Method and system for stabilizing flow and pressure of multi-branch methanol fuel supply system

Abstract

The invention discloses a flow stabilizing and pressure stabilizing method and system for a multi-branch methanol fuel supply system, and the method comprises the steps: obtaining a total flow actual value and a total flow set value according to actual flow values read by flowmeters installed on all engine branches; according to the total flow actual value and the total flow set value, the adjusted reference control quantity of the frequency of the variable frequency pump is obtained; obtaining an actual pressure value according to readings of a first pressure sensor and a second pressure sensor which are arranged on a main pipeline of an outlet of the variable frequency pump; according to the actual pressure value, the basic control quantity of the proportional valve is obtained; and obtaining a final frequency instruction of the variable frequency pump and a final opening instruction of the proportioning valve according to the adjusted reference control quantity of the frequency of the variable frequency pump and the basic control quantity of the proportioning valve. The control stability of the system is improved, the anti-interference capability of the system is enhanced, and the energy consumption of the system is reduced.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a method and system for stabilizing flow and voltage in a multi-branch methanol fuel supply system. Background Technology

[0002] Problems existing in the technology include hysteresis and fluctuations due to limitations in the control architecture, weak anti-interference capability of fixed-parameter PID controllers, and energy efficiency and equipment wear issues. Among these, the hysteresis and fluctuations caused by limitations in the control architecture include the following:

[0003] 1) Single Control Loop: Traditional systems use only the main pipe flow or pressure as a single feedback variable, controlling the variable frequency pump speed through a single PID loop. From a DCS perspective, this centralized control lacks distributed processing capabilities. When the flow demand of multiple branch motors changes simultaneously, any disturbance in any branch will be transmitted to the variable frequency pump through the main pipe, causing feedback delay. The PLC, when performing PID calculations, has limited sampling periods and processing speeds, making it unable to quickly respond to multi-variable disturbances, leading to frequent adjustments in the variable frequency pump speed and causing system pressure and flow oscillations. 2) Communication Bottleneck: Existing technologies typically use simple I / O modules or low-speed buses (such as 4-20mA analog signals) to acquire data, lacking real-time multi-branch data integration. For example, changes in branch flow cannot be promptly uploaded to the main controller, causing a lag in the PID controller's response and exacerbating fluctuations.

[0004] The weak anti-interference capability of fixed-parameter PID controllers includes the following: 1) Insufficient Adaptability: During ship navigation, operating conditions are complex and variable (such as sudden acceleration of a single branch), and PID controllers with fixed parameters cannot dynamically adjust the gain. From a PLC programming perspective, PID parameters are usually set empirically. Once operating conditions change, the controller is prone to overshoot or slow response, resulting in unstable branch flow. Although DCS supports multi-loop control, it also cannot adapt to sudden load changes without advanced algorithm support.

[0005] 2) Lack of feedforward compensation: Traditional control lacks a feedforward mechanism and cannot predict the impact of branch demand changes on the main pipeline. When branch flow changes abruptly, the PID controller can only correct based on error feedback, resulting in slow response and poor anti-interference capability.

[0006] Energy efficiency and equipment wear issues include the following: 1) Frequent speed adjustments: Under fixed-parameter PID control, variable frequency pumps require frequent and significant speed adjustments. This not only increases energy consumption (the power of a variable frequency pump is cubically related to its speed) but also leads to mechanical stress concentration, accelerating wear on the pump and piping. From a DCS monitoring perspective, the system cannot optimize the pump's operating point, resulting in low energy efficiency. 2) Lack of fault tolerance: Traditional systems often lack sensor redundancy and diagnostic functions. Pressure or flow sensor failures can directly lead to control failure, further increasing energy consumption and equipment risk. Summary of the Invention

[0007] In view of this, this application provides a method and system for stabilizing flow and pressure in a multi-branch methanol fuel supply system.

