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This paper describes the typical field of power electronic converter in the branch of traction substation. The main attention is paid to problematic of ACtraction substation. This topic is solved here due to the just started conversion from DC-traction system to ACtraction system in Czech Republic. These new ACtraction substations use semiconductor power converters for purpose to minimize un-symmetrical unbalance of input current consumption, to compensate reactive power, to filtrate high-order harmonics etc. This article describe and compare basic attributes of these modern topologies of AC-traction substation.

This paper describes the control of multilevel converter for substation balancer. The topology of substation with electronic balancer is described. The principle of power symmetrization and reactive power compensation is introduced in paper. Designed control algorithm for independent current control is main goal of this paper. This control is based on the calculation of required current by Steinmetz's method. The paper presents simulation results of designed prototype of substation with rated power of 12.5 MVA for 25 kV / 50 Hz traction catenary.

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The main goal of this paper is the analysis of an behavior for the electronic balancer of the AC traction substation. This balancer consists of three delta connected multilevel cascade H-bridge converters. The employed phase-shifted pulse width modulation causes the significant decrease of the current ripple due to multilevel nature of the voltage at the converter AC terminals. This paper describes the basic level of modulation technique for single H-bridge cell and analyzes low harmonic interferences of the converter. These results are extended to twelve cells H-bridge multilevel converter with 250 Hz switching frequency. The results of the analysis are based on a created model of the multilevel converter with the nominal power of 12.5 MVA (for traction substation use).