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This paper proposes a multi-time scale scheduling strategy for a practical port coupled hydrogen-electricity energy system (CHEES) to optimize the integration of renewable energy and manage the stochasticity of port power demand. An optimization framework based on day-ahead, intra-day and real-time scheduling is designed. The framework allows coordinating adjustable resources with different rates to reduce the impact of forecast errors and system disturbances, thus improving the flexibility and reliability of the system. The effectiveness of the proposed strategy is verified by a case study of the actual CHEES in the Ningbo Zhoushan Port, and the impact of equipment anomalies on the port power system operation is studied through simulation of different scenarios. The results show that compared with a scheduling scheme without energy management strategy, CHEES with multi-time scale scheduling can save 25.42 % of costs and reduce 14.78 % of CO2 emissions. A sensitivity analysis is performed to highlight the impact of hydrogen price and soft open points (SOP) rated power on the system economy. This study not only provides a new perspective for the optimal scheduling of port energy systems, but also provides a practical framework for managing port energy systems to achieve green transformation and sustainable development.

According to the grid codes, the higher the voltage at the point of common coupling (PCC), the longer duration that the voltage-source converters (VSC) can stay connected to the grid. In hybrid ACDC distribution networks (HADNs), owing to the low capacity, VSC-based distributed generator (DG) closest to the fault point may fail to significantly support the voltage at the PCC through current injection. Therefore, other large-capacity converters such as flexible ACDC converters (FACs) should also inject currents to help it. However, in resistive-inductive HADNs, the voltage support effect is related to the current phases of converters, and the fault conditions. In this paper, circumstances under two fault position categories (upstream and downstream fault positions of DG) for double line-to-ground fault and three-phase short-circuit fault are analyzed. The interconnected sequence networks of HADNs under these two fault positions are proposed. Based on the proposed networks, the optimal current phase angles of DG and FAC for maximumly supporting voltages at the PCC of the DG are proposed. Moreover, the line sequence impedance calculation method is proposed. The simulation results verify the proposed strategy. The proposed strategy is suitable for low-capacity DGs in resistive-inductive HADNs to achieve voltage support and fault ride-through.

Direct-driven generation is considered one of the most reliable selections in wave energy conversion systems. Therefore, a direct-driven linear-rotary wave generator (LRWG), which can transfer the low-speed linear wave motion to the high-speed rotating motion of the rotor and then generate electrical power simultaneously, is proposed in this paper. The proposed LRWG comprises three parts: translator, common rotor, and stator. From the energy view, the proposed LRWG can be divided into two sections: the energy transmission section to increase the velocity of the wave and the energy conversion section to generate power. The initial design method is given to determine the main dimensions of the proposed LRWG. To meet the maximum power tracking control requirements, a multi-mode and multi-objective optimization method, which can consider both generator and motor mode, is proposed to improve the performance of the proposed LRWG by sensitivity analysis, response surface methodology, and non-dominated sorting genetic algorithm II method. Finally, a prototype and its experimental platform are developed based on one of the optimization schemes from the possible solutions to verify the proposed approach and the performance of the proposed LRWG.

Hydrogen-electricity integrated multi-energy systems are promising approaches to reduce carbon emissions in ports. However, the stochastic nature of renewable energy and the imbalance between the renewable generation and load demand in ports necessitate the design of an appropriate coupled hydrogen-electricity energy storage systems (CHEESS). This paper proposes a multi-objective optimization model for CHEESS configuration in random imbalanced port integrated multi-energy systems (PIMES), aiming to minimize its life-cycle cost and carbon emissions through co-optimization of sizing and energy management. A hierarchical two-stage framework is proposed to solve the multi-objective model. The proposed optimization framework is applied to a real PIMES at the Ningbo-Zhoushan Port. The results show that the proposed method can save 10.54 % of the monetary cost and 19.67 % of carbon emissions over the entire life-cycle of the system. The study demonstrates that the proposed framework has the potential to generate significant economic and environmental benefits and provides a feasible solution for port authorities seeking to implement CHEESS, aiming to promote sustainability in port operations.

