A new type of solar power generation controller based on embedded system chip EP4C15F17C8 is introduced in this paper. The overall design process of the controller is described, the charge and discharge circuit is analyzed in detail, and the performance indicators of the controller are given. The results show that the controller has the characteristics of high reliability, simple structure and high precision, and the performance indicators meet the national standards. The requirements can meet the actual needs.
As a renewable energy, solar energy has been paid more and more attention by more and more countries. The main way to obtain solar energy is to convert solar energy into electricity through solar panels. Solar energy is renewable, green, pure and pollution-free, which is in line with the sustainable development strategy advocated by various countries. The use of solar energy in many developed countries has basically achieved scale, but in our country, the use of solar power is mainly concentrated in underdeveloped areas of power transmission or remote areas with inconvenient transportation. The core of solar power generation is the controller of solar power generation. The main function of the controller is to control the charging and discharging process of the storage battery and to provide effective protection or alarm when there are overload, overload and short circuit. Whether the solar power system is stable or not depends on the performance of the controller. This controller takes the FPGA as the core control device. The overall block diagram is shown in Figure 1. The batteries of the controller are connected in series with rated voltage up to 50V, and the lightning protection circuit uses transient voltage suppression (bidirectional TVS) diodes with breakdown voltage up to about 80V, so the protection effect is outstanding in practice.
The controller can actively collect the charging and discharging current parameters of the battery in real time. The parameter acquisition is realized by shunt.
After the data acquisition is processed by the FPGA, the actual current calculated is displayed on the LED screen. At the same time, the overload or short circuit of the load can be judged by this parameter.
The temperature sensor collects the temperature parameters around the system and transmits them to the FPGA. After the parameters are processed by the FPGA, the corresponding sensors are controlled to compensate the temperature.
The controller chooses EP4C15F17C8 of 60NM FPGA-Cyclone IV series.
The chip uses an optimized 60-nm low-power process. The latest generation of devices has reduced the internal nuclear power voltage by 25% compared with the previous generation. In order to improve the data processing performance of the FPGA, an EPCS64 chip with 64 Mbits flash memory, thermostatic element ISP and unlimited repetitive programming function is selected as the configuration chip of the FPGA. JTAG boundary scan is supported with a configuration voltage of 3.3V.
The configuration mode of this system is AS mode (active serial) [3]. In the process of charging batteries, solar panels will appear a floating charging state, in which the voltage of batteries will produce larger ripple. Therefore, when designing the power supply of the controller, the influence of this ripple on the whole control system should be taken into account. The controller decides whether to turn on the solar power system and charge the battery by judging the voltage of the battery.
By collecting the terminal voltage of the converter in the charging and discharging circuit, the magnitude of the current in the circuit is calculated. After many tests, four groups of data were randomly selected, as shown in Table 1.
Date: September 2015. Location: market. Temperature: 27 – 33 C in the daytime and 17 – 25 C in the evening.
As the core part of the solar power generation system, the performance of the solar power generation controller directly affects the efficiency and reliability of the power generation system. Therefore, the hardware design, software programming and debugging of the whole system are particularly important. The design can prolong the service life of the battery module, improve the power generation efficiency and maintain stability. It has the value of popularization and use.