A control device and method for load rejection of a coal mill of a thermal power generating unit

Abstract

The application provides a control device and method for load rejection of a coal mill of a thermal power generator unit, which comprises: a coal mill coding module for outputting a coding value corresponding to each coal mill operation signal; a coding summation module for obtaining a coding algebraic sum according to the coding value; a load rejection joint tripping coal mill pulse output module for outputting a pulse to a self-locking module after a preset interval time and reverse delay of a delay module; a self-locking module for keeping the coding algebraic sum unchanged and outputting after receiving the pulse output by the delay module; a joint tripping coal mill characteristic value judgment module for judging whether the matching of the coal mill characteristic value is successful according to the coding algebraic sum; and a joint tripping coal mill instruction output module for outputting a joint tripping instruction to trip the corresponding coal mill. The application uses a single coding algebraic sum m for numerical judgment, simplifies the control logic, reduces the on-site configuration difficulty and the debugging workload, and has the same reliability.

Description

Technical Field

[0001] This invention relates to the field of thermal control in thermal power plants, specifically a control device and method for load shedding from a coal mill in a thermal power generating unit. Background Technology

[0002] Many countries have experienced over a dozen large-scale urban blackouts caused by power grid failures. These failures cause generator units in the affected area to shut down, and restarting them often lacks power, resulting in long recovery times. If grid-connected generator units have Fast Cut Back (FCB) functionality, they can switch to islanded operation with auxiliary power supply after a grid failure to avoid shutdown, allowing for immediate restoration of power and shortening outage time. The most important aspect of the FCB procedure for coal-fired power plants is to trip some operating coal mills at regular intervals to reduce the coal feed rate, keeping only one mill running to maintain safe operation of the unit under extremely low load conditions.

[0003] For a thermal power generating unit with four coal mills, each mill is responsible for supplying pulverized coal to a specific area of ​​the furnace. Different mill trips have varying impacts on stable combustion. For safety, the load shedding (FCB) procedure needs to trip several operating mills at intervals according to their tripping priority, from high to low. Before executing the FCB procedure, the operation and shutdown of which mills are running is random. For two or more mills operating, there are 11 possibilities. Traditional programming requires considering every possible combination to output the trip command. This combination judgment makes configuration complex, increases debugging workload, and is prone to errors. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a control device and method for load shedding of coal mills in a thermal power generating unit using four coal mills. The device uses coding technology to encode coal mills with different tripping priorities. The operating status of all coal mills can be deduced from the sum of the coding algebra and this value. Therefore, this single analog quantity of the coding algebra can replace multiple combinations. This design results in a simple and easy-to-read control logic structure, reducing the difficulty of on-site configuration and debugging workload, while maintaining the same reliability.

[0005] A control device for load shedding from a coal mill in a thermal power generating unit includes:

[0006] The coal mill encoding module is used to receive the operating signals of each coal mill, encode the operating signals of each coal mill, and output the encoded value corresponding to the operating signal.

[0007] The encoding summation module is connected to the coal mill encoding module and is used to sum the encoded values ​​output by each coal mill encoding module to obtain the encoded algebraic sum.

[0008] The load shedding and tripping coal mill pulse output module is used to output pulses at preset intervals for logic judgment of the tripping coal mill;

[0009] The delay module is connected to the pulse output module and the self-locking module of the load-shedding coal mill. It is used to output the pulse output by the pulse output module of the load-shedding coal mill after a reverse delay to the self-locking module.

[0010] The self-locking module is connected to the delay module and the encoding summation module, and is used to maintain the encoded algebraic sum unchanged and output it after receiving the pulse output by the delay module;

[0011] The joint-jump coal mill feature value judgment module is connected to the self-locking module and is used to receive the coded algebraic sum output by the self-locking module. If the coded algebraic sum is within a preset threshold range, the coal mill feature value corresponding to the coded algebraic sum is judged to be successfully matched.

[0012] The interlocking coal mill command output module is connected to the interlocking coal mill characteristic value judgment module and the load shedding interlocking coal mill pulse output module. It is used to output an interlocking command to drive the relay to trip the corresponding coal mill when both the interlocking coal mill characteristic value judgment module and the load shedding interlocking coal mill pulse output module have pulse output.

