Daniel Garralda Sanz
Industrial engineer Daniel Garralda Sanz focused his PhD thesis on electric power supply systems in trains. In his research, developed at the Public University of Navarre (UPNA), he drew up dynamic models which enabled calculating the instantaneous power supplied by the equipment. The thesis was entitled “Connection in parallel of converters for the generation of the auxiliary network of a train”.
In concrete, the research focused on what are known as the auxiliary systems or networks, responsible for supplying power to equipment aimed at the comfort of the passengers (heating, air conditioning and lighting) and for auxiliary equipment such as refrigeration of motor, door opening, control system for the brakes, etc. In order to feed this great variety of loads, an internal network is generated that runs through the train, connecting the equipment.
According to the author of the PhD thesis, in order to avoid electric power supply failure, redundant power supplies are required; in the case of auxiliary systems, two converters being used. “Usually these converters are located at either end of the train and are not connected directly, the auxiliary network having a contactor that remains open, in such a way that this network is separated into two parts, each converter feeding only one half of the loads. In the case of failure of one of the converters, the equipment disconnects and the contactor closes, enabling the other converter to feed the loads”.
Current research is aimed at achieving greater reliability and robustness of the system, as well as reducing its overall weight and cost of installation and maintenance, the researchers seeking thus to eliminate the contactor. In this context, one of the most promising techniques is Droop Control, by which the converters adjust the voltage provided by the auxiliary network independently, based on the active and reactive power that they supply.
Proposals for improvement
In his thesis, Mr. Garralda tackled the modelling of networks fed by converters operating in parallel. He moreover provided a novel focus in defining models, being able to know and calculate the transfer of instantaneous power between equipment. “We have shown that the type power supply line decisively influences the transfer of power, not only in the permanent regime, as taken into account in previous research, but also in the dynamic one”. He also proposed other alternatives to the reactive control of power that improve the performance of conventional Droop control.
Daniel Garralda, a graduate in industrial engineering, also took a Masters in Renewable Energy and, subsequently, a PhD in Engineering. As assistant lecturer at the UPNA, he has taken part in various research projects, in collaboration with the INGETEAM company.
* Elhuyar translation, published in www.basqueresearch.com