Optimization Control Method for Improving the Flexibility of Auxiliary Equipment Fault Load Reduction in Thermal Power Units

Abstract

The present invention relates to the technical field of thermal power unit control, and is an optimized control method for improving the flexibility of load shedding in case of auxiliary equipment failure of thermal power units. The method includes locking the coal feeding amount of each mill group at the moment before the auxiliary equipment failure load shedding action when the auxiliary equipment failure load shedding action occurs; determining the mill group with the minimum coal feeding amount according to the locked coal feeding amounts of each mill group; determining the interval time for stopping the mills based on the change of furnace pressure; selecting the mills that need to be stopped when the auxiliary equipment failure load shedding action occurs; and executing the shutdown of the mills according to the mill shutdown principle until the remaining mills support the stable operation of the boiler to the target load. On the basis of the existing technology, the present invention improves the control logic, preferentially shuts down the mills determined by the minimum coal amount, optimizes the mill shutdown sequence, and based on the parameter state of the furnace pressure, estimates the risks of the machine and the boiler, anticipatively corrects the mill shutdown interval time, improves the flexible and reliable control characteristics of the unit RB working condition sequence, reduces the unit shutdown events caused by auxiliary equipment failure, and saves the unit shutdown losses.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power unit control, and is an optimized control method for improving the flexibility of load shedding during auxiliary equipment failures of thermal power units. Background Art

[0002] With the continuous increase in the installed capacity ratio of new energy, the power generation on the wind power and photovoltaic power supply sides is highly random and volatile. In addition, new types of fluctuating loads such as electric vehicle charging piles and electric heating are connected to the power grid. To adapt to the new characteristics of power sources and loads, it is necessary to deeply explore the peak shaving capacity of conventional power sources. Thermal power units, as the most stable and reliable conventional power sources, play a core peak shaving role. Operating data shows that the peak shaving capacity of thermal power units and the performance of main auxiliary equipment restrict each other. The more frequent the peak shaving, the greater the probability of auxiliary equipment tripping in the unit. To prevent the entire unit from shutting down due to the tripping of a single main auxiliary equipment, it is necessary to improve the flexible and reliable performance of the rapid load shedding (RB) control when the main auxiliary equipment of the thermal power unit trips.

[0003] First, during the period of tight thermal coal resources, in order to save coal combustion costs, some thermal power enterprises burn low-calorific-value cheap coal or high-alkali coal prone to coking. Under special conditions, a certain layer of coal mill is set as the minimum coal blending layer. When load shedding occurs due to the failure of the main auxiliary equipment, if this coal blending layer of the coal mill is not cut off, it is difficult to ensure the stability of the unit after rapid load reduction. Second, when the thermal power unit participates in the peak shaving process or during the overhaul of the coal mill, the start and stop of the coal mill are relatively frequent. If the RB action occurs when the coal mill has been in operation for a short time and is carrying a small amount of coal, and this coal mill is retained, it may cause the load of other coal mills to exceed the limit, endangering the stable operation of the unit. Third, due to the difference in the degree of combustion deterioration before and after each boiler RB action, the determined coal mill shutdown interval cannot be adaptively adjusted according to the combustion situation, and it is difficult for manual intervention. If the combustion deterioration is not curbed, the boiler will trip.

[0004] Currently, the commonly used RB coal mill shutdown control methods include top-down, bottom-up, and up-and-down interleaving. The unit adopts the control that the flame center moves in a certain direction or remains unchanged after load reduction. Although the coal mill shutdown interval varies due to different auxiliary equipment trips, it does not consider accelerating or delaying the coal mill shutdown according to the combustion situation of each boiler. In the context of the increasing prevalence of low-calorific-value coal blending and the start and stop of coal mills during the peak shaving process, there are significant technical defects in the risk of boiler shutdown.

[0005] At the same time, none of the existing technical methods consider that if the raw coal bunker of the retained coal mill is low-calorific-value coal, the combustion situation is likely to deteriorate after the RB drops to the target load; it does not consider the output of the coal mill before the RB action. If the fuel quantity of a certain layer in the retained coal mill is low before the RB action, the coal supply of the remaining coal mills may exceed the limit load value, resulting in coal blockage in the coal mill and inability to supply pulverized coal to the boiler; it does not consider the combustion situation and cannot flexibly adjust the coal mill shutdown interval according to the real-time working conditions of the boiler, and cannot adapt to the fluctuations caused by sudden changes in the working conditions during the coal mill shutdown interval.

