Biomass gas boiler drum liquid level three-impulse control system and method

Abstract

The invention discloses a biomass gas boiler drum liquid level three-impulse control system and method. The system comprises a parameter acquisition module, a central control module, an execution adjustment module and a fault diagnosis and fault tolerance module. The parameter acquisition module is used for acquiring multi-dimensional parameters of boiler operation, including steam drum liquid level data, steam flow, feed water flow, gas flow and gas components, steam drum pressure and hearth temperature; the central control module is used for performing multi-parameter fusion operation and control instruction generation through parameter preprocessing, self-adaptive three-impulse control, combustion-liquid level cooperation and pressure compensation; the execution adjusting module is used for receiving the control instruction of the central control module and adjusting the water supply amount, the gas amount, the drainage amount and the air amount; and the fault diagnosis and fault tolerance module is used for carrying out sensor fault detection and actuator fault detection on the basis of the preprocessed parameters and actuator feedback signals, starting a corresponding fault tolerance mechanism, and recording and uploading faults at the same time.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of biomass energy utilization and industrial boiler automatic control, and more specifically to a three-impulse control system and method for the steam drum liquid level of a biomass gas boiler. Background Technology

[0002] Biomass gas is produced through pyrolysis gasification technology and has zero carbon emissions. It has been widely used in industrial heating, combined heat and power, and district heating, with biomass gas boilers becoming the core equipment for energy conversion. However, the inherent characteristics of biomass gas and the complexity of the boiler operating environment pose serious challenges to the control of the boiler drum level. The core contradictions are reflected in three aspects: the instability of biomass gas, the sensitivity and safety boundary of the boiler drum level, and the complexity of multiple disturbances.

[0003] Currently, industrial boiler drum liquid level control technology is mainly divided into three categories: single-impulse, dual-impulse, and traditional three-impulse. However, none of them can adapt to the special operating conditions of biomass gas boilers. Specifically:

[0004] Single-impulse control uses the steam drum liquid level measurement value as the only input and adjusts the opening of the feedwater regulating valve through a conventional PID controller. Although the structure is simple (only one liquid level sensor is required), its anti-interference ability is extremely poor. When the biomass gas combustion load increases suddenly, the steam output rises instantly, the pressure in the steam drum drops, the boiler water saturation temperature decreases, and the boiler water vaporizes rapidly, causing the liquid level to rise briefly. At this time, the single-impulse controller misjudges that the liquid level is too high and closes the feedwater valve. However, the actual liquid level drops sharply after the flash evaporation ends because the steam output is greater than the feedwater input, forming an "overshoot-oscillation".

[0005] Dual-impulse control introduces steam flow as a feedforward variable on the basis of single-impulse control. By adjusting the water supply in advance through feedforward compensation, it can theoretically suppress the disturbance of liquid level caused by load changes. However, this technology does not consider the disturbance of the water supply system and has insufficient identification of false water levels.

[0006] Traditional three-impulse control, through its structure of "liquid level main loop + steam flow feedforward + feedwater flow secondary loop," can theoretically balance load and feedwater disturbance suppression. However, its shortcomings are more pronounced for biomass gas-fired boilers.

[0007] Poor adaptability of PID parameters: The PID parameters of traditional three-impulse control are fixed values, which are suitable for coal-fired and natural gas boilers with stable fuel composition; however, the high-frequency fluctuations in the composition and flow of biomass fuel cause frequent changes in the dynamic characteristics of boiler load. Fixed PID parameters are prone to "overshooting" when the load changes suddenly and "response lag" when the load changes slowly.

[0008] Lack of pressure compensation mechanism: Traditional three-impulse control does not compensate for the steam drum pressure of the liquid level measurement value. When the steam drum pressure fluctuates from the rated value, the liquid level measurement deviation increases, causing the controller to be unable to identify the actual liquid level, which further aggravates the influence of false water level.

[0009] In addition, the sensors of biomass gas boilers are susceptible to adverse working conditions such as level sensors being contaminated by boiler water impurities, flow sensors being blocked by gas tar, and temperature sensors being affected by furnace radiation interference. Traditional three-impulse control lacks a sensor fault detection and switching mechanism, resulting in weak fault tolerance. Once a sensor fails, it directly leads to the paralysis of the control system, requiring manual shutdown for maintenance, and the equipment has a short continuous operating time.

[0010] Traditional three-impulse control only focuses on the "liquid-flow" closed loop and does not involve the combustion system, resulting in a lack of combustion-liquid level coordination. When the gas composition deteriorates, the gas supply needs to be increased to maintain the load. If only the water supply is adjusted without coordinating the control of the combustion load, it will lead to a "water-heat" mismatch, further aggravating liquid level fluctuations.

[0011] Therefore, how to provide a three-impulse control technology that adapts to the characteristics of biomass gas and has the ability to suppress multiple disturbances and tolerate faults, so as to meet the control requirements of "high precision, anti-interference, high fault tolerance and coordination" of the boiler drum liquid level of biomass gas boiler, so as to ensure the safe and stable operation of biomass gas boiler, is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0012] In view of this, the present invention provides a three-impulse control system and method for the liquid level of a biomass gas-fired boiler drum to solve some of the technical problems mentioned in the background art.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A three-impulse control system for boiler drum liquid level in biomass gasification boiler includes: a parameter acquisition module, a central control module, an execution and regulation module, and a fault diagnosis and fault tolerance module;

[0015] The parameter acquisition module collects multi-dimensional parameters of boiler operation, including steam drum liquid level data, steam flow rate, feedwater flow rate, gas flow rate and gas composition, steam drum pressure and furnace temperature;

[0016] The central control module is used to perform multi-parameter fusion calculations and generate control commands through parameter preprocessing, adaptive three-impulse control, combustion-liquid level coordination, and pressure compensation.

[0017] The execution adjustment module is used to receive control commands from the central control module and adjust the water supply, gas supply, condensate flow, and air supply.

[0018] The fault diagnosis and fault tolerance module, based on the preprocessed parameters and actuator feedback signals, performs sensor fault detection and actuator fault detection, activates the corresponding fault tolerance mechanism, and records and uploads the faults.

[0019] Preferably, the parameter acquisition module includes a steam drum liquid level acquisition submodule, a steam flow acquisition submodule, a feedwater flow acquisition submodule, a biomass gas parameter acquisition submodule, a steam drum pressure acquisition submodule, and a furnace temperature acquisition submodule;

[0020] The steam drum liquid level acquisition submodule adopts a triple redundancy design of dual-redundant differential pressure liquid level sensor and capacitive liquid level sensor for liquid level measurement;

[0021] The steam flow acquisition submodule uses a vortex flow meter to measure the steam flow rate and measures the steam temperature and pressure using temperature and pressure sensors.

[0022] The water supply flow acquisition submodule uses an electromagnetic flow meter, a water supply temperature sensor, and a water supply pressure sensor to monitor the water supply flow, water supply temperature, and water supply pressure of the water supply system in real time.

[0023] The biomass gas parameter acquisition submodule uses a gas flow bend flow meter to acquire gas flow, a gas pressure sensor and a temperature sensor to measure gas pressure and temperature, which are used to correct the influence of gas density on flow measurement, and a gas composition analyzer to measure CH4, CO, H2 and CO2 components.

[0024] The steam drum pressure acquisition submodule uses an absolute pressure sensor to measure the steam drum pressure. On the one hand, it is used to correct the measurement deviation of the differential pressure level sensor through pressure compensation, and on the other hand, it is used to calculate the steam enthalpy value to provide a basis for combustion load calculation.

[0025] The furnace temperature acquisition submodule uses dual K-type thermocouples to measure the furnace temperature, monitor changes in combustion intensity in real time, help identify false water levels, and provide combustion status feedback for the control algorithm.

[0026] Preferably, the central control module includes a parameter preprocessing unit, an adaptive three-impulse control unit, a combustion-liquid level coordination unit, and a pressure compensation unit;

[0027] The parameter preprocessing unit is used to filter, compensate, and normalize the acquired raw parameters to eliminate noise interference and measurement deviations.

[0028] The adaptive three-impulse control unit uses the liquid level control loop as the main loop and combines the fuzzy PID algorithm to adaptively adjust the PID control parameters to obtain the initial feedwater flow setting. The initial feedwater flow setting value is corrected by the dual feedforward compensation loop of steam flow and low-level calorific value of gas. The feedwater flow control loop is used as the secondary loop to output the initial opening command of the feedwater regulating valve for feedwater flow control.

