| Photovoltaic power generation system or device has a lot of inconvenience to use photovoltaic array directly in laboratory tests. The digital photovoltaic array simulator studied in this paper can substitute the actual photovoltaic array to be used in the researches and tests by laboratory.Firstly, this paper analyzed the working principle of photovoltaic array and established the equivalent circuit of photovoltaic array on this basis. Deduced the photovoltaic array mathematical model in detail and further simplified it to a photovoltaic array engineering application mathematical model for practical engineering applications. This paper performed simulation verification on photovoltaic array engineering application mathematical model through Matlab/Simulink.Secondly, according to the existing piecewise fitting method to photovoltaic array output characteristics curve, the determination of the piecewise points need to be manually determined through observation and experience; the method to determine the fitting function of each segment is relatively rough. Also manual calculation is time-consuming and error prone. Aiming to solve these problems, this paper proposed an automatic piecewise polynomial fitting method through improving the existing automatic piecewise fitting methods, and applied it on the fitting of photovoltaic array output characteristic curve. This paper provided the specific algorithm of the fitting method and performed comparative analysis with the existing piecewise fitting method specified in the literature through two numerical examples. The results show that this method has a higher fitting precision on equal conditions. The fitting result is continuous at piecewise points. Since generalized inverse least-square solutions adopted, mathematical deduction and programming implementation have been simplified to a great extent.Finally, this paper designed a kind of digital photovoltaic array simulator based on BUCK convertor and TMS320F2812.This paper specified the simulator requirements on main circuit topology, and the calculation and selection process of main circuit components, as well as the design scheme of each part of the control circuit. It specified the simulator control algorithm and software implementation in detail. This paper performed rational validation of the design scheme under Matlab/Simulink environment and experimental tests on the debugged prototype. The results show that the designed digital photovoltaic array simulator can simulate the output characteristics of photovoltaic array very well. |
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