基于开关函数的LCC-HVDC输电系统谐波计算方法

电网中电力电子设备的增加所产生的谐波及其危害逐渐显现,并得到越来越多的重视,而换流器作为直流输电系统主要的谐波源,进一步对其进行谐波分析显得尤为重要。本文以电网换相换流器型直流输电(line commutated converter high voltage direct current,LCC-HVDC)系统为研究对象,采用基于开关函数的谐波计算模型对特征谐波进行分析。首先,根据调制理论,建立了基于开关函数的交直流谐波计算方程,并根据LCC换流器的工作原理,分别求解了电压及电流的开关函数,然后通过对直流系统的结构进行分析,得到了直流系统等值谐波阻抗模型,在此基础上,结合交流侧的潮流分析,通过联立求解谐波方程,得到了LCC换流器交直流两侧的特征谐波,最后通过与PSCAD模型的仿真结果进行对比,证明了本文谐波计算方法的准确性和可行性。本文可以为电力系统谐波分析、谐波抑制等提供理论基础和方法参考。

Harmonic Calculation Method of LCC-HVDC Transmission System Based on Switching Function

With the increase of power electronic equipment in the power grid,harmonics and their hazards gradually appear,and have drawn more and more attention.As converters are the main harmonic sources in DC transmission system,it seems particularly important to further analyze them on harmonics.Taking the line commutated converter high voltage direct current(LCC-HVDC)system as the objective,the paper uses an harmonic calculation model based on the switching function to analyze characteristic harmonics.Firs-tly,based on the modulation theory,AC-DC harmonic calculation equations considering the switching function are established,while the switching functions of voltage and current are solved based on the working principle of the converter.Then the equivalent harmonic impedance model of DC system is obtained by structure analysis of DC system.Based on the above analysis and flow analysis on the AC side,the harmonic equations are solved to obtain the LCC characteristic harmonics of AC and DC sides.Finally,by comparing with the PSCAD simulation model,the feasible and accurate of harmonic calculation method are verified.The paper can provide theoretical basis and method reference for power system harmonic analysis,harmonic suppression and so on.