IEEE Electrification Magazine - December 2019 - 76

As listed in Table 2, technology maturity is not uniform at the different control levels, represented as a
function of technology readiness level. Several functionalities must be developed and proved to access marine
microgrids as controllable resources, which are available
when the ship is connected to the land grid.
The assessment is based on publications, research
projects, experimental results availability, and industrial
survey, including R&D activities and custom projects.
Some interesting concerns arise from the potential
participation in energy and service markets. An effective
solution is to generalize the microgrid secondary control
issue based on the area control error (ACE), which is typically related to large power system applications. Applying the ACE concept to the world of microgrids is often
referred to as the microgrid control error (MCE). The participation factor defines the microgrid contribution to the
main system frequency regulation. This concept paves
the way to an integrated management vision of
microgrids in ADN control, where the DSO can set the
participation factor, offering regulation capacity defined
by a market-level negotiation. In the islanded operating
mode, there is no power exchange at the PCC and the
secondary regulation control must restore the microgrid
frequency to the nominal value. The MCE becomes equal
to the frequency error, and the MGCC shares the regulating power with the generating units and CLs according
to the participation factors of each devices involved
in the secondary regulation. The sum of the internal
participation factors is equal to one, while in the

grid-connected mode, it must be equal to the participation factor of the microgrid. Distributed frequency regulation services will be essential for future grids, which
are becoming weaker in terms of equivalent inertia, due
to the integration of inverter-driven renewables.

Integration of Shipboard Microgrids
Into the Distribution Network Operation
The SPS connection to the shore power, which is locally
managed, is a reality despite missing the coordination
between the DMS and the PMS. The focus of this article is
to show the possibility of integrating shipboard microgrids
as active resources within the terrestrial distribution network. The shore connection procedure and management
are coordinated by the DMS and PMS, from the synchronization and load transfer to the achievement of an intentional electrical island sustained by the SPS, which is an
example of active utilization of the marine microgrid for
distribution system operation purposes.
To prove the target concepts, the complete models of
the land grid and the ship were carried out in a DIgSILENT PowerFactory simulated environment. The SPS
studied is composed of two diesel generators with a
rated power of 2 MVA each. The main distribution is a
690-Vac, 50-Hz system, and it is executed by two busbars connected by a normally closed tiebreaker. This
type of system architecture covers a large variety of
applications, i.e., Ro-Ro, ferries, and naval ships, with
installed capacities from 1 to 10 MW. The propulsion
system has not been taken into account due to its

TABLE 2. The distribution system and microgrid functionalities.

I E E E E l e c t r i f i cati o n M agaz ine / DECEMBER 2019

IEEE Electrification Magazine - December 2019

Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2019