A control method and system for self-adapting unit output after mill group tripping

Abstract

The application discloses a kind of control method and system of self-adapting unit output after operating mill group trip, comprising: obtaining the trip pulse signal of operating mill group;Determine the operating mode of each mill group in remaining operating mill group;According to operating mode, the maximum output value of each remaining operating mill group is calculated and summed to obtain total coal quantity value;Obtain coal quality correction coefficient, and according to total coal quantity value and coal quality correction coefficient, the theoretical maximum output value of unit is generated;According to unit theoretical maximum output value and unit current output value, generate unit load control instruction.The application is mainly used for load self-adaptive adjustment after the trip of thermal power unit mill group, realizes the fine control of unit load.

Description

Technical Field

[0001] This invention belongs to the field of automatic control technology for thermal power units, and relates to a control method and system for automatically adapting the unit output after the running mill trips. Background Technology

[0002] During the operation of a thermal power unit, multiple coal mills (referred to as mill groups) typically operate simultaneously, jointly supplying pulverized coal to the boiler to maintain the unit load. When one of the operating mill groups trips due to a fault, the unit load must be adjusted promptly to adapt to the sudden reduction in fuel supply in order to ensure stable boiler combustion and unit safety. Currently, the commonly used control method is: when a tripping of an operating mill group is detected, the distributed control system rapidly reduces the unit load according to a preset fixed proportion or rate based on the number of remaining operating mill groups. For example, for a unit equipped with six coal mills, if one mill group trips, the unit's target load is forcibly and rapidly reduced to five-sixths of the current load or a certain preset value.

[0003] The existing control method described above has the following drawbacks: Firstly, it is a crude control method that does not take into account the actual output capacity of the remaining operating mills. Since each mill may be in different operating modes such as manual or automatic, the maximum coal feed it can actually provide may be higher or lower than the estimated value when divided equally among the mills. Rapidly reducing the load at a fixed ratio can easily cause unnecessary load loss or insufficient fuel supply.

[0004] On the other hand, this method does not take into account the impact of changes in the calorific value of the coal used. When the unit burns low-quality coal, the effective fuel quantity converted from the maximum coal feed of the remaining mills to the boiler's design calorific value will decrease significantly. The estimated load capacity based on the number of units will be higher than the actual capacity, resulting in insufficient load reduction and causing safety hazards such as a continuous drop in main steam pressure.

[0005] Therefore, existing technologies cannot accurately adapt the unit load after the mill trips, and a control method and system that can make fine-grained load adjustments based on the actual output capacity of the remaining mill and the characteristics of the coal is needed. Summary of the Invention

[0006] To address the problems existing in the background technology, this invention proposes a control method and system for automatically adapting the unit output after the operating mill trips.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a control method for automatically adapting the output of the unit after the operating mill trips, comprising the following steps: Acquire the trip pulse signal of the running grinding unit; Based on the trip pulse signal, determine the operating mode of each grinding group in the remaining operating grinding groups; Calculate the maximum output value of each remaining operating mill group based on its operating mode; The total coal quantity is obtained by summing the maximum output values ​​of each of the remaining operating mill groups. Obtain the coal quality correction coefficient, and calculate the theoretical maximum output value of the unit based on the total coal quantity and the coal quality correction coefficient; Obtain the current output value of the unit, and generate a unit load control command based on the theoretical maximum output value of the unit and the current output value of the unit.

[0008] Specifically, calculating the maximum output value of each of the remaining operating mill groups based on their operating modes includes: When the remaining operating mill is in manual mode, the current coal feed rate of the mill is obtained and the current coal feed rate is determined as the maximum output value of the mill. When the remaining operating mill group is in automatic mode, the preset maximum output value, fuel control command and actual output command of the mill group are obtained, and the maximum output value of the mill group is calculated based on the deviation between the preset maximum output value, the fuel control command and the actual output command.

[0009] Specifically, calculating the maximum output value of the grinding unit based on the deviation between the preset maximum output value, the fuel control command, and the actual output command includes: Calculate the difference between the actual output command and the fuel master control command; Determine whether the difference is negative; If the difference is not negative, then the preset maximum output value is determined as the maximum output value of the grinding unit; If the difference is negative, the difference obtained by subtracting the absolute value of the difference from the preset maximum output value is determined as the maximum output value of the grinding unit.

[0010] Specifically, the calculated theoretical maximum output value of the generating unit includes: Multiply the total coal quantity value by the coal quality correction coefficient to obtain the corrected coal quantity value; Input the corrected coal quantity value into a preset lookup table that reflects the correspondence between the corrected coal quantity and the unit's theoretical maximum output, and obtain the unit's theoretical maximum output value output by the lookup table.

[0011] Specifically, obtaining the current output value of the generator unit includes: Obtain the actual power output of the generator unit; The external gas supply of the unit is obtained, and the external gas supply is converted into an equivalent power value using thermodynamic formulas based on the flow rate, pressure and temperature of the externally supplied steam. The actual power output value and the equivalent power output value are added together to obtain the current output value of the unit.

[0012] Specifically, the generation of unit load control commands includes: Determine whether the theoretical maximum output value of the unit is less than the current output value of the unit; If the theoretical maximum output value of the unit is less than the current output value of the unit, a load reduction control command is generated, wherein the load reduction control command includes information that the theoretical maximum output value of the unit is the target load; If the theoretical maximum output value of the unit is not less than the current output value of the unit, a load maintenance control command is generated.

[0013] Based on a control method for automatically adjusting the unit output after a running mill trips, this technical solution also provides a control system for automatically adjusting the unit output after a running mill trips, including: The signal acquisition module is used to acquire the trip pulse signal of the running mill and the current output value of the unit; The mode determination module is used to determine the operating mode of each grinding group in the remaining operating grinding groups based on the trip pulse signal. The output calculation module is used to calculate the maximum output value of each of the remaining operating mill groups according to their operating modes. The total coal quantity summation module is used to sum the maximum output values ​​of each of the remaining operating mill groups to obtain the total coal quantity value. The load conversion module is used to obtain the coal quality correction coefficient, and convert the total coal quantity value and the coal quality correction coefficient to generate the theoretical maximum output value of the unit. The load conversion module includes a preset lookup table that reflects the correspondence between the corrected coal quantity and the theoretical maximum output of the unit. The load command module is used to generate unit load control commands based on the unit's theoretical maximum output value and the unit's current output value.

