A large centrifugal natural gas compressor unit land low pressure load simulation test method suitable for offshore oil and gas fields

Abstract

The present application relates to the technical field of ocean engineering, in particular to a large centrifugal natural gas compressor unit land low pressure load simulation test method suitable for offshore oil and gas fields, which comprises the following steps: obtaining real-time offshore air pressure simulation data through a sensor, and pre-processing the collected offshore air pressure simulation data; constructing a low pressure test environment based on the offshore air pressure simulation data obtained in S1; testing the compressor based on the valve opening degree, and optimizing the test by considering the influence of humidity on the test; setting power-off protection through Bang-Bang control for protecting the circuit from electrical faults. In the method, the overall performance of the compressor unit is evaluated from the aspects of efficiency, vibration and temperature rise by establishing a comprehensive performance score, solving the problem that a single index cannot comprehensively evaluate the running health condition of the equipment.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and more specifically, to a method for simulating low-pressure load testing of large centrifugal natural gas compressor units on land, applicable to offshore oil and gas fields. Background Technology

[0002] A compressor unit is a device used to compress gas, mainly composed of a motor, a transmission wheel, and a compressor. For offshore oil and gas extraction facilities, the compressor unit pressurizes the extracted natural gas for storage and export. Typically, after drilling, the compressor unit should be immediately operational for production; therefore, after installation, the compressor unit needs to undergo startup and operational testing to ensure the entire system meets the actual offshore operational requirements. However, large natural gas compressor units lack sufficient high-flow-rate natural gas for onshore testing; therefore, air is used as the medium, and back pressure is increased at the compressor outlet to meet testing requirements. Without natural gas, sealing and isolation gases also cannot function properly; therefore, line modifications and the use of alternative gases are necessary to meet operational requirements.

[0003] However, in practice, testing large compressor units directly at sea is costly, risky, and has poor repeatability. Therefore, this paper proposes a method for simulating low-pressure load testing of large centrifugal natural gas compressor units on land, suitable for offshore oil and gas fields. Summary of the Invention

[0004] The purpose of this invention is to provide a land-based low-pressure load simulation test method for large centrifugal natural gas compressor units suitable for offshore oil and gas fields, so as to solve the problems of high cost, high risk and poor repeatability of directly testing large compressor units at sea as mentioned in the background art.

[0005] To achieve the above objectives, the present invention aims to provide a method for simulating low-pressure load onshore testing of large centrifugal natural gas compressor units suitable for offshore oil and gas fields, comprising the following steps:

[0006] S1. Real-time acquisition of simulated marine air pressure data through sensors, and preprocessing of the collected simulated marine air pressure data;

[0007] S2. Construct a low-pressure test environment based on the marine pressure simulation data obtained in S1;

[0008] S3. The compressor is tested based on the valve opening degree. The test is optimized considering the influence of humidity on the test.

[0009] S4. Power failure protection is set via Bang-Bang control to protect the circuit from electrical faults.

[0010] As a further improvement to this technical solution, in S1, the marine pressure simulation data includes pressure data, temperature data, gas flow velocity data, and environmental meteorological data.

[0011] As a further improvement to this technical solution, in step S1, simulated marine air pressure data is acquired in real time through sensors, and the collected simulated marine air pressure data is preprocessed. The specific steps of the preprocessing operation are as follows:

[0012] S1.1 Identify and remove outliers using statistical methods, and fill in missing values ​​using interpolation.

[0013] S1.2. Based on S1.1, the marine pressure simulation data reduces the impact of noise on the measurement through low-pass filtering technology;

[0014] S1.3. Based on the filtered marine pressure simulation data, Z-Score normalization is performed to convert data of different scales to the same range.

[0015] As a further improvement to this technical solution, the specific steps in S2 for constructing a low-pressure test environment based on the marine pressure simulation data obtained in S1 are as follows:

[0016] S2.1 Calculate the mean value based on preprocessed marine pressure simulation data and standard deviation And through the mean and standard deviation Define the target air pressure value P target ;

[0017] S2.2 Construct a low-voltage test environment based on a PID controller and set upper and lower limits for the PID controller;

[0018] S2.3 The control output signal u(t) obtained based on S2.2 adjusts the valve opening L through the equal percentage flow characteristic.

[0019] As a further improvement to this technical solution, the specific steps for testing the compressor based on the valve opening in step S3 are as follows:

[0020] S3.1. Based on the valve opening, a loop test is performed on the compressor. Considering the influence of humidity on the loop test, the loop test is optimized.

