ratio: According to the compressor's performance curve (pressure ratio curve), the pressure ratio is at its maximum when the compressor is operating at its minimum flow rate (surge flow rate). In actual testing, the pressure ratio corresponding to the surge line is taken as the compressor's maximum pressure ratio.

[0040] Protective load line (PLL).

[0041] In this embodiment of the invention, the test load is obtained by multiplying the maximum operating flow rate of the centrifugal compressor by a first coefficient and the first coefficient of the maximum pressure ratio, respectively, and the protection load line is obtained according to the method of obtaining the limit load line; or, the protection load line is obtained by multiplying the motor current obtained from the limit load test by a first margin coefficient with the limit load line as a reference.

[0042] Specifically, the protective load line can be obtained in the following two ways.

[0043] Method 1: Actual measurement of the protective load line

[0044] A load test was conducted on the centrifugal compressor, using 98% of the compressor's maximum operating flow rate and 98% of its maximum pressure ratio as the test load. Several sets of motor current values ​​were measured at the lower limit, upper limit, and speed range of the motor. The measured data points were plotted on a coordinate system with motor speed as the abscissa and motor current as the ordinate, and the plotted data points were connected to form a line.

[0045] Method 2: Pre-install protective load line

[0046] Using the ultimate load line as a reference, keeping the motor current obtained from the ultimate load test constant, and multiplying the motor speed by a margin factor of 1.02 (which can be set), the preset protection load line of the centrifugal compressor is obtained.

[0047] Control load line (CLL).

[0048] In this embodiment of the invention, the maximum operating flow rate of the centrifugal compressor and the maximum pressure ratio multiplied by the second coefficient are used as test loads, respectively, and the protection load line is obtained according to the method of obtaining the limit load line; or, with the limit load line as a reference, the motor current obtained from the limit load experiment is kept constant, and the motor speed is multiplied by the second margin coefficient to obtain the protection load line of the centrifugal compressor.

[0049] Among them, the second coefficient is less than the first coefficient, and both the first and second coefficients are less than 1; the second margin coefficient is greater than the first margin coefficient, and both the first and second margin coefficients are greater than 1.

[0050] Specifically, the control load line can be obtained in the following two ways.

[0051] Method 1: Actual measurement of the control load line.

[0052] A load test was conducted on the centrifugal compressor, using 95% of the compressor's maximum operating flow rate and 95% of its maximum pressure ratio as the test load. Several sets of motor current values ​​were measured at the lower limit, upper limit, and speed range of the motor. The measured data points were plotted on a coordinate system with motor speed as the abscissa and motor current as the ordinate. The lines connecting the plotted data points were then used to obtain the measured protection load line of the centrifugal compressor.

[0053] Method 2: Preset control load line.

[0054] Using the ultimate load line as a reference, keeping the motor current obtained from the ultimate load test constant, and multiplying the motor speed by a margin factor of 1.05 (which can be set), the preset protection load line of the centrifugal compressor is obtained.

[0055] Limit current line (LCL): The limit current line is calculated by multiplying the motor's rated current by a first current coefficient. For example, if the motor current is set to 110% of the rated current, the limit current line is obtained.

[0056] Protective current line (PCL): The protective current line is obtained by multiplying the rated current of the motor by the second current coefficient; for example, if the motor current is set to 105% of the rated current, the protective current line is obtained.

[0057] Control current line (CCL): The rated current of the motor is used as the control current line.

[0058] Specifically, when the motor operating point is located within the control area of ​​multiple load distribution lines in the pre-designed control diagram, the control methods for the motor speed and / or compressor inlet valve position of the operating unit are as follows:

[0059] When the motor operating point is in the first load control area, the motor speed of the controlled operating unit is kept constant at the current value. The range of the first load control area is [control load line, protection load line);

[0060] When the motor operating point touches the protection load line, the motor speed of the operating unit is reduced by a first preset value; if the motor operating point moves into the first load control area within the first preset time period, the control method for the first load control area is executed; if the motor operating point remains within the second load control area within the first preset time period, the motor speed of the operating unit is reduced by a second preset value every first preset time period until the motor operating point moves into the first load control area; wherein, the range of the second load control area is [protection load line, limit load line);

[0061] When the motor operating point touches the limit load line, the motor speed of the control unit is reduced by a third preset value and the inlet valve opening is reduced by a first preset value. If the motor operating point moves into the second load control area within a second preset time period, the control method for the second load control area is executed. If the motor operating point remains within the third load control area within the second preset time period, the motor speed of the control unit is reduced by a fourth preset value and the inlet valve opening is reduced by a second preset value every second preset time period, alternating until the motor operating point moves into the second load control area, at which point the control method for the second load control area is executed. The range of the third load control area is [limit load line, above and to the left of the limit load line].

[0062] Among them, the first preset value is greater than the second preset value, the third preset value is greater than the fourth preset value, and the first preset opening degree is greater than the second preset opening degree; during the valve position opening degree control of the inlet valve, the valve position opening degree is not lower than the preset valve position opening degree.

[0063] In this embodiment of the invention, different control measures are taken for the motor speed and / or compressor inlet valve position of the operating unit according to the location of the operating unit motor operating point in the load distribution line control area. The trend of overcurrent of the operating unit is judged in advance and protection is carried out to prevent the motor current of the operating unit from increasing further and to ensure the safe operation of the compressor.

