Programmable logic controller for actively monitoring bad ground wire

Abstract

The invention relates to the technical field of programmable controllers in the field of industrial control, in particular to a programmable logic controller for actively monitoring ground wire badness, which comprises a ground wire interference detection circuit and a corresponding interference value register, a communication error rate register; a user can access the interference alarm state register; the system comprises a programmable logic controller system, a register for periodically processing interference values, bit error rates and interference alarm states, a system software module, a ground wire interference detection circuit and a corresponding interference value register, all terminal devices of a factory can be protected, EMC grounding is carried out, and the programmable logic controller system carries out real-time monitoring on return paths of ground wires of the factory. A disturbance noise monitoring channel A, a disturbance noise monitoring channel B, a disturbance noise monitoring channel C and a disturbance noise monitoring channel D are arranged in the programmable logic controller, and a component module 1, a component module 2, a module noise filtering capacitor and a component module 3 are arranged in the disturbance noise monitoring channels. And the reference basis is improved by judging the maintenance direction.

Description

Technical Field

[0001] The present invention relates to the technical field of programmable controllers in the field of industrial control, and particularly to a programmable logic controller for actively monitoring poor ground wires. Background Art

[0002] In current industrial applications, medium and small programmable logic controllers are often used in combination with complete sets of electromechanical equipment. These complete sets of electromechanical equipment are usually independently designed, installed, and debugged at the equipment manufacturing factory. However, when these devices are installed in the final actual use environment, they will face many challenges. Due to the huge differences between different use environments, the working conditions are also different. For example, the grounding at the equipment installation site is not standardized, and the unbalanced three-phase poles of the electrical equipment deteriorate the grounding environment; usually, there are also various other devices such as high-power inverters and high-frequency devices at the equipment site. During the operation of these devices, there will be strong electromagnetic interference, which further has a negative impact on the grounding situation of the entire equipment site, making the grounding condition worse. The working conditions of the programmable logic controller system will further deteriorate.

[0003] In such a complex environment, it is often very difficult for the personnel at the manufacturing site to accurately judge the potential hazards brought about by the deteriorated grounding. Under such harsh working conditions, a series of abnormal situations may occur in the PLC system. For example, during the signal acquisition process, abnormal phenomena such as inaccurate and unstable data may occur; in terms of communication, problems such as signal interruption and data transmission errors may also occur; more seriously, in key links such as temperature control, pressure control, and motion control, out-of-control situations may occur. The occurrence of these abnormal and out-of-control phenomena will undoubtedly bring serious safety hazards to the production process and may even trigger various accidents. Summary of the Invention

[0004] The purpose of the present invention is to provide a programmable logic controller for actively monitoring poor ground wires to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A programmable logic controller for actively monitoring poor ground wires, including a ground wire interference detection circuit and a corresponding interference value register; a communication error rate register; a user-accessible interference alarm status register; a periodic processing of the interference value, error rate, and interference alarm status register and a system software module, characterized in that: the ground wire interference detection circuit and the corresponding interference value register: Each terminal device in the factory will perform protection and EMC grounding, and the programmable logic controller system monitors the real-time return paths of ground wires in the factory. Four disturbance noise monitoring channels, namely A, B, C, and D, are set inside the programmable logic controller, and component module 1, component module 2, module noise filtering capacitors, and component module 3 are set inside the disturbance noise monitoring channels;

[0006] User-accessible interference alarm status register: An internal expansion bus and two field bus interfaces are respectively set on both sides of the programmable logic controller. Both are communication interfaces, and the programmable logic controller accesses the expansion IO module through this communication interface;

[0007] Communication error rate register: The data frame of the communication protocol includes parity check or CRC check;

[0008] Periodically process the interference value, error rate, and interference alarm status register: The communication processing module of the programmable controller can count the error frames through the verification of the data frame, and it is easy to obtain the error frame rate by periodically counting and dividing by the total number of data frames. This parameter is used for the composite determination of the ground wire interference alarm;

