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Page 4 of 15 Li et al. Complex Eng Syst 2023;3:1 https://dx.doi.org/10.20517/ces.2022.46

power density, advantages of the series configuration, special characteristics of the voltage of the active
bridge arm, and highly controllable current waveforms. Thus, with high-efficiency flexible commutation,
highly controllable power conversion, and the input and output DC current smooth, there is no need to
install a filter. Compared with the existing flexible DC power transmission modular multilevel converter
offshore platform, the technical economy of the proposed DC transformer topology is illustrated.

Offshore wind power is the focus of renewable energy development in China at present and in the next few
decades. However, compared with onshore wind power, offshore wind power faces challenges such as high
life-cycle electricity cost and the large impact of large-scale grid connection, and digitalization and
intelligence are the key to solving the above problems. The full DC offshore wind farm proposed by Li et al.
is a cutting-edge technology supporting the large-scale and far-reaching development of offshore wind
[15]
power , which is expected to improve the gathering and sending efficiency of wind power and reduce the
volume of offshore platforms. The 100 kV/100 MW DC transformer is a technical bottleneck for the full DC
offshore wind farm to be broken urgently. Research on key technologies of intelligent operation control and
maintenance of offshore wind farms can provide support and reference for reducing cost and increasing
efficiency of offshore wind power and large-scale safe and economic grid connection.

2.2. Floating photovoltaic power generation platform
In recent years, photovoltaic power generation technology has developed significantly. Considering issues
such as land costs, transmission costs, and water competition between power generation and agricultural
production, there is an increasing number of studies on floating PV. The offshore environment can make
full use of sunlight and is an ideal location for building photovoltaic power plants. Using floating technology
to install a solar photovoltaic system on the water is a new idea. A floating photovoltaic power station
adopts photovoltaic power station technology and floating technology, which has great development
potential.

Agrawal et al. evaluated the technical potential of floating solar photovoltaic power generation through
simulation, and discussed the development of floating solar photovoltaic technology from the aspects of
future photovoltaic potential, water saving and land-saving potential, and took Rajghat dam in southern
Uttar Pradesh, India as an example to estimate its annual power generation and reduced water
[16]
evaporation . Trapani and Redón Santafé reviewed various floating PV projects realized between 2007 and
2013 and envisaged future projects installed on the ocean using a composite laminated film material, which
will make the structure flexible and be able to adapt to the waves in the ocean and inundation of the
[17]
submersible array in adverse weather conditions . Oliveira-Pinto and Stokkermans noted that the
experience from inland floating solar energy projects can be used to expand and migrate from inshore to
offshore conditions, explore floating methods in the marine environment, and investigate photovoltaic
technology and solar power for floating in marine conditions . That paper also discussed the currently
[18]
available technologies, challenges and risks of the design and construction of the projects in the marine
environment. Floating in the sea is more flexible than a conventional rigid glass module, and thus Sahu et al.
introduced several key elements and put forward a hexagon photovoltaic array, which enables the whole
[19]
system to follow the movements of the waves, thus minimizing the waves caused damages . At the same
time, the effect of these parts and all kinds of design schemes are further described .
[19]

2.3. Photovoltaic power supply platform with energy storage
Wind speed is affected by weather, geography, and other factors, while its size and wind direction will
change regularly, and photovoltaic output is also closely related to weather changes. The change in light
intensity and temperature will affect the size of output, resulting in great randomness, volatility, and
intermittence of wind power and photovoltaic output. Scenery installed capacity of the entire network