[0013] Furthermore, the coal mill coding module is used to encode the four coal mills according to the priority level of the cascading jump. If the coal mill D with the highest cascading jump priority is running, it is coded as 8; otherwise, it is coded as 0. If the coal mill C with the second highest cascading jump priority is running, it is coded as 4; otherwise, it is coded as 0. If the coal mill B with the third highest cascading jump priority is running, it is coded as 2; otherwise, it is coded as 0. If the coal mill A with the fourth highest cascading jump priority is running, it is coded as 1; otherwise, it is coded as 0.

[0014] Furthermore, during normal operation of the unit, if a grid fault causes the generator outlet switch to disconnect, triggering a load shedding event, the load shedding and tripping coal mill pulse output module 10 will output pulses three times within 60 seconds, starting from the 0th, 20th, and 40th seconds, to perform logic judgment for tripping the coal mills. Each pulse will trip at most one coal mill, so as to achieve the purpose of intermittent tripping of the coal mills.

[0015] Further, after a load rejection event occurs, the inter-tripping coal mill eigenvalue judgment module performs three eigenvalue judgments on the coded algebraic sum m, and at most one inter-tripping coal mill instruction is generated in each judgment. If m>8.5, an inter-tripping coal mill instruction D is generated; if 4.5<m<7.5, an inter-tripping coal mill instruction C is generated; if 2.5<m<3.5, an inter-tripping coal mill instruction B is generated.

[0016] A load rejection control method for coal mills in a thermal power generating unit, which is implemented by using the above device, comprising the following steps:

[0017] A coal mill coding module correspondingly receives operation signals of each coal mill, performs coding according to the operation signals of each coal mill, and outputs a coding value corresponding to the operation signal;

[0018] A coding summation module sums the coding values output by each coal mill coding module to obtain a coded algebraic sum;

[0019] A load rejection inter-tripping coal mill pulse output module outputs pulses at preset intervals for logical judgment of inter-tripping coal mills;

[0020] A delay module is connected with the load rejection inter-tripping coal mill pulse output module and a self-locking module, and is configured to reversely delay the pulse output by the load rejection inter-tripping coal mill pulse output module and then output the delayed pulse to the self-locking module;

[0021] After receiving the pulse output by the delay module, the self-locking module keeps the coded algebraic sum unchanged and outputs the same;

[0022] The inter-tripping coal mill eigenvalue judgment module receives the coded algebraic sum output by the self-locking module, and if the coded algebraic sum falls within a preset threshold interval, it is determined that the eigenvalue matching of the coal mill corresponding to the coded algebraic sum is successful;

[0023] An inter-tripping coal mill instruction output module outputs an inter-tripping instruction to drive the relay to trip the corresponding coal mill when both the inter-tripping coal mill eigenvalue judgment module and the load rejection inter-tripping coal mill pulse output module output pulses.

[0024] The present invention abandons the traditional combination judgment method based on the initial state of coal mills, adopts the numerical judgment with a single coded algebraic sum, simplifies the control logic, reduces the difficulty of on-site configuration and the workload of debugging, and has the same reliability. Description of Drawings

[0025] Figure 1 is a schematic diagram of an embodiment of a load rejection control device for coal mills in a thermal power generating unit according to the present invention;

[0026] Figure 2 is a comparison diagram of the present invention and a traditional logic design.

[0027] In the diagram: 1—Coal mill D operating signal, 2—Coal mill C operating signal, 3—Coal mill B operating signal, 4—Coal mill A operating signal, 5—Coal mill D encoding module, 6—Coal mill C encoding module, 7—Coal mill B encoding module, 8—Coal mill A encoding module, 9—Encoding summation module, 10—Load shedding (FCB) interlocking coal mill pulse output module, 11—Delay module, 12—Self-locking module, 13—Interlocking coal mill D characteristic value judgment module, 14—Interlocking coal mill C characteristic value judgment module, 15—Interlocking coal mill B characteristic value judgment module, 16—Interlocking coal mill D command output module, 17—Interlocking coal mill C command output module, 18—Interlocking coal mill B command output module. Detailed Implementation

[0028] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings.

