基于超定线性方程组模型的HVDC地电流计算方法研究

Research on Algorithm to Calculate the Grounding Current of HVDC Based on Overdetermined Linear Equations

为进一步提高高压直流输电(HVDC)单极大地回路运行时接地极入地电流对周边交流系统影响的计算结果的准确性,提出了基于超定线性方程组模型的HVDC地电流计算方法。该方法充分利用已测量到的直流电流数据,将实测数据建立的附加方程与理论计算模型结合起来对HVDC引起的变压器中性点直流进行评估。推导了回路电流法和节点电压法的超定线性方程组模型,并使用最小二乘法对所得到的超定线性方程组数学模型进行求解从而得到流过变压器中性点直流电流。通过四网孔网络阻抗模型的算例对此方法进行了验证,并与传统模型方法的计算结果进行了比较,比较结果证明此方法简单实用、准确性高,尤其在受现实条件限制而无法获取准确原始数据的条件下,更能体现出此方法的优越性。

To improve the accuracy of the calculation results of influence on AC power system by grounding current when HVDC operates in monopole and grounding loop circuit,this paper presents an calculation method of grounding current of HVDC based on overdetermined linear equations,which makes full use of the measured DC data,and the DC in neural node of transformer caused by HVDC is evaluated by combining of additional equation built by measured data with theoretical calculation model.The overdetermind linear equations model of loop current method and nodal voltage method are derived,and the mathematical model of overdetermind linear equations with least square method is solved to get the DC in the neutral node of transformers.Taking a four network impedance model as example,the method is verified and its results are compared with that obtained by traditional model and method.The results show that this method is simple,practical and high reliability,and its superiority is reflected in such condition as lacking of accurate raw data.