[0008] This application discloses a method for stabilizing flow and pressure in a multi-branch methanol fuel supply system, which includes: Step 1: Based on the actual flow rate readings from the flow meters installed on each engine branch, obtain the actual total flow rate and the set total flow rate. Step 2: Based on the actual total flow rate and the set total flow rate, obtain the reference control value for the adjusted frequency of the variable frequency pump; Step 3: Obtain the actual pressure value based on the readings of the first and second pressure sensors installed on the main outlet pipe of the variable frequency pump; Step 4: Obtain the basic control quantity of the proportional valve based on the actual pressure value; Step 5: Based on the adjusted frequency reference control quantity of the variable frequency pump and the basic control quantity of the proportional valve, obtain the final frequency command of the variable frequency pump and the final opening command of the proportional regulating valve.

[0009] Further, step 1 includes: Step 11: The controller periodically reads the actual flow value from the flow meters installed on each engine branch; obtains the current demand flow from each engine through the CAN communication bus, and uses the current demand flow as the flow setting value of the branch where the engine is located; Step 12: Perform fusion processing on the traffic data of each branch, using the following formula:

[0010] in: This represents the flow value of the k-th branch after merging in the current cycle. The historical value of the k-th branch after fusion in the previous control cycle, i.e., the FT of the previous cycle. k _Fused;FT k _Raw is the raw flow value collected by the flow meter of the kth branch in the current cycle; w1 is a weighting factor set based on sensor reliability and historical data; Step 13: Based on the head curve of the variable frequency pump and the incompressible fluid model, estimate the theoretical flow rate using the pressure difference before and after the variable frequency pump; cross-validate the sum of the flow rates after fusion of each branch with the theoretical flow rate: if the deviation between the two exceeds the preset range, it is determined that the flow meter may have drift or malfunction, the system automatically reduces the weight w1 of the relevant sensor data in the fusion algorithm, and triggers a maintenance alarm. Step 14: The controller calculates the actual total flow rate of the entire system. and total flow set value .

[0011] Further, step 14 includes: The actual value of the total flow rate can be obtained using the following formula. :

[0012] in, This represents the flow value of the first branch after merging in the current cycle. The traffic value of the nth branch after merging in the current period, where n is the total number of branches in the entire system; The total flow rate setpoint is obtained using the following formula. :

[0013] in, Set the flow rate value for the first branch. Set the flow rate value for the nth branch.

[0014] Further, step 2 includes: Step 21: Input the total flow deviation Error and the rate of change of the total flow deviation dError / dt into the PID controller whose parameters can be dynamically adjusted. The output of the PID controller is Pump_Frequency_Base, which is the reference control quantity of the frequency converter pump frequency. Step 22: Adjust controller parameters: If the absolute value of the total flow deviation |Error| is greater than or equal to the first deviation threshold, then increase the proportional gain Kp; the first deviation threshold is greater than the second deviation threshold. If |Error| is less than or equal to the second deviation threshold, then decrease the proportional gain Kp and increase the integral gain Ki; If the absolute value of the rate of change of total flow deviation, |dError / dt|, is greater than or equal to the rate of change threshold, then increase the differential gain Kd. If |Error| is between the second deviation threshold and the first deviation threshold, then keep the current control parameters unchanged or adjust the current control parameters to meet the current requirements; Step 23: Based on the adjusted controller parameters, obtain the adjusted variable frequency pump frequency reference control quantity Pump_Frequency_Base_T through the expression of Pump_Frequency_Base.

[0015] Furthermore, the formula for calculating the total flow deviation Error is:

[0016] The expression for Pump_Frequency_Base is:

[0017] Where Kp, Ki, and Kd are all controller parameters. To control the total flow deviation at the current time t within the control period Δt.