[0029] Figure 1 The diagram shown is a schematic diagram of one embodiment of a control device for load shedding from a coal mill in a thermal power generating unit according to the present invention. The device includes:

[0030] The coal mill encoding module is used to receive the operating signals of each coal mill, encode them according to the operating signals of each coal mill, and output the encoded value corresponding to the operating signal. This embodiment of the invention includes four coal mills, namely coal mills A and D, and corresponding to coal mill D operating signal 1, coal mill C operating signal 2, coal mill B operating signal 3, and coal mill A operating signal 4. There are four coal mill coding modules: coal mill D coding module 5, coal mill C coding module 6, coal mill B coding module 7, and coal mill A coding module 8. These modules respectively receive coal mill D operating signal 1, coal mill C operating signal 2, coal mill B operating signal 3, and coal mill A operating signal 4. In this embodiment, the coal mill coding modules are used to encode the four coal mills according to their priority levels. Specifically, if coal mill D, which has the highest priority, is running, coal mill D coding module 5 encodes it as 8; otherwise, it encodes it as 0. If coal mill C, which has the second highest priority, is running, coal mill C coding module 6 encodes it as 4; otherwise, it encodes it as 0. If coal mill B, which has the third highest priority, is running, coal mill B coding module 7 encodes it as 2; otherwise, it encodes it as 0. If coal mill A, which has the fourth highest priority, is running, coal mill A coding module 8 encodes it as 1; otherwise, it encodes it as 0.

[0031] Encoding summation module 9 is connected to the coal mill encoding module and is used to sum the encoded values ​​output by each coal mill encoding module to obtain the encoded algebraic sum.

[0032] The load shedding (FCB) interlocking coal mill pulse output module 10 is used to output pulses at preset intervals for logic judgment of interlocking coal mills. In this embodiment, the load shedding (FCB) interlocking coal mill pulse output module 10 outputs pulses three times within 60 seconds, starting from the 0th, 20th, and 40th seconds, to perform logic judgment of interlocking coal mills. Each pulse can interlock at most one coal mill, achieving the purpose of intermittent tripping of coal mills.

[0033] The delay module 11 is connected to the pulse output module 10 and the self-locking module 12 of the load shedding (FCB) interlocking coal mill, and is used to output the pulse output by the pulse output module 10 of the load shedding (FCB) interlocking coal mill to the self-locking module 12 after a reverse delay.

[0034] The self-locking module 12 is connected to the delay module 11 and the encoding summation module 9, and is used to maintain the encoded algebraic sum unchanged and output it after receiving the pulse output by the delay module 11;

[0035] The interlocking coal mill feature value judgment module is connected to the self-locking module 12 and is used to receive the coded algebraic sum output by the self-locking module 12. If the coded algebraic sum is within a preset threshold range, it is determined that the coal mill feature value of the corresponding coded algebraic sum is successfully matched, and a pulse signal is output. In this embodiment, the interlocking coal mill feature value judgment module includes the interlocking coal mill D feature value judgment module 13, the interlocking coal mill C feature value judgment module 14, and the interlocking coal mill B feature value judgment module 15.

[0036] The interlocking mill command output module is connected to the interlocking mill characteristic value judgment module and the load shedding (FCB) interlocking mill pulse output module 10. It is used to output an interlocking command to drive the relay to trip the corresponding mill when both the interlocking mill characteristic value judgment module and the load shedding (FCB) interlocking mill pulse output module 10 have pulse output. In this embodiment, the interlocking mill command output module includes an interlocking mill D command output module 16, an interlocking mill C command output module 17, and an interlocking mill B command output module 18.

[0037] The specific working principle of the device is described below:

[0038] The operating signal 1 of the coal mill D is connected to the coal mill D encoding module 5; the operating signal 2 of the coal mill C is connected to the coal mill C encoding module 6; the operating signal 3 of the coal mill B is connected to the coal mill B encoding module 7; the operating signal 4 of the coal mill A is connected to the coal mill A encoding module 8; the coal mill D encoding module 5, the coal mill C encoding module 6, the coal mill B encoding module 7, and the coal mill A encoding module 8 are connected to the encoding summation module 9; the load shedding (FCB) interlocking coal mill pulse output module 10 is connected to the delay module 11; the encoding summation module 9 and the delay module 11 are simultaneously connected to the self-locking module 12; the self-locking module 12 is connected to the interlocking coal mill D characteristic value judgment module. The following modules are connected simultaneously: Module 13, Module 14 (characteristic value judgment of C-type coal mill), Module 15 (characteristic value judgment of B-type coal mill), Module 10 (pulse output module of FCB-type coal mill), and Module 13 (characteristic value judgment of D-type coal mill). Module 16 (command output module of D-type coal mill), Module 10 (pulse output module of FCB-type coal mill), Module 14 (characteristic value judgment of C-type coal mill), and Module 17 (command output module of C-type coal mill). Module 10 (pulse output module of FCB-type coal mill), Module 15 (characteristic value judgment module of B-type coal mill), and Module 18 (command output module of B-type coal mill).