[0021] S3.2. Perform functional tests on the compressor based on valve opening. Considering the impact of humidity on the functional tests, optimize the functional tests.

[0022] As a further improvement to this technical solution, the specific steps in S3.1 for performing a loop test on the compressor based on the valve opening are as follows:

[0023] S3.1.1. The valve opening L is converted into the compressor outlet natural gas pressure value P through the equal percentage characteristic. out (Q);

[0024] S3.1.2. Based on the pressure value obtained in S3.1.1, a dynamic model of the compression system is established using the laws of conservation of mass, energy, and the gas law of state. The Runge-Kutta method is then used to solve the equations. The mathematical expression for establishing the dynamic model of the compression system is:

[0025]

[0026] In the formula, Indicates the rate of change of inlet pressure; This indicates the rate of change in export pressure; P represents the rate of change in natural gas flow rate; in (t) represents the inlet pressure; V in a3 represents the inlet volume; a4 represents the coefficient of influence of flow rate on outlet pressure change; a5 represents the coefficient of influence of control signal on outlet pressure change; T(t) represents the natural decay coefficient of outlet pressure; T represents the gas temperature; T in Indicates the inlet temperature; Q in (t) represents the inflow rate; C v (L(t)) represents the valve's flow capacity; ρ represents the gas density.

[0027] As a further improvement to this technical solution, in step S3.1, considering the impact of humidity on the loop test, the specific steps for optimizing the loop test are as follows:

[0028] Calculate the partial pressure of water vapor P based on the effect of humidity on air pressure. v ;

[0029] Based on the dry air molar mass M a With water vapor molar mass M w Calculate the corrected ideal gas constant R eff (t);

[0030] The optimized control signal u(t) is obtained by optimizing the control signal u(t) based on the partial pressure of water vapor. total (t);

[0031] Based on water vapor partial pressure, the optimized control signal u total (t) If the dynamic model of the compression system is optimized, the mathematical expression of the optimized dynamic model of the compression system is:

[0032]

[0033] in,

[0034]

[0035] In the formula, This represents the optimized rate of change of inlet pressure; This represents the optimized rate of change in export pressure; This represents the optimized rate of change in natural gas flow rate; This indicates the rate of change of air temperature within the system; The mass mixing ratio of water vapor in the air represents the rate of change; ρ′(t) represents the density of moist air; c p The specific heat capacity at constant pressure is represented by m(t); the air mass in the system is represented by W. set (t) represents the motor output power set at time t; Indicates the rate at which heat enters the system; W nom Indicates the rated power of the compressor unit; This indicates the rate at which the system loses heat. Indicates the mass mixing ratio of water vapor; T c a0 represents the length of a complete load cycle; a1 represents the ratio of the base load to the rated power; a2 represents the amplitude coefficient of the sine term; and a1 represents the amplitude coefficient of the cosine term.

[0036] As a further improvement to this technical solution, the specific steps in S3.2 for performing functional testing of the compressor based on the valve opening degree are as follows:

[0037] S3.2.1. Based on thermodynamics and fluid mechanics, construct an output pressure model to obtain the theoretical output pressure P. theo (L,Q,T);

[0038] S3.2.2 Calculate the deviation ΔP between the actual output pressure and the theoretical output pressure based on the output pressure model obtained in S3.2.1.

[0039] As a further improvement to this technical solution, in step S3.2, considering the impact of humidity on functional testing, the specific steps for optimizing the functional test are as follows:

[0040] By incorporating the humid air density ρ′(t) into the output pressure model and correcting the theoretical output pressure value, we obtain the humidity-corrected theoretical output pressure P. theohumid (L,Q,T,RH), then the corrected theoretical output pressure P theohumid The mathematical expression for (L,Q,T,RH) is:

[0041]

[0042] in,

[0043] In the formula, P theohumid (L,Q,T,RH) represents the theoretical output pressure after humidity correction; β(RH) represents the humidity correction factor; γ represents the humidity influence coefficient.

[0044] Calculate the deviation ΔP between the actual output pressure and the theoretical value after humidity correction. humid Then calculate the deviation ΔP between the actual output pressure and the humidity-corrected theoretical value. humid The mathematical expression is:

[0045]

[0046] In the formula, ΔP humid This indicates the deviation between the actual output pressure and the theoretical value after humidity correction.

