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

the last decade. While microgrids have been widely developed worldwide in different areas (cities, remote
communities, islands, etc.), they are still rare in port areas. This is because of the diversity of port loads
(refrigerated containers, quay cranes, ship cold-irons, buildings, etc.) and other reasons related to energy
[9]
management, load forecasting difficulties, and megawatt power demand . In addition, the development of
microgrids involves huge investments due to the use of storage solutions and renewable energy sources,
leading to problems of investment cost-sharing between authorities and port owners and the management
of microgrids from both commercial and energy perspectives [10,11] .

This paper summarizes and analyzes the research progress of green power supply technology in port
microgrids, and its organizational structure is as follows. The first part introduces the current development
status of port green power supply technology, and the second part introduces different power systems,
describes photovoltaic power generation in detail, and lists some running cases. The third part introduces
the DC microgrid, AC micro power grid, and the scenery storage integration of micro AC/DC hybrid power
grid and compares three kinds of systems, and the fourth part introduces the port capacity of micro power
grid planning and the existing methods. The fifth part introduces the distributed control method and multi-
time scale energy management strategy of port microgrids, and the sixth part lists the existing cases in the
world. The last section summarizes the findings and prospects the future research directions.

2. FLOATING WIND-PV-STORAGE POWER SUPPLY PLATFORM
2.1. Floating offshore wind power platform
Offshore wind farms are offshore wind power plants in water depths of about 10 meters, and electricity is
generated by turning wind turbines. Compared with onshore wind farms, offshore wind farms have the
advantages of not occupying land resources, basically unaffected by topography, higher wind speed, more
abundant wind energy resources, larger wind turbine capacity (3-5 MW), and higher annual utilization
hours. However, the construction of offshore wind farms is also technically difficult, and the construction
cost is generally 2 to 3 times that of onshore wind farms.

In recent years, the UK, Germany, Denmark, the United States, Japan, and other western countries have
accelerated the research of offshore wind speed. Chen et al. introduce the general situation of the early
development of offshore wind in these countries, describe the main characteristics and trends in the
development of offshore wind, enumerate the German electric field and the ocean buoyancy postures in
typical cases such as wind turbine experiment . Luo et al. review the offshore wind power grid general
[12]
topology structure, offshore wind reliability evaluation methods and indexes, models of offshore wind
power, collection systems in offshore wind farms, the reliability evaluation method of offshore wind power
is proposed, the failure probability of different components in the offshore wind power grid and fault repair
time for each component . On this basis, the operational reliability improvement technology of offshore
[13]
wind power is discussed from the aspects of the system and components. Ge et al. introduce key
technologies of intelligent operation control and maintenance of offshore wind farms , including offshore
[14]
wind power prediction technology, offshore wind power operation control technology, offshore wind power
equipment maintenance and management technology, and the comprehensive utilization of offshore wind
power and sea area. In addition, the differences between offshore wind power and onshore wind power are
analyzed according to the factors of offshore weather environment, resource characteristics, geographical
location, equipment operation, and so on. Based on this, the challenges and possible solutions in the above
technology fields are summarized, and the research status and achievements of these technologies are
analyzed and summarized. Li et al. present a flexible high-voltage large-capacity DC transformer
topology , explored based on the active bridge arm and thyristor valve group, the diode valve combination
[15]
way of the new converter. This combines the thyristor valve, diode group, and low conduction loss, high