[0039] like Figure 1 As shown, during normal operation of the unit, the four coal mills are coded according to their operating status. First, the coal mill D, which has the highest tripping priority, is coded. If coal mill D is running, the coal mill D operation signal 1 exists, and the coal mill D coding module 5 outputs the value 8 of the Y channel. If coal mill D is stopped, the coal mill D operation signal 1 does not exist, and the coal mill D coding module 5 outputs the value 0 of the N channel. Next, the coal mill C, which has the second highest tripping priority, is coded. If coal mill C is running, the coal mill C operation signal 2 exists, and the coal mill C coding module 6 outputs the value 4 of the Y channel. If coal mill C is stopped, the coal mill C operation signal 2 does not exist, and the coal mill C coding module 6 outputs the value 0 of the N channel. Next, the third-priority pulverizer (B) is encoded. If pulverizer B is running, its operating signal 3 exists, and the pulverizer B encoding module 7 outputs a value of 2 for the Y channel. If pulverizer B is stopped, its operating signal 3 does not exist, and the pulverizer B encoding module 7 outputs a value of 0 for the N channel. Finally, the fourth-priority pulverizer (A) is encoded. If pulverizer A is running, its operating signal 4 exists, and the pulverizer A encoding module 8 outputs a value of 1 for the Y channel. If pulverizer A is stopped, its operating signal 4 does not exist, and the pulverizer A encoding module 8 outputs a value of 0 for the N channel. After encoding, the codes for pulverizer D, pulverizer C, pulverizer B, and pulverizer A are summed by the encoding summation module 9 to obtain the algebraic sum m.

[0040] During normal operation of the unit, if a power grid fault causes the generator outlet breaker to trip, a fast cut back (FCB) event is triggered. The inter-tripping coal mill pulse output module 10 for FCB outputs pulses 3 times starting from the 0th second, 20th second, and 40th second within 60 seconds, and performs inter-tripping coal mill logic judgment. Each pulse can inter-trip at most one coal mill, so as to achieve the purpose of interval tripping of coal mills. The duration of the first pulse is 3 seconds. After passing through the delay module 11, the pulse is connected to the self-locking module 12. After the self-locking module 12 receives the pulse, it keeps the coded algebraic sum m unchanged. The self-locking module 12 sends the coded algebraic sum m to the inter-tripping coal mill D characteristic value judgment module 13, the inter-tripping coal mill C characteristic value judgment module 14 and the inter-tripping coal mill B characteristic value judgment module 15 simultaneously for characteristic value judgment.

[0041] The characteristic value of the inter-tripping coal mill D characteristic value judgment module 13 is m>8.5. If the condition is satisfied, it indicates that (1) the coal mill D is in operation; (2) in addition to the coal mill D, there is at least one coal mill with a lower tripping priority than the coal mill D in operation. At this time, the condition for inter-tripping the coal mill D is satisfied, the inter-tripping coal mill D characteristic value judgment module 13 outputs 1, otherwise it outputs 0;

[0042] The characteristic value of the inter-tripping coal mill C characteristic value judgment module 14 is 4.5<m<7.5. If the condition is satisfied, it indicates that (1) the coal mill D has been shut down; (2) the coal mill C is in operation; (3) in addition to the coal mill C, there is at least one coal mill with a lower tripping priority than the coal mill C in operation. At this time, the characteristic value matching of the inter-tripping coal mill C is successful, the inter-tripping coal mill C characteristic value judgment module 14 outputs 1, otherwise it outputs 0;

[0043] The characteristic value of the inter-tripping coal mill B characteristic value judgment module 15 is 2.5<m<3.5. If the condition is satisfied, it indicates that (1) the coal mill D and the coal mill C have been shut down; (2) the coal mill B and the coal mill A are in operation. At this time, the characteristic value matching of the inter-tripping coal mill B is successful, the inter-tripping coal mill B characteristic value judgment module 15 outputs 1, otherwise it outputs 0.

