Examination of DC Power Distribution Options

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Supervisor:
Dr. Raisz Dávid Márk
Department of Electric Power Engineering

I carried out research to determine the benefits of the full or partial DC power distribution of a family house and a residential park.

In the literature I met two different DC power distribution options.

Most often we meet indoor power distribution in those facilities where electricity is produced by solar cells and the building or part of the building operates in island mode. The advantage of this system is that we avoid the unnecessary AC/DC and DC/AC conversions thereby reducing the loss.

We can meet hybrid power distribution (which means that both AC and DC power networks are present) in data centers, which usually use +380 VDC.

There are also studies which are dealing with the effective use of hybrid system in a family house. In these houses +24 VDC and 230 VAC systems are built.

My intention was to make a plan of a system which is more effective than the AC power distribution, or the previously mentioned DC or hybrid systems. In my investigation I examined four different layouts with different voltage levels.

First I define the properties of the household appliances' power consumption in order to value the loss of the lines and the consumption changes of these devices when using different supply systems. Due to the cross-section of the lines and the actual voltage levels, I categorized them into three classes: low-, medium- and high-consumption appliances. In case of the different devices I estimated which periods of the day and how long do they work in different seasons. Then I figured out how much the effectiveness of an equipment could improve in case of DC supply, and how much their price could be reduced in case of mass production.

When defining the loss of the lines, I took into consideration

 the non-linearity and the power factors of the appliances,

 furthermore that certain devices can be connected to different places of the lines and

 that more devices can be connect to the same socket.

After performing the calculations I evaluated the investment costs and the resulting line losses and appliance losses annually for the next fifty years. This way it is easy to compare the total cost of each distribution solution and the payback time of the new solutions. I took into account the life expectancy of certain devices during the experiments.

Due to the acquired knowledge from the investigation of the family house, I designed different variations of electricity supply (conventional AC or hybrid) in a residential park. I used the annual consumption data of 600 apartments in a quarter-hour resolution to determine the consumption features, so I obtained a realistic picture of the community's losses. On the basis of the investigations the costs for the entire operational life of certain distribution systems (AC and hybrid) became comparable.

In case of residential buildings the modification of DC and related pieces of equipment has brought promising result. Based on it I have extended the examination of this method to a wood-mill and to public lightning, as well.

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