[0014] Specifically, the output calculation module includes: The manual output unit is used to obtain the current coal feed rate of the remaining operating mill when the operating mode of the mill is manual mode, and to determine the current coal feed rate as the maximum output value of the mill. An automatic output unit is used to acquire the preset maximum output value, fuel control command and actual output command of the grinding group when the remaining operating grinding group is in automatic mode, and to calculate the maximum output value of the grinding group based on the deviation between the preset maximum output value, the fuel control command and the actual output command.

[0015] Specifically, the automatic power output unit includes: The deviation calculation subunit is used to calculate the difference between the actual output command and the fuel master control command; The positive bias processing subunit is used to determine the preset maximum output value as the maximum output value of the grinding group when the difference is not negative. The negative bias processing subunit is used to determine the maximum output value of the grinding group by subtracting the absolute value of the difference from the preset maximum output value when the difference is negative.

[0016] Specifically, the load command module includes: The output comparison unit is used to determine whether the theoretical maximum output value of the unit is less than the current output value of the unit. The instruction triggering unit is used to trigger a load reduction control instruction containing the theoretical maximum output value of the unit as the target load when the theoretical maximum output value of the unit is less than the current output value of the unit. When the theoretical maximum output value of the unit is not less than the current output value of the unit, the load maintenance control command is triggered.

[0017] Compared with the prior art, the present invention has the following beneficial effects: by calculating the maximum output value of each remaining operating mill according to the difference in the operating mode, and converting it into the theoretical maximum output value of the unit after the coal quality correction coefficient, and then comparing it with the current output value of the unit to generate load control commands, the fine self-adaptive adjustment of the unit load after the mill trips is realized, avoiding unnecessary load loss or safety hazards caused by insufficient fuel supply.

[0018] By determining the maximum output value of the grinding unit in manual mode as the current coal feed rate, and negatively correcting the maximum output value of the grinding unit in automatic mode based on the deviation between its actual output command and the fuel main control command, an accurate assessment of the actual output capacity of the remaining operating grinding units is achieved, solving the problem of load prediction deviation caused by ignoring the differences in the operating status of the grinding units in the existing technology.

[0019] By using a pre-set lookup table that reflects the correspondence between the corrected coal quantity and the unit's theoretical maximum output for load conversion, the load capacity of the unit is accurately mapped when the coal quality changes, eliminating the hidden danger of abnormally rapid load reduction or insufficient load reduction caused by fluctuations in the calorific value of coal. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the calculation circuit principle for the theoretical maximum output value of the unit in this invention; Figure 2 This is a schematic diagram of the RB action instruction generation loop principle; Figure 3 This is a schematic diagram of the RB action signal generation circuit principle of the present invention; Figure 4 This is a schematic diagram of the load control command generation loop principle of the present invention; Figure 5 This is a flowchart of the control method for automatically adapting the unit output after the grinding mill trips, as per the present invention. Detailed Implementation

[0021] 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.

[0022] like Figures 1-5 As shown, the technical solution adopted by the present invention is as follows: A control method for automatically adapting the output of the unit after the running mill trips, comprising the following steps: S1: Obtain the trip pulse signal of the running mill.

[0023] The operating grinding unit refers to the pulverizing unit consisting of a coal mill and its auxiliary systems in operation within a thermal power unit, used to grind raw coal into pulverized coal and transport it to the boiler for combustion.

[0024] The trip pulse signal is a momentary high- or low-level switching pulse signal generated by the distributed control system of the unit when any operating mill unit unexpectedly stops (i.e., trips) due to a fault or protection action. The acquisition of this signal signifies an unplanned fuel interruption event and serves as a trigger condition and preliminary step for initiating the entire adaptive control logic. The pulse signal is extremely short in duration and is typically captured and broadened by subsequent pulse modules to ensure that the control logic can reliably identify the trip event.

[0025] The purpose of acquiring the trip pulse signal is to initiate an immediate assessment of the current unit's fuel supply capacity to determine whether and to what extent the unit load needs to be adjusted to match the remaining fuel input capacity.

[0026] S2: Determine the operating mode of each grinding group in the remaining operating grinding groups based on the trip pulse signal.

[0027] Upon receiving the trip pulse signal from a running mill, the control logic immediately executes the operation to determine the operating mode of each of the remaining running mills. The remaining running mills refer to all mills that are currently operating and supplying pulverized coal to the boiler, excluding the mills that have tripped.

[0028] The operating mode refers to the current control state of each remaining operating mill unit. In this invention, this state is specifically divided into two types: automatic mode and manual mode. The process of determining the operating mode is as follows: the system iterates through and checks the control status flag bits of all remaining operating mill units.

[0029] If the control status flag of a certain mill unit indicates that its coal feed rate is being automatically adjusted by the unit's fuel master control command, then the operating mode of the mill unit is determined to be automatic mode; if the control status flag of a certain mill unit indicates that its coal feed rate is being manually set by the operator and does not follow the changes in the fuel master control command, then the operating mode of the mill unit is determined to be manual mode.

[0030] This step forms the basis for subsequent differentiated maximum output calculation strategies based on different modes, because grinding units in manual mode do not have the ability to automatically supplement output, while grinding units in automatic mode have a certain adjustment potential.

[0031] S3: Calculate the maximum output value of each remaining operating mill group according to its operating mode.

[0032] After determining the operating mode of each remaining operating mill unit, the system performs the step of calculating the maximum output value of each remaining operating mill unit. The maximum output value refers to the maximum amount of coal that a single mill unit can safely and continuously provide to the boiler under the current specific operating mode. This coal feed rate is the core calculation basis for converting the theoretical maximum output value of the unit. The calculation process adopts differentiated strategies according to different operating modes.

[0033] If the operating mode is manual, the maximum output of the mill is limited by the current manually set coal feed rate and does not have the ability to automatically increase output.

[0034] If the operating mode is automatic, the maximum output value of the mill is determined by its preset physical upper limit and the dynamic deviation between it and the fuel master control command, reflecting the actual maximum output potential of the mill under automatic adjustment.

