Recently, introduction of renewable energy sources like wind power
generation and photovoltaic power generation has been
increasing from the viewpoint of environmental problems. However, renewable
energy power supplies have unstable output due to the influence of weather
conditions such as wind speed variations, which may cause fluctuations of
voltage and frequency in the power system. This paper proposes fuzzy PD based
virtual inertia control system to decrease frequency fluctuations in power
system caused by fluctuating output of renewable energy sources. The proposed
new method is based on the coordinated control of HVDC interconnection line and
battery, and energy balancing control is also incorporated in it. Finally, it
is concluded that the proposed system is very effective for suppressing the
frequency fluctuations of the power system due to the large-scale wind power
generation and solar power generation and also for keeping the energy balancing
in the HVDC transmission line.