谐波源的识别及其与非谐波源的分离方法

APPROACH OF IDENTIFICATION AND SEPARATION OF HARMONIC SOURCES

通过对线性和非线性负荷的电压-电流特性的比较研究,指出了线性负荷和非线性负荷的本质区别在于:线性负荷的谐波电流仅是本次谐波电压的线性函数,而非线性负荷的谐波电流则是各次谐波电压的复杂函数; 应用谐波源的简化模型,在供电电压基波相角为零时,谐波电流的实部和虚部可分别表示为各次谐波电压实部和虚部的线性多项式,且其中由本次谐波电压引起的谐波电流只占很小 的比例。从该原理出发,提出了一种新的谐波源识别方法,它不仅能识别综合负荷中是否含有谐波源,而且能够精确地分出线性与非线性负荷各自吸收的谐波电流。文中还给出了应用最小二乘方法进行识别的具体步骤,并以一个综合负荷的计算与分析结果验证了所提谐波源识别方法的有效性。

Based on the comparison of v-i characteristics of linear and nonlinear loads, it is pointed out in this paper that the intrinsic difference between linear and nonlinear loads is that harmonic currents of a linear load are in linear proportion to its supply harmonic voltages of the same order, whereas the harmonic currents of a nonlinear load are complex nonlinear functions of its supply fundamental and harmonic voltages of all orders. Based on a simplified harmonic source model with the real and imaginary parts of harmonic currents of the nonlinear load modeled by linear polynomials of the rectangular coordinate components of harmonic voltages while neglecting the currents caused by the harmonic voltage of the same order as they are far less than the total amounts, a new principle for identifying harmonic sources is proposed. By using this method, not only the existence of harmonic source in a composite load can be determined, but also the contributions of the source and the linear part of the load can be accurately separated. Detailed procedure of harmonic source identification and harmonic contribution separation based on least squares approximation is given. Test results on a composite nonlinear load illustrate the effectiveness of this approach.