[0035] The precise calculation in this step is a key prerequisite for achieving refined self-adaptive adjustment of the unit's target load, replacing the traditional method of roughly reducing the load based on the proportion of operating mill units.

[0036] The step of calculating the maximum output value of each remaining operating mill group based on its operating mode specifically includes: When the remaining operating mill is in manual mode, the current coal feed rate of the mill is obtained and the current coal feed rate is determined as the maximum output value of the mill.

[0037] When the remaining operating mill group is in automatic mode, the preset maximum output value, fuel control command and actual output command of the mill group are obtained, and the maximum output value of the mill group is calculated based on the deviation between the preset maximum output value, the fuel control command and the actual output command.

[0038] The specific logic implementation for calculating the maximum output value of each remaining operating mill group includes two parallel processing branches, corresponding to the two operating states of manual mode and automatic mode, respectively.

[0039] The first branch is for manual mode. When the remaining operating mill is in manual mode, it does not participate in the automatic adjustment of the fuel master control, and its output is set and kept constant by the operator through the operator station.

[0040] Therefore, the system obtains the current coal feed rate of the mill unit from the weighing sensor of the corresponding coal feeder. This current coal feed rate is the actual amount of coal entering the furnace as measured in real time. The system determines this current coal feed rate as the maximum output value of the mill unit. This operation is based on the fact that mill units in manual mode have no automatic load increase capability, and their current output is the maximum output they can contribute during the remaining operation period after a tripping event.

[0041] The second branch addresses the automatic mode. When the remaining operating mill is in automatic mode, its coal feed rate is continuously adjusted by the unit's fuel control command. To calculate the maximum output of the mill, the system first acquires three key input parameters: the mill's preset maximum output, the fuel control command, and the mill's actual output command.

[0042] The preset maximum output value is the maximum coal feed limit that the grinding unit can operate stably for a long time, based on the grinding unit design parameters and operating procedures.

[0043] The fuel master control command is a common command signal issued by the unit coordination and control system to uniformly adjust the coal feed rate of all grinding units in automatic mode.

[0044] The actual output command is the final command signal actually sent to the coal feeder actuator after the fuel master control command has been corrected by the mill itself by the bias.

[0045] Subsequently, the system calculates the maximum output value of the grinding unit based on the deviation between the preset maximum output value, the fuel master control command, and the actual output command. This calculation logic aims to negatively correct the maximum output capability of the automatic grinding unit, so as to truly reflect its output potential limited by command tracking deviation.

[0046] The step of calculating the maximum output value of the grinding unit based on the deviation between the preset maximum output value, the fuel main control command, and the actual output command specifically includes: Calculate the difference between the actual output command and the fuel master control command.

[0047] Determine whether the difference is negative.

[0048] If the difference is not negative, then the preset maximum output value is determined as the maximum output value of the grinding unit.

[0049] If the difference is negative, the difference obtained by subtracting the absolute value of the difference from the preset maximum output value is determined as the maximum output value of the grinding unit.

[0050] The logic for calculating the maximum output value of the grinding unit based on the deviation in automatic mode includes three steps: deviation calculation, condition judgment, and result assignment.

[0051] First, the deviation calculation step is performed. The system subtracts the acquired actual output command and fuel control command for the grinding unit to calculate the difference between them. This difference represents the degree and direction of deviation of the actual command executed by the grinding unit from the common command.

[0052] Next, the system performs a conditional judgment step. It checks the sign of the calculated difference to determine whether the difference is negative.

[0053] Finally, based on the judgment result, different result assignment steps are entered.

[0054] If the difference is not negative, it means the actual output command of the grinding mill is greater than or equal to the fuel master control command. This indicates that the grinding mill is already operating at full power in accordance with the common command, or its output command is being raised due to positive bias. Therefore, the actual output capacity of the grinding mill is not limited by negative forces, and the system determines the preset maximum output value as the maximum output value of the grinding mill.

[0055] If the difference is negative, it means the actual output command of the grinding mill is less than the fuel control command. This indicates that the grinding mill's output has failed to reach the level required by the common command due to a negative bias or response lag. In this case, its actual output capacity is limited by this negative deviation. The system then subtracts the absolute value of the difference from the preset maximum output value, and determines the calculated difference as the maximum output value of the grinding mill. Mathematically, this operation is equivalent to correcting the preset maximum output value downwards by the magnitude of the deviation, thereby accurately reflecting the true maximum output capacity that the grinding mill can provide under constrained conditions.

[0056] Through the above branch judgments and calculations, the system determines a precise, negatively corrected maximum output value for each remaining operating mill unit in automatic mode, providing a reliable data foundation for the subsequent precise calculation of the theoretical maximum output value of the mill unit.

[0057] S4: Sum the maximum output values ​​of each of the remaining operating mill groups to obtain the total coal quantity value.

[0058] After calculating the maximum output value of each remaining operating mill unit, the system performs a summation operation to generate a total index representing the current total fuel supply capacity of the unit.

[0059] The specific operation is as follows: The system inputs the maximum output value of each remaining operating mill group into an addition module, performs arithmetic addition on these maximum output values, and the sum obtained is the total coal quantity value. This total coal quantity value represents the maximum coal feed that all remaining operating mill groups can collectively provide to the boiler under the current operating conditions, expressed in tons per hour. This total coal quantity value is a key intermediate variable connecting the individual output capacity of each mill group with the overall load capacity of the unit.

[0060] S5: Obtain the coal quality correction coefficient, and calculate the theoretical maximum output value of the unit based on the total coal quantity and the coal quality correction coefficient.

[0061] After obtaining the total coal quantity, the system executes the step of converting the unit's theoretical maximum output value. First, the system obtains the coal quality correction coefficient. This coefficient is the ratio of the lower heating value of the actual coal entering the mill to the lower heating value of the design coal type used in the boiler design. This coefficient characterizes the calorific value quality of the currently used coal relative to the design coal type. If the coal quality correction coefficient is less than one, it indicates that the actual calorific value of the coal entering the furnace is lower than the design calorific value, i.e., inferior coal is being burned; if the coefficient is greater than one, it indicates that the actual calorific value of the coal entering the furnace is higher than the design calorific value. The coal quality correction coefficient is usually manually entered by operators based on the laboratory analysis report of the incoming coal, or provided in real time by an online coal quality analyzer.

