非隔离型电流源Hx光伏并网逆变器关键问题研究

Transformerless PV systems have been received more and more attentions around the world. They are promising in practical applications due to their advantages such as the low cost, small size and high efficiency. In general, the voltage source inverter is used for the grid-connected operation. However, the voltage source inverter has the following disadvantages. Firstly, it is a step-down converter, so a boost converter should be cascaded. The two-stage converter leads to the complex structure. Secondly, it has the risk of overcurrent due to the phase-leg short circuit, which may break down the semiconductor devices. Aside from that, the voltage source inverter requires the temperature-limited electrolytic capacitors. The failure in electrolytic capacitors is one of the main causes of breakdowns and degrades the whole system’s lifetime and reliability. On the other hand, the current source inverter can solve the abovementioned problems. Therefore, the transformerless Hx current source PV grid-connected inverters will be investigated in this proposal. Considering the problems regarding the voltage source topologies, the new Hx current source PV grid-connected inverters will be presented based on the duality principle. And then the theory of the novel space vector modulations will be established. Finally, the new grid-connected control strategies will be proposed and explored. It is expected that our project will provide the fruitful ideas and solutions for operating the transformerless Hx current source PV grid-connected inverters in a safe, steady and efficient way.

非隔离型光伏系统具有成本低、体积小和效率高等优点，受到世界各国广泛关注，具有广阔的应用前景。传统非隔离型光伏系统通常采用电压源型逆变器实现并网运行，然而电压源型逆变器属于降压电路，前级需要加入Boost升压变换器，导致两级电路结构复杂。同时电压源型逆变器工作过程中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。此外，电压源逆变器直流侧通常采用低寿命的电解电容，降低了系统使用寿命和可靠性。而电流源型逆变器可以解决上述问题，基于此，本项目以非隔离型Hx电流源光伏并网逆变器为研究对象，针对电压源拓扑存在的问题，利用对偶原理，提出新型Hx电流源光伏并网逆变器拓扑及其形成规律，建立Hx电流源光伏并网逆变器空间矢量调制理论体系，探索Hx电流源光伏逆变器新型并网控制策略，为非隔离Hx电流源光伏系统安全、高效、稳定并网运行提供新的解决思路和解决方案。

非隔离型光伏系统具有成本低、体积小和效率高等优点，受到世界各国广泛关注，具有广阔的应用前景。传统非隔离型光伏系统通常采用电压源型逆变器实现并网运行，然而电压源型逆变器属于降压电路，前级需要加入Boost升压变换器，导致两级电路结构复杂。同时电压源型逆变器工作过程中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。此外，电压源逆变器直流侧通常采用低寿命的电解电容，降低了系统使用寿命和可靠性。而电流源型逆变器可以解决上述问题，基于此，本项目以非隔离型Hx电流源光伏并网逆变器为研究对象，针对电压源拓扑存在的问题，利用对偶原理，提出了新型Hx电流源光伏并网逆变器拓扑及其形成规律，建立了Hx电流源光伏并网逆变器空间矢量调制理论体系，研发了Hx电流源光伏逆变器新型并网控制策略，为非隔离Hx电流源光伏系统安全、高效、稳定并网运行提供了新的解决思路和解决方案。