MVDC Networks. Study of different architectures

Abstract

[ES] El presente Trabajo Fin de Máster tiene como objetivo el estudio de las redes de transmisión en media tensión en corriente continua (MVDC). En los últimos años, las redes MVDC han empezado a considerarse como una alternativa a las redes convencionales en corriente alterna. La gran ventaja de los sistemas en corriente continua consiste en la mayor eficiencia con respecto a los sistemas en corriente alterna. A lo largo del trabajo se analizan dos aspectos fundamentales: Por un lado, se estudia, a partir de los modelos en estado estacionario (steady state model), cómo varían los flujos de potencia dependiendo del tipo de configuración (radial, en anillo y mallada). Por otro lado, se calcula, mediante un modelo anaítico los voltages en cada nodo y se analiza cómo varía la impedancia dependiendo del tipo de configuración. En estas simulaciones hay generación y demandas dinámicas, y se estudian tres zonas diferentes. Las simulaciones se realizan por medio del software PLECS.

[EN] Energy distribution grids are mostly affected by the transition towards more sustainable energy systems. In this way, medium voltage direct current (MVDC) systems have great potential to be considered as an alternative to conventional AC networks, taking advantage on renewable and energy storage systems integration. The key advantage of DC power systems compared to AC counterparts is the higher efficiency of power transmission and distribution under the same voltage levels. Apart from that, frequency synchronization is not required , and there is no need for reactive power compensation. To promote this technology, this project investigate and analyze various types of architectures in MVDC power distribution networks. These architectures are radial, characterized by having one main path transmitting the energy from sources to consumers; ring, a closed loop that provides multiple paths between the sources and consumers; and mesh, where there are greater interconnections between the nodes. In order to analyze the three types of configurations, three areas will be considered: an urban area, a rural area and a residential area. Simulations are conducted using steady-state models over the course of one day, these incorporate dynamic energy sources, dynamic consumption points and DC transformers (DCTs). Integrating DCTs in the systems developed throughout this project and having a system with different voltage levels is also an essential part. In each section, there is a description of the different energy sources, consumption, electrical connections between different points, and the location of the DCTs, being as realistic as possible. DCTs operate in open loop, it means that there is not voltage control. In power flow study, once the simulations are implemented, different aspects are analyzed for each case, such as total consumption, the contribution of each energy source, the amount of energy flowing through each DCT, voltage at each node and losses. In this part, simulations are carried out using PLECS software. Furthermore, an analytical model is used to study impedance response of each node. First, the voltage at the nodes can be calculated with this model without having to run simulations. Following that, the method of analyzing the impedance in a grid node, a consumption point, and in DCT are explained. Finally, the effect of length on impedance is also examined.