[0006] In summary, when the auxiliary equipment of a boiler trips unexpectedly during operation, there are major safety hazards. At the least, the unit deviates from the target load, and at the worst, the boiler combustion deteriorates rapidly, resulting in the shutdown of the generator set. Summary of the Invention

[0007] The present invention provides an optimized control method for improving the flexibility of load reduction during auxiliary equipment failures in thermal power units, overcoming the above-mentioned deficiencies of the prior art. It can effectively solve the problems in the prior art that when considering the situation where the raw coal bin of the grinding unit retains low calorific value coal or low output after load reduction due to auxiliary equipment failures in thermal power units, the tripping interval of the grinding unit cannot flexibly adapt to the changing conditions of the boiler, resulting in parameter over-limit under the sudden load reduction condition of auxiliary equipment failures in the unit, and even causing the shutdown of the boiler and turbine in severe cases.

[0008] One of the technical solutions of the present invention is achieved through the following measures: an optimized control method for improving the flexibility of load reduction during auxiliary equipment failures in thermal power units, including:

[0009] Monitoring the operating status of each grinding unit, and locking the coal feeding amount of each grinding unit at the moment before the load reduction due to auxiliary equipment failure occurs;

[0010] Determining the grinding unit with the minimum coal feeding amount according to the locked coal feeding amounts of each grinding unit;

[0011] Determining the shutdown interval of the grinding unit based on the change in furnace pressure;

[0012] Real-time monitoring of the number of operating grinding units, and selecting the grinding units that need to be shut down when the load reduction due to auxiliary equipment failure occurs;

[0013] Executing the shutdown of the grinding unit according to the grinding unit shutdown principle until the remaining grinding units support the stable operation of the boiler to the target load, where the grinding unit shutdown principle includes: first, directly shutting down the grinding unit with the minimum coal feeding amount; then, shutting down the grinding units that need to be shut down from top to bottom according to the shutdown interval of the grinding unit.

[0014] The following is a further optimization and / or improvement of the above-mentioned technical solution of the invention:

[0015] The above determination of the grinding unit with the minimum coal feeding amount according to the locked coal feeding amounts of each grinding unit includes:

[0016] Screening out the minimum value among the locked coal feeding amounts of each grinding unit, and taking the minimum coal feeding amount as the target output value;

[0017] Comparing the target output value with the coal feeding amounts of each grinding unit to determine the grinding unit with the minimum coal feeding amount.

[0018] The above-mentioned method of determining the interval time of stopping the grinding group by the change of furnace pressure includes: obtaining the furnace pressure, subtracting the value of the furnace pressure from the value after the first-order inertia LEADLAG, and obtaining the actual differential of the furnace pressure, converting the actual differential of the furnace pressure in segments through a correction function, and using a switching module to select the correction coefficient when the auxiliary machine fails to reduce the load. The correction coefficient is selected based on the relatively low output of the previous cycle, and the correction coefficient for shortening the stop interval due to the abnormality of the boiler is selected; when the auxiliary machine fails to reduce the load, the initial value of the correction coefficient is maintained at 1, and the original interval time of stopping the grinding group due to different auxiliary machine failures and load reduction is multiplied by the correction coefficient to obtain the interval time of stopping the grinding group.

[0019] The above monitoring of the operating status of each grinding group, when the auxiliary machine fails and the load is reduced, locks the coal feeding amount of each grinding group at the moment before the auxiliary machine fails and the load is reduced, including:

[0020] Monitor the operating status of each grinding group, determine the status of each grinding group and the coal feeding rate per unit time;

[0021] When the auxiliary machine fails and the load is reduced, the self-selection control loop is triggered to lock the coal supply of each coal mill before the auxiliary machine fails and the load is reduced.

[0022] The second technical solution of the present invention is achieved by the following measures: an optimization control device for improving the flexibility of load reduction in case of auxiliary machine failure of a thermal power unit, comprising:

[0023] The coal feeding rate locking unit monitors the operating status of each grinding group and locks the coal feeding rate of each grinding group just before the auxiliary machine fails and reduces the load when the auxiliary machine fails and reduces the load;

[0024] The minimum coal feeding amount grinding group determination unit determines the minimum coal feeding amount grinding group according to the locked coal feeding amount of each grinding group;

[0025] The interval time determination unit determines the interval time of stopping the grinding group according to the change of furnace pressure;

[0026] The unit for determining the grinding group to be shut down monitors the number of grinding groups in real time and selects the grinding group that needs to be shut down when the auxiliary machine fails and the load is reduced;

[0027] The shutdown execution unit executes the mill shutdown according to the mill shutdown principle until the mill is retained to support the boiler to stabilize to the target load. The mill shutdown principle includes: first directly shut down the mill with the minimum coal feed; then shut down the mills that need to be shut down from top to bottom according to the shutdown interval of the mills.