[0062] Subsequently, the system performs a conversion process based on the obtained total coal quantity and the coal quality correction coefficient to generate the unit's theoretical maximum output value. The theoretical maximum output value refers to the maximum electrical power the unit can theoretically generate after coal quality calorific value correction, given the maximum coal feed rate currently available from the remaining grinding mills. The unit is measured in megawatts (MW). This conversion process uniformly converts the actual fuel quantity into a standard fuel quantity equivalent to the design coal type and further maps it to the unit's load capacity, thus providing an accurate physical basis for subsequent load comparison and decision-making.

[0063] The calculated theoretical maximum output value of the generating unit specifically includes: Multiply the total coal quantity value by the coal quality correction coefficient to obtain the corrected coal quantity value.

[0064] Input the corrected coal quantity value into a preset lookup table that reflects the correspondence between the corrected coal quantity and the unit's theoretical maximum output, and obtain the unit's theoretical maximum output value output by the lookup table.

[0065] The specific implementation of the calculation to generate the theoretical maximum output value of the unit includes two sequentially executed sub-steps.

[0066] The first sub-step is the coal quantity correction calculation. The system performs a multiplication operation between the total coal quantity value obtained in the previous step and the coal quality correction coefficient, that is, multiplying the total coal quantity value by the coal quality correction coefficient. The product is the corrected coal quantity value. The corrected coal quantity value represents the equivalent coal quantity of the actual coal input to the boiler, converted according to its calorific value and quality, and is still in tons per hour.

[0067] The second sub-step is the mapping and conversion between coal quantity and load. The system takes the corrected coal quantity value obtained in the first sub-step as input and sends it to a preset lookup table that reflects the correspondence between the corrected coal quantity and the unit's theoretical maximum output.

[0068] The lookup table is a data mapping structure based on pre-calibrated boiler thermodynamic characteristics. It stores a series of paired data between corrected coal quantity values ​​and corresponding theoretical maximum output values ​​of the unit. The lookup table can be established based on thermodynamic calculation sheets provided by the boiler manufacturer, thermodynamic performance test data after the unit is put into operation, or historical steady-state operating data accumulated over a long period of operation.

[0069] The lookup table works by finding the corresponding theoretical maximum output value of the unit based on the input corrected coal quantity value through table lookup or linear interpolation, and then outputting this value.

[0070] The system obtains the theoretical maximum output value of the unit from the lookup table, which serves as the benchmark value for final load comparison. Using a lookup table instead of a simple linear formula to convert coal quantity to load more accurately reflects the nonlinear characteristics of the boiler, such as efficiency variations and turbine heat rate changes under different load ranges. This is a common engineering practice in distributed control systems for thermal power units, ensuring the accuracy of the conversion results.

[0071] S6: Obtain the current output value of the unit, and generate a unit load control command based on the theoretical maximum output value of the unit and the current output value of the unit.

[0072] After calculating the theoretical maximum output value of the unit, the control logic enters the load comparison and command generation stage. First, the system obtains the current output value of the unit. The current output value of the unit refers to the equivalent value of the total electrical power actually output by the unit at the current moment. This value includes not only the electrical power output by the generator, but also the equivalent electrical power converted from the heat power output in the form of external heating or steam supply.

[0073] The purpose of obtaining the current output value of the generator unit is to compare it with the theoretical maximum output value of the generator unit in real time, so as to determine whether the current fuel supply capacity is sufficient to support the current load level. Subsequently, the system performs comparison and decision-making based on the theoretical maximum output value and the current output value of the generator unit, and generates corresponding generator load control commands.

[0074] The unit load control command is a target load change command sent to the unit coordination and control system, used to instruct the unit whether to maintain the current load operation or immediately reduce to a certain target load value.

[0075] The acquisition of the current output value of the generator unit includes: Obtain the actual power output of the generator unit.

[0076] The external gas supply of the unit is obtained, and the external gas supply is converted into an equivalent power value using thermodynamic formulas based on the flow rate, pressure and temperature of the externally supplied steam.

[0077] The actual power output value and the equivalent power output value are added together to obtain the current output value of the unit.

[0078] The specific implementation of obtaining the current output value of the unit includes three sequentially executed sub-steps.

[0079] The first sub-step is to obtain the actual power output value of the generator unit. The actual power output value refers to the active power signal of the generator unit, measured in real time and output by a power transmitter installed at the generator's output terminal, in megawatts. This signal directly reflects the electrical power transmitted by the generator unit to the grid.

[0080] The second sub-step involves acquiring the unit's external steam supply and converting it into an equivalent power value. For thermal power units with industrial steam extraction or external heating, the steam supplied also carries energy generated by fuel combustion. To comprehensively assess the unit's current total output, this thermal power needs to be converted into equivalent electrical power. The system acquires three real-time parameters—flow rate, pressure, and temperature—of the externally supplied steam through sensors installed on the external steam supply pipeline.

[0081] Subsequently, the system converts the externally supplied steam volume into an equivalent power value through thermodynamic calculations based on the flow rate, pressure, and temperature of the externally supplied steam.

[0082] The principle of this thermodynamic calculation is as follows: First, based on the steam pressure and temperature, the enthalpy values ​​of the supplied steam and feedwater are determined using a steam thermodynamic property table or a corresponding fitting function. Then, the difference between the supplied steam enthalpy and the feedwater enthalpy is calculated to obtain the usable enthalpy drop per unit mass of steam. Finally, this usable enthalpy drop is multiplied by the flow rate of the supplied steam, and after applying a unit conversion factor, the equivalent power value expressed in power units is obtained. This equivalent power value represents the power generation capacity corresponding to the fuel energy consumed in supplying heat to the outside.

[0083] The third sub-step is a summation operation. The system adds the actual power output value obtained in the first sub-step to the equivalent power output value obtained in the second sub-step, and the sum is the current output value of the unit. This summation operation ensures that the assessment of the current output value of the cogeneration unit is comprehensive and accurate, avoiding the underestimation of the actual load level of the unit due to ignoring the external heat supply energy.

