IEEE Power & Energy Magazine - July/August 2017 - 73

technical requirements. In turn, these derived requirements
are primary inputs to the design strategy for the integration and
interoperability of system components.
We propose to assign control functionality of key system
components based on their temporal requirements. Primary
control is predominantly hosted locally; it reacts within a
fast time scale, is autonomous, and acts on individual DERs.
Examples of this include solar photovoltaic inverter controllers, natural gas generator governor controls, and similar
devices. Secondary control has a wider sensing and command coverage area on a slower time scale and coordinates
control action across various DERs. It must be coordinated
with lower control levels and sometimes to higher levels,
according the operational requirements. Examples include
supervisory control and data acquisition (SCADA) and data
concentration. Tertiary control involves software to address
advanced control capability such as DER optimization
based on cost, CO2 emissions, or a combination of
both. Tertiary control temporal requirements
are less stringent, typically several minutes.

Systems Engineering
Principles
Systems engineering is an interdisciplinary field that focuses on how to
design and manage complex engineering systems over their life cycles.
Its methods and tools have been
embraced mostly by the aeronautical and military industries.
Its broad domain includes work
processes, optimization methods, risk management tools, and
more. It overlaps technical and
human-centered disciplines such
as control engineering, industrial
engineering, organizational studies, and project management.
The opportunity for using systems engineering principles is rising with the increase in complexity
of systems and projects in the energy
generation, transmission, and delivery
industries. Today, when modernizing
these electric power systems, a project's
complexity is significantly higher as compared to earlier decades. Such a transformation
can be attributed to higher component count,
diverse communication protocols, and a greater
number of disciplinary fields that are involved. Our
view is that systems engineering tools and processes are
applicable to integrating complex systems in energy infrastructure. This approach offers the utility industry the rigor
and framework to guarantee interoperability across components and technologies.
july/august 2017

Microgrid technology deployment, with its modern control
and monitoring components, involves the integration of complex subsystems that produces systemwide functions and features tailored to specific business, operational, and technical
needs. However, typical budgets and time frames are tighter,
for example, than those allowed for modernizing defense
systems. Therefore, the clever use of specific systems engineering methodology is proposed to transform stakeholder
input into an optimum innovative technology adoption. While
new to the energy management business, this methodology
will ensure that all likely aspects of a microgrid platform are
considered and integrated into a whole. For example, derived
technical requirements are listed in Table 1 as they relate to
a small sample list of our primary stakeholder's requirements
(our utility customers).

Microgrid Platform Definition
To start, an industry-accepted definition of a microgrid provided by the U.S. Department of Energy is: "...a group of
interconnected loads and DERs within clearly defined electrical boundaries that acts as a single controllable entity with
respect to the grid. A microgrid can connect and disconnect
from the grid to enable it to operate in either grid-connected
or island mode."
This definition presents microgrids as small-scale power
systems with the ability to self-supply, island, distribute, and
regulate the flow of electricity to local customers. A microgrid
can be thought of as an aggregator of DERs, including both generators and managed loads. A microgrid is capable of supporting a predefined number of loads but is typically not designed to
operate indefinitely without being connected to the traditional
utility infrastructure. Figure 1 offers a sample microgrid configuration on a radial distribution system.

table 1. Sample derived technical solutions
from stakeholder requirements.
Stakeholder (Customer)
Requirements

Derived Technical Solutions
for Control Architectural
Design

Reliability

Monitoring and command
of system components
for mitigating effects of
demand response events and
nondispatchable generators

Lower cost

Advanced DER portfolio
optimization based on fuel cost,
weather, locational marginal
pricing, and more

Lower emissions

Advanced DER portfolio
optimization based on CO2
emissions

Resiliency

Route energy from alternative
power sources for delivery
to load

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