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Integrated renewable energy sources with droop control techniques-based microgrid operation 41

Figure 3.2 General framework of micro grid technology.

control has two control schemes. Under the inductive condition, real power-frequency
(P/f) and reactive power-voltage (Q/V) droop control are deduced within the AC
microgrids. The application of low voltage AC network, active and reactive power
control are coupled once the resistance and inductances are considered [12]. Among
these methods, voltage and frequency droop control methods have been developed for
both AC and DC microgrids [13].
In this chapter, grid-connected hybrid solar photovoltaic (PV) and battery energy
storage system (BESS) have been studied. The aim of hybrid renewable energy sys-
tem is to extend the reliability and efficiency of the system. In distribution generation
system BESS is usually preferred because of the low cost and better efficiency of the
battery technology [14,15].

2 Framework of microgrid technology

The framework of microgrid technology consisting of five layers has been illustrated
in Fig. 3.2 [16]. Each layer acts upon various operating conditions on its own perspec-
tives. The framework of microgrid technology can be briefly discussed as given later.

2.1 Physical equipment

This layer includes various distributed energy resources like solar PV, wind, battery
energy storage, fuel cells, diesel generators, micro turbines, and point of common
coupling (PCC) that is connected to the utility grid. Additionally a load type consists
of critical and noncritical loads, dispatchable loads which can be controlled.

2.2 Protection and control
This layer deals with the microgrid system, which should be operated in abnormal
conditions by disconnecting the faulted system. Over current protection, frequency