[0028] The following are further optimizations and / or improvements to the above technical solutions:

[0029] The above-mentioned minimum coal feed rate mill group determination unit includes:

[0030] The first determination module screens out the minimum value from the coal feeding amounts of the locked grinding groups, and takes the minimum coal feeding amount as the target output value;

[0031] The second determination module compares the target output value with the coal feeding amounts of the grinding groups to determine the grinding group with the minimum coal feeding amount.

[0032] The above coal feeding amount locking unit includes:

[0033] The status acquisition module monitors the operating status of each grinding group to determine the status and coal feeding amount per unit time of each grinding group;

[0034] The locking module triggers a self-selection control loop during the auxiliary equipment fault load reduction operation, and locks the coal feeding amount of each coal mill before the auxiliary equipment fault load reduction operation.

[0035] The present invention monitors the operation of the minimum output grinding group in real time. Once an auxiliary equipment fault load reduction occurs, the auxiliary equipment fault load reduction (RB) control directly shuts down the minimum output grinding group, and then shuts down the grinding groups that need to be shut down in sequence from top to bottom or in other ways, and finally retains the grinding groups to support the boiler to be stable to the target load. If there are grinding groups in the boiler that use blended low calorific value fuels, such grinding groups can be removed in time through this method. When the RB action reaches the target value, the remaining grinding groups have less fluctuation in low load calorific value compared with the prior art; if the thermal power unit participates in the peak shaving process or when the grinding group is under maintenance and the operation time of the grinding group is short, the RB is triggered. The inventive method can directly remove the small output grinding groups, balance the instruction differences of the grinding groups, and retain the grinding groups. After the RB action, due to the large bias between the grinding groups, it is prevented that some grinding groups reach their respective output limits to balance the total coal amount of the boiler, and the occurrence of unit shutdown events caused by grinding blockage during the RB control is eliminated. At the same time, a method for correcting the shutdown interval of the grinding group is added, which can adjust the shutdown interval of the grinding group in time according to the deterioration degree of the furnace pressure value, an important parameter of the boiler, during each RB action, enhance the flexible adaptability of the RB control, and improve the action success rate. Description of the Drawings

[0036] Att Figure 1 is the flowchart of the method of the present invention.

[0037] Att Figure 2 is the grinding group status judgment logic diagram of the present invention.

[0038] Att Figure 3 is the minimum output shutdown instruction generation logic diagram of the present invention.

[0039] Att Figure 4 is the shutdown grinding group interval time generation logic diagram of the present invention.

[0040] Att Figure 5 is the shutdown grinding group interval time generation logic diagram of the present invention.

[0041] Appendix Figure 6 This is the structural diagram of the device of the present invention. Specific implementation manners

[0042] The present invention is not limited by the following embodiments, and the specific implementation manners can be determined according to the technical solution of the present invention and the actual situation.

[0043] The present invention will be further described below in conjunction with the embodiments and the drawings:

[0044] Embodiment 1: As shown in the appendix Figure 1 The embodiment of the present invention discloses an optimized control method for improving the flexibility of load shedding of auxiliary equipment in thermal power units, including:

[0045] Step S101, monitor the operating status of each grinding group, and lock the coal feeding amount of each grinding group at the moment before the load shedding action of the auxiliary equipment fails;

[0046] Step S102, determine the grinding group with the minimum coal feeding amount according to the locked coal feeding amounts of each grinding group;

[0047] Step S103, determine the shutdown interval time of the grinding group according to the change of the furnace pressure;

[0048] Step S104, monitor the number of operating grinding groups in real time, and select the grinding groups that need to be shut down when the load shedding action of the auxiliary equipment fails;

[0049] Step S105, execute the shutdown of the grinding group according to the grinding group shutdown principle until the remaining grinding groups support the boiler to be stable at the target load, where the grinding group shutdown principle includes: first directly shut down the grinding group with the minimum coal feeding amount; then shut down the grinding groups that need to be shut down from top to bottom according to the shutdown interval time of the grinding group.

