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The energy crisis has swept the whole earth in the 21st century, and all kinds of traditional fuels have been used out, and the serious pollution of environment has restricted the further development of the world. In this way, the clean and no-pollution renewable energy is very precious. And the solar technology shows great potential in many kinds of renewable energies. So if we want to have a widespread application of solar energy and connect to the grid, the grid-connected technology must be safe and reliable. And the DC power produced by photovoltaic power generation should use the inventers when it connects to the grid. We know that the topology structures of active filter and inverter are very similar. Therefore, using the similarities of them to study the unified control of photovoltaic grid system and harmonic compensation of APF can make it have two functions. This paper puts forward a design method of LCL filter circuit which can be used on both photovoltaic and APF based on summarizing the application under each situation. This paper talks the advantage of LCL circuit compared with other filtering ways, and puts forward the design principle, the choice of parameters and the simulation experiments to get a proper grid-connected photovoltaic system inverter. [ABSTRACT FROM AUTHOR]

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In order to improve the efficiency and reduce the leakage current of non-isolated single-phase PV grid-connected inverter, a soft switching technique, called zero-voltage-transition, is proposed in this paper based on H6 type transformer less single-phase PV grid-connected inverter. The zero-voltage-transition changes the traditional way of hard switching into soft switching technology, can achieve zero-voltage turn off for main switches by auxiliary switch increased. The simulation model is built in the simulation software PSIM, and simulation results show that a PV grid-connected inverter with zero-voltage-transition H6 type transformer can effectively improve the efficiency of circuit and keep the lower leakage current. [ABSTRACT FROM AUTHOR]

A novel discontinuous space-vector pulse width modulation(DSVPWM) strategy is proposed for a three-level neutralpoint-clamped(NPC) voltage source inverter. Compared with traditional space-vector pulse width modulation(SVPWM),the proposed strategy can largely reduce the switching losses of the inverter at the same switching frequency. Then,solutions to the imbalance of neutral-point voltage and the PN voltage jumps during application are proposed in this paper. At last,the three-level DSVPWM strategy is verified by simulation and experiment.