[0018] Further, step 3 includes: Step 31: Read the measured values ​​of the first pressure sensor and the second pressure sensor installed on the main outlet pipeline of the variable frequency pump in real time, and record them as P1 and P2 respectively; Step 32: Calculate the absolute difference ΔP = |P1-P2| between the readings of the first pressure sensor and the second pressure sensor, and compare it with the preset safety threshold ε; if ΔP ≤ ε, proceed to step 33; if ΔP > ε, proceed to step 34. Step 33: If ΔP is less than the preset safety threshold ε, then both the first and second pressure sensors are working normally; take the arithmetic mean of the two as the raw pressure value P_Raw at the location of the first and second pressure sensors. P_Raw=(P1+P2) / 2 Step 34: If ΔP exceeds the preset safety threshold ε, a pressure sensor fault alarm is triggered; the control system automatically isolates unreliable pressure sensor readings and reconstructs the original pressure value P_Raw based on the readings of normally functioning pressure sensors and their pressure change trends over a specified period of time. Step 35: Perform moving average filtering on the raw pressure value P_Raw to output the actual pressure value P_Actual.

[0019] Further, step 4 includes: Step 41: Pressure Deviation Calculation: Calculate the pressure deviation of the variable frequency pump outlet main pipeline. Where P_Set is the preset target pressure value; Step 42: Input P_Error into the pressure PID controller, and output Valve_Pressure_Base as the basic control quantity of the proportional control valve.

[0020] Furthermore, the formula for calculating the basic control quantity Valve_Pressure_Base of the proportional control valve is as follows:

[0021] Where ∑ represents the accumulation of historical errors, Δt is the control period, Kp_p is the proportional gain of the pressure control loop, and Ki_p is the integral gain of the pressure control loop.

[0022] Further, step 5 includes: Step 51: Synthesize the adjusted variable frequency pump frequency reference control quantity Pump_Frequency_Base_T with the proportional control valve's base control quantity Valve_Pressure_Base to generate the final frequency command Pump_Frequency for the variable frequency pump.

[0023] The final opening command for the proportional control valve is Valve_Pressure.

[0024] The final frequency command Pump_Frequency of the variable frequency pump is composed of Pump_Frequency_Base_T and the pressure correction component. It is formed by stacking.

[0025] This application also discloses a flow and pressure stabilization system for a multi-branch methanol fuel supply system, applicable to the above-described method, comprising: The controller is connected to the variable frequency pump, the first pressure sensor, the second pressure sensor, the proportional control valve, the flow meter, and the engine. After entering from the variable frequency pump, the liquid flows sequentially through the first pressure sensor, the second pressure sensor, the proportional control valve, the flow meter, and the engine. The variable frequency pump is used to send its outlet pressure data to the controller. The first pressure sensor, the second pressure sensor, and the proportional control valve are all used to send the pressure data of the liquid flowing through them to the controller. The flow meter is used to send the flow rate data of the liquid flowing through it to the controller. The engine is used to send its current required flow rate to the controller.

[0026] Due to the adoption of the above technical solution, this application has the following advantages: 1. Improve system control stability: Solve the problem of speed fluctuation of the main pipeline variable frequency pump due to response lag and disturbance when the flow of multiple branches changes independently, and realize smooth and stable control of the variable frequency pump speed.

[0027] 2. Enhance the system's anti-interference capability: enable the control system to adapt to changes in operating conditions, quickly suppress disturbances caused by changes in branch flow demand or external environment, and ensure that the flow of each branch is stable at the set value.

[0028] 3. Reduce system energy consumption: By achieving stable operation of the variable frequency pump, unnecessary work and mechanical stress are reduced, thereby achieving the goal of energy saving and consumption reduction. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0030] Figure 1 This is a schematic diagram of a multi-branch methanol fuel supply system according to an embodiment of this application; Figure descriptions: 1. Variable frequency pump; 2. DCS controller; 3. First pressure sensor; 4. Second pressure sensor; 5. Proportional regulating valve; 6. Flow meter; 7. Engine. Detailed Implementation

[0031] The present application will be further described in conjunction with the accompanying drawings and embodiments. The described embodiments are only some, not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of the present application.