[0064] Specifically, when the motor operating point is located within the control area of ​​multiple current distribution lines in the pre-designed control diagram, the control method for the motor speed and / or compressor inlet valve position of the operating unit is as follows:

[0065] When the motor operating point is in the first current control region, the motor speed of the control unit is kept constant at the current value. The range of the first current control region is [control current line, protection current line);

[0066] When the motor operating point touches the protection current line, the motor speed of the operating unit is reduced by a fifth preset value; if the motor operating point moves into the first current control area within a third preset time period, the control method of the first current control area is executed; if the motor operating point remains within the second current control area within a third preset time period, the motor speed of the operating unit is reduced by a sixth preset value every third preset time period until the motor operating point moves into the first current control area; wherein, the range of the second current control area is [protection current line, limit current line);

[0067] When the motor operating point touches the limit current line, the motor speed of the control unit is reduced by a seventh preset value and the inlet valve opening is reduced by a third preset value. If the motor operating point moves into the second current control region within a fourth preset time period, the control method of the second current control region is executed. If the motor operating point remains within the third current control region within a fourth preset time period, the motor speed of the control unit is reduced by an eighth preset value and the inlet valve opening is reduced by a fourth preset value every fourth preset time period until the motor operating point moves into the second current control region, at which point the control method of the second current control region is executed. The range of the third current control region is [limit current line, above the limit current line].

[0068] Among them, the fifth preset value is greater than the sixth preset value, the seventh preset value is greater than the eighth preset value, and the third preset opening degree is greater than the fourth preset opening degree; during the valve position opening degree control process of the inlet valve, the valve position opening degree is not lower than the preset valve position opening degree.

[0069] In this embodiment of the invention, different control measures are taken for the motor speed and / or compressor inlet valve position of the operating unit according to the location of the operating point of the motor in the current distribution line control area, so as to strictly control the motor current of the operating unit and ensure the safe operation of the compressor.

[0070] The following is a detailed description of the protective actions taken by the operating unit during the shutdown process, using a specific example.

[0071] When the motor operating point touches the control load line or runs between the control load line and the protection load line, the motor speed is kept constant at the current value.

[0072] When the motor operating point touches the protection load line, the motor speed immediately decreases by 15 rpm. If the motor operating point moves between the protection load line and the control load line within 10 seconds, the motor speed will no longer decrease and will maintain the current speed. If the motor operating point remains between the protection load line or the limit load line within 10 seconds, the motor speed will be reduced by 3 rpm at the end of the 10 seconds. The process continues for the second 10 seconds. If the motor operating point moves between the protection load line and the control load line, the motor speed will no longer decrease and will maintain the current speed. If the motor operating point remains between the protection load line or the limit load line within 10 seconds, the motor speed will be reduced by 3 rpm at the end of the 10 seconds. This cycle continues until the motor operating point moves between the protection load line and the control load line.

[0073] When the motor operating point touches the limit load line, the motor speed immediately decreases by 20 rpm, and the compressor inlet valve opening decreases by 5%. If the motor operating point moves between the limit load line and the protection load line within 10 seconds, the control method of the second load control area is executed. If the motor operating point remains at or above the limit load line within 10 seconds, the motor speed is reduced by 10 rpm or the compressor inlet valve opening is reduced by 2% at the end of 10 seconds. The judgment continues in the second 10 seconds. If the motor operating point moves between the limit load line and the protection load line within 10 seconds, the control method of the second load control area is executed. If the motor operating point remains at or above the limit load line within 10 seconds, the motor speed is reduced by 10 rpm or the compressor inlet valve opening is reduced by 2% at the end of 10 seconds. That is, if the motor operating point remains at or above the limit load line for several consecutive 10 seconds, the two actions of reducing the motor speed by 10 rpm and reducing the compressor inlet valve opening by 2% are executed alternately every 10 seconds until the motor operating point moves into the second load control area (the compressor inlet valve opening must not be lower than 70%), and then the control method of the second load control area is executed.

[0074] When the motor operates in a safe range, the compressor inlet valve opens gradually by 1%.

[0075] When the motor's operating point touches the control current line or runs between the control current line and the protection current line, the motor speed is controlled to remain unchanged at the current value.

[0076] When the motor operating point touches the protection current line, the motor speed immediately decreases by 15 rpm. If the motor operating point moves between the control current line and the protection current line within 10 seconds, the motor speed will no longer decrease and will maintain the current speed. If the motor operating point remains between the protection current line or the protection current line and the limit current line within 10 seconds, the motor speed will be reduced by 3 rpm at the end of the 10-second period. The process continues for the second 10-second period. If the motor operating point moves between the control current line and the protection current line within 10 seconds, the motor speed will no longer decrease and will maintain the current speed. If the motor operating point remains between the protection current line or the protection current line and the limit current line within 10 seconds, the motor speed will be reduced by 3 rpm at the end of the 10-second period. This cycle continues until the motor operating point moves between the protection current line and the control current line.

[0077] When the motor operating point touches the limit current line, the motor speed immediately decreases by 20 rpm, and the compressor inlet valve opening decreases by 5%. If the motor operating point moves between the protection current line and the control current line within 10 seconds, the control method of the second current control area is executed. If the motor operating point remains at or above the limit current line within 10 seconds, the motor speed is reduced by 10 rpm at the end of the 10th second, and the compressor inlet valve opening decreases by 2%. The process continues for another 10 seconds. If the motor operating point moves between the protection current line and the control current line within 10 seconds, the control method of the second current control area is executed. If the motor operating point remains at or above the limit current line within 10 seconds, the motor speed is reduced by 10 rpm at the end of the 10th second, and the compressor inlet valve opening decreases by 2%. This cycle continues until the motor operating point moves into the second current control area, at which point the control method of the second current control area is executed (the compressor inlet valve opening must not be lower than 70%).

