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Li et al. Complex Eng Syst 2023;3:1 https://dx.doi.org/10.20517/ces.2022.46 Page 11 of 15

For energy management research on a short time scale, in order to improve the system operation reliability
and reduce network losses, the drooping slop-reactive power joint optimization is carried out based on the
[55]
day-ahead scheduling results . Xiao et al. establish an intra-day rolling optimal scheduling model based on
the model predictive control method to ensure that the microgrid has a certain adjustable capacity while
consuming renewable energy . For studies on shorter time scales. Gong et al. divide microgrid energy
[56]
management into five-time scales: 1 day ahead, 30 min to 1 h within the day, 5 to 15 min, 1 min and real-
time scheduling, which make the scheduling plan more accurate and reduce the pressure of real-time
[57]
adjustment .
In the study of real-time energy management, Bao et al. comprehensively consider different generation side
[58]
resources to establish a real-time scheduling model and improve the prediction accuracy of wind power .
Ma et al. develop a real-time and cost-effective residential load scheduling framework , whose cost-
[59]
effectiveness can vary with different consumption patterns and is very sensitive to load behavior. Arun et al.
propose a heuristic algorithm for real-time load scheduling, which aims to reduce the electricity bill while
keeping the total consumption under the maximum demand limit . Ye et al. solve the real-time demand-
[60]
side management problem of microgrids equipped with renewable energy and storage systems, and show
that game-theoretic energy scheduling supported by communication networks can smooth the peak-to-
[61]
average ratio (PAR) of power consumption .
In the selection of multiple time scales, the selection of a long time scale is generally 1 day, and the selection
of a short time scale is different. A dense time scale will increase the solution time of the scheduling plan,
while a sparse time scale will increase the pressure of real-time adjustment. Therefore, it is necessary to
select an appropriate time scale for energy management research of microgrids. Table 2 lists the advantages
and disadvantages of different time scale controls.

6. SOME COMMERCIALLY OPERATIONAL CASES IN THE WORLD
Jurong Port was built in 1963 and has served Singapore as its main port of entry for more than 50 years.
Sunseap Leasing, a unit of Singapore’s leading solar system developer Sunseap Group, has partnered with
the port to develop the 76,000-square-metre system, which sits atop the Jurong Harbor Warehouse. With a
solar power system of 9.5 MWP, the port generates more than 12 million kWh of electricity per year, which
is expected to provide 60% of the port’s total electricity demand and reduce carbon dioxide emissions by up
to 5200 tons per year. The port will further integrate 5 MWp’s photovoltaic modules and eventually become
the world’s first zero-carbon footprint port. Due to the intermittency of PV integration, 10,000 to 15,000
MWh of PV energy per year will remain untapped until 2018. Therefore, Jurong Port urgently needs
microgrid technology to facilitate the integration of renewable energy .
[62]

The port of Hamburg and the city of Hamburg have invested in renewable energy since the German city of
Hamburg pioneered wind energy in the early 1990s. Wind energy has been central to Hamburg’s renewable
energy strategy, with the port area accounting for half of wind energy production and the city also
participating in the development of offshore wind farms. Large turbines are being tested off the coast at
Cuxhaven and Brunsbuttel, and the scheme is playing a major role in boosting renewable energy in the
ports to facilitate the development of solar facilities on the docks and warehouse roofs. Two units are
already in service. Hamburg’s port also uses solar thermal energy. The HPA office’s hot water is generated
by a solar thermal unit on the roof, saving 56,000 kW/h of electricity per year.

The Netherlands Energy Research Centre, the Netherlands Institute for Applied Scientific Research, the
Netherlands Institute of Oceanography, the ABU Dhabi National Energy Company, and the Ocean Energy