[0084] The generated unit load control command specifically includes: Determine whether the theoretical maximum output value of the unit is less than the current output value of the unit.

[0085] If the theoretical maximum output of the unit is less than the current output of the unit, a load reduction control command is generated, wherein the load reduction control command contains information that the theoretical maximum output of the unit is the target load.

[0086] If the theoretical maximum output value of the unit is not less than the current output value of the unit, a load maintenance control command is generated.

[0087] The specific implementation of the generated unit load control command includes a comparison and judgment step and two parallel command generation branches.

[0088] First, the system performs a comparison and judgment step. The system compares the theoretical maximum output value of the unit calculated in the previous steps with the current output value of the unit to determine whether the theoretical maximum output value of the unit is less than the current output value of the unit.

[0089] Subsequently, based on the results of the above comparison and judgment, the system enters different instruction generation branches.

[0090] The first branch corresponds to the case where the theoretical maximum output of the unit is less than its current output. This situation indicates that the unit's current fuel supply capacity is insufficient to support the existing load level, and maintaining the current load operation would lead to unsafe conditions such as a continuous drop in main steam pressure.

[0091] At this point, the system generates a load reduction control command. This load reduction control command is a control signal sent to the unit load setting circuit to forcibly reduce the unit's target load setting value. The command contains information that the unit's theoretical maximum output value is the target load; that is, the command explicitly requires the unit load to be reduced to the load level corresponding to the unit's theoretical maximum output value.

[0092] The second branch corresponds to the case where the theoretical maximum output of the unit is not less than the current output of the unit. This case indicates that although a mill trip has occurred, the maximum output capacity of the remaining operating mills, after conversion, can still meet the current load demand, and there is no need to reduce the unit load. At this time, the system generates a load maintenance control command. The load maintenance control command is a control signal used to keep the current target load setpoint of the unit unchanged. In this case, the unit's RB action will not be triggered, and the unit load remains unchanged.

[0093] Through the above-mentioned differentiation and processing, the present invention achieves a refined response to mill trip events, avoiding the crude operation of rapidly reducing the load by a fixed ratio once the mill trips in the traditional control method, and achieving the control objective of not reducing the unit load if possible, and reducing it precisely when necessary.

[0094] Based on a control method for automatically adjusting the unit output after a running mill trips, this technical solution also provides a control system for automatically adjusting the unit output after a running mill trips, including: The signal acquisition module is used to acquire the trip pulse signal of the running mill and the current output value of the unit.

[0095] The signal acquisition module includes a trip signal acquisition unit and a current output acquisition unit. The trip signal acquisition unit consists of a first pulse module, a second pulse module, a third pulse module, a fourth pulse module, a fifth pulse module, and a sixth pulse module. The input terminal of each pulse module is connected to the corresponding A-mill trip signal, B-mill trip signal, C-mill trip signal, D-mill trip signal, E-mill trip signal, and F-mill trip signal, respectively.

[0096] The output of each pulse module is connected to the input of the first or second module. The current output acquisition unit is composed of a ninth adder module. The ninth adder module has two inputs, one of which is connected to the actual power signal and the other is connected to the external gas supply converted power signal. The output of the ninth adder module outputs the current output value of the unit and is connected to one input of the tenth adder module.

[0097] When any operating mill unit trips, the corresponding mill trip signal generates a momentary state change. The connected pulse module converts this momentary state change into a pulse signal with a certain duration and outputs it to the first OR module. The first OR module performs a logical OR operation on multiple pulse signals; as long as any pulse signal is valid, the output of the first OR module is valid. Simultaneously, the ninth adder module receives the actual generated power signal and the external air supply converted power signal in real time, performs an addition operation on the two signals, and generates and outputs the current output value of the unit in real time.

[0098] The mode determination module is used to determine the operating mode of each grinding group in the remaining operating grinding groups based on the trip pulse signal.

[0099] The mode determination module is a logic discrimination unit. Its input terminal is connected to the output terminal of the first OR module in the signal acquisition module, and is used to receive the summarized trip pulse signal. The mode determination module also establishes a data reading connection with the identifier bit database storing the control status of each mill group in the distributed control system. Its output terminal outputs a switch signal indicating the operating mode to the input trigger terminal of the corresponding switching module of each mill group. For mill A, this signal is "Mill A Automatic" and is connected to the input trigger terminal of the first switching module; for mills B to F, the corresponding signals are "Mill B Automatic" to "Mill F Automatic" and are respectively connected to the input trigger terminals of the second to sixth switching modules.

[0100] When the mode determination module receives a valid trip pulse signal, it iterates through and reads the control status flag bits of all remaining operating mills except those that have already tripped. If the control status flag bit of a mill indicates that its coal feed rate is being automatically adjusted by the fuel master control command, the mode determination module sets the corresponding automatic mill signal to valid, indicating that the operating mode is automatic. If the control status flag bit of a mill indicates that its coal feed rate is being manually set by the operator, the mode determination module sets the corresponding automatic mill signal to invalid, indicating that the operating mode is manual.

[0101] The output calculation module is used to calculate the maximum output value of each of the remaining operating mill groups based on their operating modes.

[0102] Specifically, the output calculation module includes: The manual output unit is used to obtain the current coal feed rate of the remaining operating mill when the operating mode is manual, and to determine the current coal feed rate as the maximum output value of the mill.

[0103] An automatic output unit is used to acquire the preset maximum output value, fuel control command and actual output command of the grinding group when the remaining operating grinding group is in automatic mode, and to calculate the maximum output value of the grinding group based on the deviation between the preset maximum output value, the fuel control command and the actual output command.

[0104] Specifically, the automatic power output unit includes: The deviation calculation subunit is used to calculate the difference between the actual output command and the fuel master control command.

[0105] The positive bias processing subunit is used to determine the preset maximum output value as the maximum output value of the grinding group when the difference is not negative.

[0106] The negative bias processing subunit is used to determine the maximum output value of the grinding group by subtracting the absolute value of the difference from the preset maximum output value when the difference is negative.

