中文摘要：

组串式逆变器并联入网结构广泛用于光伏发电系统中，其非隔离结构可导致共模谐振问题。针对该问题，首先建立单台逆变器共模阻抗模型，并从耦合点拓展出并联逆变器的阻抗模型。为研究共模谐振特性，分别分析各共模回路导纳特性、并联连接对共模导纳的影响，并基于控制同步性将1台逆变器与2台并联逆变器输出共模电流特性对比，得出三电平组串逆变器共模电流的特性及其与谐振的关系，并实验验证理论分析的正确性。

英文摘要：

Paralleled string inverters structure is commonly employed as the interface to the utility grid. Pitfalls in non- isolation topology are potential resonance problems in output currents. Aimed at this case, inverter common-mode impedance model is established firstly, based on its couple points, paralleled inverters common-mode model is expanded. To study common-mode resonance, admittance characteristic of each common-mode path in inverter, admittance changes caused by paralleling and output common-mode current comparison of 1 inverter and 2 paralleled inverters under asynchronous control are analyzed, and common-mode current characteristic and its relationship to resonance are reached. Experimental results validate the proposed common-mode characteristics.