[0009] System software module: The system sets a periodic timer and configures system configuration parameters such as the number of detection points for the programmable logic controller, switches the analog switch of the programmable logic controller to select the detection point channel, and starts the circuit ADC for multiple samplings; detects and samples the disturbance current between the zero line and the ground wire of the detection point, and determines whether the detection channel has completed polling. When the judgment is "no", switch the analog switch of the programmable logic controller to select the detection point channel again. When the judgment is "yes", calculate the disturbance value and determine whether the disturbance value exceeds the threshold. When the disturbance value does not exceed the threshold, set the interference alarm status register of the programmable logic controller to: "good", and return to the initial state to detect the disturbance current again after the detection is completed. When the disturbance value exceeds the threshold, detect the communication error rate and determine whether it is normal. When the communication error rate detection is normal, set the interference alarm status register of the programmable logic controller to: "bad", and return to the initial state to detect the disturbance current again after the detection is completed. When the communication error rate detection is abnormal, set the interference alarm status register of the programmable logic controller to: "abnormal", and return to the initial state to detect the disturbance current again after the detection is completed.

[0010] Preferably, the component module 1 is a current transformer, and different ratio current transformers are selected according to the specification model. The ratio coefficient A of the current transformer is the ratio of the current I:

[0011]

[0012] Component module 2 is a current-to-voltage processing module, and the relationship between the output voltage V1 and the input current I2 is as follows:

[0013] V1 = I2.R a .

[0014] Preferably, the module noise filtering capacitor is selected appropriately to effectively filter out invalid high-frequency noise and effectively restore the disturbance current. A suitable filtering capacitor Ca is selected according to the controller response bandwidth and the sensitive disturbance noise frequency. The capacitance value is selected as follows in the embodiment:

[0015]

[0016] where ω is the current angular frequency.

[0017] Preferably, the component module 3 is a signal conditioning module. The signal is processed into the effective measurement range of the ADC through in-phase amplification and an adder to improve the signal-to-noise ratio. The relationship between the output voltage V2 of the component module 3 and the input voltage is as follows:

[0018]

[0019] where the input voltage of the component module 3 is the output voltage V1 of the component module 2.

[0020] Preferably, for the system configuration, monitoring points are selected in the detection schematic diagram of the workshop control system. The number of system channels and system attributes are configured through the upper computer configuration module or the programmable controller program configuration instruction. Among them, the monitoring point A is a standard configuration point, which is built into the programmable controller hardware and is default to be open.

[0021] Preferably, for obtaining the disturbance value, the noise disturbance in this software system is an AC signal, and the noise voltage collected by the ADC is a single-point DC voltage. The root mean square value V rms is an effective index for measuring AC voltage and current signals. According to the voltage V collected by the ADC, the root mean square value is obtained in the following manner;

[0022]

[0023] Preferably, for different operating times of the equipment, especially whether different power equipment is turned on or not, and differences in operating conditions will have completely different impacts on the system noise disturbance. The variance is introduced as a measure of the disturbance index, and the disturbance value is calculated through the following method.

[0024]

[0025] where μ is the sampling average value of the sample.

[0026] Preferably, the expansion IO module of the programmable controller is connected through communication. Under interference conditions, there are often certain check failures and incorrect communication data frames. The ratio of incorrect frames to correct frames in a measurement cycle is stored in a specific register, which can be used as a basis for judging ground wire interference. Similarly, for remote IO access, a similar incorrect frame rate can also be statistically calculated.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: First, by means of specific designs or methods, the reliability of the system is improved, the calculation efficiency of the circuit disturbance value is greatly increased, and this method realizes the accurate calculation of the disturbance current between the neutral line and the ground line, thus effectively solving the disturbance noise problem in the prior art;

[0028] Second, the PLC controller implemented by this method, after periodically measuring the interference voltage between the ground line and the neutral line, combines the misframe rate determination of the IO expansion communication and the remote IO expansion communication to judge the interference situation and give an alarm. The provided system alarm register can be accessed by the user in the application program to detect this status register, and control protection is made according to the potential hazard degree of the application system to prevent further out-of-control and accidents. This allows users to insight into the potential hazards caused by the defects of the ground line, providing a reference basis for rapid on-site diagnosis and determining the direction of maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the monitoring of the programmable logic controller (PLC) system in an embodiment of the present invention.

[0030] Figure 2 It is a schematic diagram of the processing of the internal circuit module of the programmable logic controller (PLC) in an embodiment of the present invention.

[0031] Figure 3 It is a schematic circuit diagram in an embodiment of the present invention.

[0032] Figure 4 It is a schematic diagram of the bus interface of the programmable logic controller (PLC) in an embodiment of the present invention.