[0029] The combustion-liquid level coordination unit is used to coordinate the liquid level control and combustion system to perform target combustion load calculation, gas supply regulation, air flow coordination regulation, and combustion efficiency optimization.

[0030] The pressure compensation unit is used to monitor water supply pressure fluctuations in real time and calculate water supply pressure deviations, correct the initial water supply regulating valve opening command to compensate for water supply flow deviations, output the final water supply regulating valve opening command, and simultaneously output the water supply pump frequency converter speed command.

[0031] Preferably, the specific content of the parameter preprocessing unit in compensating for the acquired raw parameters includes:

[0032] Liquid level pressure compensation: Based on the real-time value of the steam drum pressure, the measured value of the differential pressure liquid level sensor is corrected to obtain the actual liquid level value;

[0033] Steam flow temperature and pressure compensation: Based on the steam temperature and pressure, the steam flow compensation formula is used to correct the operating flow rate to the standard state flow rate.

[0034] Water supply flow rate temperature and pressure compensation: Based on the water supply temperature and pressure, the operating flow rate is corrected to the standard state flow rate.

[0035] The calorific value of the gas is calculated based on the volume fractions of CH4, CO, and H2 collected by the gas composition analyzer, combined with the volume fraction of moisture in the gas.

[0036] Preferably, the adaptive three-impulse control unit includes a level control loop, a dual feedforward compensation loop, and a water supply flow control loop;

[0037] The liquid level control loop uses the pre-processed actual liquid level as the controlled variable and the rated liquid level as the target value to calculate the liquid level deviation and the rate of change of liquid level deviation. A fuzzy PID controller is adopted, which is based on the adaptive rules of fuzzy PID parameters and the triangular membership function to fuzzify the liquid level deviation and the rate of change of liquid level deviation. The corresponding fuzzy subset is obtained by querying the fuzzy PID rule table. Fuzzy inference is performed by Mamdani inference method and fuzzy defuzzification by area centroid method to output PID parameter corrections ΔKp, ΔKi, and ΔKd. The actual PID parameters Kp, Ki, and Kd are calculated. The initial water supply flow setpoint is calculated by PID algorithm.

[0038] The dual feedforward compensation loop introduces steam flow and low heating value of gas as feedforward compensation signals to calculate the corrected feedwater flow setpoint, adjust the feedwater flow in advance, and suppress the impact of combustion load fluctuations on liquid level.

[0039] The water supply flow control loop uses the water supply flow as the controlled variable, the setpoint of the water supply flow output by the main loop is the target value, the water supply flow deviation is calculated, and the initial opening command of the water supply regulating valve is output through the proportional controller.

[0040] Preferably, the combustion-liquid level coordination unit includes the following specific features:

[0041] Target combustion load calculation: The target combustion load is calculated based on the deviation between steam flow rate and steam drum pressure.

[0042] Gas supply regulation: Calculate the target gas flow rate based on the target combustion load and the lower heating value of the gas, compare the actual gas flow rate with the target gas flow rate, calculate the gas flow rate deviation, and output the gas regulating valve opening command through the PID controller;

[0043] Airflow coordinated regulation: Calculate the target airflow based on the gas flow rate and the theoretical air volume of the gas, calculate the airflow deviation based on the actual airflow of the blower, output the blower frequency converter speed command to control the airflow, and output the induced draft fan frequency converter speed command based on the furnace negative pressure.

[0044] Combustion efficiency optimization: Real-time monitoring of furnace temperature and flue gas composition, increasing or decreasing airflow.

[0045] Preferably, the control module includes a water supply control submodule, a gas supply control submodule, a ventilation control submodule, and a drainage control submodule;

[0046] Water supply regulating submodule: The main regulating function is the electric regulating valve, and the auxiliary regulating function is the frequency converter. The opening degree of the water supply regulating valve is adjusted according to the final opening degree command of the water supply regulating valve, and the speed of the water supply pump frequency converter is adjusted according to the speed command of the water supply pump frequency converter.

[0047] The gas regulating submodule adopts a safe regulating mode with an electric regulating valve and an emergency shut-off valve. It adjusts the opening of the gas regulating valve according to the opening command of the gas regulating valve. The gas emergency shut-off valve remains open when there is no fault, and closes quickly when the liquid level exceeds the limit or gas leaks.

[0048] The ventilation control submodule adopts a coordinated control mode of the blower frequency converter and the induced draft fan frequency converter. It adjusts the speed of the blower according to the speed command of the blower frequency converter and adjusts the speed of the induced draft fan according to the speed command of the induced draft fan frequency converter.

[0049] The condensate regulating submodule opens or closes the steam drum condensate electric valve according to the steam drum liquid level. When the boiler starts up, condensate is discharged through the superheater condensate valve and closed during normal operation.

[0050] Preferably, the fault diagnosis and fault tolerance module includes a hardware fault detection unit, a software fault tolerance unit, and a fault recording and uploading unit;

[0051] Sensor fault detection includes redundancy deviation detection, range overrun detection, drift trend detection, and signal loss detection.

[0052] Actuator fault detection includes command-feedback deviation detection, action timeout detection, and power failure detection.

[0053] Fault tolerance mechanisms include sensor fault tolerance strategies and actuator fault tolerance strategies;

[0054] Sensor fault tolerance strategies include fault tolerance for level sensors, fault tolerance for steam flow sensors, fault tolerance for gas composition analyzers, and fault tolerance for multiple sensors.

[0055] The actuator fault tolerance strategy includes fault tolerance for feedwater regulating valves, fault tolerance for gas regulating valves, fault tolerance for frequency converters, and emergency shutdown procedures.

[0056] Preferably, the biomass gas boiler drum liquid level three-impulse control system further includes a human-machine interaction module for real-time parameter display, parameter setting function, status monitoring function, alarm prompt and historical data query.

[0057] A three-impulse control method for boiler drum liquid level in a biomass gas-fired boiler, using the aforementioned three-impulse control system for boiler drum liquid level in a biomass gas-fired boiler, the method includes the following steps:

[0058] S1. System initialization: Maintenance personnel log in with administrator privileges through the human-machine interaction module to set boiler rated parameters and control parameters; the central control module starts the parameter acquisition module, execution adjustment module, and fault diagnosis and fault tolerance module, initializes the status of each module, and the system enters standby mode;

[0059] S2. Real-time acquisition of raw parameters, including liquid level from dual differential pressure level sensors, liquid level from capacitive level sensors, steam flow rate, steam temperature, steam pressure, feedwater flow rate, feedwater temperature, feedwater pump inlet pressure, gas flow rate, gas composition, gas pressure, gas temperature, steam drum pressure, and furnace temperature. Kalman filtering is applied to all parameters to calculate the actual liquid level, standard steam flow rate, and lower heating value of the gas. The processed parameters (actual liquid level, standard steam flow rate, feedwater flow rate, lower heating value of the gas, steam drum pressure, and furnace temperature) are then transmitted to the central control module and the fault diagnosis and fault tolerance module.

[0060] S3. The fault diagnosis and fault tolerance module receives the preprocessed parameters and actuator feedback signals, starts sensor fault detection and actuator fault detection. If a fault is detected, the fault tolerance mechanism is activated according to the fault type. If the fault cannot be mitigated by the fault tolerance mechanism, an audible and visual alarm is triggered, an emergency shutdown procedure is executed, and the control process ends. If there is no fault or the fault has been tolerated, proceed to step S4.

[0061] S4. Adaptive Three-Impulse Control Calculation of the Central Control Module: The liquid level deviation and rate of change of liquid level deviation are calculated through the main liquid level control loop; the liquid level deviation and rate of change of liquid level deviation are fuzzified, the fuzzy PID rule table is queried, and the PID parameter correction is output through fuzzy inference and defuzzification, and the actual PID parameters are calculated. The initial feedwater flow setpoint is calculated using the PID algorithm; steam flow and gas calorific value are introduced for feedforward compensation, and the corrected feedwater flow setpoint is calculated; the feedwater flow deviation is calculated through the secondary water flow control loop, and the initial opening command of the feedwater regulating valve is output through the proportional controller; the feedwater pressure deviation and opening correction command are calculated to obtain the final feedwater regulating valve opening command, and the feedwater pump inverter speed command is output simultaneously.

