热稳定薄弱断面搜索及限额制定的在线算法

Online Algorithm for Searching and Limit Setting of Thermal-stability Weak Section

为解决离线断面及限额不能实时匹配系统运行方式的问题,针对热稳定断面构成元件搜索、限额制定提出了一套在线算法。采用直流法计算支路开断、有功元件跳闸、母线跳闸3类故障的潮流转移,提出了将母线跳闸转化为虚拟短线开断的方法,使潮流转移关系得以显性表达。归纳得出了3类故障潮流转移通用线性表达式,为制定断面限额奠定了基础。提出了基于“风险支路+威胁元件”构成法的热稳断面构成元件搜索方法,基于潮流转移通用表达式提出了风险加权的断面监控指标构造方法及断面限额制定方法。对于涉及并联支路的相近断面给出了合并方法,对并联支路构成的断面给出了监控指标的化简方法。为保证求解速度和计算精度,采用直流法搜索与交流法校验修正相结合的计算策略。应用于实际案例,搜索的断面将离线断面所反映的热稳风险全面覆盖,计算限额与离线限额的一致性较好,验证了方法的有效性;每一轮计算耗时约3.6 min,满足在线应用要求。

To solve the problem that offline section and its transmission limit can’t well match the system operation state,a set of algorithms are proposed for searching and limit setting of thermal stability section components.Transferring flow power of three types of faults,i.e.,branch breaking,active power component tripping and bus tripping are calculated by DC method,and a method of transforming bus tripping into breaking several virtual short lines is proposed to explicitly express the power flow transferring relationship.General linear expressions for three power flow transferring types are concluded,which lays a foundation for setting section limits.The thermal stability section searching method based on“branch line at risk+component under threat”construction is demonstrated.By using the general expressions of power flow transferring,a risk-weighted monitoring index construction method and a limit setting method for sections are proposed.The merging method is given for the similar sections consisting of parallel branches,and the simplification method for monitoring index is given for the sections composed of parallel branches.To ensure the solving speed and accuracy,the calculation strategy combining DC searching method with AC correction method is adopted.Based on an actual example,the searched sections by the proposed algorithm cover all the thermal stability risks of the offline sections.Furthermore,the consistency of section limits between caculation limit and the offline limit is proven,and thus the validity of the proposed algorithm is testified.A round of calculation takes about 3.6 minutes,which meets the requirements of online application.