单级无变压器非隔离型光伏并网逆变器关键技术研究

Compared with the conventional transformer-isolated PV systems, the transformerless PV systems have the unique features such as small size, low cost and high efficiency. Therefore, they are very attractive and promising in both academic and industrial fields. Typically, the voltage source inverter is used for power conversion and grid-tie operation in PV systems. However, it is a step-down converter, and an additional step-up stage has to be installed to boost the voltage. Obviously, the two-stage structure leads to the complex topology and reduced efficiency. In addition, there is a potential risk of overcurrent due to the short circuit of the bridge. The dead time has to be set to avoid it, but results the reduced and distorted voltage. In order to solve the problem, the single-stage transformerless PV inverter is investigated in the proposal. After analyzing the problems regarding the conventional solutions, the novel topologies of single-stage transformerless PV inverters are proposed. The new modulation schemes are explored and the novel control strategies are developed. The project will present the insightful ideas and solutions for well operating the single-stage transformerless PV systems

相比与传统变压器隔离型光伏发电系统，无变压器非隔离型光伏系统有独特优势，具有体积小，成本低和效率高等特点，受到学术界和工业界关注，应用前景广阔。传统光伏发电系统通常采用电压型逆变器实现系统功率变换和并网运行。然而，电压型逆变器具有降压特性，需安装前级升压变换器，两级功率变换导致系统结构复杂效率降低。此外，系统存在桥臂直通的风险，桥臂直通将引发开关器件过流而烧毁，而加入死区时间将导致输出电压基波降低和波形畸变。为了解决上述问题，本项目以单级非隔离型光伏并网逆变器为研究对象，在分析传统电压型光伏并网逆变器存在问题的基础上，提出新型单级非隔离光伏并网逆变器拓扑结构，探索单级非隔离光伏并网逆变器新型调制规律，研究单级非隔离光伏并网逆变器新型控制策略，为单级无变压器非隔离光伏系统安全、高效、稳定并网运行提供新的解决思路和解决方案。

相比与传统变压器隔离型光伏发电系统，无变压器非隔离型光伏系统有独特优势，具有体积小，成本低和效率高等特点，受到学术界和工业界关注，应用前景广阔。传统光伏发电系统通常采用电压型逆变器实现系统功率变换和并网运行。然而，电压型逆变器具有降压特性，需安装前级升压变换器，两级功率变换导致系统结构复杂效率降低。此外，系统存在桥臂直通的风险，桥臂直通将引发开关器件过流而烧毁，而加入死区时间将导致输出电压基波降低和波形畸变。为了解决上述问题，本项目以单级非隔离型光伏并网逆变器为研究对象，在分析传统电压型光伏并网逆变器存在问题的基础上，提出了新型单级非隔离光伏并网逆变器拓扑结构，研究了单级非隔离光伏并网逆变器新型调制方法，提出了单级非隔离光伏并网逆变器新型控制策略，本项目的研究成果为单级无变压器非隔离光伏系统高效并网运行提供了新的解决方案。