Research Of Highly Efficient Single-phase Transformerless Invevters For Grid-connected Photovaltaic System

Solar energy is a huge amount, clean, safe renewable energy. In recent years,it is widely used in various countries and various areas.Photovoltaic inverter is an important part of photovoltaic power system, its efficient conversion has become a research hotspot.According to photovoltaic grid inverter achieving three basic functions,such as high quality electrical energy conversion, system security and reliability,to choose a single stage not isolation type inverter structure.Due to the structure of the grid inverter topology are numerous, so the choice of appropriate main circuit topology to improve the whole photovoltaic grid generation system efficiency, cost and performance has important significance.Based on the contrast between a new type of high efficiency single-phase grid inverter topology and other related topology knowing this new topology is less component quantity, low cost, high efficiency, and not for the high frequency oscillation, in addition, via the modal theory and modeling analysis to realize the new topological basical theoretical analysis. We can find the essence of this new topology is composed of two buck circuit in parallel, work in a single polarity modulation method, inductive energy storage and has a filter function.Then according to the current engineering for the isolation of the inverter of common-mode current damage from this kind of problem, via the commonly used to eliminate the common-mode current several topological study and theoretical analysis, to apply the knowledge to new topology. Validating the new topology no common-mode current to the ground, to achieve the new topology analysis in engineering application. Then via the PSIM simulation software to new topological structure and the common-mode current on the open and closed loop simulation verification.At last, combined with above proposed topology structure of the main circuit and control panel drawing, welding and debugging work, and set up an experimental platform, through the digital control, to complete the single-phase grid inverter experiment, realized the consistency of the theory and practice.