Application of WEINVIEW touch screen in solar photovoltaic grid-connected inverter

Abstract: In recent years, with the establishment and grid-connected power generation of a large number of solar photovoltaic power stations at home and abroad, photovoltaic grid-connected inverters, as key equipment for photovoltaic power generation, have broad market prospects. This paper mainly introduces the application of WEINVIEW touch screen in solar photovoltaic grid-connected inverters. In this system, the touch screen communicates with the inverter controller to complete relevant data collection, data storage, alarm information logging, and graphic display of inverter operating parameters and real-time status. It also communicates remotely with the host computer through 485 or Ethernet to achieve real-time monitoring and deployment of the entire grid-connected power station.
Keywords: Photovoltaic Inverter Touch screen DSP
Abstract：In recent years, with the large number of solar photovoltaic power plants establishing and grid connection generation at home and abroad , As the key equipment in PV power generation, photovoltaic grid-connected inverter has broad market prospect. The introduction in this paper focus on the application of WEINVIEW touch screen in photovoltaic grid-connected inverter. In this system, touch screen communicates with the microcontroller, and completes related data acquisition, information saving, alarm information loginning, and shows operating parameters and real-time status of inverter on the touch screen , Remote communication with the host computer through the RS485 or the Ethernet, At last to achieve real-time monitoring and deploy of the entire grid station.
Keywords: Photovoltaic Inverter Touch screen DSP
1 Introduction
With the rapid development of the global economy, energy consumption in various industries has increased, and traditional fossil energy such as oil and coal has become increasingly exhausted. Countries around the world have turned their attention to renewable energy, hoping that renewable energy can change the energy structure of mankind and maintain long-term sustainable development. Among renewable energy sources, solar energy has become the focus of attention with its unique advantages. Solar energy is an inexhaustible, pollution-free green energy. Countries around the world are investing heavily in building large-scale solar power stations. China has also made rapid progress in photovoltaic research and industry. The Renewable Energy Law, which was implemented on January 1, 2006, marks that solar power generation has been included in China's energy development plan. According to the Medium- and Long-Term Development Plan for Renewable Energy released in September 2007, by 2020, the cumulative installed capacity of solar power generation equipment in China will reach 2000MW.
The solar photovoltaic grid-connected inverter is one of the most critical equipment in the entire photovoltaic power generation system. It is a device that converts the DC power generated by solar panels into AC power. During operation, multiple parameters need to be monitored, calculated, displayed, recorded, saved, and alarmed. It needs to communicate with the host computer, inverter controller, and wireless GPRS module to realize data exchange. This article mainly describes the application of WEINVIEW touch screen in solar photovoltaic grid-connected inverter.
2 System Principle and Solution Design
Solar photovoltaic grid-connected inverter is to invert the DC power generated by solar panels through the photovoltaic effect, convert it into AC power with the same frequency and phase as the power grid, and connect it to the power grid for external power transmission. During the operation of the inverter, the measured real-time parameters should be sent to the touch screen for display, recording and other operations, and it can also communicate with the host computer for remote monitoring. The system structure diagram is shown in the figure below:

Figure 1 System structure diagram

3 WEINVIEW screen design requirements
This system uses WEINVIEW MT8100I touch screen, high-quality 10-inch wide screen design, LED backlight module; uses 400MHz RISC CPU to make the operation faster; built-in power isolation protector improves the product's anti-interference ability and adapts to operation in complex environments; multiple standard communication interfaces and network protocols are convenient for users to use; large-capacity data storage function, and can be directly stored or backed up to a U disk, SD card or host computer to meet the massive data information generated during the operation of the inverter. 3.1 Touch screen main interface design The main interface displays various operating parameters of the inverter: PV voltage, PV current, A, B, C three AC voltages and currents, power factor, grid frequency, output power, daily power generation, total power generation, CO2 emission reduction, etc., inverter operation status indication, real-time time, and other operation menus. The following figures are the Chinese and English display menus of the main interface respectively.

