The planning of low voltage DC distribution systems under multiple criteria and constraints

Abstract

DC-based electrical energy consumption and production have exhibited a notable growth in recent years. As the demand for DC-consuming home appliances increases each year, the need for a more efficient AC-DC conversion with higher power output has also increased. Electric vehicles and intercity railways represent additional examples of DC-consuming systems with significantly higher power demands. Moreover, there has been a rapid increase in the generation based on renewable energy resources which produces electrical energy in its DC form. All of these DC consumer and producer units must be interconnected to the network which is dominantly AC. Consequently, distribution system operators and researchers worldwide have been actively seeking more efficient methods to integrate these DC systems in to their AC networks. Several researches have proposed the utilization of low-voltage DC (LVDC) distribution systems which would eliminate the need for additional conversion steps. Additionally, various benefits enabled by low-voltage DC distributions, such as improved power quality, reduced voltage oscillations, and easier integration of renewable energy sources, can be advantageous for both customers and distribution system operators. In this study, a comprehensive literature review is conducted to present the results of research in this field and the challenges that lie ahead. The structure of LVDC distribution networks is examined, and these networks are classified based on various aspects such as the number of poles, grid topology, and network configuration. The discussion covers the equipment used, grounding and protection methods, and voltage level selection methods in LVDC distribution networks. Pilot implementations of LVDC distribution networks around the world are described, with detailed discussions of the experiences gained. The study also outlines the methodology for performing cost/benefit analyses to assess the viability of investing in an LVDC distribution network from the perspective of a distribution system operator. The study demonstrates that LVDC distribution systems can be an optimal alternative to conventional AC grids under certain circumstances. As the economic lifespan of power electronics improves and costs continue to decline, LVDC distribution has the potential to become a viable alternative in many cases.