[0078] Optionally, when the motor operating point is located within the control area of ​​multiple current distribution lines in the pre-designed control diagram, the motor speed of the unit to be reduced and stopped and the opening rate of the anti-surge valve are also controlled according to the distribution position of the motor operating point in the pre-designed control diagram.

[0079] Specifically, when the operating point of the motor of at least one operating unit touches the control current line or runs between the control current line and the protection current line, and the operating point of the motor of no operating unit runs at or above the protection current line, the speed reduction rate of the motor of the shutdown unit will be reduced from the first speed reduction rate to the second speed reduction rate.

[0080] When the operating point of the motor of at least one operating unit touches the protection current line or runs between the protection current line and the limit current line, and the operating point of the motor of no operating unit runs above the limit current line / limit pressure line or the limit current line / limit pressure line, the speed reduction rate of the motor of the shutdown unit will be reduced from the second speed reduction rate to the third speed reduction rate, and the opening rate of the anti-surge valve will be reduced from the first opening rate to the second opening rate.

[0081] When the operating point of the motor of at least one operating unit touches the limit current line or runs above the limit current line, the current speed of the unit to be reduced or stopped and the opening of the anti-surge valve should be kept unchanged.

[0082] Specifically, the following is a detailed description of a protection scheme for the unit being shut down during the shutdown process, using a specific example.

[0083] 1) When the operating point of the generator motor touches the control current line or runs between the control current line and the protection current line, the speed reduction rate of the generator motor will be reduced from 255 rpm / min to 225 rpm / min.

[0084] 2) When the operating point of the generator motor touches the protection current line or the operating point is between the protection current line and the limit current line, the speed reduction rate of the generator motor will be reduced from 225 rpm / min to 195 rpm / min, and the opening rate of the anti-surge valve will be reduced from 0.2% / s to 0.1% / s.

[0085] 3) When the operating point of the generator motor touches the limit current line or runs above the limit current line, keep the current speed of the generator and the opening of the anti-surge valve unchanged.

[0086] In this embodiment of the invention, based on the location of the operating point of the motor of the running unit in the current distribution line control area, different control measures are taken on the motor speed reduction rate of the shutdown unit and / or the opening rate of the compressor anti-surge valve to slow down the reduction of the load of the shutdown unit, further control the motor current of the running unit, and ensure the safe operation of the compressor.

[0087] Optionally, embodiments of the present invention may also control the rate of decrease in motor speed and the opening rate of anti-surge valve of the generator set based on the relationship between the motor speed of the generator set and a preset speed, including:

[0088] When the motor speed of the unit being reduced or stopped is greater than or equal to the first speed threshold of the rated speed, the motor speed reduction rate of the unit being reduced or stopped is controlled to be the third reduction rate, and the valve opening rate of the anti-surge valve is the third opening rate.

[0089] When the motor speed of the shutdown unit is between the first speed threshold and the second transmission threshold of the rated speed, the motor speed reduction rate of the shutdown unit is controlled to be the second reduction rate, and the valve opening rate of the anti-surge valve is the fourth valve opening rate.

[0090] When the motor speed of the shutdown unit is between the second speed threshold of the rated speed and zero, the motor speed reduction rate of the shutdown unit is controlled to be the second reduction rate, and the valve opening rate of the anti-surge valve is the fifth opening rate.

[0091] Among them, the first speed threshold is greater than the second speed threshold, the third deceleration rate is less than the second deceleration rate, the third valve opening rate is less than the fourth valve opening rate, and the fourth valve opening rate is less than the fifth valve opening rate.

[0092] Specifically, the following is a detailed description of another protection scheme for the unit being shut down during the shutdown process, using a specific example.

[0093] When the unit motor speed is greater than or equal to 80% of the rated speed (or the shutdown speed, the speed at which the unit is shut down), the motor speed reduction rate is 195 rpm / min, and the anti-surge valve opening rate is 0.1% / s.

[0094] When the unit motor speed is between 65% and 80% of the rated speed (or the shutdown speed), the motor speed reduction rate is 225 rpm / min, and the anti-surge valve opening rate is 0.15% / s.

[0095] When the unit motor speed is between 0 and 65% of the rated speed (or the shutdown speed), the motor speed reduction rate is 255 rpm / min, and the anti-surge valve opening rate is 0.2% / s.

[0096] In this embodiment of the invention, the motor speed reduction rate of the shutdown unit and / or the opening rate of the compressor anti-surge valve are controlled in a split-range manner to gradually slow down the reduction of the load of the shutdown unit, further control the motor current of the operating unit, and ensure the safe operation of the compressor.

[0097] (ii) Overpressure protection during startup

[0098] During the compressor unit start-up process, based on the distribution of the motor operating point in the pre-designed control diagram, corresponding protection schemes are implemented for the operating unit and the start-up unit, including: when the motor operating point is located within the control area of ​​multiple pressure distribution lines in the pre-designed control diagram, the motor speed of the operating unit and / or the valve position of the compressor anti-surge valve are controlled until the motor operating point is located below the protection pressure line in the pre-designed control diagram.

[0099] Taking a certain compressor station as an example, the second control diagram is as follows: Figure 3As shown in the figure, the multiple pressure distribution lines include the ultimate pressure line LPL, the protective pressure line PPL, and the control pressure line CPL, which are distributed from top to bottom.

[0100] Limit pressure line (LPL): The limit pressure line is obtained by setting the compressor outlet manifold pressure as the first pressure value. For example, setting the compressor outlet manifold pressure to 9.3 MPa (based on the actual requirements of the pipeline network) yields the limit pressure line.

