中文摘要：

本文首先建立了两级式光伏并网逆变器严格的分段光滑状态方程，分析级联情况下光伏阵列电压对光伏并网逆变器非线性动力学行为的影响，然后探讨拓展两级式光伏并网逆变器输入电压范围的策略，并研究前后级电路内部参数变化引起并网逆变器输出电流的快变尺度分岔和慢变尺度分岔现象。研究发现：若对光伏阵列电压进行分段控制，可以有效展宽两级式光伏并网逆变器的输入电压范围；适当增加前级输出电容值、电感量，可以避免系统产生混沌运动，而后级参数的取值需避开多个不连续的混沌区域。研究结果对提高光伏发电系统的效率与稳定性有较重要的参考价值。

英文摘要：

In this paper, the piecewise smooth state equation of a two-stage photovoltaic grid-connected （TPG） inverter is established and studied; based on the solution to the piecewise smooth state equation of the TPG inverter, effects of the photovoltaic array voltage on nonlinear dynamical behaviors of the TPG inverter are analyzed by using bifurcation diagram, folded diagram, 3D phase diagram, and Poincar＆233; section. Then the nonlinear dynamical behaviors of TPG inverter are compared with the conventional one. And a strategy of expanding the input voltage range for the TPG inverter is explored. Finally, the nonlinear dynamical behaviors in it caused by the variation of main circuit parameters：such as the output inductance and capacitance of the front-stage, as well as those of the second-stage, are discussed through slow-scale bifurcation diagrams. Studies have found that it is effective to expand the input voltage range of the TPG inverter by segment control of the photovoltaic array voltage, and the chaotic phenomena in the TPG inverter can be avoided by increasing the parameter values of inertial devices such as output inductance and capacitance in the front-stage appropriately, but the values of output inductance and capacitance in the second-stage should be away from the multiple noncontiguous region, since it can cause chaotic behavior. The above work may have important guiding significance and application for improving the stability and e？ciency of two-stage photovoltaic grid-connected inverter based photovoltaic power generation system.