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J. Marchgraber, W. Gawlik:
"Investigation of Black-Starting and Islanding Capabilities of a Battery Energy Storage System Supplying a Microgrid Consisting of Wind Turbines, Impedance- and Motor-Loads";
ENERGIES, 13 (2020), 19; 1 - 24.

Microgrids are small scale electrical power systems that comprise distributed energy
resources (DER), loads, and storage devices. The integration of DER into the electrical power system
basically allows the clustering of small parts of the main grid into Microgrids. Due to the increasing
amount of renewable energy, which is integrated into the main grid, high power fluctuations are
expected to become common in the next years. This carries the risk of blackouts to be also more
likely in the future. Microgrids hold the potential of increasing reliability of supply, since they are
capable of providing a backup supply during a blackout of the main grid. This paper investigates the
black-starting and islanding capabilities of a battery energy storage system (BESS) in order to provide
a possible backup supply for a small part of the main grid. Based on field tests in a real Microgrid,
the backup supply of a residential medium voltage grid is tested. Whereas local wind turbines within
this grid section are integrated into this Microgrid during the field test, the supply of households
is reproduced by artificial loads consisting of impedance- and motor loads, since a supply of real
households carries a high risk of safety issues and open questions regarding legal responsibility.
To operate other DER during the island operation of such a Microgrid, control mechanisms have to
ensure the power capabilities and energy reserves of the BESS to be respected. Since the operation
during a backup supply of such a Microgrid requires a simple implementation, this paper presents
a simple master-slave control approach, which influences the power output of other DER based on
frequency characteristics without the need for further communication. Besides the operation of other
DER, the capability to handle load changes during island operation while ensuring acceptable power
quality is crucial for such a Microgrid. With the help of artificial loads, significant load changes of the
residential grid section are reproduced and their influence on power quality is investigated during
the field tests. Besides these load changes, the implementation and behavior of the master-slave
control approach presented in this paper is tested. To prepare these field tests, simulations in
MATLAB/SIMULINK are performed to select appropriate sizes for the artificial loads and to estimate
the expected behavior during the field tests. The field tests prove that a backup supply of a grid section
during a blackout of the main grid by a BESS is possible. By creating the possibility of operating
other DER during this backup supply, based on the master-slave control approach presented in this
paper, the maximum duration for this backup supply can be increased.

microgrid; black-start; islanding; master-slave control approach; cold load pickup

http://dx.doi.org/10.3390/en13195170