[0047] As a further improvement to this technical solution, in step S4, the specific steps for setting power-off protection through Bang-Bang control to protect the circuit from the effects of electrical faults are as follows:

[0048] Based on the equipment's rated operating power and safety margin, a maximum compressor outlet pressure is set. When the compressor outlet pressure exceeds the maximum compressor outlet pressure, a short circuit risk is considered to exist, and the power-off mechanism will be triggered immediately to quickly cut off the compressor's power supply to prevent further energy input from causing more serious damage or fire.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0050] 1. In this method for simulating low-pressure load on land for large centrifugal natural gas compressor units applicable to offshore oil and gas fields, the operating status of the offshore compressor under different load levels is simulated by setting the periodic motor output power, thereby enhancing the realism of the test and solving the problem that a single constant load cannot reflect the fluctuating operating conditions in actual operation.

[0051] 2. In the land low-pressure load simulation test method for large centrifugal natural gas compressor units applicable to offshore oil and gas fields, a comprehensive performance score is established to evaluate the overall performance of the compressor unit from three aspects: efficiency, vibration, and temperature rise, which solves the problem that a single indicator cannot comprehensively evaluate the health status of the equipment operation.

[0052] 3. In this method for simulating low-pressure load on land for large centrifugal natural gas compressor units applicable to offshore oil and gas fields, the comprehensive score is optimized by introducing a humidity factor, taking into account the influence of humidity on the compression process, improving the accuracy of performance evaluation, and solving the problem that changes in gas density under high humidity conditions can affect compression efficiency and cooling performance. Attached Figure Description

[0053] Figure 1 This is a flowchart of the overall method of the present invention. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Example: Please refer to Figure 1 As shown, this embodiment provides a method for simulating low-pressure load onshore testing of large centrifugal natural gas compressor units suitable for offshore oil and gas fields, including the following steps:

[0056] S1. Real-time acquisition of simulated marine air pressure data through sensors, and preprocessing of the collected simulated marine air pressure data.

[0057] Before formal testing, ensure that the compressor unit is installed and obtain the corresponding compressor unit installation inspection report.

[0058] In this embodiment S1, the marine pressure simulation data includes pressure data, temperature data, gas flow velocity data, and environmental meteorological data.

[0059] In this embodiment S1, simulated marine air pressure data is acquired in real time through sensors, and the collected simulated marine air pressure data is preprocessed. The specific steps of the preprocessing operation are as follows:

[0060] S1.1 Identify and remove outliers using statistical methods, and fill in missing values ​​using interpolation.

[0061] S1.2. Based on S1.1, the marine pressure simulation data reduces the impact of noise on the measurement through low-pass filtering technology;

[0062] S1.3. Based on the filtered marine pressure simulation data, Z-Score normalization is performed to convert data of different scales to the same range.

[0063] S2. Construct a low-pressure test environment based on the marine air pressure simulation data obtained from S1.

[0064] An opening is made at a suitable position at the compressor inlet to allow air to enter the compressor as a compression medium. A flow-limiting orifice plate is designed and installed at the discharge line to increase the compressor outlet back pressure, thereby preventing compressor surge that may be caused by low inlet air pressure. Low-pressure air test conditions are established, and a dedicated silencer is further installed at the compressor discharge terminal to reduce compressor operating noise.

[0065] In this embodiment S2, the specific steps for constructing a low-pressure test environment based on the marine pressure simulation data obtained in S1 are as follows:

[0066] S2.1 Calculate the mean value based on preprocessed marine pressure simulation data and standard deviation And through the mean and standard deviation Define the target air pressure value P target Then calculate the mean. The mathematical expression is:

[0067]

[0068] In the formula, T represents the average sea surface pressure; time Represents the total number of time steps; t represents the time index; P sea (t) represents the sea pressure at time t;

[0069] Calculate the standard deviation The mathematical expression is:

[0070]

[0071] In the formula, Indicates the standard deviation of sea pressure;

[0072] Define the target air pressure value P target The mathematical expression is:

[0073]

[0074] In the formula, P target Indicates the target air pressure value, used to construct a low-pressure test environment; k control The coefficient representing the degree of control deviation is given based on historical extreme air pressure data, and its value range is 1 to 3;

[0075] S2.2. A low-voltage test environment is constructed based on a PID controller, and upper and lower limits are set for the PID controller. The mathematical expression for constructing a low-voltage test environment based on a PID controller is:

[0076]

[0077] In the formula, e(t) = P target -P measured (t);

