基于改进变步长LMS算法的谐波电流检测法

Harmonic Current Detection Method Based on Improved Variable Step Size LMS Algorithm

针对传统基于瞬时无功功率理论谐波电流检测中的二阶低通滤波器无法同时满足检测精度和响应时间的问题,提出了基于改进的双曲正切函数变步长LMS算法(IVSSLMS)的低通滤波器提取p轴和q轴中直流分量的方法;将两个谐波电流的间隔时间通过适当的调节采样间隔次数来延长,目的是为了达到高次谐波的自相关性能迅速降为零。从理论上分析了算法性能的优越,给出了参数的取值,并在simulink中搭建了仿真模型,仿真实验结果表明,改进后的低通滤波器直流分量的跟踪速度提升了一倍,得到基波正弦波形的THD值下降了0.37%。并得出以下结论:在同样输电条件下,采用改进变步长LMS算法构成低通滤波器加快了直流量的跟踪,提取的基波分量更加接近于理想波形,提升了谐波检测的瞬时性和准确性。

Aiming at the problem that second-order low-pass filters in traditional harmonic current detection based on instantaneous reactive power theory cannot simultaneously meet the detection accuracy and response time,a method for extracting DC components in the p-axis and q-axis using a low-pass filter based on an improved hyperbolic tangent function variable step size LMS algorithm(IVSSLMS)is proposed.The interval time between two harmonic currents is extended by adjusting the number of sampling intervals appropriately,in order to quickly reduce the autocorrelation performance of high-order harmonics to zero.The superior performance of the algorithm was theoretically analyzed,and parameter values were given.A simulation model was built in Simulink.The simulation results showed that the tracking speed of the DC component of the improved low-pass filter was doubled,and the THD value of the fundamental sine waveform was reduced by 0.37%.And the following conclusion is drawn:under the same transmission conditions,using an improved variable step LMS algorithm to construct a low-pass filter accelerates the tracking of direct current,extracts fundamental components closer to the ideal waveform,and improves the instantaneous and accuracy of harmonic detection.