[0062] S5. Combustion-Liquid Level Coordinated Control: Calculates the steam drum pressure deviation, and calculates the target combustion load based on the steam flow rate and the steam drum pressure deviation; calculates the target gas flow rate based on the target combustion load and the lower heating value of the gas, and calculates the gas flow rate deviation based on the target gas flow rate and the real-time gas flow rate, outputting the gas regulating valve opening command through the PID controller; calculates the target air flow rate based on the real-time gas flow rate, and calculates the air flow rate deviation based on the target air flow rate and the actual air flow rate, outputting the blower frequency converter speed command; collects the furnace negative pressure, calculates the negative pressure deviation based on the target negative pressure, and outputs the induced draft fan frequency converter speed command.

[0063] S6. Execution Adjustment: The central control module transmits the final feedwater regulating valve opening command U, feedwater pump inverter speed command U2, gas regulating valve opening command U3, blower inverter speed command U4, and induced draft fan inverter speed command U5 to the execution adjustment module via the industrial bus; the execution adjustment module executes the commands to adjust the feedwater regulating valve to opening U, the feedwater pump inverter to speed U2, the gas regulating valve to opening U3, and, in the absence of faults, keeps the gas emergency shut-off valve open, adjusts the blower to speed U4, and adjusts the induced draft fan to speed U5; the steam drum drain electric valve is opened or closed according to the actual steam drum liquid level; condensate is discharged through the superheater drain valve during boiler startup and closed during normal operation;

[0064] S7. Over-limit Liquid Level Handling: If the actual steam drum liquid level exceeds the first threshold, a high liquid level alarm is triggered, the gas regulating valve opening is increased, the steam drum drain valve is opened, and the feedwater regulating valve is closed to a minimum; if the actual steam drum liquid level exceeds the second threshold, an emergency shutdown is triggered; if the actual steam drum liquid level is less than the third threshold, a low liquid level alarm is triggered, the gas regulating valve is closed to a minimum, the feedwater regulating valve is opened, and the feedwater pump frequency converter operates at full load; if the actual steam drum liquid level is less than the fourth threshold, an emergency shutdown is triggered; if the liquid level recovers, the over-limit handling is canceled, and normal control is restored.

[0065] S8. Cyclic Control and Shutdown: Return to step S2, repeat parameter acquisition, preprocessing, fault diagnosis, control calculation, and adjustment process to achieve continuous closed-loop control; when a boiler shutdown command is received, execute the normal shutdown procedure, the system enters the shutdown state, and the control flow ends.

[0066] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a three-impulse control system and method for the boiler drum liquid level of a biomass gas-fired boiler, which effectively solves the problems faced by biomass-related equipment (such as boilers) during operation, such as high-frequency fluctuations in gas composition and load, multiple disturbances, easy shutdown due to failure, high energy consumption, and complex operation and maintenance. Specifically:

[0067] Through advanced adaptive adjustment, multi-parameter compensation and collaborative control mechanisms, it can accurately adapt to disturbances such as gas composition fluctuations, steam load changes and pipeline scaling, significantly improve the control accuracy of core parameters (such as steam drum liquid level), significantly reduce parameter overshoot and shorten fluctuation recovery time; effectively reduce protection shutdowns and unplanned shutdowns caused by liquid level fluctuations, significantly extend the continuous fault-free operation time of equipment, and significantly improve equipment utilization.

[0068] Relying on dual-redundant sensor configuration, multi-parameter substitution calculation and hierarchical fault-tolerant strategy, even when sensors or actuators fail, control can still be guaranteed to remain uninterrupted; or it can automatically switch to backup control mode, with only a slight reduction in control accuracy; or it can maintain operation at a higher rated load to avoid the fault from escalating. Compared with the situation of immediate shutdown after a failure in traditional technology, the safety and continuity of equipment operation are fundamentally improved.

[0069] By optimizing combustion and core parameters in a coordinated manner, precise matching of "water volume and heat" is achieved, effectively avoiding heat loss caused by excess water and gas waste caused by incomplete combustion, significantly improving water utilization and combustion efficiency, reducing biomass gas consumption and energy costs; at the same time, it greatly reduces emissions of pollutants such as CO and NOx in flue gas.

[0070] With an intuitive human-computer interaction interface, efficient fault diagnosis and remote upload functions, and hierarchical permission management to ensure operational security, the inspection time and fault handling cycle of maintenance personnel can be significantly shortened, reducing labor costs; at the same time, the total annual maintenance cost is reduced, significantly improving equipment management efficiency and economy.

[0071] This invention achieves a comprehensive breakthrough in control performance, safety assurance, energy conservation and environmental protection, and operation and maintenance efficiency. It can effectively improve the stability, economy and environmental protection of equipment operation, and has extremely high practical value and broad application prospects. Attached Figure Description

[0072] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0073] Figure 1 A schematic diagram of a three-impulse control system for the liquid level of a biomass gas-fired boiler drum is provided by the present invention.

[0074] Figure 2 A schematic diagram of the central control module provided by the present invention;

[0075] Figure 3 This is a schematic diagram of the control structure of the adaptive three-impulse control unit provided by the present invention;

[0076] Figure 4 A schematic diagram of the inference process of the fuzzy PID controller provided by the present invention;

[0077] Figure 5 This invention provides a schematic representation of the fuzzy PID control rules.

[0078] Figure 6 This is a schematic diagram of a three-impulse control method for the boiler drum liquid level of a biomass gas-fired boiler provided by the present invention. Detailed Implementation

[0079] 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.

[0080] This invention discloses a three-impulse control system for the boiler drum liquid level in a biomass gas-fired boiler, such as... Figure 1It includes: a parameter acquisition module, a central control module, an execution adjustment module, and a fault diagnosis and fault tolerance module;

[0081] The parameter acquisition module collects multi-dimensional parameters of boiler operation, including steam drum liquid level data, steam flow rate, feedwater flow rate, gas flow rate and gas composition, steam drum pressure and furnace temperature;

[0082] The central control module is used to perform multi-parameter fusion calculations and generate control commands through parameter preprocessing, adaptive three-impulse control, combustion-liquid level coordination, and pressure compensation.

[0083] The execution adjustment module is used to receive control commands from the central control module and adjust the water supply, gas supply, condensate flow, and air supply.

[0084] The fault diagnosis and fault tolerance module, based on the preprocessed parameters and actuator feedback signals, performs sensor fault detection and actuator fault detection, activates the corresponding fault tolerance mechanism, and records and uploads the faults.

[0085] To further implement the above technical solution, the parameter acquisition module includes a steam drum liquid level acquisition submodule, a steam flow acquisition submodule, a feedwater flow acquisition submodule, a biomass gas parameter acquisition submodule, a steam drum pressure acquisition submodule, and a furnace temperature acquisition submodule.

[0086] The steam drum liquid level acquisition submodule adopts a triple redundancy design of dual-redundant differential pressure liquid level sensor and capacitive liquid level sensor for liquid level measurement;

[0087] Dual-redundant differential pressure level sensors are installed on the level lead-out pipes on both sides of the steam drum, at a height of 1 / 3 from the top of the steam drum, avoiding areas of severe disturbance caused by the steam-water mixture inside the steam drum; capacitive level sensors are installed on the outer side of the top of the steam drum, using a dielectric constant ε1 different from that on the liquid surface ε2 to avoid interference from steam in the measurement; the positive and negative pressure chambers of the differential pressure sensor are respectively connected to the steam drum level lead-out pipe and the gas phase pipe at the top of the steam drum to ensure that the differential pressure signal accurately reflects changes in the liquid level;

[0088] The steam flow acquisition submodule uses a vortex flow meter to measure the steam flow rate and measures the steam temperature and pressure using temperature and pressure sensors.

[0089] The vortex flow meter is installed on the main steam pipeline, and the temperature and pressure sensors are installed downstream of the vortex flow meter at a distance equal to one pipe diameter for temperature and pressure compensation of the steam flow.

[0090] The water supply flow acquisition submodule uses an electromagnetic flow meter, a water supply temperature sensor, and a water supply pressure sensor to monitor the water supply flow, water supply temperature, and water supply pressure of the water supply system in real time.