[0078] In the formula, u(t) represents the control output signal, which is the control quantity calculated by the PID controller based on the error, used to adjust the system and change its current air pressure state; Kp K represents the proportional term, which adjusts the controller output based on the current error e(t); i K represents the integral term, which adjusts the controller output based on the accumulated error; d The differential term is represented by e(t), which adjusts the controller output according to the rate of change of the error; e(t) represents the error signal, which is the difference between the actual air pressure and the target air pressure at the current moment, used to drive the controller action; P measured (t) represents the actual measured air pressure value, which is the current air pressure value monitored in real time by the system and is used as feedback input to the controller;

[0079] The mathematical expressions for setting the upper and lower limits of the PID controller output signal are as follows:

[0080] u min ≤u(t)≤u max ;

[0081] In the formula, u min Indicates the lower limit of the output signal; u max Indicates the upper limit of the output signal;

[0082] The mathematical expression for setting the upper and lower limits of the integral term is:

[0083]

[0084] In the formula, I min I represents the lower limit of the integral term; max Indicates the upper limit of the integral term;

[0085] S2.3. Based on the control output signal u(t) obtained in S2.2, the valve opening L is adjusted through the equal percentage flow characteristic. Then, the mathematical expression for adjusting the valve opening by converting the output signal u(t) into the output signal u(t) is:

[0086]

[0087] In the formula, L represents the valve opening degree; R represents the adjustable ratio, which is the ratio of the maximum flow rate to the minimum flow rate, and the value range is R≥50.

[0088] Calculate the required dry gas sealing volume for the test, and prepare a liquefied nitrogen tank based on the calculation results. Ensure that the liquefied nitrogen tank has sufficient gas volume to meet the test requirements. Once ready, place the liquefied nitrogen tank in a suitable location under the ship / platform.

[0089] The gas supply line of the compressor's dry gas sealing disc is modified by using a temporary hose to connect to a liquefied nitrogen tank as the gas source for the dry gas sealing disc. At the same time, the dry gas sealing disc shutdown signal is bypassed so that it can continue to work normally. The pressure difference control valve is used to adjust the pressure difference between the sealing gas and the medium gas (air) to keep it sufficient and stable, ensuring that the dry gas sealing disc works normally.

[0090] Instrument gas that meets dew point control requirements on board / platform is used as the compressor isolation gas source. The pressure is controlled to a suitable pressure using a pressure control valve, and then the corresponding pipeline is connected to allow it to enter the compressor.

[0091] Inspect all subsystems of the compressor unit, including: compressor unit, lubricating oil system, instrument gas system, nitrogen system, cooling water system, fire protection system, instrument system, and venting system, to ensure that each subsystem is working properly.

[0092] S3. The compressor is tested based on the valve opening degree. The test is optimized considering the influence of humidity on the test.

[0093] In this embodiment S3, the specific steps for testing the compressor based on the valve opening degree are as follows:

[0094] S3.1. Based on the valve opening, a loop test is performed on the compressor. Considering the influence of humidity on the loop test, the loop test is optimized.

[0095] S3.2. Perform functional tests on the compressor based on valve opening. Considering the impact of humidity on the functional tests, optimize the functional tests.

[0096] Use signal generators, frequency generators, and other equipment to simulate the signals of the instruments inside the compressor unit skid to perform loop tests on the control panel; perform operational function tests on the compressor, including compressor start-up function tests, stop function tests, and compressor safety protection function tests; start the auxiliary lubricating oil pump and confirm that the rotation direction, starting current, operating current, vibration, noise, and operating functions are normal, and confirm that the oil return of each bearing is normal; start the motor, ensure that the motor rotation direction is correct, and after confirming that it is correct, keep the motor running continuously for 120 minutes, and confirm that the key indicators of the unit, such as starting current, voltage, motor speed, motor operating status, and bearing vibration, are normal.

[0097] In this embodiment S3.1, the specific steps for performing a loop test on the compressor based on the valve opening are as follows:

[0098] S3.1.1. The valve opening L is converted into the compressor outlet natural gas pressure value P through the equal percentage characteristic. out (Q), then the mathematical expression for converting the valve opening L into flow rate Q(t) is:

[0099] Q(t) = R L-1 ·Q max ;

[0100] In the formula, Q(t) represents the actual flow rate; Q max This indicates the maximum flow rate at the valve's maximum opening.