[0032] This application provides an embodiment of a method for stabilizing flow and pressure in a multi-branch methanol fuel supply system, comprising: Step 1: Obtain the actual total flow rate and the set total flow rate based on the actual flow rate readings from the flow meters installed on each engine branch. Step 2: Based on the actual total flow rate and the set total flow rate, obtain the reference control value for the adjusted frequency of the variable frequency pump; Step 3: Obtain the actual pressure value based on the readings of the first and second pressure sensors installed on the main outlet pipe of the variable frequency pump; Step 4: Obtain the basic control quantity of the proportional valve based on the actual pressure value; Step 5: Based on the adjusted frequency reference control quantity of the variable frequency pump and the basic control quantity of the proportional valve, obtain the final frequency command of the variable frequency pump and the final opening command of the proportional regulating valve.

[0033] Optionally, step 1 includes: Step 11: The DCS (Distributed Control System) controller periodically reads the actual flow values (denoted as FT1_Raw, FT2_Raw, ..., FT n ) from the flow meters (FT1, FT2, ..., FT n _Raw) installed on each engine branch through the RS485 communication bus; obtains the current required flow from each engine through the CAN communication bus, and uses the current required flow as the flow set value (SP1, SP2, ..., SP n ) of the branch where the engine is located; Step 12: To overcome the instantaneous error and noise of a single flow meter, the flow data of each branch is respectively fused, and the specific formula is:

[0034] where: is the fused flow value of the kth branch in the current cycle; is the historical value fused in the previous control cycle of the kth branch, that is, FT k _Fused in the previous cycle; FT k _Raw is the raw flow value collected by the flow meter of the kth branch in the current cycle; w1 is a weight factor set based on sensor reliability and historical data (0 < w1 < 1); the closer w1 is to 1, the more the system trusts historical data, and the stronger the filtering effect, but the response will be slightly slower; the closer it is to 0, the faster the response to current new data, but more noise may be introduced; Step 13: According to the head curve of the variable-frequency pump and the incompressible fluid model, the theoretical flow value is estimated using the pressure difference before and after the variable-frequency pump; the sum of the fused flow values of each branch is cross-validated with the theoretical flow value: if the deviation between the two exceeds the preset range, it is determined that the flow meter may have drift or a fault, and the system automatically reduces the weight w1 of the relevant sensor data in the fusion algorithm and triggers a maintenance alarm; Step 14: The DCS controller calculates the total actual flow value and the total flow set value of the entire system.

[0035] Optionally, step 14 includes: The total actual flow value is obtained through the following formula : [[ID=​​​​​ The total flow rate setpoint is obtained using the following formula. :

[0037] in, Set the flow rate value for the first branch. Set the flow rate value for the nth branch.

[0038] Optionally, step 2 includes: Step 21: Input the total flow deviation Error and the rate of change of the total flow deviation dError / dt into the PID controller whose parameters can be dynamically adjusted. The output of the PID controller is Pump_Frequency_Base, which is the reference control quantity for the frequency of the variable frequency pump. Step 22: Adjust controller parameters: Set a first deviation threshold and a second deviation threshold, wherein; and simultaneously set a rate of change threshold.

[0039] If the absolute value of the total flow deviation |Error| is greater than or equal to the first deviation threshold, the proportional gain Kp is increased to enable the variable frequency pump to respond quickly and eliminate the large flow deviation; the first deviation threshold is greater than the second deviation threshold. If |Error| is less than or equal to the second deviation threshold, then the proportional gain Kp is reduced and the integral gain Ki is increased to avoid overshoot, improve system stability, and effectively eliminate static error. If the absolute value of the rate of change of the total flow deviation, |dError / dt|, is greater than or equal to the rate of change threshold, then the differential gain Kd is increased to suppress the system from changing too quickly, brake in advance, and prevent overshoot. If |Error| is between the second deviation threshold and the first deviation threshold, then keep the current control parameter unchanged or make a fine adjustment; Step 23: Based on the adjusted controller parameters, obtain the adjusted variable frequency pump frequency reference control quantity Pump_Frequency_Base through the expression of Pump_Frequency_Base.

