Foreword: Photovoltaic power generation is based on the principle of photovoltaic effect, using solar cells to directly convert solar energy into electrical energy. Photovoltaic power generation has a wide range of applications. They are used in transportation, communication/communication, petroleum, marine, meteorological fields, and residential electricity. It is safe and reliable, noise-free, and pollution-free. The power generation efficiency is affected by the ambient temperature. It has the advantages of small impact, small area of ​​the system, and high land utilization. Photovoltaic power generation systems are generally composed of solar cell arrays, battery packs, charge and discharge controllers, inverters, AC power distribution cabinets, sun tracking control systems and other equipment. This article will take a solar cell array as an example to introduce Haiwell PLC's application in photovoltaic power generation.
1. Principle of Sun Tracking SystemDepending on the day's trajectory tracking. As compared to a solar photovoltaic power generation system at a fixed location, the four seasons of spring, summer, autumn and winter, rising and sunset every day, the angle of the sun always changes, if the solar panel can always face the sun, the power generation efficiency will be Reach the best condition. At present, the general sun tracking control system needs to calculate the angle of the sun at different times of each day of the year according to the information such as the longitude and latitude of the placement point, and store the sun position at each time of the year in the PLC, that is, by calculation The position of the sun for tracking.
Sensor tracking. Sensor tracking is to use the light sensor to detect whether the sun's rays deviate from the baseline of the battery panel. When the sun's rays deviate from the baseline of the battery panel, the sensor outputs a deviation signal, which is amplified and converted into a standard signal, which is transmitted to the PLC through the analog input channel. After calculation, the actuator is controlled by the switch output to make the tracking device re-align the sun.
2. Introduction of solar cell phalanx networking1. Schematic diagram of a single solar cell array network:
2. Schematic diagram of the network of 10,000 trackers in photovoltaic power plants
There are often thousands of trackers in a photovoltaic power plant. Haiwell PLC and H04TCP-4 gateway are convenient and powerful. Connect multiple solar cell arrays to the optical fiber Ethernet switch and transmit via Ethernet. Thousands of PLCs are monitored in the central control room. The network diagram is as follows:
3. The main hardware configuration of the system
3.1 Haiwell PLC
The Haiwell PLC hybrid host has its own switch and analog values, 6 analog inputs, with a range of 0~10V, using 12-bit AD conversion (universal 0~20mA), and supports direct access to light sensors. The CPU host has 2 communication ports, which can be expanded to 5 communication ports. Each communication port can be programmed and networked, and both can be used as a master station or a slave station. Supports 1:N, N:1, N:N networking, supports various man-machine interfaces and configuration software, and can be connected to any third-party equipment with communication functions (such as inverters, meters, barcode readers, etc.).
3.2 Haiwell H01TCP-4 Smart Gateway
H01TCP-4 is a powerful hardware protocol gateway, which converts various protocols from the device to standard Modbus RTU or Modbus TCP protocol. The gateway supports analog linear conversion, bit selection function, high and low byte exchange function; the gateway has a built-in WEB server, users can view real-time changing data and communication status through a browser, which is convenient for on-site debugging; comes with 4 communication serial ports and 1 Ethernet Network port, each communication port has its own communication isolation. In addition, the intelligent gateway can also alarm for communication disconnection of slaves in each communication port network.
3.3 Optical fiber Ethernet switch, central control room SCADA system.
4. System data acquisition control principle
Each tracker is 1 Haiwei PLC, which always receives the solar position signal from the sensor, and sends it to the PLC through the PLC analog input channel. After the user program calculation, the PLC controls the rotation direction of the actuator so that the solar receiver is always facing the sun. Direct radiation direction to obtain the maximum effective irradiation area.
H01TCP-4 in a single solar cell array has 4 communication serial ports, each serial port is connected to 15 PLCs, and the data in the PLC is collected into the internal memory of the smart gateway for storage, monitoring and use by the host computer. The upper computer can also issue control commands, which are transmitted to the corresponding PLC of each serial port through the intelligent gateway. In addition, multiple solar cell arrays can be connected to the fiber optic Ethernet switch together, so that centralized control and monitoring of thousands of trackers in a solar photovoltaic power plant can be realized.
3. System advantages1. Haiwell H01TCP-4 can only have strong gateway networking capabilities. Multiple solar cell arrays can be connected to the fiber optic Ethernet switch together, so that the centralized control and monitoring of thousands of trackers in a solar photovoltaic power plant can be realized.
2. Compared with traditional networking, the cost is greatly reduced. Traditionally, a PLC and an Ethernet module are used for data collection and monitoring of each tracker, which is costly; Haiwell H01TCP-4 can only be used as a gateway module, and one gateway can monitor the operation of more than 60 PLCs.
3. The intelligent gateway will make a communication disconnection alarm for each slave in each network. Management is convenient, while traditional network management is difficult, troubleshooting, and manpower investment.
4. Haiwell has strong PLC communication networking capabilities. The CPU host comes with 2 communication ports, and each communication port can be programmed and networked, and both can be used as a master station or a slave station. Supports 1:N, N:1, N:N networking, supports various man-machine interfaces and configuration software, and can be connected to any third-party equipment with communication functions (such as inverters, meters, barcode readers, etc.).
5. Haiwell PLC programming software is fully simulated, and the analog quantity does not need to be converted between code value and engineering quantity through programming. It reduces the time for programming and on-site debugging, facilitates the debugging work of technicians, and improves work efficiency.
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