双频并网逆变器及其孤岛效应检测

提出一种用于分布式发电的双频并网逆变器,该逆变器由2个标准三相桥级联而成,其中一个桥工作在高频,提高输出电流性能;另一个桥工作在低频,主要输出功率,从而降低开关损耗,提高系统效率。为了检测孤岛效应,提出了基于dq变换和正反馈的新检测策略,基于该策略,提出了基于dq变换的电压正反馈和频率正反馈两种检测方法。两种方法具有无检测盲区、对电能质量影响小、检测速度快等优点。仿真结果表明,该逆变器输出电流与电网电压同相,总的谐波畸变率低,向电网输出的电能质量高。

Research on grid-connected dual frequency inverter and islanding detection

A novel grid-connected dual frequency inverter for distributed generation is proposed.The inverter consists of two cascaded standard three-phase bridges, one of the bridges works in high frequency to improve the performance of output current,the other works in low frequency to handle power thereby the switching losses can be reduced and the system efficiency can be improved.A new scheme based on dq transformation and positive feedback is provided to detect islanding.Based on the new scheme, methods of voltage positive feedback and frequency positive feedback by dq transformation are proposed in this paper.The proposed methods are showed to have no non-detection zone(NDZ) and little influence on power quality and fast acting.Simulation results show that the output current of the proposed inverter is in phase with network voltage, its total harmonic distortion is low and the electric energy output to power grid is of high quality.