[0050] The present invention monitors the operation of the minimum output mill group in real time. Once a load reduction due to auxiliary equipment failure occurs, the load reduction control for auxiliary equipment failure (RB) directly shuts down the minimum output mill group, and then shuts down the mill groups that need to be shut down in sequence from top to bottom or in other ways, and finally retains the mill groups to support the boiler to stabilize at the target load. If there are mill groups in the boiler that use blended combustion of low calorific value fuels, such mill groups can be removed in a timely manner through this method. When the RB action reaches the target value, the calorific value of the remaining mill groups at low load fluctuates less compared with the prior art. When the thermal power unit participates in the peak shaving process or the mill group is under maintenance and the operation time of the mill group is short, triggering the RB, the method of the present invention can directly remove the small output mill groups, balance the instruction differences of the mill groups, and retain the mill groups. After the RB action, due to the large bias between the mill groups, it is prevented that some mill groups reach their respective output limits to balance the total coal amount of the boiler, and the occurrence of unit shutdown events caused by blocked mills during the RB control is eliminated. At the same time, a method for correcting the mill shutdown interval is added, which can adjust the mill shutdown interval in a timely manner according to the degree of deterioration of the furnace pressure value, an important parameter of the boiler, during each RB action, enhance the flexible adaptability of the RB control, and improve the action success rate.

[0051] Embodiment 2: As shown in the appendix Figures 2 to 5 The embodiment of the present invention discloses an optimized control method for improving the flexibility of load reduction due to auxiliary equipment failure of a thermal power unit, including:

[0052] Step S201, monitor the operation status of each mill group, and lock the coal feeding amount of each mill group at the moment before the load reduction due to auxiliary equipment failure occurs.

[0053] The above steps include:

[0054] 1. Monitor the operation status of each mill group, and determine the status and coal feeding amount per unit time of each mill group (coal mill and coal feeder).

[0055] As shown in the appendix Figure 2 Taking the A mill group as an example, the operation status of the A coal mill and the A coal feeder are ANDed to output a digital quantity "operation status of the A mill group". The value of the "intermediate instruction quantity of the A mill group" is controlled by using the analog quantity switching selection algorithm TRANSFER. The mathematical description of the TRANSFER function block is: IF FLAG == TRUE THEN Output = Y ELSE Output = N, that is, when the "operation status of the A mill group" is TRUE (meaning true value or 1), the output value of the "intermediate instruction quantity of the A mill group" is the coal feeding instruction of a certain coal feeder (that is, the coal feeding amount at the moment before the load reduction due to auxiliary equipment failure occurs); when it is FALSE (meaning false value or 0), the output value is 100, which is the maximum value, and the subsequent output value is used to judge the size of the minimum mill group instruction.

[0056] 2. Trigger a self-selection control loop when the load reduction due to auxiliary equipment failure occurs, and lock the coal feeding amount of each coal mill before the load reduction due to auxiliary equipment failure occurs.

[0057] As shown in the appendix Figure 2 As shown, in the conventional logic of auxillary equipment fault load reduction (RB), an RB action digital signal is generated triggered by an auxillary equipment fault. Similarly, through the analog quantity switching selection algorithm TRANSFER, when RB does not act, that is, when "RB action" is FALSE, the output of this module "intermediate quantity of A mill group's RB action pre-instruction" is equal to "intermediate quantity of A mill group's instruction", continuously outputting upstream data. When RB acts, that is, when "RB action" is TRUE, the output of this module is equal to the output value of this module in the previous scan cycle, locking the intermediate quantity of the instruction. As long as the RB action signal is true, the output maintains the value at the previous moment before RB action.

[0058] In summary, through the above steps and the appendix Figure 2 Build the logic of step S201 for the remaining mill groups respectively and make judgments.

[0059] Step S202, determine the mill group with the minimum coal feeding amount according to the locked coal feeding amounts of each mill group;

[0060] The above steps include:

[0061] 1. Screen out the minimum value from the locked coal feeding amounts of each mill group, and use the minimum coal feeding amount as the targeted output value;

[0062] As shown in the appendix Figure 3 As shown, taking the configuration of 6 mill groups as an example, using the low selection LOSELECT function block, its mathematical description is Output = Min(IN1, IN2, IN3, IN4, IN5, IN6, IN7, IN8). After RB acts, select the minimum output value of 6 mill groups as the "targeted output value".

