基于常量附加频差平方正反馈的无功扰动孤岛检测法

Reactive Power Disturbance Islanding Detection Method Based on Constant Combined With Positive Feedback of the Square of Frequency Deviation

为解决现有孤岛检测方法存在检测盲区及检测时间较长等问题,提出一种常量小扰动复合频差影响的改进型无功扰动孤岛检测方法。分析孤岛时分布式电源注入无功功率扰动与并网点频率偏移的关系,设计常量扰动与频率差值平方正反馈扰动相结合的无功扰动生成方法,其中常量扰动产生初始频率偏移,附加扰动增强频差-无功的扰动响应速度,同时减小并网运行频率波动时的影响;综合孤岛检测时间和扰动对电能质量影响的要求,优化设计扰动系数及扰动周期等参数,并给出孤岛检测实现流程。仿真结果表明:改进型无功扰动孤岛检测方法能克服孤岛检测盲区的影响,较传统正反馈无功扰动法显著缩短孤岛检测时间,最大可缩短52.5%,且几乎不产生电能质量问题,验证了该方法的正确性和有效性。

In order to address the issues of the non-detection zone and extended detection time in existing islanding detection methods,an improved reactive power disturbance islanding detection method incorporating the effects of constant small perturbation and compound frequency difference is proposed.The relationship between the reactive power perturbation injected by distributed generation and the frequency offset at the point of common coupling is analyzed.A reactive disturbance generation method that combines constant disturbance and positive feedback of the square of frequency deviation is designed.In this method,a constant perturbation generates an initial frequency offset,while additional perturbations enhance the frequency difference-reactive power perturbation response speed and reduce the impact of frequency fluctuations in grid-connected mode.Parameters such as disturbance coefficient and disturbance period are designed by synthesizing the requirements of islanding detection time and the impact of disturbances on power quality,and the implementation process of islanding detection is provided.Simulation results indicate that the improved reactive power disturbance islanding detection method effectively overcomes the challenges posed by the non-detection zone.Compared with the traditional positive feedback reactive power perturbation method,the islanding detection time is significantly reduced,with a maximum reduction of 52.5%,while almost does not exacerbate the impact on power quality.These results substantiate the correctness and effectiveness of the proposed method.