IEEE Power & Energy Magazine - July/August 2017 - 83

Within the microgrid, encryption and authentication should be
used wherever possible. For mission-critical systems, it is important to use devices that support
secure protocols. For microgrids
that either inherit or have to use
devices that do not support any
secure protocols, the site's physical and network security must be
Absorption
Electric
Boiler
Storage
Air
Heat
designed to address the internal
Chiller
Chiller
Tank
Handler Exchanger
security requirement. Each external communication must be eval- figure 2. The South Campus microgrid.
uated to determine its nature. If
the data are private or proprietary
in nature, they must be transmitted in a secure fashion. or islanded. A diesel generator provides backup power for the
Digital certificates are an important component of Trans- campus when needed. A PV-battery combo energy management
port Layer Security (TLS, sometimes called by its older unit is connected to the main ac bus through an ac/dc inverter.
name SSL), a protocol designed to provide communication In addition, multiple rooftop vertical-blade wind generators
security over the Internet. When used with the TLS proto- are mounted on the building. The combination of solar power,
col, properly signed digital certificates prevent an attacker battery storage, and a natural-gas-burning system provides a
from impersonating a secure website or other server. If the clean ecosystem of generating resources to meet the power supdata are important but not private or proprietary, methods ply needs of the campus.
should be deployed to prevent false data from impacting
The natural-gas turbines have an efficiency rating of
the microgrid's operation.
about 33%, which is about the average efficiency of fossilfueled power plants in the United States, wasting two-thirds
of the heat energy. However, the CHP technology deployed at
Interfacing Between Layers
The data exchange between different layers of the microgrid the South Campus increases the efficiency of thermal energy
happens using data communication protocols common to conversion to electrical load consumption substantially and
industrial equipment (such as Modbus, DNP3, IEC 61850, achieves efficiencies of more than 60%. The mechanical
equipment, shown in Figure 3, that provides the data center
and BACnet).
and the rest of the building with heating and cooling is an
integral part of the CHP system.
South Campus Advanced

Microgrid Technology

In this section, we explain how these layers are implemented
in the South Campus advanced microgrid.

Layer 1: System Protection and Control
Layer 1 protection devices are those that operate in a fraction of a
second to prevent damage and stabilize the power system during

Layer 0: Physical
Equipment
The South Campus is a multistory
building data center microgrid. Figure 2 shows the power-producing
and -consuming equipment on the
campus. The power consumption
consists of critical and noncritical
loads, and the data center and life
safety equipment are considered a
critical load. The other power-consuming loads are part of the noncritical load. The campus load is served
by a combined heat and power
(CHP) microturbine as the primary
source of power. The South Campus
is connected to the electric utility
and is able to operate grid connected
july/august 2017

Utility
Connection

Small Wind

Office Space
Noncritical

Solar

Battery
Storage

Diesel
Generator

Microturbines

Critical Load
UPS
Data Center
Critical

figure 3. The South Campus heating and cooling systems.
ieee power & energy magazine

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - July/August 2017