[0091] The electromagnetic flowmeter is installed 5 times the pipe diameter downstream of the water supply regulating valve. The water supply temperature sensor is installed 0.5 times the pipe diameter upstream of the electromagnetic flowmeter to correct the influence of water supply density on flow measurement. The water supply pump inlet pressure sensor is installed in the water supply pump inlet pipe to monitor water supply pressure fluctuations in real time. The electromagnetic flowmeter is equipped with a grounding ring to avoid interference from power grid harmonics on the measurement signal and ensure the stability of flow measurement.

[0092] The biomass gas parameter acquisition submodule uses a gas flow bend flow meter to acquire gas flow, a gas pressure sensor and a temperature sensor to measure gas pressure and temperature, which are used to correct the influence of gas density on flow measurement, and a gas composition analyzer to measure CH4, CO, H2 and CO2 components.

[0093] The gas flow meter with a bend is installed on the gas header of the gas burner; the gas pressure sensor and temperature sensor are installed upstream of the gas flow sensor to correct the influence of the gas density on the flow measurement; the gas composition analyzer is equipped with a tar filter and a heated sampling tube, with the sampling probe inserted into 1 / 3 of the gas header diameter to ensure sample representativeness; the gas sampling tube is equipped with two-stage filtration (10μm coarse filter and 1μm fine filter) and a backflushing device to prevent tar and dust from clogging the sampling tube.

[0094] The steam drum pressure acquisition submodule uses an absolute pressure sensor to measure the steam drum pressure. On the one hand, it is used to correct the measurement deviation of the differential pressure level sensor through pressure compensation, and on the other hand, it is used to calculate the steam enthalpy value to provide a basis for combustion load calculation. The absolute pressure sensor is installed on the pressure lead-out pipe at the top of the steam drum.

[0095] The furnace temperature acquisition submodule uses dual K-type thermocouples to measure the furnace temperature, monitor changes in combustion intensity in real time, assist in identifying false water levels, and provide combustion status feedback for the control algorithm; the dual K-type thermocouples are installed on the side wall of the furnace.

[0096] To further implement the above technical solutions, such as Figure 2 The central control module uses a high-performance industrial PLC as its core, including a parameter preprocessing unit, an adaptive three-impulse control unit, a combustion-liquid level coordination unit, and a pressure compensation unit.

[0097] The parameter preprocessing unit is used to filter, compensate, and normalize the acquired raw parameters to eliminate noise interference and measurement deviations.

[0098] To address high-frequency noise during parameter acquisition (such as 50Hz grid interference from gas flow and random fluctuations in liquid level), a Kalman filter algorithm is used for real-time filtering. The filter window size is dynamically adjusted according to the parameter fluctuation frequency. When the fluctuation frequency is >0.5Hz, the window size is set to 5; when the fluctuation frequency is ≤0.5Hz, the window size is set to 3, ensuring that the signal-to-noise ratio of the filtered parameters is >40dB.

[0099] The adaptive three-impulse control unit uses the liquid level control loop as the main loop and combines the fuzzy PID algorithm to adaptively adjust the PID control parameters to obtain the initial feedwater flow setting. The initial feedwater flow setting value is corrected by the dual feedforward compensation loop of steam flow and low-level calorific value of gas. The feedwater flow control loop is used as the secondary loop to output the initial opening command of the feedwater regulating valve for feedwater flow control.

[0100] The combustion-liquid level coordination unit is used to coordinate the liquid level control and combustion system to perform target combustion load calculation, gas supply regulation, air flow coordination regulation, and combustion efficiency optimization.

[0101] The pressure compensation unit is used to monitor water supply pressure fluctuations in real time and calculate water supply pressure deviations, correct the initial water supply regulating valve opening command to compensate for water supply flow deviations, output the final water supply regulating valve opening command, and simultaneously output the water supply pump frequency converter speed command.

[0102] To further implement the above technical solution, the parameter preprocessing unit compensates for the collected raw parameters in the following ways:

[0103] Liquid level pressure compensation: Based on the real-time pressure value P of the steam drum, the measured value H0 of the differential pressure liquid level sensor is corrected to obtain the actual liquid level value.

[0104] H = H0 + K P ×(P-P0)

[0105] Where H is the actual liquid level value, K p This is the pressure compensation coefficient, with a value ranging from 15-25 mm / MPa. Through experimental calibration, when P = 0.7 MPa, K... p =18, P=2.0MPa, K p =22, P=2.5MPa, K p =25, P0 is the rated working pressure of the boiler; the compensated liquid level measurement error is <5mm;

[0106] In this embodiment, when the dual differential pressure sensors are functioning normally, the actual liquid level H = (H 01 +H 02 ) / 2+K p ×(PP set When the dual differential pressure sensor fails, H = H 03 +Kp ×(PP set );

[0107] Steam flow rate temperature and pressure compensation is performed based on steam temperature T and pressure P, using the steam flow rate compensation formula to adjust the operating flow rate Q. v Corrected to standard state flow Q s ;

[0108]

[0109] Where T0 = 0℃, P0 = 0.1013MPa, and the steam flow measurement error after compensation is <0.5%;

[0110] Water supply flow rate temperature and pressure compensation, based on water supply temperature T W With pressure P W The operating flow rate Q wv Corrected to standard state flow Q ws ;

[0111]

[0112] The calorific value of the gas is calculated based on the volume fractions C1, C2, and C3 of CH4, CO, and H2 collected by the gas composition analyzer, combined with the volume fraction of moisture C4. net ;

[0113] Q net = 0.358×C1 + 0.127×C2 + 0.108×C3 - 0.002×C4

[0114] Among them, 0.358, 0.127, and 0.108 are the lower heating coefficients of CH4, CO, and H2, respectively.

[0115] In this embodiment, all preprocessed parameters are converted into 0-1 standardized values ​​to facilitate unified operation of the control algorithm.

[0116] To further implement the above technical solutions, such as Figure 3 and Figure 4 The adaptive three-impulse control unit includes a level control loop, a dual feedforward compensation loop, and a water supply flow control loop.

[0117] The liquid level control loop uses the pre-processed actual liquid level H as the controlled variable, and the rated liquid level H set To calculate the target value, the liquid level deviation ΔH = H set-H and the rate of change of liquid level deviation ΔH / Δt, where Δt is the control period; a fuzzy PID controller is adopted, based on the adaptive rules of fuzzy PID parameters and the triangular membership function, to fuzzify the liquid level deviation and the rate of change of liquid level deviation, and to obtain the corresponding fuzzy subset by querying the fuzzy PID rule table. Fuzzy inference is performed by the Mamdani inference method and fuzzy defuzzification is performed by the area centroid method to output the PID parameter correction amount ΔK. p ΔK i ΔK d Calculate the actual PID parameter K p K i K d The initial water supply flow setpoint Q is calculated using a PID algorithm. wset0 ;

[0118] Q wset0 =K p ×ΔH+K i ×∫ΔHdt+K d ×d(ΔH) / dt

[0119] A dual feedforward compensation loop is introduced, introducing steam flow rate Q. s Using the lower heating value of the gas as a feedforward compensation signal Q net Calculate the corrected water supply flow rate setpoint Q wset Adjust the water supply in advance to suppress the impact of combustion load fluctuations on the liquid level;

[0120] Q wset =Q wset0 +K f1 ×Q s +K f2 ×Q net

[0121] Among them, K f1 The steam flow rate feedforward coefficient has a value of 0.3-0.6m. 3 / (h·t), when the load is <10t / h, K f1 =0.3, when 10t / h ≤ load ≤ 50t / h, K f1 =0.45, K when load > 50t / h f1 =0.6; K f2 The feedforward coefficient for the calorific value of the gas is 0.02-0.05m. 3 / (h·MJ / Nm 3 ), Q net <10MJ / Nm 3 At that time, K f2 =0.02,10MJ / Nm 3 ≤Q net ≤14MJ / Nm 3 At that time, K f2=0.035, Q net >14MJ / Nm 3 At that time, K f2 =0.05;

[0122] The water supply flow control loop uses the water supply flow rate Q. w The controlled variable is the setpoint Q of the feedwater flow rate output from the main loop. wset0 Calculate the water supply flow deviation ΔQ to get the target value. w =Q wset0 -Q w The proportional controller outputs the initial opening command U1 = K for the water supply regulating valve. p2 ×ΔQ w The proportional coefficient K of the proportional controller p2 =0.8~1.2, calibrated according to the resistance characteristics of water supply pipelines; for pipe diameter DN50, K p2 =0.8, K when DN100 p2 =1.0, K when DN200 p2 =1.2;

[0123] The pressure compensation unit monitors water supply pressure fluctuations in real time and calculates the water supply pressure deviation ΔP. w =P wset -P w P w P is the inlet pressure of the water pump. wset Given the rated water supply pressure, if |ΔPw|>0.05MPa, calculate the opening correction command ΔU=K. p5 ×ΔP w K p5 The water supply pressure correction factor is set at 5-10% / MPa. For Pw < 0.5MPa, Kp5 = 5; for 0.5MPa ≤ Pw, Kp5 = 5. w When Pw ≤ 1.5MPa, Kp5 = 7.5; when Pw > 1.5MPa, Kp5 = 10), the final water supply regulating valve opening command U = U1 + ΔU; simultaneously output the water supply pump inverter speed command U2: if |ΔQ w |>5%,U2=U2 prev +0.02×ΔQ w U2 prev The speed command is from the previous cycle; otherwise, U2 = U2. prev .

