Page 34 - From Smart Grid to Internet of Energy

Introduction to smart grid and internet of energy systems Chapter 1 23

The Smart Grid is accepted as the integration of distributed system automa-
tion and data transmission network by contributions of IEC 61850 standard.
Therefore, the matured power grid can be converted to Smart Grid infrastruc-
ture with automation and communication systems from generation to consump-
tion layers. The required comprehensive automation and communication
infrastructure are ensured by IEC 61850 services and protocols. Smart Grid
enables distributed automation for distribution generation, microgrid aggrega-
tion, transmission and distribution network management, ESSs, and manage-
ment concepts such as control, resiliency, and flexibility depending to IEC
61850 standards. These infrastructures and concepts are discussed in the follow-
ing sub headings as enablers of Smart Grid evolution.

1.2.2 Distributed generation and microgrid
The conventional electricity generation has been depended to primary energy
sources such as coal, natural gas, oil, and other fossil fuels. It is noted that
the annual global power generation is around 20,250 TWh in 2012, and it is
foreseen to reach up to 25,500 TWh in 2020 [14]. The conventional power
plants are based on thermal, hydraulic, and chemical systems. However, devel-
opment of power networks has promoted innovative researches on alternative
energy sources such as wind, solar, wave, geothermal, and biomass. The alter-
native sources are defined as DERs which play crucial role in the improvement
of Smart Grid in the context of power system. The DER integration to conven-
tional power grid enabled transforming the centralized generation to distributed
generation (DG) to facilitate Smart Grid evolution in power generation layer.
The integration of RESs to centralized generation cycle improved a new con-
cept called the decentralized generation where the consumers are also able to
generate by using micro-sources. Besides, high level penetration of wind tur-
bines, solar plants, geothermal plants, hydro-plants and various other sources
at multi MW level provide flexibility to generation initiatives.
The integration of DERs to existing power grid has brought a new concept,
microgrid, which is comprised by DERs, manageable loads, ESSs, and central-
ized or decentralized controllers. The generation capacity of a microgrid can be
a few kilowatts to multi megawatts regarding to its installation layer throughout
the power grid. The regular operation of a microgrid is described as grid-
connected (or grid-tied) to provide two-way power flow either generating or
consuming cycles of operation. The second operation mode of a microgrid is
performed when a fault or maintenance requirement occurred in main grid,
and thus microgrid shifts to islanded operation mode [15]. On the contrary of
its advantages, the penetration of large DERs cause to several challenging
issues for distribution grid and main grid. The intermittent structure of RESs
may pose fluctuations on injected power to the distribution grid and it can dam-
age overall stability of power grid at high integration levels of different power
plant types. Moreover, DERs are expected to tackle with extraordinary