[0033] Figure 5 It is a flowchart of the software system of the method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to deepen the understanding and recognition of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described and introduced with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments, and no formal restrictions are imposed on this embodiment. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] Please refer to Figures 1-5, the present invention provides a technical solution: a programmable logic controller for actively monitoring the ground wire fault, including a ground wire interference detection circuit and a corresponding interference value register; a communication error rate register; a user-accessible interference alarm status register; a periodic processing module for interference value, error rate, and interference alarm status register, and a system software module. The ground wire interference detection circuit and the corresponding interference value register: Each terminal device in the factory will perform protection and EMC grounding. The programmable logic controller system monitors the real-time ground wire return paths in the factory. Four disturbance noise monitoring channels, namely A, B, C, and D, are set inside the programmable logic controller. Component module 1, component module 2, module noise filtering capacitors, and component module 3 are set inside the disturbance noise monitoring channels. As Figure 1 shown: When the high-voltage power grid is connected to the factory workshop, it will be stepped down to the industrial common voltage level such as AC380V through the last-level substation. At the substation, the functions of the PE line and the N line are integrated, and a conductor called the PEN line undertakes both functions at the same time, that is, the TN-C power distribution system. After coming out of the factory workshop distribution box connected through the urban power grid, the protective neutral line PEN is repeatedly grounded and divided into a protective line PE and a neutral line N. After the two are separated, they must not be merged again in the subsequent circuit system, and the two must be insulated from each other, that is, it is converted into a TN-S power distribution system. Terminal devices such as factory workshop distribution cabinets, controller system cabinets, PLC controllers, drivers such as inverters and servos, motors, fans, and sensor shields will all perform protection and EMC grounding to improve the safety and reliability of the system. Interference noise will flow into the ground through the path of least impedance, that is, the nearest grounding point. If the downstream grounding point is in poor contact or the grounding impedance is too large, the noise interference can only flow into the ground through the upstream grounding point. By detecting the return path current or the voltage of the PE line and the N line, it is possible to judge whether each grounding point is good and the disturbance noise situation of the same-level grounding points. Through the real-time monitoring of the ground wire return paths by the PLC system of the present invention, the grounding system conditions such as equipment grounding, controller driver grounding, cabinet grounding, and workshop grounding can be effectively judged, thereby ensuring the safe and reliable operation of the system.

[0036] Through the detection point A of the built-in system of the programmable logic controller, it is possible to effectively evaluate whether the programmable logic controller and its sensors are well grounded; whether the equipment is well grounded; whether the drivers and equipment of the common grounding system are well grounded; whether the disturbance noise exceeds the EMC range that the controller can withstand, etc.

[0037] More preferably, monitoring the detection point B at the same time can further improve the accuracy of judging whether the drivers and equipment of the common grounding system are well grounded; and make a more detailed evaluation of the controller disturbance noise.

[0038] More preferably, by monitoring the detection point C, it is possible to effectively evaluate whether the cabinet grounding is good.

[0039] More preferably, by monitoring the detection point D, whether the grounding of the workshop is good can be included in the monitoring scope.

[0040] As Figure 2 shown, it is a schematic diagram of the processing of the internal circuit module of the programmable logic controller. It includes 4 disturbance noise monitoring channels. In this embodiment, the detection signal sensor uses a current transformer, and of course, the direct voltage detection method can also be used. Among them, channel A is a fixed detection channel built into the PLC. Channels B, C, and D are connected at appropriate points according to the configuration of the workshop system so that the ground wire passes through the current transformer and is connected to the corresponding PLC detection channel, and the relevant software configuration can be completed.

[0041] The user can access the interference alarm status register: As Figure 4 shown, an internal expansion bus and two field bus interfaces are respectively set on both sides of the programmable logic controller. Both of them are communication interfaces, and the programmable logic controller accesses the expansion IO module through this communication interface;

[0042] Communication error rate register: The data frame of the communication protocol includes parity check or CRC check;

[0043] Periodically process the interference value, error rate, and interference alarm status register: The communication processing module of the programmable controller can count the error frames through the verification of the data frame, and it is easy to obtain the error frame rate by periodically counting and dividing by the total number of data frames. This parameter is used for the composite determination of the ground wire interference alarm;