[0107] The output calculation module consists of six parallel calculation channels corresponding to mills A to F. Each calculation channel includes a manual output unit, an automatic output unit, and a channel switching unit. Taking the calculation channel corresponding to mill A as an example, its manual output unit consists of the mill A flow signal line directly connected to the Y end of the first switching module. Its automatic output unit consists of a first selection module, a first addition module, and the connecting lines between them.

[0108] The specific connections are as follows: one input of the first sub-selection module is connected to the coal quantity bias of mill A, and the other input is connected to the first constant module. One input of the first adder module is connected to the maximum coal quantity of mill A, and the other input is connected to the output of the first sub-selection module. The output of the first adder module is connected to the N terminal of the first switching module. The channel switching unit is the first switching module, and its input trigger terminal is connected to the automatic signal of mill A output by the mode judgment module. The output of the first switching module outputs the maximum output value of mill A. The calculation channels from mill B to mill F have the same structure as mill A.

[0109] For any remaining operating mill unit, the output calculation module selects a channel based on its corresponding automatic mill signal control channel switching unit. If the operating mode is manual, the automatic mill signal is invalid, the channel switching unit selects the Y terminal, and the current coal feed rate (i.e., mill flow rate) provided by the manual output unit is determined as the maximum output value of the mill unit. If the operating mode is automatic, the automatic mill signal is valid, the channel switching unit selects the N terminal, and the corrected maximum output value calculated by the automatic output unit is determined as the maximum output value of the mill unit. Inside the automatic output unit, the first sub-selection module performs a minimum operation on the output of the coal feed rate bias and constant module, and the first addition module adds the maximum coal feed rate of the mill unit to the minimum operation result, thereby achieving the bias correction of the preset maximum output value.

[0110] The total coal quantity summation module is used to sum the maximum output values ​​of each of the remaining operating mill groups to obtain the total coal quantity value.

[0111] The total coal quantity summation module is implemented by a seventh addition module. This seventh addition module has multiple input terminals, each connected to a corresponding output terminal of the first, second, third, fourth, fifth, and sixth switching modules. The output terminal of the seventh addition module is connected to one input terminal of the first multiplication module.

[0112] In terms of its working principle, the seventh addition module receives the maximum output value signals of each remaining operating mill group from each switching module in real time, performs analog addition operations on them, and sums up the values ​​of each input signal. The seventh addition module uses the sum obtained from the calculation as the total coal quantity value and outputs it in real time through its output terminal.

[0113] The load conversion module is used to obtain the coal quality correction coefficient and convert the total coal quantity and the coal quality correction coefficient to generate the theoretical maximum output value of the unit. The load conversion module includes a preset lookup table that reflects the correspondence between the corrected coal quantity and the theoretical maximum output of the unit.

[0114] The load conversion module includes a multiplication unit and a lookup table unit. The multiplication unit is implemented by a first multiplication module. The first multiplication module has two input terminals: one connected to the output of the seventh addition module to receive the total coal quantity value; the other connected to a signal source providing coal type correction coefficients. The lookup table unit is implemented by a first function module. The input of the first function module is connected to the output of the first multiplication module. The first function module internally contains a lookup table that stores pairing data between multiple corrected coal quantity values ​​and their corresponding theoretical maximum output values ​​of the unit. The output of the first function module outputs the theoretical maximum output value of the unit, i.e., the RB target value.

[0115] The first multiplication module performs a multiplication operation on the input total coal quantity value and the coal quality correction coefficient to generate a corrected coal quantity value, and sends this value to the first function module. After receiving the corrected coal quantity value, the first function module uses it as an input index and determines the theoretical maximum output value of the unit corresponding to the corrected coal quantity value through table lookup or linear interpolation in an internally preset lookup table, and uses this value as the final output of the load conversion module.

[0116] The load command module is used to generate unit load control commands based on the unit's theoretical maximum output value and the unit's current output value.

[0117] Specifically, the load command module includes: The output comparison unit is used to determine whether the theoretical maximum output value of the unit is less than the current output value of the unit.

[0118] The instruction triggering unit is used to trigger a load reduction control instruction containing the theoretical maximum output value of the unit as the target load when the theoretical maximum output value of the unit is less than the current output value of the unit.

[0119] When the theoretical maximum output value of the unit is not less than the current output value of the unit, the load maintenance control command is triggered.

[0120] The load command module includes an output comparison unit, a command triggering logic unit, and a command switching unit. The output comparison unit consists of a tenth adder module and a second greater than module. The tenth adder module has two input terminals: one connected to the output of the ninth adder module in the signal acquisition module to receive the current output value of the generator set; the other connected to the output of the first function module in the load conversion module to receive the theoretical maximum output value of the generator set, i.e., the RB target value. The output of the tenth adder module is connected to the input of the second greater than module. The output of the second greater than module is connected to one input of the first AND module. The command triggering logic unit consists of a first AND module and a second AND module. The other input of the first AND module is connected to the output of the first OR module. The output of the first AND module outputs an action command and is connected to one input of the second AND module. The other input of the second AND module is connected to the RB action condition signal. The output of the second AND module outputs an RB action signal. The command switching unit is implemented by a seventh switching module. The N terminal of the seventh switching module is connected to the RB target value, the Y terminal is connected to the target load, and the input trigger terminal is connected to the RB action signal. The seventh switching module outputs the RB target load.

[0121] The tenth addition module in the output comparison unit calculates the difference between the current output value of the unit and the theoretical maximum output value of the unit. The second greater module determines whether the difference is greater than zero, that is, whether the current output value of the unit is greater than the theoretical maximum output value of the unit. If the determination result is yes, and the first addition module outputs a valid trip pulse summary signal, then the first addition module outputs a valid RB action command. When the RB action command is valid and the RB action condition is met, the second addition module outputs a valid RB action signal. The RB action signal acts on the command switching unit, causing the seventh switching module to select its N-terminal input, thereby outputting the RB target value as the RB target load and generating a load reduction control command containing information that the theoretical maximum output value of the unit is the target load. If the output comparison unit determines that the current output value of the unit is not greater than the theoretical maximum output value of the unit, then the RB action command is invalid, and the seventh switching module maintains the selected Y-terminal input target load and generates a load maintenance control command.

