Effective loadflow technique with non-constant MVA load for the Hong Kong Mass Transit Railway urban lines power distribution system

The power distribution systems of Hong Kong´s Mass Transit Railway Corporation consist of loads having different voltage dependent characteristics. However, conventional load flow methods are not adequate for accurate power system studies and for fast contingency studies. A load modelling technique, in which each voltage dependent load is modelled by a Norton equivalent comprising of a 2×2 admittance matrix and a current vector, is introduced in this paper. Because this load model is always tangential to the actual load characteristics, a primitive nodal method can be employed. The proposed technique is easily programmed and converges rapidly. The advantages of the proposed technique are further discussed with respect to conventional load flow methods with constant MVA loads