[0044] As Figure 5 shown, the system software module: The system sets a periodic timer and configures system configuration parameters such as the number of detection points for the programmable logic controller, switches the analog switch of the programmable logic controller to select the detection point channel, and starts the circuit ADC for multiple samplings; detects and samples the disturbance current between the neutral wire and the ground wire of the detection point, and determines whether the detection channel has completed polling. When the judgment is "no", switch the analog switch of the programmable logic controller to select the detection point channel again. When the judgment is "yes", calculate the disturbance value and determine whether the disturbance value exceeds the threshold. When the disturbance value does not exceed the threshold, set the interference alarm status register of the programmable logic controller to: "good", and return to the initial state after the detection to detect the disturbance current again. When the disturbance value exceeds the threshold, detect the communication error rate and determine whether it is normal. When the communication error rate detection is normal, set the interference alarm status register of the programmable logic controller to: "bad", and return to the initial state after the detection to detect the disturbance current again. When the communication error rate detection is abnormal, set the interference alarm status register of the programmable logic controller to: "abnormal", and return to the initial state after the detection to detect the disturbance current again.

[0045] As Figure 3As shown in the figure, component module 1 is a current transformer. Different ratio current transformers are selected according to the specification model. The ratio coefficient A of the current transformer is the ratio of the current I:

[0046]

[0047] Component module 2 is a current-to-voltage processing module. The relationship between the output voltage V1 and the input current I2 is as follows:

[0048] V1 = I2.R a .

[0049] Selecting a suitable module noise filtering capacitor can effectively filter out invalid high-frequency noise and effectively restore the disturbed current. A suitable filtering capacitor Ca is selected according to the controller response bandwidth and the sensitive disturbance noise frequency. The capacitance value selection in the embodiment is as follows:

[0050]

[0051] Where ω is the current angular frequency.

[0052] Component module 3 is a signal conditioning module. The signal is processed within the effective measurement range of the ADC through in-phase amplification and an adder to improve the signal-to-noise ratio. The relationship between the output voltage V2 of component module 3 and the input voltage is as follows:

[0053]

[0054] Among them, the input voltage of component module 3 is the output voltage V1 of component module 2.

[0055] System configuration: Select a monitoring point in the detection schematic diagram of the workshop control system. Configure the number of system channels and system attributes through the upper computer configuration module or the programmable controller program configuration instruction. Among them, monitoring point A is the standard configuration point, and the hardware is built into the programmable controller and is kept open by default.

[0056] Obtain the disturbance value. The noise disturbance in this software system is an AC signal, and the noise voltage collected by the ADC is a single-point DC voltage. The root mean square value V rms is an effective index for measuring AC voltage and current signals. According to the voltage V collected by the ADC, the root mean square value is obtained in the following way;

[0057]

[0058] At different operating times of the equipment, especially whether different power equipment is turned on or not, and differences in operating conditions will have completely different impacts on the system noise disturbance. The variance is introduced as a measure of the disturbance index, and the disturbance value is calculated in the following way,

[0059]

[0060] Among them, μ is the sampling average value of the sample.

[0061] Read the current communication error rate. The expansion IO module of the programmable controller is connected through communication. Under interference conditions, there are often certain verification failures and incorrect communication data frames. The ratio of incorrect frames and correct frames in a measurement period is stored in a specific register, which can be used as a basis for judging ground wire interference. Similarly, for remote IO access, a similar incorrect frame rate can also be statistically calculated.

