基于定位d轴谐波电压偏移的孤岛检测新方法

A New Islanding Detection Method Based on the Locating d-axis Harmonic Voltage Offset

针对传统谐波域电量变化的被动式孤岛检测法检测盲区大、灵敏度低的问题,提出一种基于定位d轴谐波电压偏移的孤岛检测新方法。首先,通过计算公共耦合点处谐波有功功率贡献量,选择来自光伏侧和系统侧方向的代表频次谐波;然后,利用滑动加窗傅里叶变换和Park变换,求取代表谐波频次d轴谐波电压偏移,并作为孤岛特征量,依此建立检测判据。若来自光伏侧和系统侧的特征量均超过检测阈值,则判定孤岛。另外,分析计算孤岛特征理论阈值,提高孤岛检测的准确性。设置极端工况下孤岛和并网的多种故障进行仿真验证。结果表明,该方法简单可靠,不仅可以区分孤岛和非孤岛故障,而且在强背景谐波场景下能实现快速、无盲区检测。

Aiming at the problems of large blind areas and low sensitivity of the traditional passive islanding detection method for power changes in the harmonic domain,a new method of islanding detection based on the locating d-axis harmonic voltage offset was proposed.First,the representative harmonics from the photovoltaic side and the system side were selected by calculating the contribution of harmonic active power at the point of common coupling(PCC).Then,the sliding windowed Fourier transform and Park transform were used to calculate the d-axis harmonic voltage offset of the harmonic frequency of the substitution table as the islanding characteristic quantity,and the detection criterion was established accordingly.If the parameters from the photovoltaic side and the system side both exceed the threshold,there is an island.In addition,the theoretical threshold of islanding was analyzed to improve the accuracy of detection.Various faults of islanding and grid connection under extreme conditions were set up for simulation verification.The results show that the method is simple and reliable,it not only distinguishes islanding and non-islanding faults,but also can achieve fast and no blind spot detection in strong background harmonic scenes.