[0063] 2. Compare the targeted output value with the coal feeding amounts of each mill group to determine the mill group with the minimum coal feeding amount.

[0064] As shown in the appendix Figure 3 As shown, subtract the intermediate quantity of the instruction before RB action of 6 mill groups from the "targeted output value" and input it into the high and low limit alarm algorithm HL. The mathematical description of this algorithm is: high limit value = HILIMIT, low limit value = LOLIMIT; IF (input ≥ high limit value) or (input ≤ low limit value) THEN output = TRUE; ELSE IF (input ≤ high limit value) or (input ≥ low limit value) THEN output = FALSE; where: HILIMIT and LOLIMIT are the constant high limit and constant low limit respectively. HL outputs the digital quantity state, and the NOT gate gives the shutdown instruction for the minimum output of the mill group. Among them, the high and low limit settings of HL are close to zero, that is, the mill group with a value close to the "targeted output value" is the mill group with the minimum output.

[0065] Step S203: Determine the interval time between the shutdown of the pulverizing mills based on the change in furnace pressure;

[0066] The interval time between the shutdown of the pulverizing mills can be corrected by the change in parameters that can characterize the operating state of the boiler. If corrected by furnace pressure, the strategy is as shown in the appendix. Figure 4 As shown, subtract the value after the first-order inertia LEADLAG of this value from the furnace pressure value. The transfer function is described as G(s)=Ts / (Ts + 1) to obtain the actual differential of the furnace pressure. Through the f(x) correction function, the actual differential of the furnace pressure can be segmented and converted. Figure 4 The left-side RB action signal uses the switching module TRANFER. It can select the correction coefficient for shortening the shutdown interval of the pulverizing mills due to boiler abnormalities in a way of low-selection output based on the comparison in the previous cycle when the RB acts, and maintain the initial value of the correction coefficient as 1 when the RB does not act. Multiply the original shutdown interval time of different auxiliary equipment RB by the correction coefficient to form a reasonable, advanced, and flexible shutdown interval time of the pulverizing mills.

[0067] Step S204: Monitor the number of operating pulverizing mills in real time and select the pulverizing mills that need to be shut down when the auxiliary equipment failure load reduction action occurs;

[0068] The shutdown commands for the pulverizing mills are divided into two categories. One category is the pulverizing mills that have no other shutdown commands except the minimum output shutdown command, namely pulverizing mills A, B, and C. The other category is the pulverizing mills that also need to participate in the top-down shutdown, namely pulverizing mills D, E, and F. As shown in the appendix. Figure 5 As shown, the function of the digital quantity statistical module DSCOUNT is to count the number of TRUE values of the input-side digital quantities. Connect the "operating state of each pulverizing mill" judged and output in each step to the input pins of DSCOUNT in turn, and output the counted number of operating pulverizing mills to H in real time. H is the high-limit alarm module, and HISP is its settable parameter. H can be described as: IF HISP is connected to an analog quantity THEN the high-limit value = the value of point HISP ELSE the high-limit value = HILIMIT IF the input ≥ the high-limit value THEN the output = TRUE ELSE IF the input ≤ the high-limit value the output = FALSE. The analog quantity connected to HISP is the reserved number of pulverizing mills for RB, and the variable parameter controlled by the TRANSFER module can be set according to the output capacity of a single auxiliary equipment. If the number of pulverizing mills is greater than the reserved number of pulverizing mills, then the output of H is TRUE. As shown in the appendix. Figure 5 As shown, the combination of "H output" AND "RB action" forms the "precondition" for all the shutdown commands of the pulverizing mills, that is, "RB action" and "the number of pulverizing mills is greater than the reserved number of pulverizing mills". Then, when "the minimum output shutdown command of the pulverizing mills is TRUE", the "shutdown command for the corresponding pulverizing mill" is TRUE. This command channel directly reaches the tripping condition of the pulverizer protection to execute the shutdown of the pulverizing mill.

[0069] Step S205: Execute the shutdown of the grinding units according to the grinding unit shutdown principle until the remaining grinding units support the boiler to stabilize at the target load. The grinding unit shutdown principle includes: First, directly shut down the grinding unit with the minimum coal feeding amount; then, shut down the grinding units to be shut down from top to bottom according to the shutdown interval time of the grinding units.

