Industrial control cross-platform clock synchronization method based on zero pulse and communication link

Abstract

The invention discloses an industrial control cross-platform clock synchronization method based on a zero pulse and a communication link, and the method comprises the following steps: S1, confirming that a DCS system accesses a Beidou or GPS for time correction, and enabling a clock to be standard Beijing time; s2, confirming that communication data transmission between the DCS and the PLC is normal, wherein the data transmission period is between a second level and a millisecond level; s3, extracting the current clock of the system in the DCS system, and generating a timing pulse signal at the zero moment of each day through logical configuration setting; s4, the timing pulse signal is sent to the PLC through a communication link between the DCS and the PLC; s5, after the PLC receives the timing pulse signal, a clock setting function block in the PLC is triggered, and the system time of the PLC is set to be the zero moment; and S6, after time calibration is completed, the PLC continues to operate according to the independent clock until the next time calibration period. According to the method, the problem that the PLC cannot correct time under the condition that a time correction device is not added is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of industrial automation control technology, in particular to an industrial control cross-platform clock synchronization method and system based on zero-point pulse and communication link, which is suitable for clock synchronization between DCS and PLC in the industries of thermal power generation, chemical industry, metallurgy and the like. BACKGROUND

[0002] Large thermal power plant control adopts DCS system, due to the particularity of algorithm and secrecy, some subsystems (such as coordination, denitration automation, etc.) control adopt PLC external hanging machine. DCS sends unit working condition parameters to PLC, and PLC performs operation on the received working condition parameters and then sends them to DCS for control of actual equipment in the field. There is a communication network for real-time exchange of data between DCS and PLC. The DCS system generally accesses Beidou (or GPS) for time correction, while the PLC does not access for time correction, and uses a controller independent clock, resulting in a clock deviation between PLC and DCS (monthly cumulative deviation can reach several minutes). When the deviation is large, manual time correction is logged on the PLC. However, many control parameters are related to real-time average based on Beijing time, so the clock deviation in the PLC seriously affects the control accuracy and economy. A time correction device can be installed on the PLC to access Beidou (or GPS) for time correction, but the special time correction card for PLC costs tens of thousands to hundreds of thousands of yuan, so this method is relatively high in cost. SUMMARY

[0003] The technical problem to be solved by the present application is that the installation of a special time correction card for PLC in the prior art is costly, and manual time correction is inefficient. To solve the above problems, an industrial control cross-platform clock synchronization method based on zero-point pulse and communication link is provided.

[0004] The purpose of the present application is achieved in the following manner: An industrial control cross-platform clock synchronization method based on zero-point pulse and communication link, the method comprising the following steps: S1: confirming that the DCS system accesses Beidou or GPS for time correction, and the clock is standard Beijing time; S2: confirming that the communication data transmission between DCS and PLC is normal, and the data transmission period is between seconds and milliseconds; S3: extracting the current clock of the system in the DCS system, and generating a time correction pulse signal at zero o'clock through logical configuration setting; S4: sending the time correction pulse signal to the PLC through the communication link between the DCS and the PLC; S5: after the PLC receives the time correction pulse signal, triggering the clock setting function block in the PLC to set the PLC system time to zero o'clock; S6: After the time setting is completed, the PLC continues to operate according to the independent clock until the next time setting period.

[0005] In the step S3, the generation of the time setting pulse signal is realized by a system clock extraction function block and a logic configuration in the DCS system, and the logic configuration includes time comparison logic and pulse trigger logic.

[0006] The time setting pulse signal is BOOL type data.

[0007] In the step S5, the clock setting function block in the PLC is a CPU clock setting function block, the enable end of the function block is connected to the time setting pulse signal, and the write-in value is preset as the current year, month and day zero time.

[0008] In the step S3, the sending time of the time setting pulse signal can be set in advance to compensate for the communication delay and system scanning time, so that the actual time setting time of the PLC is close to the standard zero time.

[0009] The present application has the following advantages: compared with the prior art, the present application does not require additional hardware, has low cost, simple logic and high reliability, the time setting accuracy can be controlled within 1 second, and is suitable for various industrial control scenes. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a method flowchart of the present application. DETAILED DESCRIPTION

[0011] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0012] It should be pointed out that the following detailed description is exemplary and is intended to provide further description of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same technical meaning as understood by ordinary skilled persons in the technical field to which the present application belongs.

[0013] The present application discloses an industrial control cross-platform clock synchronization method based on zero point pulse and communication link, which comprises the following steps: S1: confirming that the DCS system accesses the Beidou or GPS time setting, and the clock is the standard Beijing time; S2: confirming that the communication data transmission between the DCS and the PLC is normal, and the data sending period is between the second level and the millisecond level; S3: extracting the current clock of the DCS system, and generating a time setting pulse signal at the zero time of each day through logic configuration setting; S4: sending the time setting pulse signal to the PLC through the communication link between the DCS and the PLC; S5: After the PLC receives the time calibration pulse signal, a clock setting function block in the PLC is triggered to set the PLC system time to zero time; S6: After the time calibration is completed, the PLC continues to operate according to its independent clock until the next time calibration period.

