Research On Micro-inverter For Single PV Panel

With the development of the building integrated photovoltaic (BIPV) technology, single photovoltaic module equipped with independent micro inverter or micro inverter grid structure in recent years become a hot research topic in the field of photovoltaic power generation technology. As a kind of small power grid module, micro inverter has many characteristics such as small volume, flexible grid-connecting, simple controlling. The main research content of this article is to design a practical single photovoltaic inverter which is suitable for single power photovoltaic modules, the design rated power is250W.Consider from the practical, this thesis analyzes the volt-ampere characteristic curve of high-power single photovoltaic module and several kinds of commonly used method of maximum power tracking (MPPT). A Variable Step Size P&O MPPT Method is finally chosen.This thesis takes the two stage micro-inverter as the research object and mainly focuses on the hardware design of preceding stage MPPT controller and the backward stage inverter. The micro inverter is in the service of single photovoltaic module, but the open circuit output voltage of the single photovoltaic module is low, so the micro inverter must have high step-up ratio in order to realize grid generation. Therefore, this article chooses a kind of high voltage gain converter as the topology of the preceding stage MPPT controller. Compared with the conventional DC-DC converter in same power level, the converter has a better ability of boost, higher conversion efficiency and lower voltage stress on power switch tubes. Based on these we completed the schematic diagram design of the MPPT controller, devices selection, control strategy selection and the programing of control algorithm.This paper has also described in details about the preceding stage inverter topology design, grid-connection control strategy and the PWM debugging mode. We completed the main power circuit of full bridge inverter and the analysis and design of control circuit at last.Finally, we designed and manufactured a micro-inverter prototype rated power at250W, and completed the function on the prototype. Experiment results show that the design is reasonable and can meet the practical requirements.