[0040] Optionally, the formula for calculating the total flow deviation Error is:

[0041] The expression for Pump_Frequency_Base is:

[0042] Where Kp, Ki, and Kd are all controller parameters. To control the total flow deviation at the current time t within the control period Δt.

[0043] Optionally, step 3 includes: Step 31: Read the measured values ​​of the first pressure sensor and the second pressure sensor installed on the main outlet pipeline of the variable frequency pump in real time, and record them as P1 and P2 respectively; Step 32: Calculate the absolute difference ΔP = |P1-P2| between the readings of the first pressure sensor and the second pressure sensor, and compare it with the preset safety threshold ε; if ΔP ≤ ε, proceed to step 33: normal processing; if ΔP > ε, proceed to step 34: fault handling. Step 33: If ΔP is less than the preset safety threshold ε, then both the first and second pressure sensors are working normally; take the arithmetic mean of the two as the raw pressure value P_Raw at the location of the first and second pressure sensors. P_Raw=(P1+P2) / 2 Step 34: If ΔP exceeds the preset safety threshold ε, a pressure sensor fault alarm is immediately triggered; the control system automatically isolates unreliable pressure sensor readings and reconstructs a reliable raw pressure value P_Raw based on the readings of normal pressure sensors and their recent pressure change trends, ensuring that the control loop is not interrupted; Step 35: Perform moving average filtering on the reliable raw pressure value P_Raw to suppress high-frequency pressure pulsations and transient interference in the pipeline, and output a smooth and reliable actual pressure value P_Actual.

[0044] Optionally, step 4 includes: Step 41: Pressure Deviation Calculation: Calculate the pressure deviation of the main pipeline. Wherein, P_Set is the target pressure value that the system pre-sets according to operational requirements and aims to maintain; Step 42: Input P_Error into the pressure PID controller, and output Valve_Pressure_Base as the basic control quantity of the proportional control valve.

[0045] Optionally, the formula for calculating the base control quantity Valve_Pressure_Base of the proportional control valve is:

[0046] Where ∑ represents the accumulation of historical errors, Δt is the control period; Kp_p is the proportional gain of the pressure control loop, which determines the controller's response strength to the current pressure deviation; the larger the value of Kp_p, the faster and stronger the proportional control valve's correction action on pressure fluctuations, which helps to quickly suppress disturbances, but too large a value may cause system oscillation; Ki_p is the integral gain of the pressure control loop, which aims to completely eliminate steady-state pressure error (static error) through the accumulation (integration) of historical pressure deviations; Ki_p ensures that the system pressure can be accurately and stably maintained at the setpoint P_Set for a long time; the pressure PID controller operates independently to drive the proportional control valve with fast response speed, thereby realizing rapid closed-loop fine adjustment of the main pipeline pressure, and coordinating with the frequency control loop of the variable frequency pump that handles slow flow changes.

[0047] Optionally, step 5 includes: Step 51: Synthesize the base control quantity Pump_Frequency_Base of the variable frequency pump frequency with the base control quantity Valve_Pressure_Base of the proportional control valve to generate the final frequency command Pump_Frequency of the variable frequency pump. Pump_Frequency indicates that the variable frequency pump is primarily responsible for responding to the reference frequency determined by the total flow demand, while introducing a small correction term from the pressure control loop output (k is a small gain coefficient, ranging from 0 to 0.3). This makes the pump's rotational speed smooth, primarily tracking flow changes, while also assisting in pressure stabilization; The final opening command for the proportional control valve is Valve_Pressure.

[0048] Valve_Pressure indicates that the proportional control valve is primarily responsible for rapidly absorbing pressure fluctuations. Its main weight is allocated using (1-k) to ensure it can fully utilize its rapid response characteristics for high-frequency fine-tuning.

[0049] The final opening command of the proportional control valve indicates that the proportional control valve is used to absorb pressure fluctuations. The final frequency command Pump_Frequency of the variable frequency pump is composed of the reference control quantity Pump_Frequency_Base of the variable frequency pump frequency and the pressure correction component. It is formed by stacking.

