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42 Hybrid-Renewable Energy Systems in Microgrids

protection, generator control, and voltage protection devices are considered as this
protection and control systems.

2.3 Automation and control
This automation and control layer is used by the programmable logic controllers,
which are used to execute the program in automated process.

2.4 Monitoring, scheduling, optimization, and dispatch
This layer provides observance, scheduling, optimization, and dispatch of microgrid
resources such as solar PV, wind, and storage systems from the utility grid to reduce
the full running cost of the microgrid.

2.5 Energy market and coordinating the response of smart grid
operation
This method performs the interaction between the grid and grid applications like out-
age management, and asset management.

3 DC microgrid and AC microgrid

In this section, we discuss briefly on general topology and concept of DC microgrid
and AC microgrid.

3.1 DC microgrid

The concept of DC microgrid is strictly related to the local power generation of DC
grid and it could be executed in 21st century generation and distribution power system.
Nowadays, the DC microgrids are used for power distribution networks in marine,
automotive, and manufacturing industries [17]. The power generation sources and the
connected load distance should be at a minimum; cost-effective wind and solar power
also need the requirement of DC microgrid [18,19]. The structure of DC microgrid can
be illustrated in Fig. 3.3. Solar panel, wind turbines, ESSs, and grid is connected to
the DC bus through the converter. Solar panels are connected to the DC bus through a
DC–DC converter. The wind turbines are connected to the DC bus through an AC–DC
converter. The ESS through battery technology connected to the DC bus via a DC–DC
converter [20].
In the distribution system, the DC microgrid can be classified into three types:
monopolar, bipolar, and homopolar configurations [21]. Power loss reduction, volt-
age drop reduction, and increase in electric lines capacity are the advantages of DC
distribution system. The low voltage DC link in DC microgrids is simply supported by
bipolar operation wherever the loads can be connected between the two polarities of