[0124] In this embodiment, as Figure 5ΔH is divided into 7 fuzzy subsets (negative large NB, negative medium NM, negative small NS, zero ZO, positive small PS, positive medium PM, positive large PB), with a universe of discourse of [-100, 100] mm. The fuzzy subset divisions are: NB (-100~-60), NM (-80~-20), NS (-40~20), ZO (-20~20), PS (20~60), PM (40~100), PB (60~100); ΔH / Δt is divided into 7 fuzzy subsets (same as ΔH), with a universe of discourse of [-50, 50] mm / s. The fuzzy subset divisions are: NB (-50~-30), NM (-40~-10), NS (-20~10), ZO (-10~10), PS (10~30), PM (20~50), PB (30~50).

[0125] The formula for calculating the membership degree of a triangle membership function is:

[0126]

[0127] For any input value x (e.g., ΔH = x), the membership degree μ(x) of a certain fuzzy subset is calculated by substituting x into the corresponding formula according to the interval where x is located.

[0128] The specific content of fuzzy reasoning using the Mamdani reasoning method is as follows:

[0129] Rule activation strength calculation: For each rule, take the minimum value of the membership degree of the input fuzzy subset as the activation strength;

[0130] Output fuzzy subset clipping: Using the activation intensity of the rule as the height, clip the membership function of the corresponding output fuzzy subset;

[0131] Merge all rule outputs: Maximize the membership functions of all trimmed rules and merge them into a comprehensive fuzzy output membership function (taking the maximum membership degree of each point);

[0132] The fuzzy resolution method (area centroid method) uses the following formula:

[0133]

[0134] Where μ(y) is the membership function after aggregation, and ymin and ymax are the domain ranges of the output variables;

[0135] ΔK p ΔK i ΔK d Calculate: for K respectively p K i K d Integrate the aggregate membership distribution to obtain the corresponding correction amount;

[0136] If K p If the aggregation membership distributions are PB and PM, then the centroid position is calculated by integration, and ΔK is obtained. p Assume K p Given the aggregate membership distributions PB and PM, calculate the area and centroid of each fuzzy subset, and calculate the combined centroid ΔK. p Output PID parameter correction ΔK p ΔK i ΔK d The final PID parameters are:

[0137] K p =K p0 +ΔK p ,K i =K i0 +ΔK i ,K d =K d0 +ΔK d

[0138] Among them, K p0 =2.0, K i0 =0.5, K d0 =0.1, which is the PID reference parameter under rated operating conditions.

[0139] To further implement the above technical solution, the specific contents of the combustion-liquid level coordination unit include:

[0140] Target combustion load calculation: Based on the steam flow rate Qs and the deviation ΔP from the drum pressure, ΔP = P set -P, Pset is the rated steam drum pressure, calculate the target combustion load Qreq;

[0141] Q req =Qs×h fg +K p3 ×ΔP

[0142] Among them, h fg Latent heat of vapor;

[0143] Gas supply regulation: based on the target combustion load Q req With the lower heating value Q of gas net Calculate the target gas flow rate Q gasreq Q gasreq =Q req / Q net Compare with the actual gas flow rate Q gas With the target gas flow rate Q gasreq Calculate the gas flow deviation ΔQ gas =Q gasreq -Q gasThe PID controller outputs the gas regulating valve opening command.

[0144] Gas regulating valve opening command U3 = K p4 ×ΔQ gas +K i4 ×∫ΔQ gas dt+K d4 ×d(ΔQ gas ) / dt

[0145] Airflow coordinated regulation: based on gas flow Q gas Calculating the target airflow rate Q using the theoretical air volume of the gas airreq Qairreq = Qgas × V0 × α, where V0 is the theoretical air volume of the fuel gas and α is the excess air coefficient; the air flow deviation ΔQ is calculated by combining the actual air flow of the blower. air =Q airreq -Q air Q air The actual airflow rate is calculated from the blower speed; the output blower frequency converter speed command controls the airflow rate, and at the same time, the induced draft fan frequency converter speed command is output according to the furnace negative pressure.

[0146] Blower inverter speed command U4 = U4 prev +0.03×ΔQ air ;

[0147] induced draft fan inverter speed command U5 = U5 prev +0.05×ΔP neg Negative pressure deviation ΔP neg =P negset -P neg P neg For negative pressure in the furnace, P negset The target negative pressure;

[0148] Combustion efficiency optimization: Real-time monitoring of furnace temperature and flue gas composition, increasing or decreasing airflow. Specifically, equipping the system with a flue gas analyzer to monitor O2 and CO content; when CO content > 100 mg / m³... 3 When the O2 content is >6%, increase the airflow (α increases by 0.05); when the O2 content is >6%, decrease the airflow (α decreases by 0.05) to ensure combustion efficiency >92%.

[0149] To further implement the above technical solution, the control module includes a water supply control submodule, a gas supply control submodule, a ventilation control submodule, and a drainage control submodule;

[0150] Water supply regulating submodule: The main regulating function is the electric regulating valve, and the auxiliary regulating function is the frequency converter. The opening of the water supply regulating valve is adjusted according to the final opening command U, and the speed of the water supply pump frequency converter is adjusted according to the speed command U2.

[0151] Under normal operating conditions, the electric regulating valve is the main regulator and the frequency converter is the auxiliary regulator. When the water supply flow deviation is greater than 5% of the rated water supply flow, the pump speed is adjusted. When the regulating valve fails, the system switches to the frequency converter for independent control, and the flow is adjusted by the speed.

[0152] The gas regulating submodule adopts a safe regulating mode with an electric regulating valve and an emergency shut-off valve. It adjusts the opening of the gas regulating valve according to the gas regulating valve opening command U3. The gas emergency shut-off valve remains open when there is no fault, and closes quickly when the liquid level exceeds the limit or gas leaks.

[0153] The gas emergency shut-off valve is pneumatically driven and equipped with a manual operating handle. When the liquid level exceeds the limit (H > H), it will shut off. set +30mm or H < H set In case of a gas leak (-30mm) or gas detector concentration > 10% of the lower explosive limit, shut off immediately;

[0154] The ventilation control submodule adopts a coordinated control mode of the blower frequency converter and the induced draft fan frequency converter. The speed of the blower is adjusted according to the speed command U4 of the blower frequency converter, and the speed of the induced draft fan is adjusted according to the speed command U5 of the induced draft fan frequency converter.

[0155] The condensate regulating submodule opens or closes the steam drum condensate electric valve according to the steam drum liquid level. When the boiler starts up, condensate is discharged through the superheater condensate valve and closed during normal operation.

[0156] When the steam drum liquid level H > H set When H ≤ H, open the steam drum drain valve (opening degree 10%-50%, adjust according to liquid level deviation) to drain excess boiler water; set When the temperature reaches +10mm, close the steam trap; the superheater steam trap is used to drain condensate when the boiler starts up and is closed during normal operation.

[0157] To further implement the above technical solution, the fault diagnosis and fault tolerance module includes a hardware fault detection unit, a software fault tolerance unit, and a fault recording and uploading unit.

[0158] Sensor fault detection includes redundancy deviation detection, range exceedance detection, drift trend detection, and signal loss detection; specifically:

[0159] Redundancy deviation detection: Compare the measured values ​​of the dual redundant differential pressure level sensors. If the difference is >15mm and lasts for 3 control cycles (300ms), one of the sensors is determined to be faulty. Compare the measured values ​​of the differential pressure sensor and the capacitive level sensor. If the difference is >20mm and lasts for 3 control cycles, the differential pressure sensor is determined to be faulty.

