Comparison of Two Cascaded Converter Topologies for Voltage Balancing in AC Railway Substations
Résumé
Abstract — Due to the increase in rail traffic, the 25 kV/50 Hz
single-phase substations can cause an unbalance in the phase
voltages of the upstream three-phase network. This situation
becomes unacceptable for the electricity transmission system
operator and the implementation of an unbalance compensator is
inevitable. In recent years, several power electronic solutions have
been proposed. They are based on Power Electronic Building
Blocks (PEBB) which can be connected in series or in parallel in
order to achieve the required power level. They offer advantages
in terms of modularity and implementation of low voltage power
devices which thus improve the global system efficiency. In this
paper, the authors present two modular topologies based on the
principle of the Steinmetz load-balancing circuit. The first
topology relies on cascaded AC choppers and the second one is
based on cascaded H-bridge inverters. Analytical calculations and
simulations allow a comparative analysis of these two topologies in
terms of power semiconductor losses and stored energy in reactive
devices.