[0050] The reference control quantity Pump_Frequency_Base for the frequency of the variable frequency pump enables the pump to primarily track changes in total flow demand; the pressure correction component introduces the output of the pressure control loop proportionally (coefficient k) to make minor adjustments to the pump speed.

[0051] This design enables coordinated control of the variable frequency pump and the proportional control valve: the variable frequency pump responds smoothly to changes in the main flow rate while also assisting in pressure regulation; the proportional control valve focuses on rapidly suppressing pressure fluctuations. Through their collaborative efforts, they jointly improve the stability of the system's flow rate and pressure.

[0052] See Figure 1 This application also provides an embodiment of a multi-branch methanol fuel supply system with stabilizing flow and pressure, applicable to the methods described in the above embodiments, comprising: DCS controller 2 is connected to variable frequency pump 1, first pressure sensor 3, second pressure sensor 4, proportional control valve 5, flow meter 6, and engine 7 respectively. After entering from variable frequency pump 1, the liquid flows sequentially through first pressure sensor 3, second pressure sensor 4, proportional control valve 5, flow meter 6, and engine 7. Variable frequency pump 1 is used to send its outlet pressure data to DCS controller 2. First pressure sensor 3, second pressure sensor 4, and proportional control valve 5 are all used to send the pressure data of the liquid flowing through them to DCS controller 2. Flow meter 6 is used to send the flow rate data of the liquid flowing through it to DCS controller 2. Engine 7 is used to send its current required flow rate to DCS controller 2.

[0053] The embodiments of this application have the following beneficial technical effects: 1. Multi-bus integration and data fusion improve control accuracy: Real-time data acquisition: Raw data from each branch flow meter is acquired via RS485 bus, and engine demand flow signals (i.e., the flow targets of each branch) are obtained from each engine control unit via CAN bus, realizing distributed data exchange. From the DCS architecture perspective, the main controller (DCS controller) calculates the total flow measurement value (i.e., the sum of the actual flow of each branch) and the total flow target value (i.e., the sum of the demand flow signals of each engine) based on this real-time data. This distributed acquisition and centralized calculation method reduces intermediate communication delays and provides a timely data foundation for precise control.

[0054] Data fusion and cross-validation: using a weighted fusion formula ( Cross-validation with incompressible fluid models improves the reliability of flow data. Programming is implemented through algorithm modules, reducing the impact of sensor errors on control and enhancing system robustness.

[0055] 2. Adaptive PID control improves dynamic response: Dynamic parameter adjustment: The total flow deviation (Error) and its rate of change (dError / dt) are input to the PID controller, and the parameters Kp, Ki, and Kd are dynamically adjusted according to rules. For example, when the deviation is large, Kp is increased for a faster response, and when the deviation is small, Ki is increased to eliminate steady-state error. This adaptive algorithm can be implemented as an advanced control module in a DCS, enabling the system to adapt to changes in operating conditions and reduce overshoot and fluctuations.

[0056] Feedforward-feedback composite control: The controller generates a feedforward control quantity through the total flow target value (Total_Setpoint), and combines it with the feedback output of the adaptive PID controller to form the basic frequency control quantity Pump_Frequency_Base of the variable frequency pump.

[0057] The adaptive PID controller incorporates a feedforward-feedback composite structure. The feedback channel takes the total flow deviation (Error) and its rate of change as input, dynamically adjusts parameters, and outputs a feedback control quantity. The feedforward channel takes the total flow target value (Total_Setpoint) or its trend as input, and outputs a feedforward control quantity via a feedforward compensator (such as a proportional element or model prediction element). Finally, the variable frequency pump base frequency control quantity, Pump_Frequency_Base, is generated by superimposing the feedforward and feedback control quantities, thereby achieving early suppression of anticipated disturbances.

[0058] 3. Sensor redundancy and filtering enhance reliability: Pressure sensor redundancy: Two pressure sensors (PT201, PT202) are installed at the outlet of the variable frequency pump on the main pipeline. The main controller compares the readings and performs fault diagnosis (such as alarm when the difference exceeds the limit and data reconstruction). From a safety programming perspective, this complies with the IEC61131-3 standard and improves system availability.