[0160] Over-range detection: If the measured value of any sensor exceeds the rated range for two consecutive control cycles (200ms), the sensor is determined to be faulty.

[0161] Drift trend detection: Through Kalman filter residual analysis (residual = actual measured value - filtered estimated value), if the absolute value of the residual of a certain sensor is >5%FS and lasts for 5 control cycles (500ms), the sensor is determined to be drift faulty.

[0162] Signal loss detection: If the sensor output signal is 0mA or >22mA and lasts for one control cycle (100ms), a sensor signal loss fault is determined.

[0163] Actuator fault detection includes command-feedback deviation detection, action timeout detection, and power supply fault detection; specifically:

[0164] Command-feedback deviation detection: Compare the actuator command (such as the opening command U of the water supply regulating valve) output by the central control module with the actuator feedback signal (such as the actual opening of the regulating valve U_f). If |U-U_f|>5% and continues for 3 control cycles, it is determined that the actuator is stuck or the positioner is faulty.

[0165] Action timeout detection: If the actuator fails to reach the target opening degree / speed within the set time (5s for water supply regulating valve, 3s for gas regulating valve, 2s for frequency converter) after receiving the command, the actuator action timeout fault is determined.

[0166] Power supply fault detection: The actuator power supply voltage is monitored by a voltage sensor. If the voltage is <20VDC or >26VDC and continues for one control cycle, the actuator power supply is determined to be faulty.

[0167] Fault tolerance mechanisms include sensor fault tolerance strategies and actuator fault tolerance strategies;

[0168] Sensor fault tolerance strategies include fault tolerance for level sensors, fault tolerance for steam flow sensors, fault tolerance for gas composition analyzers, and fault tolerance for multiple sensors; specifically:

[0169] Level sensor fault tolerance: If one differential pressure level sensor fails, it automatically switches to another differential pressure sensor; if both differential pressure sensors fail, it switches to a capacitive level sensor, and simultaneously uses the difference between steam flow rate and feedwater flow rate to estimate the level (H). est =Hprev +(Q w -Q s )×Δt / V,H prev (where V is the liquid level before the fault and V is the volume of the steam tank), the estimation error is <15mm;

[0170] Steam flow sensor fault tolerance: If the steam flow sensor fails, the equivalent steam flow rate (Q) is calculated using the gas flow rate and calorific value. s' =Q gas ×Q net / h fg It replaces the actual steam flow rate in the control, with a calculation error of <8%;

[0171] Gas composition analyzer fault tolerance: If the gas composition analyzer malfunctions, the average calorific value Q of the gas over the past 5 minutes will be used. netavg It replaces the real-time value and reduces the boiler load to 80% of the rated load, thus reducing the impact of calorific value fluctuations on control.

[0172] Multi-sensor fault tolerance: If two or more sensors fail simultaneously, the simplified control mode is activated, retaining only the liquid level (backup sensor) and water flow sensor. The control method of single impulse and water flow feedback is adopted, and the liquid level control accuracy is maintained within ±25mm.

[0173] Actuator fault tolerance strategies include feedwater regulating valve fault tolerance, gas regulating valve fault tolerance, frequency converter fault tolerance, and emergency shutdown procedures; specifically:

[0174] Fault tolerance of water supply regulating valve: If the water supply regulating valve fails, switch to the water supply pump frequency converter to control the water supply flow separately, change the flow rate by adjusting the pump speed, and at the same time increase the proportional coefficient Kp of the liquid level control (increase by 20%) to speed up the response speed;

[0175] Gas regulating valve fault tolerance: If the gas regulating valve fails, close the emergency gas shut-off valve, open the backup gas regulating valve after 10 seconds, and reduce the boiler load to 50% of the rated load to avoid sudden load changes; if there is no backup regulating valve, start the emergency shutdown procedure.

[0176] Inverter fault tolerance: If the blower inverter fails, switch to mains frequency operation (air flow is fixed at 70% of the rated value) and reduce the gas supply to ensure stable combustion; if the induced draft fan inverter fails, immediately close the gas shut-off valve and initiate emergency shutdown.

[0177] Emergency shutdown procedure: When a fault occurs that cannot be mitigated by fault-tolerant mechanisms (such as failure of both level sensors, gas leakage, or excessive level), H > H. set +50mm or H < H set When the temperature drops to -50mm, an emergency shutdown should be performed.

[0178] The emergency shutdown procedure is as follows: close the emergency gas shut-off valve, stop the feedwater pump and blower, open the steam drum drain valve to drain the boiler water, continue running the induced draft fan for 5 minutes to drain the residual gas in the furnace, issue an audible and visual alarm through the human-machine interface module, and record the fault information.

[0179] To further implement the above technical solution, a three-impulse control system for the steam drum liquid level of a biomass gas boiler also includes a human-machine interaction module for real-time parameter display, parameter setting function, status monitoring function, alarm prompts, and historical data query.

[0180] A three-impulse control method for boiler drum liquid level in a biomass gas-fired boiler, employing a three-impulse control system for boiler drum liquid level in a biomass gas-fired boiler, such as... Figure 6 The method includes the following steps:

[0181] S1. System initialization: Maintenance personnel log in with administrator privileges through the human-machine interaction module to set boiler rated parameters and control parameters; the central control module starts the parameter acquisition module, execution adjustment module, and fault diagnosis and fault tolerance module, initializes the status of each module, and the system enters standby mode;

[0182] Rated parameters include rated liquid level Hset, rated steam drum pressure Pset, rated load Qset, and rated feedwater pressure Pwset; control parameters include PID reference parameters (K). p0 =2.0, K i0 =0.5, K d0 =0.1), feedforward coefficient (K) f1 =0.45, K f2 =0.035), pressure compensation coefficient (K) p =22, K p5 =7.5), fault thresholds (sensor deviation threshold 15mm, actuator command-feedback deviation threshold 5%);

[0183] S2. Real-time acquisition of raw parameters, including liquid level from dual differential pressure level sensors, liquid level from capacitive level sensors, steam flow rate, steam temperature, steam pressure, feedwater flow rate, feedwater temperature, feedwater pump inlet pressure, gas flow rate, gas composition, gas pressure, gas temperature, steam drum pressure, and furnace temperature. Kalman filtering is applied to all parameters to calculate the actual liquid level, standard steam flow rate, and lower heating value of the gas. The processed parameters (actual liquid level, standard steam flow rate, feedwater flow rate, lower heating value of the gas, steam drum pressure, and furnace temperature) are then transmitted to the central control module and the fault diagnosis and fault tolerance module.

[0184] S3. The fault diagnosis and fault tolerance module receives the preprocessed parameters and actuator feedback signals, starts sensor fault detection and actuator fault detection. If a fault is detected, the fault tolerance mechanism is activated according to the fault type. If the fault cannot be mitigated by the fault tolerance mechanism, an audible and visual alarm is triggered, an emergency shutdown procedure is executed, and the control process ends. If there is no fault or the fault has been tolerated, proceed to step S4.

[0185] S4. Adaptive Three-Impulse Control Calculation of the Central Control Module: The liquid level deviation and rate of change of liquid level deviation are calculated through the main liquid level control loop; the liquid level deviation and rate of change of liquid level deviation are fuzzified, the fuzzy PID rule table is queried, and the PID parameter correction is output through fuzzy inference and defuzzification, and the actual PID parameters are calculated. The initial feedwater flow setpoint is calculated using the PID algorithm; steam flow and gas calorific value are introduced for feedforward compensation, and the corrected feedwater flow setpoint is calculated; the feedwater flow deviation is calculated through the secondary water flow control loop, and the initial opening command of the feedwater regulating valve is output through the proportional controller; the feedwater pressure deviation and opening correction command are calculated to obtain the final feedwater regulating valve opening command, and the feedwater pump inverter speed command is output simultaneously.

[0186] S5. Combustion-Liquid Level Coordinated Control: Calculates the steam drum pressure deviation, and calculates the target combustion load based on the steam flow rate and the steam drum pressure deviation; calculates the target gas flow rate based on the target combustion load and the lower heating value of the gas, and calculates the gas flow rate deviation based on the target gas flow rate and the real-time gas flow rate, outputting the gas regulating valve opening command through the PID controller; calculates the target air flow rate based on the real-time gas flow rate, and calculates the air flow rate deviation based on the target air flow rate and the actual air flow rate, outputting the blower frequency converter speed command; collects the furnace negative pressure, calculates the negative pressure deviation based on the target negative pressure, and outputs the induced draft fan frequency converter speed command.

