Research on the integrated application of PLC system and power supply monitoring system

1 Introduction

Power supply monitoring is an important monitoring system for railway signals. Before this, the power supply monitoring system of signals basically used single-chip microcomputers as the core of the signal acquisition system. On the one hand, the single-chip microcomputer monitoring system has technical limitations such as slow acquisition speed, unfriendly interface, and inconvenient operation. On the other hand, due to the relatively independent monitoring of the power module part, it brings many inconveniences to the power supply system, such as difficult maintenance and cumbersome interface display. Based on the above reasons, this project has developed a power supply monitoring system based on Delta PLC as the signal acquisition core and Delta HMI touch screen as the operation and monitoring interface. The monitoring subsystem and the power module are interconnected through the industrial bus network to realize the integration of an economical, practical, and technologically advanced railway signal power supply monitoring system.

2 Hardware and Software System Design

2.1 Hardware system design

The design of the railway signal power supply monitoring hardware system is shown in Figure 1. System scale: 44 digital inputs; 1 digital output; 6 power modules; 39 analog inputs .

Figure 1 Hardware system design

The control system is configured as follows: touch screen: DOPA75CSTD; PLC: DVP16EH00T + 1 DVP04AD-H + ​​3 DVP16HM11N; 1 power module communication card; 1 time-sharing acquisition circuit card.

The touch screen is mainly used to display collected data, alarm, alarm upper and lower limit settings, fine-tuning of collected data display, alarm data display, historical trend chart display, etc. PLC mainly collects data and calculates. Considering that the system does not have a very high requirement for the speed of analog quantity acquisition, in order to save costs, a DVP04AD-H is used in the system to collect 39 analog quantities in a time-sharing manner. In order to achieve this function, we have jointly developed an electronic switch circuit with the manufacturer, and divided the 39 analog quantities into ten groups, each with 4 channels, and collected them by outputting different groups. The power supply communication card is mainly responsible for summarizing the data of the 6 power supply modules and communicating with the PLC through the RS484 interface using the MODBUS protocol, so that the PLC can collect the data of the 6 power supply modules. To achieve this function, our company's power supply R&D department has done a lot of work, and finally the PLC and the communication card of the power supply module have achieved communication, and the information of the power supply module has been collected.

2.2 Software System Design

(1) System function design: 44 digital quantity acquisition and display, fault judgment; 6 power supply module data acquisition and display, display of power supply module working status and alarm judgment; 39 analog quantity display, and judgment of upper and lower limit alarms; display of alarm screen, alarm information, current alarm, alarm frequency; alarm upper and lower limit settings; data fine-tuning function, and display of fine-tuning value; historical trend chart display; different screen opening authority settings; It is necessary to explain the data fine-tuning function above. Since there will be errors in the measurement of the primary measuring element on site, and this error is fixed and unchanged in a short period of time, this part of the function is added to the program so that the final displayed value is the value after the error is eliminated;

(2) The system structure design is divided into the HMI human-machine dialogue interface part and the PLC field monitoring part. The main structure of the HMI part is shown in Figure 2.

Figure 2 HMI human-machine dialogue interface

The PLC monitoring part mainly includes: power module communication; time-sharing acquisition of 40 analog quantities, 4 at a time; calculation of the acquired analog quantities 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, display value fine-tuning, and negative value elimination; faults and alarms; digital quantity acquisition and display, fault judgment;

3 Engineering Debugging

When debugging the time-sharing acquisition function, you need to pay attention to the time of time-sharing acquisition. If it is too large, it will affect the overall data acquisition time. If it is too small, it will cause confusion in the collected data. In addition, you need to add an interval between two data acquisitions to avoid the overlap of the two sets of data. Calculate the collected analog quantity according to the range to get the display value. Fine-tune the value calculation, fine-tune the display value, and eliminate negative values; note that negative values ​​may appear during fine-tuning, so consider eliminating negative values. Power module communication Pay attention to the communication protocol during power supply communication must be set in the communication card, including the station number setting, and pay attention to the address correspondence. Faults and alarms; because there are 79 alarm points in total, it is very cumbersome and requires clear thinking.

4 Conclusion

A typical case based on the solution provided by Zhongda Telecom integrates two different types of products, reflecting the integration characteristics of a single technology platform in integration engineering.