考虑换流阀阻尼电路的LCC-HVDC系统小信号精准建模

Small Signal Accurate Modeling of LCC-HVDC System Considering Converter Valve Damping Circuit

电网换相换流器型高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)技术广泛应用于远距离输电,对LCC-HVDC在小干扰下的稳定性进行分析具有十分重要的意义。在LCC-HVDC实现交直流转化的过程中,势必会存在换相过程,对换相过程的刻画和处理是电网换相换流器实现精准建模的关键;此外,换流阀两端一般并联RC阻尼回路以抑制暂态过电压和过高的电压变化率,但目前暂未有文献研究阻尼回路对换流器建模的影响。该文在考虑换流阀阻尼电路的基础上,首先对换流器换相过程进行分析和讨论,建立换流器的传递函数模型;接着通过PSCAD/EMTDC平台对换流器传递函数进行扫频验证;为了说明模型的有效性,最后建立交流导纳模型并对直流输电系统的小干扰稳定性进行分析验证。

As LCC-HVDC technology is widely used in the long-distance power transmission,it is of great significance to analyze the stability of the LCC-HVDC technology under the small disturbances.In view of the inevitable commutation phenomenon in the process of AC-DC conversion of the LCC-HVDC,the description and treatment of the commutation overlap process is the key to realize the accurate modeling of the power grid commutation converter.In practical engineering application,the RC damping circuit is generally connected in parallel at both ends of the converter valve to suppress the transient overvoltage and thehigh voltage change rate.At present,there is seldom literature on the studies of the influence of damping circuit on converter modeling.Firstly,considering the damping circuit of the converter valve,the commutation process of the converter is analyzed and discussed,and the transfer function between the variables of the converter is established;Then,in order to illustrate the accuracy of the transfer function modeling,the frequency scanning is carried out on the PSCAD/EMTDC platform;Finally,the AC admittance model is established and the stability of the DC transmission system is simply analyzed and verified.