[0101] Convert the flow rate Q(t) into the outlet pressure P. out (Q), then the flow rate Q(t) is converted into the outlet pressure P. out The mathematical expression for (Q) is:

[0102] P out (Q)=aQ(t) 3 +bQ(t) 2 +cQ(t)+d;

[0103] In the formula, P out (Q) represents the compressor outlet pressure; a represents the coefficient of the cubic term of the control curve, reflecting the effect of flow rate Q(t) on outlet pressure P. out The nonlinear effect of (Q) is usually related to the aerodynamic characteristics of the compressor (such as impeller efficiency and gas flow loss), and its value ranges from -10. -6 ~-10 -3 ; b represents the quadratic coefficient of the control curve, adjusting the curvature of the curve, with a value ranging from 10. -3 ~10 -1 ;c represents the coefficient of the first-order term of the control curve, reflecting the linear effect of flow rate Q(t) on outlet pressure, with a value range of -10. -1 ~10 -1 d represents the outlet pressure when the flow rate Q(t) = 0, and its value ranges from 10. 1 ~10 2 ;

[0104] S3.1.2. Based on the pressure value obtained in S3.1.1, a dynamic model of the compression system is established using the laws of conservation of mass, energy, and the gas law of state. The Runge-Kutta method is then used to solve the equations. The mathematical expression for establishing the dynamic model of the compression system is:

[0105]

[0106] In the formula, Indicates the rate of change of inlet pressure; This indicates the rate of change in export pressure; P represents the rate of change in natural gas flow rate; in (t) represents the inlet pressure; V in T represents the inlet volume; T(t) represents the gas temperature; T in Indicates the inlet temperature; Q in (t) represents the inflow rate; a3 represents the influence coefficient of the flow rate on the outlet pressure change, with a value ranging from 0.1 to 1; a4 represents the influence coefficient of the control signal on the outlet pressure change, with a value ranging from 10 to 100; a5 represents the natural attenuation coefficient of the outlet pressure, with a value ranging from 0.01 to 1; C v(L(t)) represents the valve's flow capacity; ρ represents the gas density.

[0107] In this embodiment S3.1, considering the impact of humidity on the loop test, the specific steps for optimizing the loop test are as follows:

[0108] Calculate the partial pressure of water vapor P based on the effect of humidity on air pressure. v Then calculate the partial pressure of water vapor P. v The mathematical expression is:

[0109] P v =RH·P sat (T);

[0110] In the formula, P v Represents water vapor partial pressure; RH represents relative humidity, with a value range of [0,1]; P sat (T) represents the saturated water vapor pressure at temperature T;

[0111] Based on the dry air molar mass M a With water vapor molar mass M w Calculate the corrected ideal gas constant R eff (t), then calculate the corrected ideal gas constant R. eff The mathematical expression for (t) is:

[0112]

[0113] in,

[0114] In the formula, R eff (t) represents the corrected ideal gas constant; M eff M represents the molar mass of moist air; a This represents the molar mass of dry air, with a value of 28.97 g / mol; M w The value of P represents the molar mass of water vapor, which is 18.02 g / mol; P represents the total pressure, which is the total pressure of dry air and water vapor.

[0115] The optimized control signal u(t) is obtained by optimizing the control signal u(t) based on the partial pressure of water vapor. total (t), then the optimized control signal u total The mathematical expression for (t) is:

[0116] u total (t)=u(t)+u h ;

[0117] Among them, u h =K h ·w v (t);

[0118] In the formula, u total (t) represents the optimized control signal; u h This indicates a feedforward term that adjusts the valve opening in advance to adapt to changes in humidity; K h Indicates the humidity compensation gain coefficient; w v (t) represents the specific humidity of water vapor in the air, and its value ranges from [0 to 0.03].

[0119] Based on water vapor partial pressure, the optimized control signal u total (t) If the dynamic model of the compression system is optimized, the mathematical expression of the optimized dynamic model of the compression system is:

[0120]

[0121] in,

[0122]

[0123] In the formula, This represents the optimized rate of change of inlet pressure; This represents the optimized rate of change in export pressure; This represents the optimized rate of change in natural gas flow rate; This indicates the rate of change of air temperature within the system; The mass mixing ratio of water vapor in the air represents the rate of change; ρ′(t) represents the density of moist air; c p The specific heat capacity at constant pressure is represented by m(t); the air mass in the system is represented by W. set (t) represents the motor output power set at time t; Indicates the rate at which heat enters the system; W nom Indicates the rated power of the compressor unit; This indicates the rate at which the system loses heat. Indicates the mass mixing ratio of water vapor; T c The value represents the length of a complete load cycle; a0 represents the proportion of the base load to the rated power, which is usually not used for full load operation to avoid frequent overload, and its value ranges from 0.6 to 0.95; a1 represents the sine term amplitude coefficient, which is used to simulate periodic load fluctuations, and its value ranges from 0.05 to 0.3; a2 represents the cosine term amplitude coefficient, which is used to simulate higher frequency or asymmetric load fluctuation characteristics, and its value ranges from 0 to 0.2.

