IEEE Electrification Magazine - September 2017 - 37

Segment-Based Power Systems
with Distributed Control
The development of power systems toward segmented
systems containing microgrids, which will operate independently and interact with each other for optimized system performance, has found its use in shore-based power
systems. The rapid development of marine power systems
and electrification of the marine industry will be pushed in
this direction, as illustrated in Figure 5. This will allow for
more efficient and environmentally friendly power producMicrogrid 1
Microgrid 2
Microgrid 3
tion and will contribute to more resilient power systems.
System resilience and robustness, in the sense of power
system control, refers to the ability to adapt to unexpected
situations where the remaining microgrid segments must
Figure 5. A concept illustration of a shipboard electrical microgrid
cope with a new situation after one or several faults. Methphilosophy. (Photo courtesy of Ulstein Power & Control AS.)
ods for making systems more robust and improving their
ability to handle changes are the key factors when designing
strategies. Each microgrid will know the master plan for
resilient systems. As an example, the IIoT architecture, as
collaborated operation and the other microgrids' funcshown in Figure 3, can increase system resilience when used
tions. Each microgrid also will have an individual what-if
as part of microgrid coordination and control. The exchange
strategy for enhanced system resilience.
of status and performance data between microgrids will
The definition of the collaborative control strategy for
allow for variable control and protection strategies on the
the example in Figure 6 will need to consider the consumer
microgrid level that are coordinated with the collaboration
demand and priorities, power production, and energy storlevel. A variety of definitions for consumer priority and criteage. A typical setup for the consumer priority can be seen in
ria for balancing the power production, energy storage, and
the following example, where the priority loads (PLs) are
energy consumption will be key elements of the control
defined as three different PL groups: PL1, PL2, and PL3. The
strategies. When utilizing the individual microgrids' inherent capabilities and resilience as part of
Microgrid 1
Microgrid 2
collaborative energy management
strategies, there will be a great potenX-Connect IIOT-Based-Platform
X-Connect IIOT-Based-Platform
tial for efficient power production
SCU1
SCU2
and energy savings.

ME
CONV

CONV

BESS

Another example of system resilience is a green approach to harbor
operation, i.e., all-electric operation,
where the energy flow is coordinated between the individual
microgrids. In Figure 6, the power
system for a vessel, together with
the mechanical driven system, has
been defined as independent microgrids. However, they will have
collaborative strategies for utilizing
the energy and fault handling during a pure electric vessel operation.
This could be described in a more
generic way, where each microgrid
will have a clear definition of the
role in the system and the ability to
exchange and validate data as part
of individual microgrid control

Main ac System 2

G/M

Load

CPP

BESS

Main ac System 1

Green Approach to Harbor:
An Example of System
Resilience Utilization

Load

CPP

Figure 6. A two-split microgrid topology with segment-controlled power distribution. BESS: battery
energy storage system; CONV: conversion; ME, main engine; G: generator; M: electric motor; CPP:
controllable pitch propeller; SCU: segment control unit.

IEEE Elec trific ation Magazine / S EP T EM BE R 2 0 1 7

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