中文摘要：

首先分析利用谐波电压电流自然波动量之比来计算系统偕波阻抗及谐波发射水甲的要点及关键问题，理论上分析并证明基于波动量比值实部符号判别的阻抗计算方法（简称“符号判别法”）是不完备且有较大局限性的。其样本筛选过程只能排除一部分相角不正确的结果，却剔除了一部分相对误筹较小的结果，同时误保留了一些实部为正但误差较人的结果。从两侧谐波电流波动的随机特性出发，提出一种基于阻抗归一化趋势判别的谐波发射水平估计方法，通过判别阻抗趋势图中的盲区和聚合区，筛选出更有价值的阻抗计算样本点。仿真及实际工程算例验证该方法的准确性和有效性，同时说明了符号判别法的局限性。

英文摘要：

This paper first analyzes the essentials and crucial problems in measuring harmonic impedance by calculating the ratio of natural harmonic voltage fluctuation to harmonic current fluctuation. Theoretical analysis shows that the traditional approach which is based on the sign judgment of the real part of the ratio of two fluctuations （＂symbolic discriminated method＂） is incomplete and has great limitations, it only excludes those impedance samples whose phase angles are theoretically incorrect; at the same time, some valuable results with small relative errors are excluded and some inaccurate results with positive resistances are kept. Starting from the random characteristic of harmonic fluctuation, this paper presents a novel approach for harmonic impedance and emission calculation, it selects more valuable impedance samples from all the measured ones at the point of common coupling （PCC） by discriminating the blind zone and aggregation zone from the impedance gathering trend figure. Simulation and field tests show that the proposed approach is accurate and effective, and has applications; meanwhile the strong prospects in practical limitations of ＂symbolic discriminated method＂ are illustrated .