Research On Grid Connected Inverters With High Efficiency

With the rapid development of our country’s modernization process, it is an inevitable trendthat renewable energy sources will replace the traditional fossil energy. Renewable energy gridgeneration also becomes the research focus. Because of the huge initial investment and highgeneration cost of renewable energy systems, the efficiency improvement of grid-connected inverteris important for shortening payback time and creating economic benefits faster.Five Level Dual-Buck Full Bridge Inverter (FLDBFBI) is analysised and researched in thispaper. By the analysis of a topology of five level full bridge inverter, the topology generation ofFLDBFBI can be summarized. Three new topologies of FLDBFBI which combines Dual-BuckInverter (DBI) with multilevel technology are introduced. In FLDBFBI, the step voltages both onthe filter inductor and across the switches are only half of the input voltage, resulting in a smallersize of the inductor. Furthermore, only one of these switches is operating at high switchingfrequency in any switching cycle, thus reducing switching losses. Therefore, FLDBFBI has apotential to achieve both high power density and high efficiency.The operation principle and modulation strategy of these three topologies of FLDBFBI arediscussed in detail. Besides, the voltage stress of switch device and power loss is researched. Themethod of calculating switching losses is analysised in detail. The analysis and calculation resultsshow that the efficiency of FLDBFBI is high.Based on the theoretical analysis, three1kw prototypes of the new topologies are builtrespectively. The prototypes are controlled by DSP TMS320F2808. The experiment results verifythe operation principle and modulation strategy of FLDBFBI. Efficiency measurement shows thatthe European efficiency of the three prototypes is higher than98.5%.