**Abstract:**
This paper presents a real-time temperature monitoring system for photovoltaic (PV) power generation equipment, developed using the LabVIEW platform. The system is designed to monitor key components such as PV modules, combiner boxes, grid-connected inverters, transformers, and ambient temperatures. By continuously tracking these parameters, the system ensures the safe and stable operation of the PV plant while providing critical data for predicting power output. Additionally, it enables real-time monitoring of lightning protection bus boxes and transformer conditions, including temperature, operational status, and fault information. This helps in identifying potential issues early, reducing failure rates, and improving the overall reliability of the power generation system.
**1. Introduction**
Photovoltaic power systems consist of several key components, including PV modules, combiner boxes, inverters, and transformers. During operation, high temperatures can lead to equipment failures, which may compromise the system’s performance and lifespan. For example, if a transformer's cooling fan fails, it can cause overheating, potentially leading to damage or downtime. Similarly, excessive heat in inverters can shorten the life of internal components like IGBTs, increasing the risk of failure. To address these challenges, real-time temperature monitoring is essential. It not only allows for early detection of abnormal conditions but also enables timely preventive actions, enhancing system safety and reliability.
Currently, most photovoltaic plants rely on manual inspections, which are time-consuming and less efficient. To overcome this, this paper introduces a LabVIEW-based temperature monitoring system that offers automated, real-time data collection and analysis. The system provides features such as temperature alarms, data storage, graphical representation, and report generation, making it user-friendly and highly functional.
**2. Monitoring System Hardware Architecture**
**2.1 System Hardware Structure**
The hardware setup includes outdoor temperature sensors, combiner boxes, inverters, transformer temperature control units, 485 hubs, and RS485-RS232 converters. Outdoor temperature sensors are used to collect both PV module and ambient temperatures, aiding in forecasting PV output. Each combiner box is equipped with a sensor to monitor internal temperatures, ensuring that any deviations from normal operating conditions are detected promptly. Inverters and transformers are monitored for their internal device temperatures and terminal conditions, with alarms triggered for over-temperature events or fan failures. Communication between devices is facilitated via RS485, known for its reliability and cost-effectiveness.
**2.2 RS485 Topology Design**
The system uses a hybrid topology combining a main bus structure with star connections. While star topologies offer fast communication, they require more wiring and are costly. Tree topologies allow for scalability but need repeaters. The hand-in-hand bus structure is preferred due to its simplicity, low cost, and ability to cover long distances, which is ideal for large photovoltaic plants. A 485 hub is used to enhance signal stability and reduce interference, ensuring reliable data transmission between the control room and field devices.
**3. Monitoring System Software Design**
**3.1 Programming Environment**
LabVIEW, developed by National Instruments, is used for the software implementation. Unlike traditional text-based programming, LabVIEW employs a graphical interface called G, allowing users to create block diagrams for program logic. Key advantages include modular design, ease of use, and powerful data processing capabilities, making it well-suited for real-time monitoring applications.
**3.2 Communication Protocol**
The system utilizes the ModBus RTU protocol over RS485, configured at 9600 baud, no parity, 8 data bits, and 1 stop bit. Data integrity is ensured through CRC checks. The host computer sends query commands, and the lower devices respond accordingly, enabling seamless communication between the control system and field devices.
**3.3 System Software Implementation**
The software architecture involves serial communication modules for data exchange between the host and field devices. The main program flow includes initialization, data acquisition, processing, and display. Subroutines handle serial communication and CRC calculations, ensuring accurate and reliable data transfer.
**4. Experiments and Debugging**
The system was deployed at a 5 MW photovoltaic demonstration plant in Hohhot, Inner Mongolia. It monitored 172 combiner boxes, 28 inverters, and 5 transformers across five units. Field testing confirmed the system's ability to display real-time temperatures, generate reports, and trigger alarms. Manual verification via walkie-talkies and debuggers validated the accuracy of the data, while simulated temperature thresholds tested the alarm functionality.
**5. Conclusion**
This paper presents a LabVIEW-based real-time temperature monitoring system for photovoltaic power plants. Designed with modularity and scalability in mind, the system enhances operational efficiency, reduces maintenance workload, and improves system reliability. Its application in large-scale PV plants demonstrates its effectiveness in ensuring safe and efficient power generation, paving the way for future advancements in renewable energy technologies.
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