[0044] The joint trip coal mill D command output 16 simultaneously receives the output of the load shedding (FCB) joint trip coal mill pulse output module 10 and the output of the joint trip coal mill D characteristic value judgment module 13. If both are 1, the joint trip coal mill D command output 16 drives the relay to trip coal mill D; the joint trip coal mill C command output 17 simultaneously receives the output of the load shedding (FCB) joint trip coal mill pulse output module 10 and the output of the joint trip coal mill C characteristic value judgment module 14. If both are 1, the joint trip coal mill C command output 17 drives the relay to trip coal mill C; the joint trip coal mill B command output 18 simultaneously receives the output of the load shedding (FCB) joint trip coal mill pulse output module 10 and the output of the joint trip coal mill B characteristic value judgment module 15. If both are 1, the joint trip coal mill B command output 18 drives the relay to trip coal mill B.

[0045] The function of the self-locking module 12 is to keep the coding algebra and m unchanged during this judgment process. Since the feature values ​​of the joint trip coal mill D feature value judgment module 13, the joint trip coal mill C feature value judgment module 14, and the joint trip coal mill B feature value judgment module 15 do not overlap, only one joint trip coal mill instruction can be generated at most. Otherwise, during a trip pulse process, as the coal mill trips, the coding algebra and m change and rematch with the lower-level trip feature value, causing multiple coal mills to trip at the same time, which does not meet the design requirements of load shedding (FCB).

[0046] The delay module 11 keeps the coded algebra and m self-locked for 1 second after the trip pulse disappears, preventing premature release of the self-lock due to different module scanning sequences, thus improving the safety margin. The second and third pulses are both 3 seconds long, and the judgment process is exactly the same as the first pulse judgment process. Regardless of how many coal mills are running before the load shedding (FCB), by performing characteristic value judgments on the coded algebra and m three times, the corresponding coal mills are tripped sequentially, ensuring that one coal mill remains running, thus meeting the fuel control requirements during the load shedding (FCB) process.

[0047] This invention also provides a method for controlling the load shedding of a coal mill by a thermal power generating unit, using the aforementioned device, and the method includes the following steps:

[0048] The coal mill coding module receives the operating signals of each coal mill, encodes them according to the operating signals of each coal mill, and outputs the coded values ​​corresponding to the operating signals.

[0049] The encoding summation module sums the encoded values ​​output by each coal mill encoding module to obtain the encoded algebraic sum.

[0050] The pulse output module of the load shedding and tripping coal mill outputs pulses at preset intervals to perform logic judgments for the tripping coal mill.

[0051] The delay module is connected to the pulse output module and the self-locking module of the load-shedding coal mill, and is used to output the pulse output by the pulse output module of the load-shedding coal mill after a reverse delay to the self-locking module;

[0052] After receiving the pulse output by the delay module, the self-locking module keeps the encoded algebra sum unchanged and outputs it;

[0053] The joint-jump coal mill feature value judgment module receives the coded algebraic sum output by the self-locking module. If the coded algebraic sum is within the preset threshold range, the coal mill feature value corresponding to the coded algebraic sum is judged to be successfully matched.

[0054] When both the inter-pulse mill characteristic value judgment module and the load shedding inter-pulse mill pulse output module have pulse outputs, the inter-pulse mill tripping command output module outputs an inter-pulse tripping command to drive the relay to trip the corresponding mill.

