基于二阶盲辨识的系统谐波阻抗计算

Utility harmonic impedance assessment based on SOBI

文章指出随机独立矢量法的误差是由于将公共耦合点的谐波电流近似等效为用户侧谐波电流引起的,根据误差分析,提出基于二阶盲辨识的系统谐波阻抗估计方法。首先分离测量得到的谐波电压和电流信号为快速变化部分和缓慢变化部分。根据系统侧和用户侧谐波电流快速变化部分近似独立性的性质,对公共耦合点的谐波电流和电压快速变化部分进行二阶盲辨识计算,得到4个独立信号;根据公共耦合点的谐波电流近似等于用户侧谐波电流,即具有较大的相关系数,计算独立信号与公共耦合点谐波电流之间的相关系数,根据相关系数的大小判断4个独立信号中的用户谐波电流实虚部;最后,根据随机矢量协方差为零的性质,计算得到系统谐波阻抗值。通过仿真计算表明,文中方法有效的提高了随机独立矢量法的计算精度,具有较高的准确性。

This paper points out that the error of the random independent vector method is due to that the harmonic current at the common point of coupling is approximately equivalent to the customer-side harmonic current. According to the error analysis, the method of the utility harmonic impedance assessment based on the second order blind identi- fication （SOBI） is proposed. Firstly, the fast-changing parts and slow-changing parts are obtained by filtering from the harmonic voltages and currents measured at the PCC. According to the nature that the fast-changed part of utility harmonic current is approximately independent to the fast-changed part of customer-side harmonic current, the four in- dependent components can be calculated by SOBI from the harmonic voltage and current at the PCC. Then, the cus- tomer harmonic current is picked out through using the correlation coefficients, which is because the harmonic current at the PCC is approximately equal to the harmonic current of customer, i. e. , the correlation coefficient between the harmonic current at the PCC and the harmonic current of customer is much larger than the correlation coefficient be- tween the harmonic current at the PCC and the utility harmonic current. Finally, based on the nature that the random vector covariance is zero, the utility harmonic impedance is attained. Through the simulation calculation, it is easily seen that the method effectively improves the calculation precision of the random independent vector method, which has high accuracy.