[0059] Moving average filtering: Filters pressure data to suppress high-frequency noise and ensure stable control signals. In the DCS signal processing module, it reduces malfunctions.

[0060] 4. Decoupling control of pressure and flow optimizes energy efficiency: Rapid pressure stabilization via proportional control valve: The pressure PID controller outputs the basic control quantity to the proportional control valve, utilizing its fast response to instantly absorb pressure fluctuations. This achieves rapid closed-loop control of the pressure control circuit in the DCS, reducing the burden on the variable frequency pump.

[0061] Variable frequency pump and valve coordinated control: Ultimately, the frequency control signal of the variable frequency pump and the control signal of the proportional control valve demonstrate the division of labor between the variable frequency pump and the valve. The variable frequency pump handles the mainstream flow demand, while the valve handles sudden load changes. This decoupled control reduces the frequency adjustment of the variable frequency pump, thereby reducing energy consumption and equipment wear.

[0062] 5. Improved system energy efficiency: By smoothly controlling the variable frequency pump speed, the pump operates within a more efficient range, reducing wasted energy. Data fusion and adaptive algorithms further optimize system efficiency, contributing to reduced overall fuel consumption from a DCS energy management perspective.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this application. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of the claims of this application.

Claims

1. A method for stabilizing the current and voltage of a multi-branch methanol fuel supply system, characterized in that, Comprising: Step 1: Obtain total flow actual value and total flow set value according to actual flow value read by flow meter installed on each engine branch; Step 2: Obtain adjusted frequency reference control value of variable frequency pump according to total flow actual value and total flow set value; Step 3: Obtain pressure actual value according to readings of first pressure sensor and second pressure sensor installed on main pipe at outlet of variable frequency pump; Step 4: Obtain basic control value of proportional valve according to pressure actual value; Step 5: Obtain final frequency command of variable frequency pump and final opening command of proportional regulating valve according to adjusted frequency reference control value of variable frequency pump and basic control value of proportional valve.

2. The method of claim 1, wherein, The step 1 comprises: Step 11: The controller periodically reads actual flow value from flow meter installed on each engine branch; obtains current demand flow of each engine through CAN communication bus and takes the current demand flow as flow set value of the branch where the engine is located; Step 12: Perform fusion processing on flow data of each branch respectively, and the specific formula is: wherein: is the fused flow value of the kth branch at the current cycle; is the historical value of the kth branch fused at the last control cycle, i.e., FT of the last cycle k _Fused; FT k _Raw is the raw flow value collected by the flow meter of the kth branch at the current cycle; w1 is a weight factor set based on sensor reliability and historical data; Step 13: Estimate theoretical flow value according to head curve of variable frequency pump and incompressible fluid model by using pressure difference before and after the variable frequency pump; cross-verify the sum of flow values of each branch after fusion with the theoretical flow value: if the deviation between the two exceeds the preset range, it is determined that the flow meter may have drift or failure, the system automatically reduces the weight w1 of related sensor data in the fusion algorithm and triggers a maintenance alarm; Step 14: The controller calculates the total flow actual value for the entire system and the total flow setpoint .

3. The method of claim 2, wherein, The step 14 comprises: The total flow actual value is obtained by the following equation : wherein, the flow value of the first branch after fusion in the current cycle, the flow value of the nth branch after fusion in the current cycle, n being the total number of branches in the system. The total flow set value is obtained by the following equation : wherein Q1 is the flow set value for the first branch, Qn is the flow set value for the nth branch.

