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Ingeniare. Revista chilena de ingeniería

versión On-line ISSN 0718-3305

Ingeniare. Rev. chil. ing. vol.29 no.3 Arica set. 2021

http://dx.doi.org/10.4067/S0718-33052021000300403 

Articles

The future electrical networks

2* Universidad de Tarapacá Departamento de Ingeniería y tecnologías Iquique, Chile E-mail: pguichar@academicos.uta.cl

In recent years, significant efforts have been made to encourage the use of new energy sources in electricity generation, thereby reducing the use of fossil fuels in the search for sustainability and environmental preservation. These incentives have generated a new scenario for electricity grids, where the concepts of flexibility, resilience, and Smart Grids acquire great importance1, considering the permanent needs of quality and stability. On the one hand, it is required flexibility to include new energy sources, new types of consumption and to allow hybrid operation by interconnecting grids of different frequencies, voltage levels, alternating current, or direct current. On the other hand, Resilience is required to keep the system's operation or recover it when it faces problematic natural phenomena that could threaten its infrastructure and the continuity of supply.

Traditionally, electrical systems operate by classifying their components into three sectors according to the role they play: Generation, Transmission, and Distribution. The first sector transforms the energy from a primary source into electrical energy. The second sector, Transmission, provides the infrastructure and ancillary services to transport electrical energy to the consumers. The third sector, Distribution, delivers energy to low and medium voltage levels, i.e., delivers it to industrial, urban, or residential centers. This last sector allows the power flow in only one direction, from the substation to the consumers, giving no possibility to implement flexibility, bidirectional power flows, or strategies that allow microgrids formation or island isolated operation mode. Along with this paradigm, it is possible to find traditional devices to preserve the stability and quality of service, among them, tap changing transformers, capacitors banks, and reactors. These devices have a high level of reliability and efficiency, but with a low control capacity and flexibility, not allowing the use of updated control strategies, the use of technological progress in new topologies, and new power electronics devices.

However, some technological advances have impacted the transmission sector, using Flexible Alternating Current Transmission Systems2 (FACTS) or high-voltage direct-current power transmission, allowing flexibility when controlling power flows and other dynamic characteristics of the system. Nevertheless, it is still possible to give one step further in the operation of power grids, making them more flexible, without compromising system stability and resilience, particularly with applications into the distribution sector.

Currently, the research and developments in areas such as Power Electronics, Automatic Control, Computing, Communications, Energy Storage, among others, have allowed us to expand the number of participants in the electrical networks. They have set as a key requirement the need to integrate Distributed Generation Means, Microgrids, Electric Vehicles, and Prosumers3 into the grid. All of them are enabled by power converters, which allow decentralizing the electricity generation, but on the other hand, they set the challenge of thinking about how electrical networks will work in the coming decades.

A first approach to the future characteristics that the electric grids may require are: a flexible, resilient, stable, and reliable distribution sector that allows the interconnection of new actors at different levels, in a distributed form across the grid, and with bidirectional power flows; a transmission sector, also flexible, that allows the integration of new means of generation, in direct or alternating current, and a large-scale of energy storage systems; finally, a generation sector that reduces the use of fossil fuels. With the above, it is possible to foresee that the whole operation of each sector into the electrical system, necessarily, have to be opened to include new actors, from an economic point of view, as well as technical assessment. The first step towards that direction is the implementation of Distributed Generators, which consists of the connection of generator systems into the distribution network. The installation of home generation systems has also been an outstanding contribution. However, new challenges continue appearing, such as the connection of electric vehicles (both as loads and generators), and new topologies for low-power networks such as microgrids.

Nowadays, mainly in the academic context, one of the topics that is getting more attention is precisely how to integrate all these elements keeping a stable, resilient, reliable, and quality operation, considering the integration of different sources and loads, with different frequencies in the case of alternating current or direct current. This integration of elements will be possible only with the use of solid-state converters. New devices based on silicon carbide (SiC), which allow the operation on a wider frequency range and at higher voltage levels, are expected to support the development and design of new converters for this task. In addition, progress in the generation of new converters connection topologies, such as multilevel converters, new control strategies, and advances in computational capacity, will make these systems more reliable and, over time, more economical. These last two characteristics (reliability and cost) are precisely the only two advantages of the traditional devices. However, the future will help to overcome them.

There is an interesting new architecture proposal for future electrical grids at the distribution level, and it is based on conceiving the grid in a similar way to an internet network. In this conception, the connection of prosumers (microgrids, electric vehicles, distributed generation means, and others.) into the electric grid would be as simple as connecting a computer to the Internet. In this framework, the current distribution substations would operate as network routers, allowing the interconnection and the intelligent management of power flows. This concept for the future electrical network is called Energy Internet4, and the replacement for substations are called Energy Router, Intelligent Power Transformer, Smart Transformer, Power Router, among others5. The cornerstone to implementing it lies in the study of solid-state transformers6 (SST) and integrating the characteristics of new power electronics, control, computing, and cybersecurity devices, to become not only efficient and reliable but also intelligent.

All the above will be possible in the future, provided that further progress in academia is achieved, higher popularity in the industrial sector is received, and, above all, greater awareness of sustainability in the use of new means of electricity generation is reached. It has to start from home users, through industries, to the generation, transmission, and distribution sectors, i.e., becoming an active part of the electricity grid as energy generators or consumers and becoming an active part of the cycle of transforming nature into electrical energy.

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