As a major carbon emitter, how to create an effective path for low-carbon actions in the ports is extremely urgent. In view of the abundant renewable energy resources and hydrogen equipment in the ports, a multi-source output hydrogen storage coordination system in the ports is built to achieve the purpose of carbon reduction. From the perspective of multi-energy and low-carbon economic operation in the ports, an optimal operation method of multi-source output in the ports based on the optimal carbon emission flow(CEF) is proposed to take into account both carbon emission and economy. Based on the calculation method of the nodal carbon intensity of the power system, the calculation model of the carbon potential of the electric energy storage device and the electric hydrogen conversion device under the new power system is defined; Then, a multi-objective function with the lowest carbon emission and the maximum system economic benefit is established considering the influence of the charging and discharging depth and the number of cycles of the energy storage device; Finally, a non-dominated sorting genetic algorithm II (NSGA-II) is used to analyze a ports scenario integrated with new energy, electric energy storage equipment, and electric hydrogen conversion equipment. The results show that the proposed optimal operation method can effectively reduce the carbon emissions of the ports and improve the economy of the power system in the ports.

To reduce carbon emissions and promote the consumption of renewables in port areas, in this paper, a hybrid energy storage system (HESS) energy management method combined with the transportation-electricity coupling characteristics of ports is proposed. The proposed method solves the energy imbalance and mitigates random power fluctuations through day-ahead scheduling and intraday adjustment, respectively. In day-ahead scheduling, a load power model based on berth-quay crane (B-QC) scheduling is presented. Furthermore, to optimize the operation economy of ports in consideration of carbon emission cost, a day-ahead transportation-electricity scheduling method combined with B-QC is presented, which realizes the integrated demand-side management of port transportation and power load. In intraday adjustment, a variable structure scenario tree prediction model of random power is formulated, and a stochastic model predictive control (SMPC) strategy is proposed to reduce the power disturbance to the main grid. Simulation results based on historical data show that in sunny and cloudy scenarios, compared with no collaborative operation, the operation cost under the proposed method is reduced by 31.9% and 7.5%, respectively, and the total carbon emissions are reduced by 9.4% and 3.8%, respectively. The average power fluctuation of the main grid is lower under the SMPC strategy.

A carbon responsibility allocation method based on the complex structure carbon emission flow theory is proposed to address the problem posed by the unclear carbon responsibility allocation of each link in the low-carbon development of electric power. First, the calculation method, distribution characteristics, and mechanism of carbon emission flow were analyzed. The “carbon potential of complex structure” concept was introduced to track “carbon trajectory” and “green trajectory” by harnessing the ability of complex structures to retain two-dimensional information. Subsequently, the carbon responsibility allocation methods for network loss and users’ electricity consumption behavior were developed to realize the accurate carbon responsibility allocation of each system link. Finally, the effectiveness and advancement of the proposed carbon responsibility allocation method were verified using the improved IEEE 6-bus and 30-bus test systems. The application of the proposed complex structure carbon potential in the carbon emission flow theory expands the research dimension of electric power carbon emission for low-carbon development from the “carbon perspective,” provides a novel optimization space for the operation of the distribution network and realizes the carbon emission flow theory, which serves as a bridge from calculation evaluation to optimization decision.

The analysis and calculation of the short-circuit fault current in the DC grid is of great significance to the design and configuration of the converter station and DC circuit breaker parameters. The existing flexible DC system not only includes the modular multilevel converter (MMC) converter, but also needs power equipment such as the fault current limiter and DC circuit breaker. Therefore, the system modeling and short circuit calculation of the multi-terminal DC system after adding the DC circuit breaker are also of great significance for the design of DC power system parameters and the grid troubleshooting ability. In this paper, firstly, the parameters of the four-terminal DC system of the modular multilevel converter (MMC) are simplified, and the analytical solution of the short circuit fault current of the multi-terminal DC system is given. Then, the external characteristics of the cascaded hybrid DC circuit breaker are modeled. Based on the equivalent circuit of the fault current in different stages, the short circuit calculation method of four-terminal MMC system with DC circuit breaker is obtained. This method can effectively describe the overall trend of fault current and provide the basis for the configuration of DC line protection settings and DC circuit breaker related parameters.