4. The method of claim 3, wherein, The step 2 comprises: Step 21: Input total flow deviation Error and change rate dError / dt of total flow deviation into PID controller with dynamically adjustable parameters, and the output of the PID controller is Pump_Frequency_Base, which is the reference control value of variable frequency pump frequency; Step 22: Adjust controller parameters: If the absolute value |Error| of total flow deviation is greater than or equal to the first deviation threshold, increase the proportional gain Kp; the first deviation threshold is greater than the second deviation threshold; If |Error| is less than or equal to the second deviation threshold, decrease the proportional gain Kp and increase the integral gain Ki; If the absolute value |dError / dt| of change rate of total flow deviation is greater than or equal to the change rate threshold, increase the differential gain Kd; If |Error| is between the second deviation threshold and the first deviation threshold, keep the current control parameters unchanged or adjust the current control parameters to meet the current requirements; Step 23: Obtain adjusted reference control value Pump_Frequency_Base_T of variable frequency pump frequency according to the expression of reference control value Pump_Frequency_Base of variable frequency pump frequency through adjusted controller parameters.

5. The method of claim 4, wherein, The formula for calculating the total flow deviation Error is: The expression of Pump_Frequency_Base is: wherein Kp, Ki and Kd are controller parameters, is the total flow deviation at the current time t in the control period Δt.

6. The method of claim 1, wherein, The step 3 comprises: Step 31: Real-time reading of the measurement values of the first pressure sensor and the second pressure sensor installed on the outlet main pipeline of the variable frequency pump, respectively recorded as P1 and P2; Step 32: Calculate the absolute difference ΔP = |P1-P2| of the readings of the first pressure sensor and the second pressure sensor, and compare it with the preset safety threshold ε; if ΔP≤ε, go to step 33; if ΔP>ε, go to step 34; Step 33: If ΔP is less than the preset safety threshold ε, both the first pressure sensor and the second pressure sensor are working normally; take the arithmetic mean of the two as the pressure raw value P_Raw at the position of the first pressure sensor and the second pressure sensor: P_Raw=(P1+P2) / 2 Step 34: If ΔP exceeds the preset safety threshold ε, trigger a pressure sensor failure alarm; the control system automatically isolates the unreliable pressure sensor reading, and reconstructs the pressure raw value P_Raw based on the reading of the normally working pressure sensor and its pressure change trend in the past specified time; Step 35: Perform sliding average filtering on the pressure raw value P_Raw to output the pressure actual value P_Actual.

7. The method of claim 1, wherein, The step 4 includes: Step 41: pressure deviation calculation: calculate the pressure deviation of the variable frequency pump outlet main pipeline ; wherein P_set is a preset target pressure value; Step 42: Input P_Error into the pressure PID controller, and output the basic control amount Valve_Pressure_Base of the proportional regulating valve.

8. The method of claim 7, wherein, The formula for calculating the basic control amount Valve_Pressure_Base of the proportional regulating valve is: Where ∑ represents the accumulation of historical errors, Δt is the control period, Kp_p is the proportional gain of the pressure control loop, and Ki_p is the integral gain of the pressure control loop.

9. The method of claim 1, wherein, The step 5 includes: Step 51: Synthesize the reference control amount Pump_Frequency_Base_T of the adjusted variable frequency pump frequency and the basic control amount Valve_Pressure_Base of the proportional regulating valve to generate the final frequency command Pump_Frequency of the variable frequency pump: The final opening command Valve_Pressure of the proportional regulating valve: The final frequency command of the variable frequency pump Pump_Frequency is obtained by superimposing Pump_Frequency_Base_T and the pressure correction component is obtained by superimposing 10. A multi-branch methanol fuel supply system flow and pressure stabilizing system, suitable for use in the method of any one of claims 1-9, characterized in that, It includes: The controller is connected with the variable frequency pump, the first pressure sensor, the second pressure sensor, the proportional regulating valve, the flow meter, and the engine; after the liquid enters the variable frequency pump, it flows through the first pressure sensor, the second pressure sensor, the proportional regulating valve, the flow meter, and the engine in sequence; the variable frequency pump is used to send its outlet pressure data to the controller; the first pressure sensor, the second pressure sensor, and the proportional regulating valve are used to send the pressure data flowing through them to the controller; the flow meter is used to send the flow data flowing through it to the controller; and the engine is used to send its current demand flow to the controller.

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