[0055] This invention uses 8421 coding technology to encode coal mills with different tripping priorities. Due to the characteristics of 8421 coding, the operating status of all coal mills can be deduced from the code algebra and this value. Therefore, the code algebra and this single analog quantity can be used to replace 11 combinations (such as...). Figure 2 As shown in the figure, the control logic structure under this design is simple and easy to read, which reduces the difficulty of on-site configuration and debugging workload, while having the same reliability.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A control device for load shedding from a coal mill in a thermal power generating unit, characterized in that: comprising a coal mill coding module, configured to respectively receive operation signals of each coal mill, encode according to the operation signals of each coal mill, and output a coding value corresponding to the operation signal; a coding summation module, connected to the coal mill coding module, configured to sum the coding values output by each coal mill coding module to obtain an algebraic sum of codes; a pulse output module for inter-tripping coal mills during load rejection, configured to output pulses at preset intervals to perform logical judgment on inter-tripping of coal mills; a delay module, connected to the pulse output module for inter-tripping coal mills during load rejection and a self-locking module, configured to reversely delay the pulse output by the pulse output module for inter-tripping coal mills during load rejection and then output the delayed pulse to the self-locking module; the self-locking module, connected to the delay module and the coding summation module, configured to keep the algebraic sum of codes unchanged and output the same after receiving the pulse output by the delay module; an eigenvalue judgment module for inter-tripping coal mills, connected to the self-locking module, configured to receive the algebraic sum of codes output by the self-locking module, and if the algebraic sum of codes falls within a preset threshold range, judge that the eigenvalue of the coal mill corresponding to the algebraic sum of codes is successfully matched; an inter-tripping instruction output module for coal mills, connected to the eigenvalue judgment module for inter-tripping coal mills and the pulse output module for inter-tripping coal mills during load rejection, configured to output an inter-tripping instruction to drive the relay to trip the corresponding coal mill when both the eigenvalue judgment module for inter-tripping coal mills and the pulse output module for inter-tripping coal mills during load rejection output pulses.

2. The control device for load shedding of the coal mill by a thermal power generating unit as described in claim 1, characterized in that: the coal mill coding module is configured to perform 8421 coding on four coal mills according to the inter-tripping priority. If coal mill D with the first inter-tripping priority is in operation, the coding is 8, otherwise the coding is 0; if coal mill C with the second inter-tripping priority is in operation, the coding is 4, otherwise the coding is 0; if coal mill B with the third inter-tripping priority is in operation, the coding is 2, otherwise the coding is 0; if coal mill A with the fourth inter-tripping priority is in operation, the coding is 1, otherwise the coding is 0.

3. The control device for load shedding of the coal mill by a thermal power generating unit as described in claim 1, characterized in that: During normal operation of the unit, if a power grid fault causes the generator outlet switch to trip and triggers a load rejection event, the pulse output module for inter-tripping coal mills during load rejection outputs pulses three times starting from the 0th second, 20th second and 40th second within 60 seconds to perform logical judgment on inter-tripping of coal mills, and at most one coal mill is inter-tripped per pulse, so as to achieve the purpose of interval tripping of coal mills.

4. The control device for load shedding of coal mill by a thermal power generating unit as described in claim 2, characterized in that: After the load rejection event occurs, the eigenvalue judgment module for inter-tripping coal mills performs three times of eigenvalue judgment on the algebraic sum of codes m, and at most one inter-tripping instruction for coal mills is generated per judgment. If m>8.5, an inter-tripping instruction for coal mill D is generated; if 4.5<m<7.5, an inter-tripping instruction for coal mill C is generated; if 2.5<m<3.5, an inter-tripping instruction for coal mill B is generated.

5. A method for controlling load shedding from a coal mill in a thermal power generating unit, characterized in that: The method is implemented by adopting the device according to any one of claims 1 to 4, and comprises the following steps: the coal mill coding module respectively receives operation signals of each coal mill, encodes according to the operation signals of each coal mill, and outputs a coding value corresponding to the operation signal; the coding summation module sums the coding values output by each coal mill coding module to obtain an algebraic sum of codes; The pulse output module of the load shedding and tripping coal mill outputs pulses at preset intervals to perform logic judgments for the tripping coal mill. The delay module is connected to the pulse output module and the self-locking module of the load-shedding coal mill, and is used to output the pulse output by the pulse output module of the load-shedding coal mill after a reverse delay to the self-locking module; After receiving the pulse output by the delay module, the self-locking module keeps the encoded algebra sum unchanged and outputs it; The joint-jump coal mill feature value judgment module receives the coded algebraic sum output by the self-locking module. If the coded algebraic sum is within the preset threshold range, the coal mill feature value corresponding to the coded algebraic sum is judged to be successfully matched. When both the inter-pulse mill characteristic value judgment module and the load shedding inter-pulse mill pulse output module have pulse outputs, the inter-pulse mill tripping command output module outputs an inter-pulse tripping command to drive the relay to trip the corresponding mill.

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