ABSTRACT:
A
dc microgrid is a low inertia system dominated by power converters. As a
result, the change rate of the dc voltage is very fast under power variation.
In this study, a distributed virtual inertia control is proposed to enhance the
inertia of the dc microgrid and decrease the change rate of the dc voltage. The
inertia of the dc microgrid can be enhanced by the kinetic energy in the rotor
of the permanent magnet synchronous generators (PMSG)-based wind turbine, the
energy stored in batteries and the energy from the utility grid. By introducing
a virtual inertia control coefficient, a general expression of the inertial
power provided by each controllable power sources is defined. The proposed
inertia control is simply a first-order inertia loop and is implemented in the
grid-connected converter, the battery interfaced converter and the PMSG
interfaced converter, respectively. The small-signal model of the dc microgrid
with the proposed inertia control is established. The range of virtual inertia
control coefficient is determined through stability analysis. Finally, a
typical dc microgrid is built and simulated in Matlab/Simulink, and the
effectiveness of the proposed control strategy and correctness of the stability
analysis are verified.
CONCLUSION:
In this paper,
the virtual inertia control of the dc microgrid is proposed and the small-signal
stability analysis is carried out for the dc microgrid with virtual inertia
control. Conclusions are summarised as follows:
i.
Considering the potential of inertial support capability of rotating equipment
and storage equipment in the dc microgrid, the virtual inertial control of
G-VSC, W-VSC and B-DC, are designed to provide a virtual inertial support for
the system. Especially, the inertia power provided by the utility grid, wind turbine
and battery can be adjusted by modifying the corresponding coefficient of
virtual inertia control.
ii.
A small-signal model of the dc microgrid is established. The stability of the
dc microgrid with additional virtual inertia control is analysed and the range
of the virtual inertia control coefficient is determined.
iii.
The proposed virtual inertia control is suitable for both ac/dc converters and
dc/dc converters, and is unconstrained by the voltage hierarchical coordinated
control strategy. Once the voltage fluctuation occurs, the inertia power provided
by the proposed virtual inertia control can help to improve the inertia of the
system.
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