Research On Fast Method For Transmission Section Total Transfer Capability Evaluation Under Scheduling Mode

The continuous development of power system puts forward new requirements for the refinement and lean of dynamic safety check of dispatching plan.The limit assessment of cross-section transmission in the planned way is an important content of safety check.The current calculation method of section transmission limit is too conservative and time cost is too large to meet the requirements of dispatching department for section transmission limit evaluation of planned power flow.In this paper,the on-line calculation method of section transmission limit is taken as the core,and the idea of screening the worst working condition in off-line calculation method is used for reference.By dividing the maintenance interval and reducing the calculation period,the speed of section transmission limit evaluation calculation under the plan mode is greatly improved on the premise of ensuring the accuracy of calculation results.Mainly includes the following contents:(1)The existing off-line calculation method and the principle of on-line calculation method of section transmission limit are studied,and the calculation process of on-line calculation method of section transmission limit is analyzed emphatically.The advantages and disadvantages of off-line calculation method and on-line calculation method are summarized,as well as the factors that need to be considered in on-line calculation of section transmission limit: power grid topology,equipment failure and various constraints.(2)Study the quantitative evaluation method of transmission limit factors.The influences of equipment maintenance and power load change on the section static stability limit,thermal stability limit and transient stability limit are analyzed respectively.The influence degree is quantitatively evaluated by means of Thevenin equivalent impedance,approximate static stability limit,DC breaking distribution coefficient and track sensitivity,and the corresponding calculation method of influence factor is put forward.(3)To study the rapid evaluation method of transmission limit of cross-section under the plan mode.Selecting a section-related equipment maintenance set by using an influence factor of equipment maintenance on the section transmission limit;Dividing 96 planned time periods into a plurality of maintenance intervals;In each maintenance interval,the worst working condition period is screened out by using the influence factor of the change of the power generation load on the transmission limit of the cross section;Carry out detailed section transmission limit evaluation calculation only for the worst working condition period;The calculated results are used to form the sectional transmission limit curve.(4)Using the actual plan data of central China,Hebei and Anhui power grid to simulate and analyze.By comparing the calculation results of the fast cross-section transmission limit evaluation method with the calculation results of the online calculation method,it is verified that the proposed algorithm greatly improves the calculation speed of the cross-section transmission limit evaluation of the previous planning mode on the premise that the calculation accuracy meets the engineering application requirements.