Research On The Multi-level Current Source Photovoltaic Inverter And Its Low Voltage Ride-Through Technology

In recent years,non-renewable resources have become increasingly scarce,people’s awareness of environmental protection has become stronger and stronger,and the development of renewable energy is particularly important.Due to the cleanliness of photovoltaic power generation and the inexhaustible use of solar energy,photovoltaic power generation has become one of the most promising renewable energy generation methods in recent years.The traditional two-level or three-level grid-connected photovoltaic inverters often need to increase the filter link to realize grid-connected because of the small number of levels and the non-negligible harmonic component of the output current.The multi-level current source photovoltaic inverter topology adopts the harmonic injection theory,which can eliminate the specific number of harmonics,and can be connected to the grid without additional filtering links.With the large-scale development of photovoltaic grid-connected power generation system,the impact of photovoltaic power generation on the grid is also growing.The photovoltaic grid-connected power generation system must have a certain low voltage traversing ability.On the basis of introducing the background and significance of the topic,this paper gives a full description of the development status and prospects of photovoltaic power generation.Secondly,the topology of traditional three-phase 12-pulse converter is introduced and its working principle is deduced mathematically.The ideal injection current waveform is given.Taking five-level converter as an example,the multi-level current source converter is modeled by simulation software,and the rationality of its topology is analyzed.It lays a foundation for the research of multi-level current source photovoltaic inverters.Thirdly,the working principle and topology of multi-level current source photovoltaic inverters are analyzed and discussed in detail.Based on this,the grid-connected control strategy is designed and modeled in the simulation software.Finally,the low voltage traversal control strategy of multi-level current source photovoltaic inverters is studied,and the low voltage traversal control strategies of the topology under three-phase symmetrical and asymmetrical drop faults are studied respectively.