In the late nineteenth century there was a great dispute over how the electricity known as “war of currents” should be distributed. On one side, Nikola Tesla and George Westinghouse argued that Alternating Current (AC) was the best way to distribute energy, and on the other side Thomas Edison insisted that Direct Current (DC) was the right choice for a distribution network. Thanks to the invention of the transformer, which allows to increase the voltages, AC networks tend to get less losses, thus winning this “war”. However, with the development of power semiconductors in recent years, DC micro networks are once again seen as a possible way of distributing high yield electricity, contributing to the reduction of greenhouse gas emissions. Guilherme Paraíso’s MSc thesis focuses on these networks and their advantages, which won him the REN award (2nd place) in MSc Theses category.
“I am very pleased to have won this coveted award in the Energy field and to see my work recognised”, says Guilherme Paraíso. “My thesis includes the development of a DC network prototype with several interconnected loads and a control system that ensures the stability of the DC network voltage, considering that most loads are of constant power”, explains Guilherme Paraíso. According to the Técnico student, “the change to a DC distribution network or a combination of a DC / AC hybrid system is a disruptive technological evolution”. “My thesis is an important contribution to the progress of these networks and to the stability of DC networks in the future. I proposed nonlinear controllers capable of ensuring DC network stability by feeding constant power loads without the need to install bulky, expensive and low reliability DC capacitors”, says the Técnico student. Guilherme Paraíso’s work stood out from the rest because it allows to obtain high reliable and low cost DC networks.
There are many advantages of a DC power distribution network. As Guilherme Paraíso recalls, “about 40% of electricity is consumed in the residential sector. Most of the electrical loads connected to the low voltage grid are electronic loads that need a DC voltage to operate”, says Guilherme Paraíso. For this reason, and as the Técnico student points out, “it is advantageous, from a performance point of view, to rethink the way we use the low voltage distribution network”. “DC micro networks are now seen as a possible way to complement the existing AC distribution networks, in order to reduce losses”. Therefore, and as stressed by Guilherme Paraíso, “it is obvious that a DC power distribution network will contribute to the modernization of the electrical grid, allowing a direct integration of renewable energy sources and increasing energy efficiency in electric vehicle fast charging stations and energy storage systems”.
Recently, Guilherme Paraíso started a PhD in Electrical and Computer Engineering at Técnico and he intends to develop “new two-way power electronic converters, with high-frequency galvanic isolation, by using film capacitors to increase reliability and reduce short-circuit power”. “The converters will have low losses and a protection system based on power semiconductor devices that ensures the safety of DC network users and equipment”, says the Técnico student.