[0062] Although the embodiments of the present invention have been shown and described, it should be emphasized that the above description is only an introduction and description of the usage mode of the embodiments of the present invention, and does not impose any formal limitation on the present invention. For those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A programmable logic controller for actively monitoring the poor condition of a ground wire, comprising a ground wire interference detection circuit and a corresponding interference value register; a communication error rate register; a user-accessible interference alarm status register; a periodic processing of the interference value, error rate, and interference alarm status register and a system software module, characterized in that: Ground wire interference detection circuit and corresponding interference value register: Each terminal device in the factory will perform protection and EMC grounding. The programmable logic controller system monitors the real-time return paths of ground wires in the factory. Four disturbance noise monitoring channels, namely A, B, C, and D, are set inside the programmable logic controller. Inside the disturbance noise monitoring channels, there are component module 1, component module 2, module noise filtering capacitor, and component module 3; User-accessible interference alarm status register: One internal expansion bus and two field bus interfaces are respectively set on both sides of the programmable logic controller. Both are communication interfaces. The programmable logic controller accesses the expansion IO module through this communication interface; Communication error rate register: The data frame of the communication protocol includes parity check or CRC check; Periodically process the interference value, error rate, and interference alarm status register: The communication processing module of the programmable controller can count the error frames by checking the data frames, and it is easy to obtain the error frame rate by periodically counting and dividing by the total number of data frames. This parameter is used for the composite determination of ground wire interference alarms; System software module: The system sets a periodic timer and configures system configuration parameters such as the number of detection points for the programmable logic controller, switches the programmable logic controller analog switch to select the detection point channel, and starts the circuit ADC for multiple samplings; Detect and sample the disturbance current between the zero wire and the ground wire of the detection point, and determine whether the detection channel has completed polling. When the judgment is "no", switch the programmable logic controller analog switch to select the detection point channel again. When the judgment is "yes", calculate the disturbance value and determine whether the disturbance value exceeds the threshold. When the disturbance value does not exceed the threshold, set the interference alarm status register of the programmable logic controller to: "good", and return to the initial state after the detection to detect the disturbance current again. When the disturbance value exceeds the threshold, detect the communication error rate and determine whether it is normal. When the communication error rate detection is normal, set the interference alarm status register of the programmable logic controller to: "bad", and return to the initial state after the detection to detect the disturbance current again. When the communication error rate detection is abnormal, set the interference alarm status register of the programmable logic controller to: "abnormal", and return to the initial state after the detection to detect the disturbance current again.

2. The programmable logic controller for actively monitoring the defect of a ground wire according to claim 1, wherein: The component module 1 is a current transformer. Different ratio current transformers are selected according to the specification model. The ratio coefficient A of the current transformer is the ratio of the current I: Component module 2 is a current-to-voltage processing module. The relationship between the output voltage V1 and the input current I2 is as follows: V1 = I2.R a 。 3. The programmable logic controller for actively monitoring the defect of the ground wire according to claim 1, wherein: The selected module noise filtering capacitor can effectively filter out invalid high-frequency noise and effectively restore the disturbance current. Select a suitable filtering capacitor Ca according to the controller response bandwidth and sensitive disturbance noise frequency. The capacitance value selection in the embodiment is as follows: Where, ω is the current angular frequency.

4. A programmable logic controller for actively monitoring the defects of ground wires according to claim 1, characterized in that: The component module 3 is a signal conditioning module. It processes the signal into the effective measurement range of the ADC through in-phase amplification and an adder to improve the signal-to-noise ratio. The relationship between the output voltage V2 of the component module 3 and the input voltage is as follows: Among them, the input voltage of the component module 3 is the output voltage V1 of the component module 2.

5. The programmable logic controller for actively monitoring the poor condition of the ground wire according to claim 1, wherein: For the described system configuration, select a monitoring point in the detection schematic diagram of the workshop control system. Configure the number of system channels and system attributes through the host computer configuration module or programmable logic controller (PLC) program configuration instructions. Among them, monitoring point A is a standard configuration point, and the hardware is built into the PLC internally and is default to be open.

6. The programmable logic controller for actively monitoring the defect of the ground wire according to claim 1, characterized in that: Regarding the calculation of the disturbance value, the noise disturbance in this software system is an AC signal, and the noise voltage collected by the ADC is a single-point DC voltage. The root mean square value V rms is an effective indicator for measuring AC voltage and current signals. According to the voltage V collected by the ADC, the root mean square value is calculated in the following manner; 7. The programmable logic controller for actively monitoring the defect of the ground wire according to claim 1, wherein: For different operating times of the equipment, especially whether high-power equipment is turned on or not, and different operating conditions, etc., will have completely different impacts on the system noise disturbance. Variance is introduced as a measure of the disturbance index, and the disturbance value is calculated through the following method. Among them, μ is the sampling average value of the sample.

8. The programmable logic controller for actively monitoring the poor condition of a ground wire according to claim 1, wherein: The expansion IO module of the described PLC is connected through communication. Under interference conditions, there are often certain verification failures and incorrect communication data frames. The ratio of incorrect frames to correct frames in a measurement cycle is stored in a specific register, which can be used as a basis for judging ground wire interference. Similarly, a similar incorrect frame rate can be statistically calculated for remote IO access.

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