Single/Three-Phase Transformer with Variable Frequency for Electric Locomotives


Electric rail transport is positioned as environ-ment-friendly technology that has good future prospects for development. The supply of electric rail transport from DC or AC power lines requires the use of specialized transform-ers that form the three-phase system in the low-voltage cir-cuit to power this load. Solid State Transformer (SST) are very attractive for use in power systems of electric locomo-tives. This paper examines a new architecture for the reali-zation of SST transformers for their use in power systems of electric locomotives. The proposed SST transformer has the bidirectional high-frequency power transmission capability and at the same time ensures multiplication of phases in the low voltage circuit. The SST transformer is a single-phase / three-phase transformer, which can be supplied both from the high-voltage DC power network and from the AC net-work frequently used in electric rail transport. Changing the power supply type (of the current) does not lead to changes in the topology of the SST. The transformer is de-signed as an object made of identical functional modules. The ferromagnetic core is made of separate portions for each functional module. This simplifies the problem of en-suring the electrical stiffness of the transformer. The tran-sistors of the module operate at variable switching fre-quency, have soft switching mode. Energy conversion takes place in a single step. This ensures that losses are diminished and transformer efficiency is increased in all load regimes. Mathematical simulations have confirmed that this trans-former has a very low impact on the power supply, whether the power supply is DC or AC. Under-load operation of the SST transformer does not lead to pollution of the power supply network with higher current harmonics. images