主动移频法在多机并联时防孤岛保护失效机理分析

因为分布式发电系统的非计划孤岛会严重影响检修安全、损害电网设备等，因此，并网逆变器要求具备孤岛检测功能。主动移频（ AFD）式孤岛检测法是常用的检测孤岛的方法，但是很多单机性能优异的主动移频防孤岛方法在多逆变器并联运行时孤岛检测性能变差甚至失效。采用相位原理和基于负载品质因数与谐振频率坐标系的盲区空间理论，分析多逆变器并联运行防孤岛保护失效机理，并通过仿真和实验验证理论分析的正确性，为多逆变器的孤岛检测设计和多机联合运行提供理论指导。

Analysis of failure mechanism of active frequency drift method anti-islanding protection in multimachine parallel connection

Because unplanned islanding of distributed generation system seriously affect the maintenance security, damage network equipment and have other damages,therefore grid-connected inverter requires islanding detection. Active frequency drift( AFD)islanding detection method is commonly used for detecting island,but many anti-islanding active frequency shift methods active in single inverter while deteriorate or even fail in a multiple inverter parallel system. Based on resonant frequency coordinate and non-detection zones( NDZ)theory of load quality-factor,failure mechanisms are analyzed under multi-parallel system. Simulation and experimental results are presented to validate the correctness of theoretical analysis,provide theoretical guidance for multi-inverter islanding detection design and multi-machine parallel operation.