1 Introduction
Power supply monitoring is a crucial monitoring system for railway signaling. Previously, power supply monitoring systems primarily used microcontrollers as the core of the signal acquisition system. However, microcontroller-based monitoring systems suffer from limitations such as slow acquisition speed, unfriendly interfaces, and inconvenient operation. Furthermore, the relatively independent monitoring of the power supply modules introduces numerous inconveniences to the power supply system, including difficult maintenance and cumbersome interface displays. To address these issues, this project developed a power supply monitoring system based on a Delta PLC as the signal acquisition core and a Delta HMI touchscreen as the operation and monitoring interface. The monitoring subsystem and power supply modules are interconnected via an industrial bus network, achieving an integrated, economical, practical, and technologically advanced power supply monitoring system for railway signaling.
2 Hardware and Software System Design
2.1 Hardware System Design
Figure 1 Hardware architecture design
The hardware architecture design for railway signal power supply monitoring is shown in Figure 1. System specifications: 44 digital inputs; 1 digital output; 6 power supply modules; 39 analog inputs.
The control system is configured as follows: Touch screen: DOPA75CSTD; PLC: DVP16EH00T + 1 DVP04AD-H + 3 DVP16HM11N; Power module communication card: 1; Time-division acquisition circuit card: 1.
The touchscreen is mainly used to display acquired data, alarms, alarm upper and lower limit settings, fine-tuning of acquired data display, alarm data display, and historical trend chart display. The PLC primarily acquires and calculates data. Considering the system's relatively low requirements for analog signal acquisition speed, and to save costs, a single DVP04AD-H was used to acquire 39 analog signals in a time-division multiplexing manner. To achieve this function, we collaborated with the manufacturer to develop an electronic switch circuit, dividing the 39 analog signals into ten groups of four, acquiring data by outputting different groups. The power communication card is mainly responsible for aggregating data from six power modules and communicating with the PLC via an RS484 interface using the MODBUS protocol, enabling the PLC to acquire data from the six power modules. Our company's power supply R&D department did a lot of work to achieve this function, ultimately enabling communication between the PLC and the power module communication card, thus allowing the power module information to be acquired.
2.2 Software Architecture Design
(1) System function design: 44 digital quantities are acquired and displayed, and fault judgment is performed; data acquisition and display of 6 power modules are performed, the working status of the power modules is displayed and alarms are judged; 39 analog quantities are displayed and upper and lower limit alarms are judged; alarm screen, alarm information, current alarm, and alarm frequency are displayed; alarm upper and lower limit settings are performed; data fine-tuning function is performed and the fine-tuning value is displayed;
Historical trend charts show different screen access permissions.
It is necessary to explain the data fine-tuning function above. Since there will be errors in the measurement of a single measuring element on site, and this error is fixed and does not change in a short period of time, this function is added to the program so that the final displayed value is the value after eliminating the error.
(2) The system structure design is divided into the HMI human-machine interface part and the PLC field monitoring part. The main architecture of the HMI part is shown in Figure 2.
Figure 2 HMI Human-Computer Interface
The PLC monitoring section mainly includes: power module communication; time-division acquisition of 40 analog signals, 4 signals at a time; calculation of the acquired analog signals according to the range to obtain the display value, display the working status of the power module and judge the alarm; fine-tuning value calculation, fine-tuning of the display value and elimination of negative values; fault and alarm; digital signal acquisition and display, fault judgment;
3. Engineering commissioning
When debugging the time-sharing data acquisition function, pay attention to the acquisition time. Too long a time will affect the overall data acquisition time, while too short a time will cause data corruption. Additionally, an interval should be added between two data acquisitions to avoid overlap. Calculate the displayed value based on the acquired analog quantity according to the range. Fine-tune the value calculation and display, and eliminate negative values; note that negative values may occur during fine-tuning, so negative value elimination must be considered. For power module communication, ensure the communication protocol is correctly configured in the communication card, including station number settings, and ensure address correspondence. Faults and alarms; there are 79 alarm points, which is quite complex and requires a clear approach.
4. Conclusion
The typical case based on the solution provided by Delta Electronics integrates two different types of products, demonstrating the integrated characteristics of a single technology platform in integration engineering.
