IEEE Electrification Magazine - June 2017 - 58

Solar Inverter

Battery Inverter

Diesel
(a)

Battery Inverter

(b)

Figure 1. A configuration of different types of remote microgrids with different power ratings. (a) Remote microgrids with lower power ratings
(2-4 kW). (b) Remote microgrids with higher power ratings (6-24 kW).

microgrids are also promising candidates because of their
significant advantages in terms of high energy conversion
efficiency, absence of harmonics and reactive power, and
low complexity in resynchronization and disconnection

+Vdc

Converter
Interface

Converter
Interface
Energy
Storage

PV
Converter
Interface

Converter
Interface

Wind

dc Load
Inverter
Interface

Converter
Interface

ac Load

Diesel
Diesel
Generator

(a)
+Vdc 0 -Vdc
Converter
Interface

Converter
Interface

Energy
Storage
Converter
Interface

Converter
Interface

Inverter
Interface

Converter
Interface

Wind

dc Load

ac Load

Diesel
Diesel
Generator

Voltage
Balancer
(b)
Figure 2. A configuration of dc remote microgrids. (a) Unipolar
configuration. (b) Bipolar configuration.

I E E E E l e c t r i f i c ati o n M agaz ine / j un e 2017

of individual DERs, among others. Because many DERs
feature dc output (e.g., PVs and battery storage), it is a
straightforward concept to integrate them by using dc
common coupling.
With the deployment of dc remote microgrids, com-
pared with ac remote microgrids, two types of system
architectures can be used: unipolar configuration and bipo-
lar configuration. As illustrated in Figure 2, for remote
microgrids with unipolar configuration, the common dc
bus features only two voltage potentials, +Vdc and 0, where-
as for remote microgrids with bipolar configuration, the
common dc bus features three voltage potentials: +Vdc, 0,
and −Vdc. The unipolar microgrid configuration is easily
implemented, whereas the bipolar microgrid configuration
features agile operation and high reliability. The deploy-
ment of different types of configurations is determined by
the operation requirements of remote microgrids.

Maximized Capabilities: Optimal Design
Implemented by using DeRs
To guarantee the cost-efficient and reliable operation of
remote microgrids, a proper design is essential. This
design depends on an optimization problem for remote
microgrids that is formulated to determine the optimal
size and siting (location) of DERs, energy storage, thermal
devices, and loads. The objective of this optimization
problem is to minimize the total cost of remote
microgrids, including both investment and operation
cost. Because different operation requirements may be
considered when developing remote microgrids, the
objective of the optimization problem can be changed on
the basis of specific needs. For example, it can be formu-
lated to minimize carbon dioxide (CO2) emission. Mean-
while, different objectives can be combined by using
specific weighting factors.
To derive an effective model with sufficient details and
accuracy, multiple parameters should be taken into
account for each device. Using a PV panel as an example,
the formulation of the optimization problem is affected by

Table of Contents for the Digital Edition of IEEE Electrification Magazine - June 2017