[0124] In this embodiment S3.2, the specific steps for performing functional testing on the compressor based on the valve opening degree are as follows:

[0125] S3.2.1. Based on thermodynamics and fluid mechanics, construct an output pressure model to obtain the theoretical output pressure P.theo Given (L,Q,T), the mathematical expression for constructing the output pressure model is:

[0126]

[0127] in,

[0128] In the formula, P theo (L,Q,T) represents the theoretical output pressure; n represents the number of moles; R represents the universal gas constant, with a value of 8.314 J / mol·K; T absolute V represents absolute temperature; A(L) represents the volume of the compression chamber; A(L) represents the flow area function related to the valve opening; k represents the influence index of flow rate on pressure, with a value range of 1.5 to 2; C0 represents the basic pressure ratio offset, which is the minimum boosting capacity of the compressor at zero flow; A max This indicates the maximum flow area when the valve is fully open.

[0129] S3.2.2 Based on the output pressure model obtained in S3.2.1, the deviation ΔP between the actual output pressure and the theoretical output pressure is calculated. The mathematical expression for calculating the deviation between the actual output pressure and the theoretical predicted value is as follows:

[0130] ΔP=P out (Q)-P theo (L,Q,T);

[0131] In the formula, ΔP represents the difference between the actual output pressure and the theoretical pressure.

[0132] In this embodiment S3.2, considering the impact of humidity on functional testing, the specific steps for optimizing the functional testing are as follows:

[0133] By incorporating the humid air density ρ′(t) into the output pressure model and correcting the theoretical output pressure value, we obtain the humidity-corrected theoretical output pressure P. theohumid (L,Q,T,RH), then the corrected theoretical output pressure P theohumid The mathematical expression for (L,Q,T,RH) is:

[0134]

[0135] in,

[0136] In the formula, P theohumid (L,Q,T,RH) represents the theoretical output pressure after humidity correction; β(RH) represents the humidity correction factor, reflecting the influence of humidity on flow rate; γ represents the humidity influence coefficient.

[0137] Calculate the deviation ΔP between the actual output pressure and the theoretical value after humidity correction. humid Then calculate the deviation ΔP between the actual output pressure and the humidity-corrected theoretical value. humid The mathematical expression is:

[0138] ΔP humid =P out (Q)-P theohumid (L,Q,T absolute ,RH);

[0139] In the formula, ΔP humid This indicates the deviation between the actual output pressure and the theoretical value after humidity correction.

[0140] Start the motor and compressor normally as required to conduct a simulated test of the compressor unit. The simulated test time should be at least 120 minutes. During the test, focus on monitoring and recording the bearing temperature, speed, lubricating oil system pressure and compressor outlet pressure to ensure that all parameters of the compressor unit are normal and the operation is stable. If any problems occur, the test should be stopped immediately.

[0141] After the compressor unit simulation test is completed, all pipelines are restored, and all actions before the compressor starts are simulated to ensure that the compressor unit can start normally when it is put into operation at sea.

[0142] S4. Power failure protection is set via Bang-Bang control to protect the circuit from electrical faults.

[0143] In this embodiment S4, the specific steps for setting up power failure protection through Bang-Bang control to protect the circuit from the effects of electrical faults are as follows:

[0144] Based on the equipment's rated operating power and safety margin, a maximum compressor outlet pressure is set. When the compressor outlet pressure exceeds the maximum compressor outlet pressure, a short circuit risk is considered to exist, and the power-off mechanism will be triggered immediately to quickly cut off the compressor's power supply to prevent further energy input from causing more serious damage or fire.