Figure 2 Chinese display on the touch screen main interface

Figure 3 English display of the touch screen main interface

3.2 Design of power curve display function
Real-time power is a very important parameter in the operation of the inverter. The power curve reflects the historical operation status and trend of the inverter. The inverter power curve display is completed by two macro instructions:
A: Real-time power calculation and storage of inverter operation
The power calculation macro instruction is executed once a minute to calculate the three-phase output power. The address of power storage is calculated according to the current time, and the current power value is saved in the address corresponding to RW_A.
Storage address = day * 1440 + hour * 60 + minute. Save once every minute, and the power data occupies one unit (the power data is saved as the full-day data starting from 0 o'clock).
B: Power curve display
The power curve display on the touch screen is realized through the XY curve element.
The XY curve display macro instructions are as follows:
macro_command main()
short i,add,add0,day
int z
i=3
SetData(i, "Local HMI", LW, 402, 1) //XY curve display control unit
i=720
SetData(i, "Local HMI", LW, 403, 1) //XY curve display length
for i="0" to 720 step 1
add=500+i
SetData(i, "Local HMI", LW, add, 1) //X-axis data assignment, starting from 500 units, assign values ​​from 0 to 720
next i
GetData(day, "Local HMI", LW, 9020, 1) //Read the current date
add=day*1440+360 //Starting from 6 a.m., the unit address is added with 6*60=360 offset
for i="0" to 720 step 1
GetData(z, "Local HMI", RW_A, add, 1) //Read power value from RW_A
add=add+1
add1=i+1300
SetData(z, "Local HMI", LW, add1, 1) //Assign Y-axis data, starting from unit 1300
next i
end macro_command
After touching the corresponding key, execute this macro instruction, write the display control address content to 3 (clear the original curve and display the new curve), the curve length is 720 (12*60), the X-axis data starts from the 500th unit of LW, and the content is 0 to 720, the Y-axis data starts from the 1300th unit of LW, and the content is the power data from 6 am to 6 pm.

Figure 4 Power curve [page]

The XY curve display configuration is as follows:

Figure 5 XY curve configuration

4 Touch screen communication design
The touch screen mainly plays the role of monitoring and data transmission in the normal operation of the photovoltaic grid-connected inverter system: 1. The real-time parameters and status of the system during operation should be transmitted to the touch screen in time for calculation, display, recording and alarm; 2. The remote host computer needs to monitor and deploy the system through the touch screen. Its communication configuration is shown in the figure below:

Figure 6 Touch screen communication topology

The conditions for adding communication devices in the touch screen are as follows:

Figure 7 Device List

4.1 Touch screen and inverter communication settings
The photovoltaic inverter main controller uses TI's TMS320F2812 digital processor, and the touch screen communicates with it through the MODBUS RTU (Adjustable) communication protocol. The communication baud rate is 9600Kbps and the RS232 interface type is used. The system parameter settings are as follows:

Figure 8 Touch screen and DSP communication parameter settings

4.2 Host computer monitoring
and deployment settings When the photovoltaic grid-connected inverter needs to monitor the grid-connected power generation with the host computer, the 458 bus communication is adopted, the master-slave mode, and the touch screen is used as the MODBUS Server device. It is distinguished according to the set station number. When the host computer sends a command to read the inverter operation data, if it matches the touch screen station number, the touch screen returns the content of the corresponding unit and completes the data transmission. The monitoring function of the photovoltaic power station is realized. The system parameter settings are as follows:

Figure 9 Host computer communication settings

The touch screen automatically saves the data content of the inverter at regular intervals. The host computer realizes the monitoring function of the photovoltaic power station by reading the inverter data saved in the touch screen. The touch screen uses a timed data transmission element to obtain inverter data. The settings are as follows: 1 second timing to read the data of the 12 units starting from inverter unit 0, and the real-time operation data of the inverter is saved in 12 consecutive address units of LW100.

Figure 10 Touch screen reads inverter data settings

5 Conclusion
This system uses WEINVIEW MT8100I touch screen to achieve real-time communication with DSP digital signal processor. The various parameters and status of the grid-connected inverter are displayed with pictures and texts, and the curve coordinates show the power parameters of the inverter and its trend effect diagram. The large-capacity data storage function saves the detailed historical operation data of the inverter. The flexible and diverse communication interface facilitates the monitoring of photovoltaic grid-connected power stations. The reliable and stable operation of the touch screen and the convenient and flexible operation have greatly improved the market competitiveness of grid-connected inverter products and achieved good social and economic benefits.