Page 158 - Decision Making Applications in Modern Power Systems

122 Decision Making Applications in Modern Power Systems

this chapter, the OpenDSS, has been used by researchers worldwide and will
be presented with more details in the next topics.

5.2 Active electrical distribution systems
In recent years the characteristics of the current distribution networks are in
transformation. A passive network is becoming active with the increasing
penetration level of DG units, mainly wind and PV. The insertion of these
new types of generation, near the consumer centers, brings significant bene-
fits to the energy matrix of a country, to its economic, and its social and
technological development. DG can also bring economic benefits for both
customers and companies in the electricity sector if proper regulation is
applied. On the customer side, the decrease in dependence on centrally
generated energy, minimizing the generation from thermal power plants
which, besides environmental impacts, usually has high electricity costs, for
example, and brings advantages to economy [1].
On the side of companies in the electricity sector, the increase in DG
reduces the demand of the traditional system, thus postponing investments in
the construction of new lines and large power plants, provided that there is
quality control in the energy injected by the DGs. The peak periods of power
demand may also decrease, reducing costs of maintenance and replacement
of equipment, besides the decongestion of transmission and distribution lines
[1]. The losses in the system may also be reduced because the DG is prefera-
bly installed near the consumption center, which minimizes the power flow
in the transmission lines and consequently the power losses. Although these
changes in the distribution network bring benefits, there are also many
challenges linked to the insertion of DG in the network.
The direction of power flow in the traditional distribution network is
from a substation transformer to loads (residences, commercial centers, and
industries). However, with an increasing number of DG systems, it might
have moments on a day when the power flow reverses—that is, it goes from
the low voltage to medium and high voltage—which increases complexity
and uncertainty in the distribution system [2]. The reverse flow can lead
the system to an overvoltage condition, may cause protection devices to
malfunction, and can decrease system safety.
The following sections will present some problems that may arise with
the high penetration of DGs in the distribution systems.

5.2.1 Impact of high penetration of distributed generation
on power distribution systems
5.2.1.1 Voltage issues
Many texts in the literature report the problem of overvoltage due to the
high penetration of distributed PV systems. The usual voltage profile