A method for modeling the power flow in train auxiliaries fed by two inverters set in parallel

Nowadays trains offer a level of comfort and services that obviously imply a higher energy consumption to feed the auxiliary train power systems. Usually, the auxiliary power systems are fed by two power converters placed in opposite ends of the train. These power converters share the demanded power and depending on how over-dimensioned the system is, they offer a certain level of redundancy. The correct functioning of the converters set in parallel may only happen if the right synchronization of the voltage generated by each of them is guaranteed. Otherwise, there would be an inadequate flux of power flowing between them. There is an increasing interest on operating the converters set in parallel without the need of a communication line to transmit the signals to synchronize the converters so as to simplify the system and make it more robust. The Droop Control technique, based on the steady-state regime power flux analysis, enables such goal. This article analyzes the decisive impact of the supply line on the dynamics and the stability of the system based on the Droop Control technique. Furthermore, a simplified model that integrates the control loops of both converters and the line dynamics is proposed. This model accurately analyzes the train auxiliary system power flux behavior both during steady-state and transient regimes. Hence, the suggested model is an adequate tool to study control strategies.