[0187] S6. Execution Adjustment: The central control module transmits the final feedwater regulating valve opening command U, feedwater pump inverter speed command U2, gas regulating valve opening command U3, blower inverter speed command U4, and induced draft fan inverter speed command U5 to the execution adjustment module via the industrial bus; the execution adjustment module executes the commands to adjust the feedwater regulating valve to opening U, the feedwater pump inverter to speed U2, the gas regulating valve to opening U3, and, in the absence of faults, keeps the gas emergency shut-off valve open, adjusts the blower to speed U4, and adjusts the induced draft fan to speed U5; the steam drum drain electric valve is opened or closed according to the actual steam drum liquid level; condensate is discharged through the superheater drain valve during boiler startup and closed during normal operation;

[0188] S7. Handling of Excessive Liquid Level: If the actual steam drum liquid level exceeds the first threshold, H > H set +30mm, high liquid level alarm, increase the opening of the gas regulating valve, open the steam drum drain valve, and simultaneously close the feedwater regulating valve; if the actual steam drum liquid level exceeds the second threshold, H>Hset +50mm triggers an emergency shutdown; if the actual steam drum level is less than the third threshold, H < H set -30mm, low liquid level alarm, and partially close the gas regulating valve, open the feedwater regulating valve, and the feedwater pump frequency converter runs at full load; if the actual steam drum liquid level is less than the fourth threshold, H < H set -50mm triggers an emergency shutdown; if the liquid level returns to the normal range (i.e., the actual liquid level is at the rated liquid level H), the boiler will be shut down. set Within ±20mm), cancel the over-limit handling and restore normal control;

[0189] S8. Cyclic Control and Shutdown: Return to step S2, repeat parameter acquisition, preprocessing, fault diagnosis, control calculation, and adjustment process to achieve continuous closed-loop control; when a boiler shutdown command is received, execute the normal shutdown procedure: gradually reduce the gas supply until the gas shut-off valve is closed, the feedwater pump continues to run for 10 minutes, and the steam drum liquid level is maintained at H. set +10mm, the blower and induced draft fan continue to run for 5 minutes to discharge the residual flue gas in the furnace, then the feed water pump, blower, and induced draft fan are turned off, the system enters the shutdown state, and the control process ends.

[0190] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0191] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-impulse control system for the steam drum level of a biomass gas-fired boiler, characterized in that, include: Parameter acquisition module, central control module, execution and adjustment module, and fault diagnosis and fault tolerance module; The parameter acquisition module collects multi-dimensional parameters of boiler operation, including steam drum liquid level data, steam flow rate, feedwater flow rate, gas flow rate and gas composition, steam drum pressure and furnace temperature; The central control module is used to perform multi-parameter fusion calculations and generate control commands through parameter preprocessing, adaptive three-impulse control, combustion-liquid level coordination, and pressure compensation. The execution adjustment module is used to receive control commands from the central control module and adjust the water supply, gas supply, condensate flow, and air supply. The fault diagnosis and fault tolerance module, based on the preprocessed parameters and actuator feedback signals, performs sensor fault detection and actuator fault detection, activates the corresponding fault tolerance mechanism, and records and uploads the faults.

2. The three-impulse control system for the steam drum level of a biomass gas boiler according to claim 1, characterized in that, The parameter acquisition module includes a steam drum liquid level acquisition submodule, a steam flow acquisition submodule, a feedwater flow acquisition submodule, a biomass gas parameter acquisition submodule, a steam drum pressure acquisition submodule, and a furnace temperature acquisition submodule; The steam drum liquid level acquisition submodule adopts a triple redundancy design of dual-redundant differential pressure liquid level sensor and capacitive liquid level sensor for liquid level measurement; The steam flow acquisition submodule uses a vortex flow meter to measure the steam flow rate and measures the steam temperature and pressure using temperature and pressure sensors. The water supply flow acquisition submodule uses an electromagnetic flow meter, a water supply temperature sensor, and a water supply pressure sensor to monitor the water supply flow, water supply temperature, and water supply pressure of the water supply system in real time. The biomass gas parameter acquisition submodule uses a gas flow bend flow meter to acquire gas flow, a gas pressure sensor and a temperature sensor to measure gas pressure and temperature, which are used to correct the influence of gas density on flow measurement, and a gas composition analyzer to measure CH4, CO, H2 and CO2 components. The steam drum pressure acquisition submodule uses an absolute pressure sensor to measure the steam drum pressure. On the one hand, it is used to correct the measurement deviation of the differential pressure level sensor through pressure compensation, and on the other hand, it is used to calculate the steam enthalpy value to provide a basis for combustion load calculation. The furnace temperature acquisition submodule uses dual K-type thermocouples to measure the furnace temperature, monitor changes in combustion intensity in real time, help identify false water levels, and provide combustion status feedback for the control algorithm.

3. The three-impulse control system for the steam drum level of a biomass gas boiler according to claim 1, characterized in that, The central control module includes a parameter preprocessing unit, an adaptive three-impulse control unit, a combustion-level coordination unit, and a pressure compensation unit; The parameter preprocessing unit is used to filter, compensate, and normalize the acquired raw parameters to eliminate noise interference and measurement deviations. The adaptive three-impulse control unit uses the liquid level control loop as the main loop and combines the fuzzy PID algorithm to adaptively adjust the PID control parameters to obtain the initial feedwater flow setting. The initial feedwater flow setting value is corrected by the dual feedforward compensation loop of steam flow and low-level calorific value of gas. The feedwater flow control loop is used as the secondary loop to output the initial opening command of the feedwater regulating valve for feedwater flow control. The combustion-liquid level coordination unit is used to coordinate the liquid level control and combustion system to perform target combustion load calculation, gas supply regulation, air flow coordination regulation, and combustion efficiency optimization. The pressure compensation unit is used to monitor water supply pressure fluctuations in real time and calculate water supply pressure deviations, correct the initial water supply regulating valve opening command to compensate for water supply flow deviations, output the final water supply regulating valve opening command, and simultaneously output the water supply pump frequency converter speed command.

4. The three-impulse control system for the steam drum level of a biomass gas boiler according to claim 3, characterized in that, The specific steps taken by the parameter preprocessing unit to compensate for the acquired raw parameters include: Liquid level pressure compensation: Based on the real-time value of the steam drum pressure, the measured value of the differential pressure liquid level sensor is corrected to obtain the actual liquid level value; Steam flow temperature and pressure compensation: Based on the steam temperature and pressure, the steam flow compensation formula is used to correct the operating flow rate to the standard state flow rate. Water supply flow rate temperature and pressure compensation: Based on the water supply temperature and pressure, the operating flow rate is corrected to the standard state flow rate. The calorific value of the gas is calculated based on the volume fractions of CH4, CO, and H2 collected by the gas composition analyzer, combined with the volume fraction of moisture in the gas.

5. The three-impulse control system for the steam drum level of a biomass gas boiler according to claim 3, characterized in that, The adaptive three-impulse control unit includes a level control loop, a dual feedforward compensation loop, and a feedwater flow control loop. The liquid level control loop uses the pre-processed actual liquid level as the controlled variable and the rated liquid level as the target value to calculate the liquid level deviation and the rate of change of liquid level deviation. A fuzzy PID controller is adopted, which is based on the adaptive rules of fuzzy PID parameters and the triangular membership function to fuzzify the liquid level deviation and the rate of change of liquid level deviation. The corresponding fuzzy subset is obtained by querying the fuzzy PID rule table. Fuzzy inference is performed by Mamdani inference method and fuzzy defuzzification by area centroid method to output PID parameter corrections ΔKp, ΔKi, and ΔKd. The actual PID parameters Kp, Ki, and Kd are calculated. The initial water supply flow setpoint is calculated by PID algorithm. The dual feedforward compensation loop introduces steam flow and low heating value of gas as feedforward compensation signals to calculate the corrected feedwater flow setpoint, adjust the feedwater flow in advance, and suppress the impact of combustion load fluctuations on liquid level. The water supply flow control loop uses the water supply flow as the controlled variable, the setpoint of the water supply flow output by the main loop is the target value, the water supply flow deviation is calculated, and the initial opening command of the water supply regulating valve is output through the proportional controller.

