三相无变压器型光伏并网逆变器拓扑调制及并网控制研究

Transformerless photovoltaic (PV) grid-connected inverters gain more and more attention and are very promising in PV applications due to the small size, low cost and high efficiency. The technical challenges should be dealt with in order to achieve grid-connected operation of the tranformerless PV systems. Because of lacking the isolated transformer, there is a galvanic circle between the PV system and grid, which may lead to the leakage current. On the other hand, the short term grid fault may threaten the safe operation of PV systems due to the direct connection of the PV inverter and grid. Further investigation should be carried out to achieve the fault ride through with an elaborated control solution. This project will attempt to research three-phase transformerless PV grid-connected inverters in terms of topology, modulation and grid connection control. By using the theoretical analysis with the simulation and experiment verification, the novel topologies and modulation schemes are discussed, and the new grid-connected control methods for the fault ride through are explored. It is expected that this project will provide the new ideas and solutions for operating three-phase transformerless PV grid-connected inverters in a safe and efficient way.

无变压器型光伏并网逆变器具有体积小、成本低和效率高等优点，受到各国的广泛关注，具有广阔的应用前景。为了实现无变压器型光伏系统并网运行，需要解决诸多技术挑战。一方面，由于缺少变压器隔离，光伏系统和电网之间存在电气回路，容易引发系统漏电流问题。另一方面，光伏并网逆变器直接与电网相连接，电网短时故障将威胁到光伏系统的安全稳定运行，如何设计并网控制保证光伏系统实现故障穿越有待深入研究。本项目以三相无变压器型光伏并网逆变器为研究对象，从拓扑、调制和并网控制基本问题出发，通过理论分析结合仿真实验研究，寻求适用于三相无变压器型光伏并网逆变器漏电流抑制的新拓扑及其调制策略，探索三相无变压器型光伏并网逆变器故障穿越并网控制的新方法，为三相无变压器型光伏系统安全、高效、稳定并网运行提供新的解决思路和解决方案。

无变压器型光伏并网逆变器具有体积小、成本低和效率高等优点，受到各国的广泛关注，具有广阔的应用前景。为了实现无变压器型光伏系统并网运行，需要解决诸多技术挑战。一方面，由于缺少变压器隔离，光伏系统和电网之间存在电气回路，容易引发系统漏电流问题。另一方面，光伏并网逆变器直接与电网相连接，电网短时故障将威胁到光伏系统的安全稳定运行，如何设计并网控制保证光伏系统实现故障穿越有待深入研究。本项目以三相无变压器型光伏并网逆变器为研究对象，从拓扑、调制和并网控制基本问题出发，通过理论分析结合仿真实验研究，提出了三相无变压器型光伏并网逆变器漏电流抑制的新拓扑，建立了三相无变压器型光伏并网逆变器漏电流抑制单载波调制理论体系，提出了三相无变压器型光伏并网逆变器故障穿越并网控制的新方法，为三相无变压器型光伏系统安全、高效、稳定并网运行提供新的解决思路和解决方案。