[0101] Protective pressure line (PPL): The protective pressure line is obtained by setting the compressor outlet manifold pressure to the second pressure value. For example, setting the compressor outlet manifold pressure to 9.1 MPa (based on the actual requirements of the pipeline network) yields the protective pressure line.

[0102] Control pressure line (CPL): The control pressure line is obtained by setting the compressor outlet manifold pressure to the third pressure value. For example, setting the compressor outlet manifold pressure to 9 MPa (based on actual pipeline requirements) yields the control pressure line.

[0103] Specifically, when the motor operating point is located within the control area of ​​multiple pressure distribution lines in the pre-designed control diagram, the control methods for the motor speed and / or compressor anti-surge valve position of the operating unit are as follows:

[0104] When the motor operating point is in the first pressure control zone, the motor speed of the control unit is kept constant at the current value. The range of the first pressure control zone is [control pressure line, protection pressure line].

[0105] When the motor operating point touches the protection pressure line, the motor speed of the operating unit is reduced by a ninth preset value; if the motor operating point moves into the first pressure control area within a fifth preset time period, the control method of the first pressure control area is executed; if the motor operating point remains within the second pressure control area within a fifth preset time period, the motor speed of the operating unit is reduced by a tenth preset value every fifth preset time period until the motor operating point moves into the first pressure control area; wherein, the range of the second pressure control area is [protection pressure line, limit pressure line];

[0106] When the motor operating point touches the limit pressure line, the motor speed of the control unit is reduced by an eleventh preset value and the anti-surge valve opening is increased by a fifth preset value. If the motor operating point moves into the second pressure control area within a sixth preset time period, the control method of the second pressure control area is executed. If the motor operating point remains within the third pressure control area within a sixth preset time period, the motor speed of the control unit is reduced by a twelfth preset value and the anti-surge valve opening is increased by a sixth preset value every sixth preset time period until the motor operating point moves into the second pressure control area, at which point the control method of the second pressure control area is executed. The range of the third pressure control area is [limit pressure line, above and to the left of the limit pressure line].

[0107] Among them, the ninth preset value is greater than the tenth preset value, the eleventh preset value is greater than the twelfth preset value, and the fifth preset opening degree is greater than the sixth preset opening degree.

[0108] Specifically, the protection scheme for the operating unit during the startup process is described in detail below with a specific example.

[0109] When the motor's operating point touches the control pressure line or runs between the control pressure line and the protection pressure line, the motor speed is controlled to remain unchanged at the current value.

[0110] When the motor operating point touches the protection pressure line, the motor speed immediately decreases by 15 rpm. If the motor operating point moves between the control pressure line and the protection pressure line within 10 seconds, the motor speed will no longer decrease and will maintain the current speed. If the motor operating point remains between the protection pressure line or the protection pressure line and the limit pressure line within 10 seconds, the motor speed will be reduced by 3 rpm at the end of the 10-second period. The process continues for the second 10-second period. If the motor operating point moves between the protection pressure line and the control pressure line, the motor speed will no longer decrease and will maintain the current speed. If the motor operating point remains between the protection pressure line or the protection pressure line and the limit pressure line within 10 seconds, the motor speed will be reduced by 3 rpm at the end of the 10-second period. This cycle repeats until the motor operating point moves between the protection pressure line and the control pressure line.

[0111] When the motor operating point touches the limit pressure line, the motor speed immediately decreases by 20 rpm, and the compressor anti-surge valve opening increases by 5%. If the motor operating point moves between the protection pressure line and the control pressure line within 10 seconds, the control method of the second pressure control zone is executed; if the motor operating point remains at or above the limit pressure line within 10 seconds, the motor speed is reduced by 10 rpm at the end of the 10th second, and the compressor anti-surge valve opening increases by 2%. The process continues for another 10 seconds. If the motor operating point moves between the protection pressure line and the control pressure line within 10 seconds, the control method of the second load control zone is executed; if the motor operating point remains at or above the limit pressure line within 10 seconds, the motor speed is reduced by 10 rpm at the end of the 10th second, and the compressor anti-surge valve opening increases by 2%. This cycle repeats until the motor operating point moves into the second pressure control zone, at which point the control method of the second negative pressure control zone is executed (the compressor inlet valve opening must not be lower than 70%).

[0112] In this embodiment of the invention, different control measures are taken on the motor speed of the operating unit and / or the valve position of the compressor anti-surge valve according to the location of the operating point of the motor in the pressure distribution line control area, so as to reduce the load of the operating unit, further control the manifold pressure, and ensure the safe operation of the compressor and pipeline.

[0113] Optionally, when the motor operating point is located within the control area of ​​multiple pressure distribution lines in the pre-designed control diagram, the motor speed reduction rate and anti-surge valve closing rate of the booster unit are also controlled according to the distribution position of the motor operating point in the pre-designed control diagram.

[0114] Specifically, when the motor operating point of at least one operating unit touches the control pressure line or runs between the control pressure line and the protection pressure line, and the motor operating point of no operating unit runs at or above the protection pressure line, the motor speed acceleration rate of the additional starting unit will be reduced from the first acceleration rate to the second acceleration rate.

[0115] When the operating point of the motor of at least one operating unit touches the protection pressure line or runs between the protection pressure line and the limit pressure line, and the operating point of the motor of no operating unit runs above the limit pressure line / limit pressure line or the limit pressure line / limit pressure line, the speed increase rate of the starting unit motor will be reduced from the second speed increase rate to the third speed increase rate, and the valve closing rate of the anti-surge valve will be reduced from the first valve closing rate to the second valve closing rate.

