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Li et al. Complex Eng Syst 2023;3:1 https://dx.doi.org/10.20517/ces.2022.46 Page 9 of 15

Figure 3. AC/DC hybrid microgrid topology.

and ships, and designed the required communication lines. The system has a maximum power of 30 MW
and the required communication lines are designed to minimize operating costs, pollutant emissions and
wind power fluctuations. Gutierrez-Romero et al. design port power grids that meet the requirements of
[38]
onshore power supply and RES scale based on the needs of different types of ships . Considering the
available area of PV, its output power can reach 9.7 MW, onshore wind turbine 36.3 MW and offshore wind
turbine 16 MW, with a daily output of 314 MWh and a maximum power of 13.1 MW. Cold ironing of ships
via land power and the use of the RES system can reduce carbon dioxide emissions from moored auxiliary
generators by 10,000 tons per year. These three systems include a cold ironing system but no energy storage
system. The microgrid referred to Kotrikla et al. contains a 5 MW PV system and a 6 MW wind turbine
with a daily output of 22 MW hours and a maximum power of 900 kW . While the system also has no
[39]
energy storage, it connects the surplus of renewable generation to the onshore grid to power other loads.
Renewable energy provides the energy needed for cold ironing through the main grid at low power without
storage. Ahamad et al. introduce the optimal design of microgrid, give the size and energy planning of
microgrid, and evaluate the performance of microgrid for load power supply . The integrated system
[40]
consists of a 200 KW PV, a 4.95 MW wind generator and a 465 MWh grid-connected battery, with a daily
output of 39 MWh and a maximum power of 5.2 MW. The optimization results and sensitivity were
analyzed by using the HOMER software. Wang et al. propose a two-stage optimization framework to solve
[41]
the optimal design problem of a seaport hybrid renewable energy system . Kumar et al. propose a
microgrid suitable for electric ferry charging and cold ironing, which includes a 33 MW photovoltaic power
generation device, a 30 MW wind turbine, and a 35 MWh lithium-ion battery . However, the system is
[42]
limited due to line congestion, battery power and capacity.