基于阻抗辨识的下垂控制并网逆变器孤岛检测方法

为了保障安全及并网电能质量,基于并网逆变器的分布式发电系统需要具备孤岛检测功能。传统孤岛检测方法不适用于下垂控制并网逆变器,而现有适用于下垂控制并网逆变器的孤岛检测方法需要改变下垂特性且存在检测盲区的问题。为了解决上述问题,提出一种基于阻抗辨识的下垂控制并网逆变器孤岛检测方法。该方法在公共耦合点注入电压扰动,通过电压、电流扰动信号辨识阻抗,进而依据阻抗变化判定是否出现孤岛效应。利用谐波扰动注入放大孤岛前后特征量差异,提高检测灵敏性。另外,通过递归离散傅里叶变换提取扰动信号,提高了阻抗辨识的准确度和时效性。实验结果验证了所提方法的有效性。

Impedance Identification Based Islanding Detection Method for Grid-connected Inverter with Droop Control

In order to ensure the safety and power quality, the distributed generation system based on grid-connected inverters needs islanding detection function. The conventional islanding detection methods are not suitable for the grid-connected inverter with droop control, and the existing islanding detection methods designed for grid-connected inverters with droop control have to change the droop characteristics and exist non-detection zone. To solve the problems above, this paper proposes an islanding detection method for the grid-connected inverter with droop control based on impedance identification. The method injects voltage disturbance at the point of common coupling, identifies the impedance by voltage and current disturbance signals, and then decides whether the islanding effect occurs according to the impedance variation. In order to improve the detection sensitivity, the harmonic disturbance injection is adopted to amplify the differences of characteristic parameters before and after islanding. In addition, the disturbance signals are extracted by recursive discrete Fourier transform, which improves the accuracy and timeliness of impedance identification. The experimental results verify the effectiveness of the proposed method.