交直流混合系统状态估计算法研究与分析

Research and analysis on algorithm of state estimation of AC/DC systems

采用最小二乘法对交直流输电系统的状态估计问题做了详细的分析和评价。在四种典型的交直流系统状态估计算法的基础上,增加了一类处理交直流系统之间关系的状态估计方法。针对五种算法对交流、直流系统的处理方法,采用一含有双端直流输电系统的14节点算例和一含有两条直流输电线路的300节点系统算例,进行多样本采样计算,从算法的优化效果、估计误差、迭代次数、对量测系统的适应性和计算速度等方面进行了详细的对比分析,总结了五种算法在不同的交流、直流系统量测配置情况下的计算性能,详细分析了几种算法的优缺点和实用性。针对电力系统状态估计的研究现状和现场需求,提出了直流系统状态变量的选取原则,对每个换流站只需选择两个状态变量即可,一个是直流电压,另一个是换流器控制角或换流变压器分接头。归纳出直流系统量测配置的特殊问题,即直流系统量测方程中必须包括无功量测或者触发角(熄弧角)量测,否则交直流混合系统状态估计发散的可能性比较大。

Power system state estimation is analyzed and evaluated by using Weighed Least Square （WLS） method in this paper. Upon four typical AC/DC State Estimation （SE） methods, another AC/DC SE algorithm is presented. Two test systems, one is a 14-bus with a High Voltage Direct Current （HVDC） system and another is a 300-bus with two HVDC systems, are used to contrast to the five methods in the aspects of optimal effect, estimation error, iteration times, the adaptation of measurement system and calculation speed. The calculation performances of these five SE methods under different measurement configuration of AC systems and HVDC systems are summarized in this paper. The merit/demerit and practicability of these five methods are analyzed too. Aiming at the status in quo of power system SE and the practice requirement, a principle of selecting the state parameters of DC system is presented that each converter should have two state parameters： one is DC voltage and the other is ignition （extinction） angle or converter transformer tap. In addition, an especial problem of configuring measurement system is concluded. That is, the positive power measure or the ignition （extinction） angle measure should be included in the system measurement functions. Otherwise the hybrid power system SE may be likely to diverge.