Household Electrical Consumptions Modeling and Management Through Neural Networks and Fuzzy Logic Approaches - Complex System Modelling and Control Through Intelligent Soft Computations - page 431

1 Introduction

The rapid depletion of conventional energy sources and the ever-increasing demand
for more energy coupled with the focus on environmental issues has encouraged
intensive research into new sources of energy and clean fuel technologies that
utilize the latest technology. Most renewable sources use wind, micro-hydro, tidal,
geothermal, biomass and solar energy. This energy is then converted into electrical
energy to be delivered either to the utility grid directly or to isolated loads. From
ancient times, the human race has harnessed solar energy, radiant light and heat
from the sun using a range of different technologies. Some modern solar energy
technologies include solar heating, solar photovoltaic, solar thermal and solar
architecture. These methods can have the potential to make a signi cant contri-

bution to resolving the pressing energy problems that the world faces.
Photovoltaic (PV) systems and some other renewable energy systems (such as
wind, tidal, waves, geothermal) are excellent choices in remote areas for low to
medium power levels due to the easy scaling of the input power source (e.g. the use
of solar inverters). The main attraction of the PV systems is that they produce
electric power without harming the environment by directly transforming the free
inexhaustible solar energy into electricity. Distributed grid-connected photovoltaics
(PV) is playing an increasingly signi cant role as an electric supply resource and as

an integral part of the electrical grid, due to the continual decrease in costs and the
increase in their ef ciency. Although inferior to other technologies in terms of

installed capacity, PV is currently the most important Distributed Generation (DG)
technology all over the world, due to

financial support from the government

(Timilsina et al. 2012 ; Yang 2010 ).
As is well known, electricity systems can bene t from the integration of small-

scale PV-DG. For instance, since distributed generation produces electricity where
needed, it helps reducing the electric load on transmission lines and the need for
costly new lines associated with new power plants far from towns and cities.
However, PV poses notable challenges to grid engineers, planners and operators.
Sometimes and especially when having high penetration of PV in parts of the
distribution system dominated by residential end-users, the amount of power gen-
erated by the PV may exceed the total demand being served by a given part of the
distribution system. In those circumstances, “ excess ” power can have a dramatic

effect on the electric service voltage.
Another effect is known as

“ back- fl ow ” . This entails the current fl flow from the

“ low voltage side ” of electrical transformers (also known as the transformers '

secondary side) to the higher voltage side (also known as the transformers primarily

side). This challenge tends to be more common in parts of the distribution system
that serve primarily residential end-users, because demand in those parts of the grid
tend to be relatively low during the day (residents may be at work or school).

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