Available Transfer Capability Calculation Based On Fast Correction Of AC Sensitivity

ATC, a technological term in deregulated system, is referred to as the standard ofmeasuring the throughput capacity as well as the physical transfer capacity in the powernetwork which are used for developing diverse commercial activities and the existing users.As power transaction between public and domestic applications can enhance theeconomical and reliable electric supply, ATC should be updated as the required time. In theelectric power market, power business changes frequently, all kinds of outages effect thesystem, the uncertainty of the system increase. So a fast and accurate identification of ATCin time is indispensable.In order to satisfy the request of ATC’s (Available Transfer Capability) on-linecalculation, a fast ATC calculation based on correction of AC sensitivity is proposed. Thefour main aspects in this arcticle are as follows.Firstly, power market in the past several years was reviewed and transfer capabilitycalculated methods were presented. Deterministic solutions and probabilistic resolutionswere outlined simply.Secondly, continuous power flow model in polar coordinates was establishing, therepresentative calculation method of each link in continuous flow were introduced briefly.Thirdly, Combining with continuation power flow(CPF) model, Considering thebranch overload constraint. The ATC can be estimated by the higher order Taylor series ofthe branch active power to power control parameters in base case. Compared with CPF,OPF method, this method avoid multiple power flow calculation and have fast calculationspeed. Higher order Taylor series ensure the precision.Fourthly, the relationship of ATC to generation output change parameters can becalculated by correcting the branch active power and sensitivity of the branch active powerto power control parameters in the case of generator output changing. The new ATC can beestimated very fast after generator output varied. The effective interval of sensitivity canensure the creditability while this sensitivity is applied. When generation output changeparameters changes in the interval，ATC will be calculated by the relationship of ATC togeneration output change parameters, otherwise, ATC will be calculated by the method inbase case.Finally， the proposed method has been tested with IEEE30bus and IEEE57bus-systems. The calculation results of continual power flow method were used to test thevalidity and rapidity of the proposed method.