[0116] When the operating point of the motor of at least one operating unit touches the limit pressure line or runs above the limit pressure line, the current speed of the additional unit and the opening of the anti-surge valve remain unchanged.

[0117] Specifically, the following is a detailed description of a protection scheme for the additional start-up unit during the additional start-up process, using a specific example.

[0118] When the operating point of the generator motor touches the control pressure line or runs between the control pressure line and the protection pressure line, the speed increase rate of the generator motor will be reduced from 255 rpm / min to 225 rpm / min.

[0119] When the operating point of the generator motor touches the protection pressure line or the operating point is between the control pressure line and the protection pressure line, the speed increase rate of the generator motor will be reduced from 225 / min to 195 / min, and the valve closing rate of the anti-surge valve will be reduced from 0.2% / s to 0.1% / s.

[0120] When the operating point of the generator motor touches the limit pressure line, or runs above the limit pressure line, keep the current speed of the generator and the opening of the anti-surge valve unchanged.

[0121] In this embodiment of the invention, different control measures are taken on the motor speed increase rate and / or compressor anti-surge valve closing rate of the start-up unit according to the location of the operating point of the motor in the pressure distribution line control area, so as to slow down the increase of the load of the start-up unit, further control the pipeline pressure, and ensure the safe operation of the compressor and pipeline.

[0122] Optionally, embodiments of the present invention may also control the rate of increase of the motor speed of the booster unit and the closing rate of the anti-surge valve based on the relationship between the motor speed of the booster unit and the preset speed, including:

[0123] When the motor speed of the booster unit is greater than or equal to the first speed threshold, the motor speed of the booster unit is controlled to increase at the third increase rate, and the valve closing rate of the anti-surge valve is controlled to close at the third valve closing rate.

[0124] When the motor speed of the booster unit is between the first speed threshold and the second speed threshold of the rated speed, the motor speed of the booster unit is controlled to increase at the second speed increase rate, and the valve closing rate of the anti-surge valve is controlled to close at the fourth valve closing rate.

[0125] When the motor speed of the booster unit is between the second speed threshold of the rated speed and zero, the motor speed of the booster unit is controlled to increase at the first speed increase rate, and the valve closing rate of the anti-surge valve is controlled to close at the fifth valve closing rate.

[0126] Among them, the first speed threshold is greater than the second speed threshold, the third valve lifting rate is less than the second valve lifting rate, the second valve lifting rate is less than the first valve lifting rate, the third valve closing rate is less than the fourth valve closing rate, and the fourth valve closing rate is less than the fifth valve closing rate.

[0127] Specifically, the following is a detailed description of another protection scheme for the additional start-up unit during the additional start-up process, using a specific example.

[0128] When the generator set motor speed is between 0 and 65% of the rated speed, the motor speed increase rate is 255 rpm / min, and the anti-surge valve closing rate is 0.2% / s.

[0129] When the generator set motor speed is between 65% and 80% of the rated speed, the motor speed increase rate is 225 rpm / min, and the anti-surge valve closing rate is 0.15% / s.

[0130] When the generator set motor speed exceeds 80% of the rated speed, the motor speed increase rate is 195 rpm / min, and the anti-surge valve closing rate is 0.1% / s.

[0131] In this embodiment of the invention, the motor speed increase rate and / or compressor anti-surge valve closing rate of the booster unit are controlled in a split-range manner to gradually slow down the increase in load of the booster unit, further control pipeline pressure, and ensure the safe operation of the compressor and pipeline.

[0132] This invention also provides a protection and control device for the start-up and shutdown process of a natural gas long-distance pipeline compressor, including a monitoring module and a control module. The monitoring module monitors the operating point of the motor of the operating unit during the compressor unit's shutdown / start-up process. The control module executes corresponding protection schemes for the operating unit and the shutdown / start-up units based on the distribution of the motor operating points in a pre-designed control diagram; or, based on the relationship between the motor speed of the shutdown / start-up units and a preset speed, it controls the motor speed reduction rate of the shutdown unit / motor speed increase rate of the start-up unit, as well as the anti-surge valve rate.

[0133] During the compressor unit's reduction and shutdown process, the operating point of the running unit's motor is recorded as the first motor operating point, and the pre-made control diagram is recorded as the first control diagram; the horizontal axis of the first motor operating point is the motor speed of the running unit, and the vertical axis is the motor current of the running unit; the horizontal axis of the first control diagram is the motor speed, and the vertical axis is the motor current, including multiple load distribution lines and multiple current distribution lines;

[0134] During the compressor unit start-up process, the operating point of the motor of the running unit is recorded as the second motor operating point, and the pre-made control diagram is recorded as the second control diagram. The horizontal axis of the second motor operating point is the motor speed of the running unit, and the vertical axis is the compressor outlet manifold pressure. The horizontal axis of the second control diagram is the motor speed, and the vertical axis is the compressor outlet manifold pressure, including multiple pressure distribution lines.

[0135] This invention also provides a protection and control device for the start-up, de-starting, and shutdown process of a natural gas long-distance pipeline compressor, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the protection and control method for the start-up, de-starting, and shutdown process of the natural gas long-distance pipeline compressor provided by the above-mentioned technical solution.

