Page 40 - From Smart Grid to Internet of Energy

Introduction to smart grid and internet of energy systems Chapter 1 29

operate in DC, DERs can be easily integrated to microgrid and utility grid with
light controllers. The DC microgrid eliminates installation cost and line losses
due to a smaller number of power converters are required.
The microgrid controllers should comply with IEEE P2030.7 Standard for
the Specification of Microgrid Controllers and IEEE P2030.8 Standard for the
Testing of Microgrid Controllers () standards in addition to IEEE P1547-2003
Standard for Interconnection and Interoperability of Distributed Energy
Resources with Associated Electric Power Systems Interfaces. IEEE P2030.7
standard describes fundamental control operations and functions for transmis-
sion and dispatching conditions of microgrid. Thus, a microgrid can be capable
to autonomously operate and administer interconnection requirements itself.
The communication protocols and infrastructure are also highly required as well
as power sources in microgrid. The MGCC provides a standard and manageable
communication interface such as SCADA systems for supervisory control and
energy management systems [20].

1.2.3 Transmission and distribution networks
Transmission systems are used to carry multi MW rated power of high-voltages
at the output of bulk generation plants. Therefore, smart grid transformation of
conventional power grids should consider to improve transmission and distri-
bution networks as well. The integration of microgrids and large-scale RESs
makes existing transmission and distribution networks more complicated and
interconnected to serve power delivery. In addition to conventional AC trans-
mission networks, high-voltage direct current (HVDC) networks are intensively
being improved to enhance efficiency by decreasing line losses in long distance
transmissions. However, the high installation and operation costs of HVDC
networks limit the widespread utilization. The highly complex infrastructure
of transmission and distribution networks due to integration of distributed
generation requires sophisticated monitoring and control systems to ensure reli-
ability, sustainability and efficiency of smart grid deployment. Moreover, mon-
itoring and control technologies are required to prevent system faults caused by
excessive power demand, resource failures or unexpected system faults. Some
of smart grid systems used for transmission networks perform preventing
actions for automatic control of network by a centralized monitoring and control
center while others are based on decentralized control infrastructures where
TSO and DSOs take action against occurred faults [4, 22].
In the conventional power grid, generated high-voltage is transmitted to sub-
stations that are closely located to consumers and the distribution networks are
used to adjust and deliver low-voltage from substations to residential and indus-
trial consumers. Besides substation technologies in smart grid transformation of
conventional power grid, the grid-tie inverters play a crucial role in integration
of DERs to transmission substations and distribution networks. The grid-tie
inverters are essential devices to integrate DER and RES based microgrids to