1 Introduction
With the continuous advancement of microcomputer technology and automatic control technology, computer-aided automatic detection and control technology has been introduced into many fields. Moreover, as research in various fields continues to deepen and develop, the requirements for computer-aided automatic measurement and control systems are becoming increasingly stringent. Industrial control configuration software is a new type of software development technology that has emerged in the field of industrial automation in recent years. Developers typically do not need to write overly complex program code; they can complete the development of the required application software simply by using the tools in the configuration software package to perform data configuration, graphic image configuration, and other tasks. It has advantages such as easy secondary development, short development cycle, strong versatility, and high reliability.
In recent years, my country's industry has developed rapidly, and the corresponding industrial control field has also moved towards scientific and modern directions. This is exemplified by the requirements for controlling various high-voltage frequency converters operating in the field. Since high-voltage frequency converters are almost always key equipment in industrial and mining enterprises, the high reliability requirements are self-evident. Therefore, real-time monitoring of high-voltage frequency converter data, operating status, fault status, and operating parameters, and making corresponding controls based on specific circumstances, is particularly important. To achieve this goal, we designed and developed a frequency converter monitoring system using the industrial control configuration software MCGS as the development platform.
2. Requirements for frequency converter monitoring system
2.1 Technical Requirements for Monitoring Systems
(1) The monitoring system is required to ensure the real-time accuracy and reliability of all monitoring data, reduce the impact of human factors, and provide reliable on-site data support;
(2) It should have good maintainability, enabling convenient maintenance of the system's normal operation;
(3) It can provide a user-friendly human-computer interaction interface, making it convenient for on-site personnel to operate;
(4) It can provide data processing for real-time data and management of historical data;
(5) It can provide flexible interfaces, provide users with good secondary development functions, and can integrate information with other management information systems.
2.2 Specific Requirements for Monitoring Systems
(1) Signal acquisition and data processing: Non-standard signal data from the field are converted into standard signals by configuration software.
(2) Status display:
The inverter's start-up, stop, ready, closed, connected, running, bypass, alarm, and external control status are dynamically displayed on the monitoring screen through configuration software, providing a real-time and dynamic effect.
(3) Monitoring operation: Automatic real-time monitoring of frequency, temperature, current, voltage, wind pressure, etc.
(4) Operation screen:
The user interface allows users to query real-time and historical data such as voltage, current, power, and temperature of the device. Users can also query real-time and historical curves and device status, and set and print real-time and historical reports as required.
3. Hardware components of the frequency converter monitoring system
Figure 1. Schematic diagram of the inverter monitoring system
The inverter monitoring system mainly consists of an industrial control computer, a printer, and an inverter control cabinet (mainly including a PLC, analog input/output modules, digital input/output modules, fiber optic trigger modules, a UPS power supply, and some communication cables, etc.), as shown in Figure 1. The industrial control computer acts as the monitoring center, transmitting all the inverter's operating data and parameters via serial communication (RS-485) through shielded twisted-pair cables to the computer for real-time display on the human-machine interface. The industrial control computer can also issue commands to control the inverter's start, stop, and reset. This completes the acquisition and transmission of all data and commands. Simultaneously, it can also perform management-level functions, such as local area network management tasks, generating records, reports, and statistical reports required by management departments.
4. Monitoring System Software Configuration
The software configuration section completes the interaction interface between the monitoring system and the operators, and is the core for realizing the monitoring, control, scheduling and management of the entire system. The human-machine interface is divided into two parts: one is the main interface for daily monitoring and system parameter settings, and the other is the sub-interface for indicating and managing non-daily monitoring information, such as various reports, curves and trend graphs, historical records, etc.
After the configuration software is running, clicking the company information image will take you to the main interface of the frequency converter system monitoring. At the top of the main interface is a row of indicator lights to show the status of the frequency converter system. In the lower left corner is an alarm description status bar to display all current alarm information for the frequency converter. The data display bar on the right displays real-time data such as frequency, stator voltage, stator current, and pressure. At the bottom of the main screen are four buttons for accessing other functions of the software system: system parameter settings, real-time curve display, historical data list, and alarm record viewing. Pressing the corresponding button will take you to its corresponding screen, as shown in Figure 2.
Figure 2 Main monitoring screen
4.1 Parameter setting function
Pressing the parameter setting button will bring up a user login dialog box. Only by entering the correct password can you access this screen to make settings, effectively preventing accidental operation by non-professionals. This screen is mainly used to set all parameters of the frequency converter. Operators can press the "Parameter Table" button to view the specific uses of the corresponding parameters.
4.2 Curve Function
When the curve button is pressed, the curve screen is displayed. It can automatically detect various specified monitoring quantities, including various data screens that reflect the real-time operating status such as current, voltage, frequency, and power factor, and conveniently provide real-time monitoring curves for specified parameters.
4.3 Historical Data List Function
After pressing the historical data button, you will enter the historical data table. The historical data list function can automatically detect and store the specified monitoring quantities, and can display different types of data on multiple different tables. You can use the selection keys to easily select the desired table screen, and you can also recall the data record at that time by entering a specific time.
4.4 Alarm Log Viewing List Function
Pressing the alarm record button will take you to the alarm information browsing table, which is mainly used to store fault alarm information of the monitoring system. The operator can also retrieve the system fault record at that time by entering a specific time, and can print the record, as shown in Figure 3.
Figure 3 Alarm recording screen
5. Implementation and Effect of Monitoring Function of Variable Frequency System
The programmed monitoring and control system, tailored to the characteristics of variable frequency systems, integrates real-time display, process control, data acquisition, data transmission, engineering reports, historical curves, and real-time curve display functions. It can also save and print historical data for system analysis. It can perform the following functions:
(1) Real-time monitoring of equipment operating status to achieve real-time management of the entire production process. The operating status of high-voltage frequency converters is very important, and the establishment of a monitoring system provides management departments with real-time dynamic information, which can effectively help on-duty personnel to understand the operating status of equipment in a timely manner.
(2) Provides flexible real-time and historical curve display functions. By comparing current and historical trend data, especially in combination with the multi-parameter model of equipment safe operation, potential faults can be reported early.
(3) Real-time report management conveniently solves the problems of on-site timed data copying, maintenance and tedious data processing. Recorders no longer need to spend a lot of energy filling in reports every day, which improves the company's office automation capabilities and management level, and achieves significant economic and social benefits.
(4) Data-driven and networked management improves the transparency of enterprise data and eliminates human factors, and incorporates cost accounting into a more standardized management system.
(5) The monitoring system has the advantages of user-friendly interface, easy operation, reliable operation, easy modification, expansion and upgrade. At the same time, the system cost is very low and has a high cost performance.
6. Conclusion
This system has been put into actual operation, realizing online real-time monitoring and control of various parameters of high-voltage frequency converters. It has achieved good results in practical use, strengthening the monitoring of high-voltage frequency converters by functional departments and standardizing employee behavior. It has enabled systematic management of high-voltage frequency converters, improved the reliability of frequency converter operation, and ensured safe operation on site.