[0145] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for simulating low-pressure load onshore testing of large centrifugal natural gas compressor units suitable for offshore oil and gas fields, characterized in that: Includes the following steps: S1. Real-time acquisition of simulated marine air pressure data through sensors, and preprocessing of the collected simulated marine air pressure data; S2. Construct a low-pressure test environment based on preprocessed marine pressure simulation data to obtain valve opening; S2.1 Calculate the mean value based on preprocessed marine pressure simulation data and standard deviation and through the mean and standard deviation Define target air pressure value ; This represents the average sea pressure. Indicates the standard deviation of sea pressure; S2.2 Construct a low-voltage test environment based on a PID controller, and set upper and lower limits for the PID controller. The mathematical expression for constructing a low-voltage test environment based on a PID controller is: ； In the formula, ; In the formula, This represents the control output signal, which is the control quantity calculated by the PID controller based on the error, used to adjust the system and change its current air pressure state. This represents the proportional term, based on the current error. Adjust the controller output; This represents the integral term, which adjusts the controller output based on the accumulated error. This represents the differential term, which adjusts the controller output based on the rate of change of the error. The error signal represents the difference between the actual air pressure and the target air pressure at the current moment, and is used to drive the controller to act. This represents the actual measured air pressure value, which is the current air pressure value monitored in real time by the system and is used as feedback input to the controller; S2.3, Control output signal obtained based on S2.2 Adjust valve opening by equal percentage flow characteristics. Output signal The mathematical expression for adjusting the valve opening is as follows: ； In the formula, Indicates the valve opening degree; This indicates the adjustable ratio, which is the ratio of the maximum flow rate to the minimum flow rate; S3. The compressor is tested based on the valve opening degree. The test is optimized considering the influence of humidity on the test. S4. Power failure protection is set via Bang-Bang control to protect the circuit from electrical faults.

2. The method for simulating low-pressure load onshore applications of large centrifugal natural gas compressor units suitable for offshore oil and gas fields according to claim 1, characterized in that: In S1, the marine pressure simulation data includes pressure data, temperature data, gas flow velocity data, and environmental meteorological data.

3. The method for simulating low-pressure load onshore applications of large centrifugal natural gas compressor units suitable for offshore oil and gas fields according to claim 1, characterized in that: In step S1, simulated marine air pressure data is acquired in real time via sensors, and the collected simulated marine air pressure data is preprocessed. The specific steps of the preprocessing operation are as follows: S1.1 Identify and remove outliers using statistical methods, and fill in missing values ​​using interpolation. S1.

2. Based on S1.1, the marine pressure simulation data reduces the impact of noise on the measurement through low-pass filtering technology; S1.

3. Based on the filtered marine pressure simulation data, Z-Score normalization is performed to convert data of different scales to the same range.

4. The method for simulating low-pressure load on land for large centrifugal natural gas compressor units applicable to offshore oil and gas fields according to claim 1, characterized in that: In step S3, the specific steps for testing the compressor based on the valve opening are as follows: S3.

1. Based on the valve opening, a loop test is performed on the compressor. Considering the influence of humidity on the loop test, the loop test is optimized. S3.

2. Perform functional tests on the compressor based on valve opening. Considering the impact of humidity on the functional tests, optimize the functional tests.

5. The method for simulating low-pressure load onshore applications of large centrifugal natural gas compressor units suitable for offshore oil and gas fields according to claim 4, characterized in that: In S3.1, the specific steps for performing a loop test on the compressor based on the valve opening are as follows: S3.1.1, Valve opening is adjusted using an equal percentage characteristic. Converted to the pressure value of natural gas at the compressor outlet ; Adjust valve opening Convert into traffic The mathematical expression is: ； In the formula, Indicates actual traffic volume; This indicates the maximum flow rate at the valve's maximum opening. Traffic Converted into export pressure , will traffic Converted into export pressure The mathematical expression is: ； In the formula, Indicates the compressor outlet pressure; The coefficient of the cubic term in the control curve reflects the flow rate. Pressure on exports The nonlinear effect is related to the aerodynamic characteristics of the compressor, and its value range is [value range missing]. ; This represents the quadratic coefficient of the control curve, adjusting the curvature of the curve; its value range is... ; The coefficient of the first term in the control curve reflects the flow rate. The linear effect on export pressure, with a range of values. ; Indicates when the flow The export pressure at that time, the range of values ​​is ; S3.1.

2. Based on the pressure value obtained in S3.1.1, a dynamic model of the compression system is established using the laws of conservation of mass, energy, and the gas law of state. The Runge-Kutta method is then used to solve the equations. The mathematical expression for establishing the dynamic model of the compression system is: ； In the formula, Indicates the rate of change of inlet pressure; This indicates the rate of change in export pressure; Indicates the rate of change in natural gas flow rate; Indicates inlet pressure; Indicates the inlet volume; This represents the coefficient indicating the influence of flow rate on changes in outlet pressure. This represents the coefficient indicating the influence of the control signal on changes in outlet pressure. The natural attenuation coefficient represents the pressure at which exports decrease. Indicates gas temperature; Indicates the inlet temperature; Indicates inflow flow; Indicates the valve's flow capacity; This indicates the density of the gas.