[0122] In a specific embodiment, a control method and system for automatically adapting unit output after a mill trip is applied to the distributed control system of a 600MW coal-fired power unit with six coal mills (numbered A to F). This power unit is equipped with industrial steam extraction, and flow transmitters, pressure transmitters, and temperature sensors are installed on the external steam supply pipeline. The distributed control system uses a Siemens T3000 system, and the control logic is implemented through continuous function chart and sequential function chart configurations.

[0123] During normal operation of this thermal power unit, five coal mills (Mills A, B, C, D, and E) are in operation, while Mill F is in standby. The unit's actual power output is 480MW, and the target load is also 480MW. Mill A operates in manual mode, with its coal feed rate set to a constant 30 tons per hour by operators via the operator station. Mills B, C, D, and E operate in automatic mode, with their coal feed rates automatically adjusted according to fuel control commands. Based on the design parameters of each mill, the preset maximum output of mills B, C, D, and E is 60 tons per hour. Operators input a coal quality correction factor of 0.90 into the distributed control system based on the coal quality test report of the incoming coal.

[0124] At a certain moment, mill A tripped due to a motor failure. The control method and system for automatically adjusting the unit's output after the mill trips are implemented according to the following steps: The A-mill trip signal is generated by the auxiliary contacts of the circuit breaker of the A-mill motor, and this signal is connected to the digital input card of the distributed control system. The first pulse module in the distributed control system captures the rising edge of the A-mill trip signal and widens it into a pulse signal with a duration of 500 milliseconds. This pulse signal is output to the input of the first OR module, making the output of the first OR module logically valid. At the same time, the ninth adder module receives in real time the actual power value of 480MW from the generator power transmitter and the equivalent power value of 20MW from the external gas supply conversion power module, performs an addition operation on the two signals to obtain the current output value of the unit as 500MW, and sends this value to one input of the tenth adder module.

[0125] After receiving a valid pulse signal from the first or second switching module, the mode determination module immediately reads the control status flag bits of the four remaining operating mill groups (mills B, C, D, and E) in the distributed control system. The readings show that the control status flag bits of mills B, C, D, and E all indicate that they are in automatic adjustment mode. Therefore, the mode determination module sets the automatic signals of mills B, C, D, and E to valid levels and sends them to the input trigger terminals of the second, third, fourth, and fifth switching modules, respectively.

[0126] For mill B, the automatic signal is valid, and the second switching module selects its N-terminal input. At this time, the main fuel control command for mill B is 48 tons per hour, and the actual output command for mill B is 53 tons per hour (i.e., there is a positive bias of 5 tons per hour). The deviation calculation subunit calculates the difference between the actual output command and the main fuel control command as a positive 5 tons per hour. The positive bias processing subunit determines that the difference is not negative, so it sets the preset maximum output value of mill B, 60 tons per hour, as the maximum output value of mill B and outputs it to the seventh adder module.

[0127] For mill C, the automatic signal is valid, and the third switching module selects its N-terminal input. At this time, the main fuel control command for mill C is 48 tons per hour, and the actual output command for mill C is 40 tons per hour (i.e., there is a negative bias of 8 tons per hour). The deviation calculation subunit calculates the difference between the actual output command and the main fuel control command as negative 8 tons per hour. The negative bias processing subunit determines that the difference is negative, subtracts the absolute value of this difference of 8 tons per hour from the preset maximum output value of 60 tons per hour, and determines the resulting difference of 52 tons per hour as the maximum output value of mill C, and outputs it to the seventh addition module.

[0128] For mill D, the calculation process is similar to that of mill B. Assuming no bias, the maximum output value is determined to be 60 tons per hour and output to the seventh addition module.

[0129] For mill E, the calculation process is similar to that of mill B. Assuming no bias, the maximum output value is determined to be 60 tons per hour and output to the seventh addition module.

[0130] The seventh addition module receives the maximum output values ​​of mill B (60 tons per hour), mill C (52 tons per hour), mill D (60 tons per hour), and mill E (60 tons per hour), performs addition operations, obtains a total coal quantity value of 232 tons per hour, and outputs the total coal quantity value to one input terminal of the first multiplication module.

[0131] The other input of the first multiplication module receives a coal quality correction coefficient of 0.90, input by the operator. The first multiplication module multiplies the total coal quantity of 232 tons per hour by the coal quality correction coefficient of 0.90 to obtain a corrected coal quantity of 208.8 tons per hour, and outputs this corrected coal quantity to the first function module.

[0132] The first function module contains a pre-defined lookup table reflecting the correspondence between the corrected coal quantity and the unit's theoretical maximum output. This lookup table is based on thermal calculations provided by the boiler manufacturer and data obtained from performance testing. Some of the correspondences are as follows: when the corrected coal quantity is 200 tons per hour, the unit's theoretical maximum output is 460 MW; when the corrected coal quantity is 210 tons per hour, the unit's theoretical maximum output is 484 MW. The first function module receives the corrected coal quantity value of 208.8 tons per hour and, through linear interpolation, determines the corresponding theoretical maximum output value of 479.2 MW from the lookup table. The first function module uses this theoretical maximum output value as the target value for RB and outputs it to another input of the tenth adder module and the N terminal of the seventh switching module.

[0133] The difference between the current output value of 500MW and the theoretical maximum output value of 479.2MW in the tenth addition module of the output comparison unit is positive 20.8MW. The second greater than module determines that the difference is greater than zero, that is, it determines that the current output value of the unit is greater than the theoretical maximum output value of the unit, and its output becomes a logically valid state and is connected to one input terminal of the first AND module.

[0134] The first AND module receives a valid pulse signal from the first OR module at its other input. Since both inputs are logically valid, the first AND module outputs a valid RB action command to the second AND module. Assuming the RB action condition is met at this time (e.g., the unit is not in a RB-disabled operating condition), the second AND module outputs a valid RB action signal to the input trigger terminal of the seventh switching module.

[0135] After receiving a valid RB action signal, the seventh switching module in the command switching unit switches to its N-terminal input, thereby outputting the RB target value of 479.2MW from the N-terminal input as the RB target load to the unit's load setting circuit. This process generates a load reduction control command containing a target load of 479.2MW, the unit's theoretical maximum output. Upon receiving this load reduction control command, the unit's coordinated control system reduces the target load from 480MW to 479.2MW and automatically adjusts the turbine control valve opening and boiler combustion rate to smoothly transition the unit's actual power output to 479.2MW.

