Research On High Efficiency Non-isolated Grid-tied Photovoltaic Inverter With H6-Type

With the rapid expansion of the distributed generation, inverter plays a crucial role inthe solar power system, improving which performance is essential for the system to increaseefficiency, reliability, and reduce cost. Non-isolated grid-tied photovoltaic inverter has highefficiency, small size, low cost and other advantages; therefore it has been widely used in thefield of photovoltaic grid system. However, leakage current of non-isolated system is asecurity risk for users and equipments. In order to suppress leakage current effectively underthe condition of the highest efficiency, the paper studies a kind of high efficiency, lowcommon-mode current non-isolated photovoltaic grid inverter.This paper has analyzed the common mode leakage current model of non-isolated gridinverter, discussed the reasons for common mode currents generated in different invertertopology structure and inhibition conditions, studied a six switching non-isolatedphotovoltaic grid inverters （H6bridge）. Two stages of main circuit structure has beendesigned, the first stage is two group independent Boost circuit, and the second is H6bridgetopology inverter circuit. Auxiliary power supply circuit used dual flyback converter. Principlehas been analyzed respectively, and crucial parameters of the main circuit have beendesigned.The key issues in non-isolated grid inverter have been studied in detail, including theinhibition of output DC component, the sampling signal processing, temperature driftcompensation and maximum power tracking control of multimodal effects, separatelyanalyzed the causes of the problem, proposed control strategy, designed related softwarealgorithm flow.An experiment platform has been established for grid testing, and the correctness ofthe control strategies is verified by the experimental results. Compared unipolar, bipolarmodulation and H6bridge topology for the inhibitory effect of common mode current,combined with CEI0₂1grid authentication standards, tested the grid function and outputperformance of5KW non-isolated grid inverter. The experiment results show that, the designscheme of non-isolated single-phase grid-tied photovoltaic inverter is feasible.