[0136] The embodiments of the present invention realize overpressure protection of the outlet pressure during the compressor start-up process and overcurrent protection of the motor current during the compressor shutdown process. It can predict abnormal conditions of outlet pressure and motor current and perform protection control in advance to prevent the abnormal conditions of the compressor unit from further expanding, avoid emergency shutdown of the compressor unit, and ensure the safe and stable operation of the compressor and pipeline network.

[0137] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described apparatus and unit can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0138] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0139] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of the present invention, depending on actual needs.

[0140] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0141] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0142] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A protection and control method for the start-up, de-starting, and shutdown process of a compressor in a long-distance natural gas pipeline, characterized in that, include: During the compressor unit's shutdown / start-up process, the operating point of the motor of the operating unit is monitored. Based on the distribution of the motor operating point in the pre-made control diagram, corresponding protection schemes are implemented for the operating unit and the shutdown / start-up unit. Alternatively, based on the relationship between the motor speed of the reduced / increased-start unit and the preset speed, the rate of decrease of the motor speed of the reduced / increased-start unit and the rate of opening / closing of the anti-surge valve can be controlled. During the compressor unit's reduction and shutdown process, the operating point of the motor of the operating unit is recorded as the first motor operating point, and the pre-made control diagram is recorded as the first control diagram; the horizontal axis of the first motor operating point is the motor speed of the operating unit, and the vertical axis is the motor current of the operating unit; the horizontal axis of the first control diagram is the motor speed, and the vertical axis is the motor current, including multiple load distribution lines and multiple current distribution lines; During the compressor unit start-up process, the operating point of the motor of the operating unit is recorded as the second motor operating point, and the pre-made control diagram is recorded as the second control diagram; the horizontal axis of the second motor operating point is the motor speed of the operating unit, and the vertical axis is the compressor outlet manifold pressure; the horizontal axis of the second control diagram is the motor speed, and the vertical axis is the compressor outlet manifold pressure, including multiple pressure distribution lines.

2. The method for protection and control of the start-up and shutdown process of a natural gas long-distance pipeline compressor according to claim 1, characterized in that, The step of implementing corresponding protection schemes for operating units and units that have been reduced or stopped / operating units and units that have been increased or increased in operation, based on the distribution of the motor operating points in the pre-designed control diagram, includes: When the motor operating point is located within the control area of ​​multiple load distribution lines in the pre-designed control diagram, the motor speed and / or inlet valve position of the operating unit are controlled until the motor operating point is located to the lower right of the protection load line in the pre-designed control diagram; When the motor operating point is located within the control area of ​​multiple current distribution lines in the pre-designed control diagram, the motor speed and / or inlet valve position of the operating unit are controlled until the motor operating point is located below the protection current line in the pre-designed control diagram; and the motor speed reduction rate and anti-surge valve opening rate of the shutdown unit are controlled according to the distribution position of the motor operating point in the pre-designed control diagram. When the motor operating point is located within the control area of ​​multiple pressure distribution lines in the pre-designed control diagram, the motor speed and / or anti-surge valve position of the operating unit are controlled until the motor operating point is located below the protection pressure line in the pre-designed control diagram; and the motor speed ramp-up rate and anti-surge valve closing rate of the start-up unit are controlled according to the distribution position of the motor operating point in the pre-designed control diagram. The multiple load distribution lines include, from left to right, a limit load line, a protection load line, and a control load line; the multiple current distribution lines include, from top to bottom, a limit current line, a protection current line, and a control current line; and the multiple pressure distribution lines include, from top to bottom, a limit pressure line, a protection pressure line, and a control pressure line.

3. The method for protection and control of the start-up and shutdown process of a natural gas long-distance pipeline compressor according to claim 2, characterized in that, When the motor operating point is located within the control area of ​​multiple load distribution lines in the pre-designed control diagram, the control of the motor speed and / or inlet valve position of the operating unit includes: When the motor operating point is located in the first load control area, the motor speed of the control unit is kept constant at the current value. The range of the first load control area is [control load line, protection load line); When the motor operating point touches the protective load line, the motor speed of the operating unit is reduced by a first preset value; if the motor operating point moves into the first load control area within a first preset time period, the control method for the first load control area is executed; if the motor operating point remains within the second load control area within the first preset time period, the motor speed of the operating unit is reduced by a second preset value every first preset time period until the motor operating point moves into the first load control area; wherein, the range of the second load control area is [protective load line, extreme load line]; When the motor operating point touches the limit load line, the motor speed of the operating unit is reduced by a third preset value and the inlet valve opening is reduced by a first preset value. If the motor operating point moves into the second load control area within a second preset time period, the control method for the second load control area is executed. If the motor operating point remains within the third load control area within the second preset time period, the motor speed of the operating unit is reduced by a fourth preset value and the inlet valve opening is reduced by a second preset value every second preset time period, alternating until the motor operating point moves into the second load control area, at which point the control method for the second load control area is executed. The range of the third load control area is [limit load line, above and to the left of the limit load line]. Among them, the first preset value is greater than the second preset value, the third preset value is greater than the fourth preset value, and the first preset opening degree is greater than the second preset opening degree; during the valve position opening degree control of the inlet valve, the valve position opening degree is not lower than the preset valve position opening degree.