[0136] As can be seen from the above process, although mill A tripped, calculations show that the output capacity of the remaining operating mills is sufficient to support the current load level of approximately 480MW (with only a minor shortfall of less than 1MW). Therefore, the system only issues a small load reduction command, avoiding the crude operation of rapidly reducing the load to below 400MW triggered by a single mill tripping, as is common in traditional control methods. This significantly improves the stability and economy of unit operation. This embodiment verifies the effectiveness of the control method and system that adapts to the unit output after an operating mill trips.

[0137] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for automatically adjusting the unit output after a grinding mill trips, characterized in that, Includes the following steps: Acquire the trip pulse signal of the running grinding unit; Based on the trip pulse signal, determine the operating mode of each grinding group in the remaining operating grinding groups; Calculate the maximum output value of each remaining operating mill group based on its operating mode; The total coal quantity is obtained by summing the maximum output values ​​of each of the remaining operating mill groups. Obtain the coal quality correction coefficient, and calculate the theoretical maximum output value of the unit based on the total coal quantity and the coal quality correction coefficient; Obtain the current output value of the unit, and generate a unit load control command based on the theoretical maximum output value of the unit and the current output value of the unit.

2. The control method for automatically adapting the unit output after a grinding mill trips, as described in claim 1, is characterized in that... The step of calculating the maximum output value of each remaining operating mill group based on its operating mode specifically includes: When the remaining operating mill is in manual mode, the current coal feed rate of the mill is obtained and the current coal feed rate is determined as the maximum output value of the mill. When the remaining operating mill group is in automatic mode, the preset maximum output value, fuel control command and actual output command of the mill group are obtained, and the maximum output value of the mill group is calculated based on the deviation between the preset maximum output value, the fuel control command and the actual output command.

3. The control method for automatically adapting the unit output after a grinding mill trips, as described in claim 2, is characterized in that... The step of calculating the maximum output value of the grinding unit based on the deviation between the preset maximum output value, the fuel main control command, and the actual output command specifically includes: Calculate the difference between the actual output command and the fuel master control command; Determine whether the difference is negative; If the difference is not negative, then the preset maximum output value is determined as the maximum output value of the grinding unit; If the difference is negative, the difference obtained by subtracting the absolute value of the difference from the preset maximum output value is determined as the maximum output value of the grinding unit.

4. The control method for automatically adapting the unit output after a grinding mill trips, as described in claim 1, is characterized in that... The calculated theoretical maximum output value of the generating unit specifically includes: Multiply the total coal quantity value by the coal quality correction coefficient to obtain the corrected coal quantity value; Input the corrected coal quantity value into a preset lookup table that reflects the correspondence between the corrected coal quantity and the unit's theoretical maximum output, and obtain the unit's theoretical maximum output value output by the lookup table.

5. The control method for automatically adapting the unit output after a grinding mill trips according to claim 1, characterized in that, The acquisition of the current output value of the generator unit includes: Obtain the actual power output of the generator unit; The external gas supply of the unit is obtained, and the external gas supply is converted into an equivalent power value using thermodynamic formulas based on the flow rate, pressure and temperature of the externally supplied steam. The actual power output value and the equivalent power output value are added together to obtain the current output value of the unit.

6. The control method for automatically adapting the unit output after a grinding mill trips, as described in claim 1, is characterized in that... The generated unit load control command specifically includes: Determine whether the theoretical maximum output value of the unit is less than the current output value of the unit; If the theoretical maximum output value of the unit is less than the current output value of the unit, a load reduction control command is generated, wherein the load reduction control command includes information that the theoretical maximum output value of the unit is the target load; If the theoretical maximum output value of the unit is not less than the current output value of the unit, a load maintenance control command is generated.

7. A control system for automatically adapting the unit output after a mill trips, characterized in that, include: The signal acquisition module is used to acquire the trip pulse signal of the running mill and the current output value of the unit; The mode determination module is used to determine the operating mode of each grinding group in the remaining operating grinding groups based on the trip pulse signal. The output calculation module is used to calculate the maximum output value of each of the remaining operating mill groups according to their operating modes. The total coal quantity summation module is used to sum the maximum output values ​​of each of the remaining operating mill groups to obtain the total coal quantity value. The load conversion module is used to obtain the coal quality correction coefficient, and convert the total coal quantity value and the coal quality correction coefficient to generate the theoretical maximum output value of the unit. The load conversion module includes a preset lookup table that reflects the correspondence between the corrected coal quantity and the theoretical maximum output of the unit. The load command module is used to generate unit load control commands based on the unit's theoretical maximum output value and the unit's current output value.

8. The control system for automatically adapting the unit output after the running mill trips, as described in claim 7, is characterized in that... The output calculation module includes: The manual output unit is used to obtain the current coal feed rate of the remaining operating mill when the operating mode of the mill is manual mode, and to determine the current coal feed rate as the maximum output value of the mill. An automatic output unit is used to acquire the preset maximum output value, fuel control command and actual output command of the grinding group when the remaining operating grinding group is in automatic mode, and to calculate the maximum output value of the grinding group based on the deviation between the preset maximum output value, the fuel control command and the actual output command.

9. A control system for automatically adapting to unit output after a mill trip, as described in claim 8, is characterized in that... The automatic power output unit includes: The deviation calculation subunit is used to calculate the difference between the actual output command and the fuel master control command; The positive bias processing subunit is used to determine the preset maximum output value as the maximum output value of the grinding group when the difference is not negative. The negative bias processing subunit is used to determine the maximum output value of the grinding group by subtracting the absolute value of the difference from the preset maximum output value when the difference is negative.

10. A control system for automatically adapting to unit output after a mill trip, as described in claim 7, is characterized in that... The load command module includes: The output comparison unit is used to determine whether the theoretical maximum output value of the unit is less than the current output value of the unit. The instruction triggering unit is used to trigger a load reduction control instruction containing the theoretical maximum output value of the unit as the target load when the theoretical maximum output value of the unit is less than the current output value of the unit. When the theoretical maximum output value of the unit is not less than the current output value of the unit, the load maintenance control command is triggered.

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