[0014] In the step S3, the generation of the time calibration pulse signal is realized by a system clock extraction function block and a logic configuration in the DCS system, and the logic configuration includes a time comparison logic and a pulse trigger logic.

[0015] The time calibration pulse signal is a BOOL type data.

[0016] In the step S5, the clock setting function block in the PLC is a CPU clock setting function block, an enable end of the function block is connected to the time calibration pulse signal, and a write-in value of the function block is preset as the current year, month and day zero time.

[0017] In the step S3, the sending time of the time calibration pulse signal can be set in advance to compensate for the communication delay and system scanning time, so that the actual time calibration time of the PLC is close to the standard zero time.

[0018] As shown in the figure, Figure 1 1. Confirm that the DCS system accesses the Beidou (or GPS) time calibration, and the clock is the standard Beijing time. This step mainly guarantees the accuracy of the time calibration source clock. Confirm that the communication data transmission between the DCS and the PLC is normal, and the data sending period (between seconds and milliseconds). If there is no communication link between the two systems, the time calibration signal cannot be sent out, and a too large communication sending period may affect the accuracy of the time calibration. Confirm that the "use computer clock to synchronize PLC clock" in the PLC system is not checked. When this item is not checked, the time calibration function block is effective.

[0019] 2. Extract the current clock of the DCS by using the system clock extraction function block in the DCS system, and trigger the DCS side time calibration pulse (data type is BOOL) at zero time every day through logic configuration. The extraction of the current clock function block is different for different DCS systems, and the difficulty is different. It needs to be combined with the actual situation or consult the manufacturer.

[0020] 3. The DCS side time calibration pulse (data type is BOOL) signal is sent to the PLC side through the communication network between the DCS and the PLC.

[0021] 4. After the PLC side receives the time calibration pulse, the enable end of the clock setting CUP clock function block in the PLC system is triggered, and the CUP clock is set to zero time when the pulse trigger is triggered. After the pulse instruction is ended, the PLC operates according to its independent clock until the next zero time for time calibration. Generally, the write-in clock value is set to * year * month * day 0: 0: 0 in advance, and the enable end of the time calibration pulse trigger function block is used to realize it.

[0022] 5. The application is affected by the communication cycle and the DCS and PLC scanning time, the accuracy is generally between 0-2 seconds, and the optimization can be carried out by means of pre-time correction (such as sending a time correction pulse at 23:59:58 at the DCS end).

[0023] 6. The application is only used for clock time correction, and more communication points and logic are required for year and month time correction, which is less used in actual engineering sites.

[0024] The application does not need to increase additional time correction devices, and time correction is carried out through a data exchange link between two control platforms. The time correction is completed by setting the zero point of the system clock, which is simple and convenient, small in data amount and simple and reliable in logic. The application effectively solves the problem that the PLC cannot be time corrected without increasing time correction devices. Through the implementation of clock time correction between the DCS system and the denitration external machine PLC of Linzhou Company, the problem of affecting the control accuracy and economy due to the clock deviation in the PLC is effectively solved.

[0025] The above only describes the preferred embodiments of the application, and it should be noted that, for those skilled in the art, without departing from the overall concept of the application, a number of changes and improvements can be made, which should also be considered as the protection range of the application.

Claims

1. A cross-platform clock synchronization method for industrial control based on zero-point pulse and communication link, characterized in that: The method includes the following steps: S1: Confirm that the DCS system is connected to BeiDou or GPS time synchronization and the clock is standard Beijing time; S2: Confirm that the communication and data transmission between DCS and PLC is normal, and the data transmission cycle is between seconds and milliseconds. S3: Extract the current system clock from the DCS system and, through logic configuration settings, generate a time synchronization pulse signal at midnight every day; S4: The time synchronization pulse signal is sent to the PLC through the communication link between the DCS and the PLC; S5: After receiving the time synchronization pulse signal, the PLC triggers the clock setting function block inside the PLC to set the PLC system time to zero. S6: After the time synchronization is completed, the PLC continues to operate according to its independent clock until the next time synchronization cycle.

2. The cross-platform clock synchronization method for industrial control based on zero-point pulse and communication link according to claim 1, characterized in that: In step S3, the generation of the time synchronization pulse signal is achieved through the system clock extraction function block and logic configuration in the DCS system. The logic configuration includes time comparison logic and pulse triggering logic.

3. The cross-platform clock synchronization method for industrial control based on zero-point pulse and communication link according to claim 1, characterized in that: The time synchronization pulse signal is BOOL type data.

4. The cross-platform clock synchronization method for industrial control based on zero-point pulse and communication link according to claim 1, characterized in that: In step S5, the clock setting function block inside the PLC is the CPU clock setting function block. The enable terminal of this function block is connected to the time synchronization pulse signal, and its written value is preset to the current year, month, and day at midnight.

5. The cross-platform clock synchronization method for industrial control based on zero-point pulse and communication link according to claim 1, characterized in that: In step S3, the sending time of the time synchronization pulse signal can be set in advance to compensate for communication delay and system scan time, so that the actual time synchronization of the PLC is close to the standard zero point.

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