Harmonic Filters Planning of Traction System with Specially Connected Transformers Considering Probability Characteristic

This paper presents a method for combining hybrid differential evolutionand orthogonal arrays (HDEOA) in the planning of harmonic filters for the tractionsystem of a distributed generation (DG) system with specially connectedtransformers in unbalanced three-phase power systems. The objective is tominimize total demand distortion of harmonic currents and total harmonicdistortion of voltages. An orthogonal array is first conducted to obtain theinitial solution set; the set is then treated as the initial sample. Next, theHDEOA method parameters are determined by using matrix experimentswith an orthogonal array, in which a minimal number of experiments have aneffect that approximates the full factorial experiments. This HDEOA methodis then applied to design optimal harmonic filters in a traction system, whereboth rectifiers and inverters with IGBT are used. From the results of the illustrativeexamples, the feasibility of the HDEOA to design an optimal passiveharmonic filter of traction system is verified and the design approachcan greatly reduce the harmonic distortion. Three design cases are comparedthat V-V connection suppressing the 3rd order harmonic and Le Blanc for theharmonic improvement is superior to those of the V-V and Scott connection.