6. The three-impulse control system for the steam drum level of a biomass gas boiler according to claim 3, characterized in that, The specific contents of the combustion-liquid level coordinated unit include: Target combustion load calculation: The target combustion load is calculated based on the deviation between steam flow rate and steam drum pressure. Gas supply regulation: Calculate the target gas flow rate based on the target combustion load and the lower heating value of the gas, compare the actual gas flow rate with the target gas flow rate, calculate the gas flow rate deviation, and output the gas regulating valve opening command through the PID controller; Airflow coordinated regulation: Calculate the target airflow based on the gas flow rate and the theoretical air volume of the gas, calculate the airflow deviation based on the actual airflow of the blower, output the blower frequency converter speed command to control the airflow, and output the induced draft fan frequency converter speed command based on the furnace negative pressure. Combustion efficiency optimization: Real-time monitoring of furnace temperature and flue gas composition, increasing or decreasing airflow.

7. A three-impulse control system for the steam drum level of a biomass gas-fired boiler according to claim 6, characterized in that, The control module includes a water supply control submodule, a gas supply control submodule, a ventilation control submodule, and a drainage control submodule; Water supply regulating submodule: The main regulating function is the electric regulating valve, and the auxiliary regulating function is the frequency converter. The opening degree of the water supply regulating valve is adjusted according to the final opening degree command of the water supply regulating valve, and the speed of the water supply pump frequency converter is adjusted according to the speed command of the water supply pump frequency converter. The gas regulating submodule adopts a safe regulating mode with an electric regulating valve and an emergency shut-off valve. It adjusts the opening of the gas regulating valve according to the opening command of the gas regulating valve. The gas emergency shut-off valve remains open when there is no fault, and closes quickly when the liquid level exceeds the limit or gas leaks. The ventilation control submodule adopts a coordinated control mode of the blower frequency converter and the induced draft fan frequency converter. It adjusts the speed of the blower according to the speed command of the blower frequency converter and adjusts the speed of the induced draft fan according to the speed command of the induced draft fan frequency converter. The condensate regulating submodule opens or closes the steam drum condensate electric valve according to the steam drum liquid level. When the boiler starts up, condensate is discharged through the superheater condensate valve and closed during normal operation.

8. The three-impulse control system for the steam drum level of a biomass gas boiler according to claim 1, characterized in that, The fault diagnosis and fault tolerance module includes a hardware fault detection unit, a software fault tolerance unit, and a fault recording and uploading unit; Sensor fault detection includes redundancy deviation detection, range overrun detection, drift trend detection, and signal loss detection. Actuator fault detection includes command-feedback deviation detection, action timeout detection, and power failure detection. Fault tolerance mechanisms include sensor fault tolerance strategies and actuator fault tolerance strategies; Sensor fault tolerance strategies include fault tolerance for level sensors, fault tolerance for steam flow sensors, fault tolerance for gas composition analyzers, and fault tolerance for multiple sensors. The actuator fault tolerance strategy includes fault tolerance for feedwater regulating valves, fault tolerance for gas regulating valves, fault tolerance for frequency converters, and emergency shutdown procedures.

9. A three-impulse control system for the steam drum level of a biomass gas boiler according to claim 1, characterized in that, It also includes a human-computer interaction module for real-time parameter display, parameter setting function, status monitoring function, alarm prompts and historical data query.

10. A three-impulse control method for the liquid level in the steam drum of a biomass gas-fired boiler, characterized in that, Using the three-impulse control system for boiler drum liquid level of a biomass gas-fired boiler according to any one of claims 1-9, the method includes the following steps: S1. System initialization: Maintenance personnel log in with administrator privileges through the human-machine interaction module to set boiler rated parameters and control parameters; the central control module starts the parameter acquisition module, execution adjustment module, and fault diagnosis and fault tolerance module, initializes the status of each module, and the system enters standby mode; S2. Real-time acquisition of raw parameters, including liquid level from dual differential pressure level sensors, liquid level from capacitive level sensors, steam flow rate, steam temperature, steam pressure, feedwater flow rate, feedwater temperature, feedwater pump inlet pressure, gas flow rate, gas composition, gas pressure, gas temperature, steam drum pressure, and furnace temperature. Kalman filtering is applied to all parameters to calculate the actual liquid level, standard steam flow rate, and lower heating value of the gas. The processed parameters (actual liquid level, standard steam flow rate, feedwater flow rate, lower heating value of the gas, steam drum pressure, and furnace temperature) are then transmitted to the central control module and the fault diagnosis and fault tolerance module. S3. The fault diagnosis and fault tolerance module receives the preprocessed parameters and actuator feedback signals, starts sensor fault detection and actuator fault detection. If a fault is detected, the fault tolerance mechanism is activated according to the fault type. If the fault cannot be mitigated by the fault tolerance mechanism, an audible and visual alarm is triggered, an emergency shutdown procedure is executed, and the control process ends. If there is no fault or the fault has been tolerated, proceed to step S4. S4. Adaptive Three-Impulse Control Calculation of the Central Control Module: The liquid level deviation and rate of change of liquid level deviation are calculated through the main liquid level control loop; the liquid level deviation and rate of change of liquid level deviation are fuzzified, the fuzzy PID rule table is queried, and the PID parameter correction is output through fuzzy inference and defuzzification, and the actual PID parameters are calculated. The initial feedwater flow setpoint is calculated using the PID algorithm; steam flow and gas calorific value are introduced for feedforward compensation, and the corrected feedwater flow setpoint is calculated; the feedwater flow deviation is calculated through the secondary water flow control loop, and the initial opening command of the feedwater regulating valve is output through the proportional controller; the feedwater pressure deviation and opening correction command are calculated to obtain the final feedwater regulating valve opening command, and the feedwater pump inverter speed command is output simultaneously. S5. Combustion-Liquid Level Coordinated Control: Calculates the steam drum pressure deviation, and calculates the target combustion load based on the steam flow rate and the steam drum pressure deviation; calculates the target gas flow rate based on the target combustion load and the lower heating value of the gas, and calculates the gas flow rate deviation based on the target gas flow rate and the real-time gas flow rate, outputting the gas regulating valve opening command through the PID controller; calculates the target air flow rate based on the real-time gas flow rate, and calculates the air flow rate deviation based on the target air flow rate and the actual air flow rate, outputting the blower frequency converter speed command; collects the furnace negative pressure, calculates the negative pressure deviation based on the target negative pressure, and outputs the induced draft fan frequency converter speed command. S6. Execution Adjustment: The central control module transmits the final feedwater regulating valve opening command U, feedwater pump inverter speed command U2, gas regulating valve opening command U3, blower inverter speed command U4, and induced draft fan inverter speed command U5 to the execution adjustment module via the industrial bus; the execution adjustment module executes the commands to adjust the feedwater regulating valve to opening U, the feedwater pump inverter to speed U2, the gas regulating valve to opening U3, and, in the absence of faults, keeps the gas emergency shut-off valve open, adjusts the blower to speed U4, and adjusts the induced draft fan to speed U5; the steam drum drain electric valve is opened or closed according to the actual steam drum liquid level; condensate is discharged through the superheater drain valve during boiler startup and closed during normal operation; S7. Over-limit Liquid Level Handling: If the actual steam drum liquid level exceeds the first threshold, a high liquid level alarm is triggered, the gas regulating valve opening is increased, the steam drum drain valve is opened, and the feedwater regulating valve is closed to a minimum; if the actual steam drum liquid level exceeds the second threshold, an emergency shutdown is triggered; if the actual steam drum liquid level is less than the third threshold, a low liquid level alarm is triggered, the gas regulating valve is closed to a minimum, the feedwater regulating valve is opened, and the feedwater pump frequency converter operates at full load; if the actual steam drum liquid level is less than the fourth threshold, an emergency shutdown is triggered; if the liquid level recovers, the over-limit handling is canceled, and normal control is restored. S8. Cyclic Control and Shutdown: Return to step S2, repeat parameter acquisition, preprocessing, fault diagnosis, control calculation, and adjustment process to achieve continuous closed-loop control; when a boiler shutdown command is received, execute the normal shutdown procedure, the system enters the shutdown state, and the control flow ends.

Images