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Li et al. Complex Eng Syst 2023;3:1 https://dx.doi.org/10.20517/ces.2022.46 Page 7 of 15

Figure 1. Marine propulsion system based on AC shore power.

Figure 2A depicts a DC marine propulsion system based on DC shore power. By comparing the power
converters in Figures 1A and 2A, it is clear that the shipborne converter C15 has been replaced by the land-
based C35. In this scheme, the charger converter (C32) can be removed, and the shipboard battery pack can
be connected directly to the DC main bus. Onshore DC/DC converters can be installed at plugs to control
charging power and reduce ship weight. Figure 2B depicts an AC marine propulsion system based on DC
shore power. The ship bus is connected to the input end of the converter C42, so the charging path is the
same as in Figure 2A

3.3. Harbor AC/DC hybrid microgrid
Hybrid AC-DC microgrids are a promising alternative to existing distribution systems to achieve near/net
zero energy building goals. However, hybrid microgrid has increasingly high requirements for compact
structure, seamless integration of distributed generators and load, and flexibility of control, which cannot be
fully met by traditional grid architecture. Yu et al. proposed an integrated, reconfigurable AC-DC hybrid
[28]
microgrid architecture and its layered control strategy with flexible control . Yu et al. proposed a scalable
and reconfigurable cluster architecture for hybrid microgrids and the corresponding decentralized control
[29]
method .

Due to the gradual popularization of medium voltage direct current (MVDC) ships, namely the
diversification of new energy sources in the port area, the future port is actually an AC/DC hybrid power
system, as shown in Figure 3. Table 1 compares the advantages and disadvantages of the three microgrids.

4. CAPACITY PLANNING OF MICROGRID SYSTEM NEAR PORT
How to plan the capacity of photovoltaic and energy storage will directly affect the cost and benefit of grid-
connected optical storage microgrid. Effectively solving this problem can greatly impact the promotion of
new energy microgrids. However, capacity planning research based on limited historical data faces two
major difficulties: firstly, photovoltaic power generation is uncertain, and it is difficult to accurately estimate
its corresponding probability distribution; secondly, the photovoltaic power generation has high
dimensionality, that is, the photovoltaic power generation situation of each day and time period in a longer
dispatch period should be considered. Therefore, Xu et al. put forward the research idea of dimensionality
reduction based on scene clustering analysis and then proposed an optimization method to deal with the
uncertainty of photovoltaic power generation . Wang et al. proposed a flexible DC grid capacity planning
[30]