[0070] In the grinding unit shutdown principle, first shutting down this grinding unit can, for special working conditions where the load of the grinding unit burning low calorific value coal is the lowest and the load at the initial stage of starting and stopping the grinding unit to be put into or withdrawn is the lowest, preferentially stop the small load and low calorific value coal grinding units to improve the stability of the boiler after load reduction.

[0071] As shown in the appendix Figure 5 The "Instruction to Stop F Grinding Unit" consists of two shutdown conditions composed of "Preconditions" AND or (OR): One shutdown condition is the shutdown condition of the first grinding unit with the minimum coal amount in the sixth step; the other shutdown condition is the RB action after a delay of 1, that is, if F is not the first shutdown grinding unit, it is the second shutdown grinding unit. The E grinding unit also has two conditions: One is the same as the first condition of F; the other condition is the RB action after a delay of 1 AND the non-"F grinding unit running" after a delay of 2, that is, if the upper grinding unit of E is in the shutdown state, it is the second shutdown grinding unit and trips after a delay of 1, and if the upper grinding unit of E is running, it is the subsequent standby shutdown grinding unit and trips after a delay of 2 after the upper grinding unit shuts down. The D grinding unit is the same as the E grinding unit, with the addition of a non-logical judgment on the operation of the E and F grinding units. Stop the grinding units in the logical judgment order of steps five and six until the "Preconditions" are not met. The delay times of the delays 1, 2, and 3 are determined by the "Shutdown Interval Time of Grinding Units" in the third step.

[0072] Example 3: As shown in the appendix Figure 6 The embodiment of the present invention discloses an optimized control device for improving the flexibility of load reduction during auxiliary equipment failures of a thermal power unit, including:

[0073] A coal feeding amount locking unit, which monitors the operating states of each grinding unit and locks the coal feeding amount of each grinding unit at the moment before the auxiliary equipment failure load reduction action;

[0074] Here, the coal feeding amount locking unit includes:

[0075] A state acquisition module, which monitors the operating states of each grinding unit and determines the state and coal feeding amount per unit time of each grinding unit;

[0076] A locking module, which triggers a self-selection control loop during the auxiliary equipment failure load reduction action to lock the coal feeding amount of each coal mill before the auxiliary equipment failure load reduction action.

[0077] A minimum coal feeding amount grinding unit determination unit, which determines the grinding unit with the minimum coal feeding amount according to the locked coal feeding amounts of each grinding unit;

[0078] Here, the minimum coal feeding amount grinding unit determination unit includes:

[0079] The first determination module screens out the minimum value from the coal feeding amounts of the locked grinding groups, and takes the minimum coal feeding amount as the targeted output value;

[0080] The second determination module compares the targeted output value with the coal feeding amounts of the grinding groups to determine the grinding group with the minimum coal feeding amount.

[0081] The interval time determination unit determines the interval time for the out-of-service grinding groups based on the change in furnace pressure.

[0082] The out-of-service grinding group determination unit monitors the number of operating grinding groups in real time and selects the grinding groups that need to be out of service when the auxiliary equipment fault load reduction action occurs.

[0083] The out-of-service execution unit executes the out-of-service of the grinding groups according to the grinding group out-of-service principle until the remaining grinding groups support the boiler to be stable at the target load. The grinding group out-of-service principle includes: first, directly out-of-service the grinding group with the minimum coal feeding amount; then, out-of-service the grinding groups that need to be out of service from top to bottom according to the out-of-service grinding group interval time.