4. The method for protection and control of the start-up and shutdown process of a natural gas long-distance pipeline compressor according to claim 2, characterized in that, When the motor operating point is located within the control area of ​​multiple current distribution lines in the pre-designed control diagram, the control of the motor speed and / or inlet valve position of the operating unit includes: When the motor operating point is in the first current control region, the motor speed of the control unit is kept constant at the current value. The range of the first current control region is [control current line, protection current line); When the motor operating point touches the protection current line, the motor speed of the operating unit is reduced by a fifth preset value; if the motor operating point moves into the first current control region within a third preset time period, the control method for the first current control region is executed; if the motor operating point remains within the second current control region within the third preset time period, the motor speed of the operating unit is reduced by a sixth preset value every third preset time period until the motor operating point moves into the first current control region; wherein, the range of the second current control region is [protection current line, limit current line); When the motor operating point touches the limit current line, the motor speed of the operating unit is reduced by a seventh preset value and the inlet valve opening is reduced by a third preset value. If the motor operating point moves into the second current control region within a fourth preset time period, the control method of the second current control region is executed. If the motor operating point remains within the third current control region within the fourth preset time period, the motor speed of the operating unit is reduced by an eighth preset value and the inlet valve opening is reduced by a fourth preset value every fourth preset time period until the motor operating point moves into the second current control region, at which point the control method of the second current control region is executed. The range of the third current control region is [limit current line, above the limit current line]. Among them, the fifth preset value is greater than the sixth preset value, the seventh preset value is greater than the eighth preset value, and the third preset opening degree is greater than the fourth preset opening degree; during the valve position opening degree control process of the inlet valve, the valve position opening degree is not lower than the preset valve position opening degree.

5. The method for protection and control of the start-up, de-starting, and shutdown process of a natural gas long-distance pipeline compressor according to claim 2, characterized in that, When the motor operating point is located within the control area of ​​multiple pressure distribution lines in the pre-designed control diagram, the control of the motor speed and / or anti-surge valve position of the operating unit includes: When the motor operating point is located in the first pressure control zone, the motor speed of the control unit is kept constant at the current value. The range of the first pressure control zone is [control pressure line, protection pressure line]. When the motor operating point touches the protection pressure line, the motor speed of the operating unit is reduced by a ninth preset value; if the motor operating point moves into the first pressure control area within a fifth preset time period, the control method for the first pressure control area is executed; if the motor operating point remains within the second pressure control area within the fifth preset time period, the motor speed of the operating unit is reduced by a tenth preset value every fifth preset time period until the motor operating point moves into the first pressure control area; wherein, the range of the second pressure control area is [protection pressure line, limit pressure line]; When the motor operating point touches the limit pressure line, the motor speed of the operating unit is reduced by an eleventh preset value and the anti-surge valve opening is increased by a fifth preset value. If the motor operating point moves into the second pressure control area within a sixth preset time period, the control method of the second pressure control area is executed. If the motor operating point remains within the third pressure control area within the sixth preset time period, the motor speed of the operating unit is reduced by a twelfth preset value and the anti-surge valve opening is increased by a sixth preset value every sixth preset time period until the motor operating point moves into the second pressure control area, at which point the control method of the second pressure control area is executed. The range of the third pressure control area is [limit pressure line, above and to the left of the limit pressure line]. Among them, the ninth preset value is greater than the tenth preset value, the eleventh preset value is greater than the twelfth preset value, and the fifth preset opening degree is greater than the sixth preset opening degree.

6. The method for protection and control of the start-up, de-starting, and shutdown process of a natural gas long-distance pipeline compressor according to claim 2, characterized in that, The control of the motor speed reduction rate and anti-surge valve opening rate of the unit based on the distribution position of the motor operating point in the pre-made control diagram includes: When the operating point of the motor of at least one operating unit touches the control current line or runs between the control current line and the protection current line, and the operating point of the motor of no operating unit runs on or above the protection current line, the speed reduction rate of the motor of the unit to be stopped will be reduced from the first speed reduction rate to the second speed reduction rate. When the operating point of the motor of at least one operating unit touches the protection current line or runs between the protection current line and the limit current line, and the operating point of the motor of no operating unit runs at or above the limit current line, the speed reduction rate of the motor of the unit to be stopped will be reduced from the second speed reduction rate to the third pre-reduction rate, and the opening rate of the anti-surge valve will be reduced from the first opening rate to the second opening rate. When the operating point of the motor of at least one operating unit touches the limit current line or runs above the limit current line, the current speed of the unit to be reduced or stopped and the opening of the anti-surge valve should be kept unchanged.

7. The method for protection and control of the start-up, de-starting, and shutdown process of a natural gas long-distance pipeline compressor according to claim 2, characterized in that, The control of the motor speed ramp-up rate and anti-surge valve closing rate of the booster unit based on the distribution position of the motor operating point in the pre-made control diagram includes: When the motor operating point of at least one operating unit touches the control current line or runs between the control current line and the protection current line, and the motor operating point of no operating unit runs on or above the protection current line, the motor speed acceleration rate of the additional starting unit will be reduced from the first acceleration rate to the second acceleration rate. When the operating point of the motor of at least one operating unit touches the protection current line or runs between the protection current line and the limit current line, and the operating point of the motor of no operating unit runs at or above the limit current line, the speed increase rate of the starting unit motor will be reduced from the second speed increase rate to the third speed increase rate, and the valve closing rate of the anti-surge valve will be reduced from the first valve closing rate to the second valve closing rate. When the operating point of the motor of at least one operating unit touches the limit current line or runs above the limit current line, the current speed of the additional starting unit and the opening of the anti-surge valve remain unchanged.

