Research On The Detailed Model Of Bus-fed Static System

Power system usually uses IEEE or IEC bus-fed static exciting system currently. Thesemodels are applicable to the case that the thyristor chooses the way of cosine phase-shifttrigger, but can’t be used for the case of non-complete cosine phase-shift trigger. However,in the field of modern microcomputer excitation systems, thyristor uses non-completecosine phase-shift trigger in most cases. IEEE and IEC bus-fed static system models can’treflect the actual power system conditions accurately then.This paper proposes a new bus-fed static detailed model which can be applied to thecase that the way of thyristor triggering is non-complete cosine phase-shift trigger. The newmodel has considered the feedback impact of terminal voltage based on the IEEE and IECmodels, and introduced the feedback amount of terminal voltage. This model can accuratelysimulate the actual condition of power system under the way of non-complete cosinephase-shift trigger.Then, author researched the small signal stability of the new proposed bus-fed staticdetailed excitation system. Firstly, author researched the stability of small disturbance insingle machine infinite system to compare the IEEE and detailed model of bus-fed staticsystem; then build a s single machine infinite system in PSCAD to compare the conditionof IEEE, IEC and detailed models under the same initial steady state and the same fault.Through the theory and simulation analysis, author found that when the system with IEEEand IEC model is unstable, the system with bus-fed static detailed model is stable under thesame disturbance. Therefore, this paper concludes that in the case of non-complete cosinephase-shift trigger, the new proposed bus-fed static detailed model is applicable andnecessary.At the last, author researched the transient stability of the new proposed bus-fed staticdetailed excitation system. Author built a three-machine nine-code system in PSCAD tocompare the length of fault clearing time in each system with different models. The studyfound that in the case of non-complete cosine phase-shift trigger, using IEEE and IECmodel could easily lead to malfunction protection which can’t effectively protect the powersystem. Therefore, this paper concludes that in the case of non-complete cosine phase-shifttrigger, the new proposed bus-fed static detailed model is applicable and necessary.