6. The method for simulating low-pressure load onshore applications of large centrifugal natural gas compressor units suitable for offshore oil and gas fields according to claim 5, characterized in that: In step S3.1, considering the impact of humidity on the loop test, the specific steps for optimizing the loop test are as follows: Calculate the partial pressure of water vapor based on the effect of humidity on air pressure. ; Based on dry air molar mass Molar mass of water vapor Calculate the corrected ideal gas constant ; Control signal based on water vapor partial pressure The optimized control signal is obtained through optimization. ; Based on water vapor partial pressure, optimized control signal After optimizing the dynamic model of the compression system, the mathematical expression of the optimized dynamic model of the compression system is: ； in, ; ； In the formula, This represents the optimized rate of change of inlet pressure; This represents the optimized rate of change in export pressure; This represents the optimized rate of change in natural gas flow rate; This indicates the rate of change of air temperature within the system; This indicates the rate of change in the mass mixing ratio of water vapor in the air; Indicates the density of moist air; This indicates the specific heat capacity at constant pressure. Indicates the air quality within the system; Indicates at time The set motor output power; Indicates the rate at which heat enters the system; Indicates the rated power of the compressor unit; This indicates the rate at which the system loses heat. Indicates the mass mixing ratio of water vapor; Indicates the duration of a complete load cycle; This indicates the percentage of base load to rated power; Represents the amplitude coefficient of the sine term; This represents the magnitude coefficient of the cosine term.

7. The method for simulating low-pressure load on land for large centrifugal natural gas compressor units applicable to offshore oil and gas fields according to claim 5, characterized in that: In step S3.2, the specific steps for performing functional testing of the compressor based on valve opening are as follows: S3.2.

1. Based on thermodynamics and fluid mechanics, construct an output pressure model to obtain the theoretical output pressure. ; The mathematical expression for constructing the output pressure model is: ； in, ; In the formula, Indicates the theoretical output pressure; Indicates the number of moles; This represents the universal gas constant, and its value is... ; Indicates absolute temperature; Indicates the volume of the compression chamber; This represents a flow area function related to valve opening. The index representing the impact of flow rate on pressure has a range of values. ; This represents the baseline pressure ratio offset, which is the compressor's minimum boosting capacity at zero flow. This indicates the maximum flow area when the valve is fully open. S3.2.2 Calculate the deviation between the actual output pressure and the theoretical output pressure based on the output pressure model obtained in S3.2.

1. The mathematical expression for calculating the deviation between the actual output pressure and the theoretical predicted value is: ； In the formula, This represents the difference between the actual output pressure and the theoretical pressure.

8. The method for simulating low-pressure load on land for large centrifugal natural gas compressor units applicable to offshore oil and gas fields according to claim 7, characterized in that: In step S3.2, considering the impact of humidity on functional testing, the specific steps for optimizing the functional testing are as follows: density of moist air By incorporating this into the output pressure model and correcting the theoretical output pressure value, we obtain the humidity-corrected theoretical output pressure. The corrected theoretical output pressure The mathematical expression is: ； in, ; In the formula, This represents the theoretical output pressure after humidity correction; Indicates the humidity correction factor; Indicates the humidity influence coefficient; Calculate the deviation between the actual output pressure and the theoretical value after humidity correction. Then calculate the deviation between the actual output pressure and the theoretical value after humidity correction. The mathematical expression is: ； In the formula, This indicates the deviation between the actual output pressure and the theoretical value after humidity correction.

9. The method for simulating low-pressure load on land for large centrifugal natural gas compressor units applicable to offshore oil and gas fields according to claim 1, characterized in that: In step S4, the specific steps for setting up power-off protection via Bang-Bang control to protect the circuit from electrical faults are as follows: Based on the equipment's rated operating power and safety margin, a maximum compressor outlet pressure is set. When the compressor outlet pressure exceeds the maximum compressor outlet pressure, a short circuit risk is considered to exist, and the power-off mechanism will be triggered immediately to quickly cut off the compressor's power supply to prevent further energy input from causing more serious damage or fire.

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