8. The method for protection and control of the start-up and shutdown process of a natural gas long-distance pipeline compressor according to any one of claims 1 to 7, characterized in that, The control of the motor speed reduction rate of the shutdown unit / motor speed increase rate of the start-up unit and the anti-surge valve opening / closing rate, based on the relationship between the motor speed of the shutdown / start-up unit and the preset speed, includes: When the motor speed of the unit that is stopped / started is greater than or equal to the first speed threshold, the motor speed reduction rate of the unit that is stopped / the motor speed increase rate of the unit that is started is controlled to be the third increase / decrease rate, and the opening / closing rate of the anti-surge valve is the third opening / closing rate. When the motor speed of the unit that is stopped / started is between the first and second speed thresholds of the rated speed, the motor speed reduction rate of the unit that is stopped / the motor speed acceleration rate of the unit that is started is the second acceleration / deceleration rate, and the opening / closing rate of the anti-surge valve is the fourth opening / closing rate. When the motor speed of the unit that is reduced off / increased on is between the second speed threshold of the rated speed and zero, the motor speed reduction rate of the unit that is reduced off / increased on is the first speed increase / decrease rate, and the opening / closing rate of the anti-surge valve is the fifth opening / closing rate. Among them, the first speed threshold is greater than the second speed threshold, the third acceleration / deceleration rate is less than the second acceleration / deceleration rate, the second acceleration / deceleration rate is less than the first acceleration / deceleration rate, the third valve opening / closing rate is less than the fourth valve opening / closing rate, and the fourth valve opening / closing rate is less than the fifth valve opening / closing rate.

9. The method for protection and control of the start-up, de-starting, and shutdown process of a natural gas long-distance pipeline compressor according to claim 2, characterized in that, Also includes: Using the centrifugal compressor's maximum operating flow rate and maximum pressure ratio as test loads, multiple sets of motor current values ​​were measured at the lower limit of motor operating speed, the upper limit of motor operating speed, and the motor operating speed range. The measured data points were plotted on a coordinate system with motor speed as the abscissa and motor current as the ordinate. The plotted data points were then connected to obtain the centrifugal compressor's limit load line. The motor current value at the data point on the limit load line was taken as the minimum value among the motor current values ​​obtained with the maximum operating flow rate and maximum pressure ratio as test loads at the same speed. The test load is obtained by multiplying the maximum operating flow rate of the centrifugal compressor by the first coefficient and the first coefficient of the maximum pressure ratio, respectively, and obtaining the protection load line according to the method of obtaining the ultimate load line; or, with the ultimate load line as the reference, keeping the motor current obtained from the ultimate load test unchanged, the protection load line is obtained by multiplying the motor speed by the first margin coefficient. The protection load line is obtained by using the second coefficient of the maximum operating flow rate of the centrifugal compressor and the second coefficient of the maximum pressure ratio as test loads, respectively, and obtaining the protection load line in the same way as obtaining the limit load line; or, with the limit load line as the reference, keeping the motor current obtained from the limit load test unchanged, the motor speed is multiplied by the second margin coefficient to obtain the protection load line of the centrifugal compressor. Among them, the second coefficient is less than the first coefficient, and both the first and second coefficients are less than 1; the second margin coefficient is greater than the first margin coefficient, and both the first and second margin coefficients are greater than 1.

10. The method for protection and control of the start-up and shutdown process of a natural gas long-distance pipeline compressor according to claim 2, characterized in that, Also includes: The limiting current line is determined by multiplying the motor's rated current by the first current coefficient. The protection current line is determined by multiplying the motor's rated current by the second current coefficient. The rated current of the motor is used as the control current line; wherein, the first current coefficient is greater than the second current coefficient, and both the first current coefficient and the second current coefficient are greater than 1.

11. The method for protection and control of the start-up and shutdown process of a natural gas long-distance pipeline compressor according to claim 2, characterized in that, Also includes: Set the compressor outlet manifold pressure as the first pressure value to obtain the ultimate pressure line; Set the compressor outlet manifold pressure to the second pressure value to obtain the protection pressure line; The compressor outlet manifold pressure is set as the third pressure value to obtain the control pressure line; wherein the first pressure value is greater than the second pressure value, and the second pressure value is greater than the third pressure value.

12. A protection and control device for the start-up, de-starting, and shutdown process of a natural gas long-distance pipeline compressor, characterized in that, include: The monitoring module is used to monitor the operating point of the motor of the operating unit during the compressor unit's shutdown / start-up process; The control module is used to execute corresponding protection schemes for the operating units and the reduced-stop units / operating units and the increased-start units according to the distribution of the motor operating points in the pre-made control diagram; Alternatively, based on the relationship between the motor speed of the reduced / increased-start unit and the preset speed, the rate of decrease of the motor speed of the reduced / increased-start unit and the rate of opening / closing of the anti-surge valve can be controlled. During the compressor unit's reduction and shutdown process, the operating point of the motor of the operating unit is recorded as the first motor operating point, and the pre-made control diagram is recorded as the first control diagram; the horizontal axis of the first motor operating point is the motor speed of the operating unit, and the vertical axis is the motor current of the operating unit; the horizontal axis of the first control diagram is the motor speed, and the vertical axis is the motor current, including multiple load distribution lines and multiple current distribution lines; During the compressor unit start-up process, the operating point of the motor of the operating unit is recorded as the second motor operating point, and the pre-made control diagram is recorded as the second control diagram; the horizontal axis of the second motor operating point is the motor speed of the operating unit, and the vertical axis is the compressor outlet manifold pressure; the horizontal axis of the second control diagram is the motor speed, and the vertical axis is the compressor outlet manifold pressure, including multiple pressure distribution lines.

13. A protection and control device for the start-up, de-start-up, and shutdown process of a natural gas long-distance pipeline compressor, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the protection and control method for the start-up and shutdown process of the natural gas long-distance pipeline compressor as described in any one of claims 1 to 11.

Images