Page 28 - Hybrid-Renewable Energy Systems in Microgrids

Hybrid PV–wind renewable energy sources for microgrid application: an overview 13

connection in a hybrid system. However, such configurations depend on the type of
the ESS used in that hybrid system. With a BSS or Supercapacitor (SC), such arrange-
ments might be possible, whereas for the pumped hydrostorage (PHS) or compressed
air energy storage (CAES), aggregated configuration is preferable.
There are several types of ESSs available in the existing literature, and in prac-
tice, they are extensively used in a hybrid energy system. Nonetheless, all the ESSs
have not been used in HRES-based MG yet, but they are used in typical MG on the
basis of at least one renewable energy technology. BSS has widely been used in all
the levels of power system for a long time for different purposes. Recent trend in
smart grid has considered the BSS as a primer of the smart grid, including smart
home energy management, smart building management, sustainable energy move-
ment, smart city, etc. A downward trend in battery price, operational flexibility,
higher energy density, etc. has resulted in the increasing use of BSS in power sys-
tem. In a MG concept, BSS is used either as a support to the system along with the
diesel system or taking the responsibility to retain the reliability and quality of the
hybrid system. The feasibility study of hybrid configuration is determined in Ref.
[11] using a BSS with PV–wind hybrid system on the basis of the demand, installa-
tion, and operation costs.
PHS has been widely used in MG operation as an ESS. The operational principle of
PHS is the same as in a typical hydropower plant, filling the higher reservoir using sur-
plus energy and using the stored water to drive the turbine in peak time. In Ref. [42], a
study of demand response (DR) and PHS contribution is discussed to curtail the oper-
ating cost and reduce the burden on the connected grid. However, less efficiency and
high investment cost can be considered to carry out cost–benefit analysis of the PHS.
Flywheel energy storage system (FESS) follows the kinetic energy principle to
store the energy [43]. Out of many possible applications, the study of overall system
stability improvement in a PV–wind–ESS MG in terms of volt/hertz control is carried
out by using a FESS in Ref. [44].
In a CAES, air is compressed using the surplus energy and releases the stored
energy during the peak time to meet the demand. A study in Ref. [45] investigated the
overall prospects of CAES in a wind–diesel hybrid system and the feasibility to satisfy
the technical, economic impediment of the wind farm.
With 10–100 times higher power density than those of batteries [46], SC can
provide high-power support, but only for a short-term period. It can provide the
voltage support in a MG, thereby reducing the adverse effects of DG into the main
grid [47].
Superconducting magnetic energy storage (SMES) with high power and energy
density can improve the dynamic stability of a wind-connected MG system [48].
They can also be used for the short-term support in case of unintentional islanded
operation of a grid-connected MG due to disturbances, power quality support,
and reduction of energy buffer in MG. A brief summary of ESSs is given in
Table 1.3.