[0084] The above technical features constitute the best embodiment of the present invention, which has strong adaptability and the best implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. An optimized control method for improving the flexibility of load shedding in auxiliary equipment failures of thermal power units, characterized in that, it includes: Monitoring the operating status of each coal mill group, and locking the coal feeding amount of each coal mill group at the moment before the auxiliary equipment failure load shedding action occurs; Determining the coal mill group with the minimum coal feeding amount according to the locked coal feeding amounts of each coal mill group; Determining the interval time for shutting down coal mill groups based on the change in furnace pressure; Real-time monitoring of the number of operating coal mill groups, and selecting the coal mill groups that need to be shut down during the auxiliary equipment failure load shedding action; Performing the shutdown of coal mill groups according to the coal mill group shutdown principle until the remaining coal mill groups support the boiler to stabilize at the target load, where the coal mill group shutdown principle includes: first directly shutting down the coal mill group with the minimum coal feeding amount; then shutting down the coal mill groups that need to be shut down from top to bottom according to the shutdown interval time of coal mill groups; Among them, determining the coal mill group with the minimum coal feeding amount according to the locked coal feeding amounts of each coal mill group includes: Screening out the minimum value among the locked coal feeding amounts of each coal mill group, and taking the minimum coal feeding amount as the target output value; Comparing the target output value with the coal feeding amounts of each coal mill group to determine the coal mill group with the minimum coal feeding amount; Among them, determining the interval time for shutting down coal mill groups based on the change in furnace pressure includes: obtaining the furnace pressure, subtracting the value after the first-order inertia LEADLAG of this value from the furnace pressure value to obtain the actual differential of the furnace pressure, performing piecewise conversion on the actual differential of the furnace pressure through a correction function, using a switching module to select the correction coefficient for shortening the coal mill shutdown interval due to boiler abnormalities in a lower selection output manner based on the previous cycle during the auxiliary equipment failure load shedding action, and maintaining the initial value 1 of the correction coefficient when the auxiliary equipment failure load shedding does not occur, and multiplying the original different auxiliary equipment failure load shedding coal mill shutdown interval times by the correction coefficient to obtain the shutdown interval time of coal mill groups.

2. The optimized control method for improving the flexibility of load shedding in auxiliary equipment failures of thermal power units according to claim 1, characterized in that, The monitoring of the operating status of each coal mill group and locking the coal feeding amount of each coal mill group at the moment before the auxiliary equipment failure load shedding action occurs includes: Monitoring the operating status of each coal mill group and determining the status and coal feeding amount per unit time of each coal mill group; Triggering a self-selection control loop during the auxiliary equipment failure load shedding action to lock the coal feeding amount of each coal mill before the auxiliary equipment failure load shedding action.

3. An optimized control device for improving the flexibility of load shedding in auxiliary equipment failures of thermal power units applying the method according to claim 1 or 2, characterized in that, it includes: A coal feeding amount locking unit, which monitors the operating status of each coal mill group and locks the coal feeding amount of each coal mill group at the moment before the auxiliary equipment failure load shedding action occurs; A minimum coal feeding amount coal mill group determining unit, which determines the coal mill group with the minimum coal feeding amount according to the locked coal feeding amounts of each coal mill group; An interval time determining unit, which determines the interval time for shutting down coal mill groups based on the change in furnace pressure; A shutdown coal mill group determining unit, which real-time monitors the number of operating coal mill groups and selects the coal mill groups that need to be shut down during the auxiliary equipment failure load shedding action; The shutdown execution unit shuts down the coal mills according to the coal mill shutdown principle until the remaining coal mills support the boiler to stabilize at the target load. The coal mill shutdown principle includes: first, directly shutting down the coal mill with the minimum coal feeding amount; then, shutting down the coal mills to be shut down from top to bottom according to the shutdown interval of the coal mills. Among them, the minimum coal feeding amount coal mill determination unit includes: The first determination module screens out the minimum value among the coal feeding amounts of the locked coal mills and takes the minimum coal feeding amount as the targeted output value. The second determination module compares the targeted output value with the coal feeding amounts of the coal mills to determine the coal mill with the minimum coal feeding amount. Among them, determining the shutdown interval of the coal mills based on the change in furnace pressure includes: obtaining the furnace pressure, subtracting the value after the first-order inertia LEADLAG of this value from the furnace pressure value to obtain the actual differential of the furnace pressure, performing piecewise conversion on the actual differential of the furnace pressure through a correction function, using a switching module to select the correction coefficient for shortening the coal mill shutdown interval due to boiler abnormality in a lower selection output mode based on the previous cycle when the auxiliary equipment fault load reduction action occurs, and maintaining the initial value 1 of the correction coefficient when the auxiliary equipment fault load reduction action does not occur, and multiplying the original shutdown intervals of the coal mills during the auxiliary equipment fault load reduction by the correction coefficient to obtain the shutdown interval of the coal mills.

4. The optimized control device for improving the flexibility of auxiliary equipment fault load reduction of a thermal power unit according to claim 3, characterized in that the coal feeding amount locking unit includes: The status acquisition module monitors the operating status of each coal mill and determines the status and coal feeding amount per unit time of each coal mill. The locking module triggers a self-selection control loop when the auxiliary equipment fault load reduction action occurs and locks the coal feeding amount of each coal mill before the auxiliary equipment fault load reduction action.

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