Design Of Portable Testing System For PV Array Based On FPGA

Nowadays, the industry of solar energy has been more and more important, because of the lack of energy recourses. So the demand of the PV array testing devices has gained popularity at the same time. For those PV arrays already set outdoors, we need a portable testing system to test the characteristics. And the testing system must be portable, fast in measurement, low in power consumption and accurate.The paper has designed a PV array testing system based on FPGA. A capacitor is used as the electronic load in this paper. While the PV array is charging the capacitor, the designed system collects the data of charging current and voltage continuously. After analyzing these data, the system shows the related characteristics and parameters of the PV array on an LCD. In contrast to the traditional systems based on MCU, the testing system with a sampling module based on FPGA in this paper has a much higher sampling rate, and employs rate-variable sampling, as to solve the problem that the data acquired by traditional capacitive testing systems are over-concentrated in a small area near open-circuit voltage in the I-V curve, while the quantity of data in the main part of the curve is far from enough.the whole designed system could be divided into two parts, the system hardware design section and the FPGA digital logic design section. The system hardware design section includes: power sources design, charging circuits design, amplifier design, sampling circuits design, environment parameters acquiring section design, FPGA configuration circuits design; FPGA digital logic design section includes the main controlling section, initial section, rate-variable sampling section, storage section, filtering section, display section and RS232 transmitting section.To test the systemwe have a PV array with V_oc =72. 3V and I_sc=18A tested. The comparative testing result of the system desgined in this paper and the tradional system shows that this system could acquire much more data distributed in the main part of the I-Vcurve than the traditional system, while the total quantity of data is the same, helping to save storage space. This makes the system capable to provide a more smooth I-V curve with the acquired data being filtered and the repeatability of Im, Vm, Pm, FF acquired by traditional system has been improved from 5. 5%, 5. 9%, 1. 41%, 1. 41% to 2. 7%, 2. 8%, 0. 37%, 0. 37% by the designed system in this paper.