Jul 16, 2020
With the rapid development of communication networks, it has brought great convenience to all walks of life, and so does the photovoltaic industry. To build a photovoltaic power station, you can use your mobile phone to check the operation information of the power station at any time, such as DC voltage, current, output power, daily power generation, etc. If you encounter a power station failure, the mobile phone APP monitoring program will be notified at the first time , And the fault type can be found. Many problems can be solved remotely, shortening the maintenance time of the power station and reducing the power cost loss of the power station. So, how does the operating data of the inverter appear on the mobile phone APP monitoring software?
In fact, the operation data of the inverter cannot be directly uploaded to the mobile phone APP monitoring software, which requires more than 4 conversion processes. The operating data of the inverter is generally stored on the DSP control chip, such as Texas Instruments’ TMS320F28075. To transmit to the outside, a dedicated communication chip is also required. Now 90% of the inverters use chips with the ARM structure. Very strong strength. Then through the communication hardware interface, upload to the inverter manufacturer's cloud platform server with a certain communication protocol, and then turn it into data after being decoded. Our mobile terminal or computer terminal can access the cloud platform server through the website, and you can see the reverse The operating data of the transformer.
Communication hardware interface
Communication hardware interface. The current photovoltaic inverter has three interfaces: RS485, RS232, and USB. These interfaces have their own characteristics and uses.
RS232 and RS485 are the most classic interfaces. Most inverters released before 2019 will be equipped. The difference between the two is that RS-232 is suitable for communication between local devices. The transmission distance is generally not more than 20 meters. Only one pair is allowed. One communication, that is, a data collector with an inverter, suitable for household power stations or small industrial and commercial power stations; RS-485 transmission distance is tens of meters to thousands of meters, and the interface allows one-to-many, that is, one data The collector is equipped with multiple inverters and is suitable for medium and large power stations.
USB (Universal Serial Bus) is a widely used interface specification on computers. It has fast interface speed, simple connection, and no external power supply. Due to the good compatibility of USB externally, it has become more and more widely used. In the inverter developed, the USB interface gradually replaces the RS232 interface. The USB interface can be connected to the collector one-to-one or directly to the computer. The USB can also connect up to 127 devices in series.
Monitoring data transmission method
The data is transmitted from the inverter to the server. There are currently three commonly used schemes for data transmission, GPRS, WIFI, and LAN. GPRS data collector, built-in mobile phone SIM data card, such as China Mobile, China Unicom, etc., the inverter data is first sent to the server of the mobile phone operator, and then uploaded to the server of the inverter company. GPRS is currently the most widely used transmission solution in China. Its advantage is that it does not require a broadband network and is suitable for places where it is not convenient to build a network. The disadvantage is that it requires traffic costs and the communication network will be frequently upgraded. For example, there are no signals in 2G networks. The difference between WIFI and LAN is that WIFI is for wireless data transmission, and LAN is for wired transmission. Its advantage is that it does not require traffic costs. The disadvantage is that wireless WIFI has a limited distance. For wired LAN, a network cable is required and a broadband network is required.
Communication protocols, from inverters to data collectors, and some equipment and instruments. Data must be uploaded to the cloud server. Each company’s technology is different. In order to unify and facilitate the transmission of data between different equipment, it is generally used on-site Field bus technology, there are many types of field buses, such as Profibus, Interbus, DeviceNet, ControINet, Modbus, CC-link, HART, etc. Modbus is widely used in the photovoltaic industry. ModBus features:
(1) Standard and open, users can use the Modbus protocol free of charge, without worrying about paying license fees and infringing intellectual property rights. Currently, there are more than 400 manufacturers supporting Modbus and more than 600 products supporting Modbus.
(2) Modbus can support a variety of electrical interfaces, such as RS-232, RS-485, USB, etc., and can also be transmitted on various media, such as twisted pair, optical fiber, and wireless. The inverter generally adopts RS485 interface for Modbus communication.
to sum up
The data from the inverter to the mobile phone requires various technologies such as hardware and software. RS485, 232 and USB are a physical interface, which is simply hardware. MODBUS is an international standard communication protocol, which is simply software. GPRS, WIFI, and LAN are physical transmission channels.