The distributed frequency control system of microgrids, which relies on classical communication networks between distributed generations (DGs) for frequency regulation and restoration, is vulnerable to cyber-attacks. Quantum distributed controllers offer a secure quantum communication scheme but are less efficient because of continuous communication in quantum systems. This paper proposes a quantum distributed event-triggered secondary frequency control strategy for the islanded AC microgrid. The suggested event-triggered control significantly lessens the communication load and is Zeno-free. Furthermore, a novel false data injection attack (FDIA) scenario is introduced for the quantum-microgrid system. The non-periodic nature of communication can be exploited to directly identify and isolate compromised communication links, thereby enhancing the resilience of the quantum-microgrid system. Finally, simulation results on an AC microgrid with four DGs validate the effectiveness of the suggested control scheme.

In autonomous AC microgrids under short-circuit fault or overload conditions, the semiconductor switches of grid-forming inverter-based distributed energy resources are subject to serious damage due to the overcurrent issue caused by these low-voltage phenomena. Limiting the current of the grid-forming inverter at the primary level control structure and as a result, improving the low-voltage ride-through capability of the isolated microgrid is more desirable than using hardware protection equipment. The current limiting capability has been implemented for single-loop control structure to protect the inverter under overload conditions. The existing methods for limiting the current of grid-forming inverter during fault conditions, which are often implemented by considering two inner loops of current and voltage control, can be considered in three general categories: 1) limiting the reference current derived from the voltage controller, 2) changing the reference voltage obtained from the power-sharing loop by utilizing the concept of virtual impedance, and 3) changing the inverter's control structure. In fact, besides the current limiting strategy, other parts of the multi-loop control system could be efficient in the low-voltage ride-through operation. The effects of the reference frame of the control system for the independent control of the phases, the power-sharing method in autonomous microgrids including three-phase and single-phase grid-forming inverter-based distributed energy resources, and preventing voltage distortion when restricting the inverter current under voltage drop conditions are critical issues that are discussed in the literature review presented in this paper.

AbstractWe assessed hepatocellular carcinoma (HCC) risk associated with smoking and alcohol consumption and their interactions, using both questionnaire data and objective serum biomarkers. Information on smoking and alcohol consumption was collected at baseline from 450,112 participants of the EPIC cohort, among whom 255 developed HCC after a median follow‐up of 14 years. In a nested case–control subset of 108 HCC cases and 108 matched controls, known biomarkers of smoking (cotinine, nicotine) and habitual alcohol consumption (2‐hydroxy‐3‐methylbutyric acid) were annotated from untargeted metabolomics features. Multivariable‐adjusted hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (CIs) were computed, and multiplicative and additive interaction parameters were calculated. Compared to never smokers, current smokers had a higher HCC risk (HR = 2.46, 95% CI = 1.77–3.43) dose‐dependently with the number of cigarettes smoked per day (Ptrend <.001). Compared to light drinkers, HCC risk was higher in former (HR = 3.20, 95% CI = 1.70–6.03), periodically heavy (HR = 1.98, 95% CI = 1.11–3.54), and always heavy (HR = 5.51, 95% CI = 2.39–12.7) drinkers. Higher HCC risk was also observed in the highest versus the lowest tertiles of cotinine (OR = 4.88, 95% CI = 1.52–15.70), nicotine (OR = 5.80, 95% CI = 1.33–25.30) and 2‐hydroxy‐3‐methylbutyric acid (OR = 5.89, 95% CI = 1.33–26.12). Questionnaire‐assessed smoking and alcohol exposures did not demonstrate an HCC risk interaction at the multiplicative (MI = 0.88, 95% CI = 0.40–1.96) or additive (RERI = 0.71, 95% CI = −10.1 to 23.6; attributable proportion = 0.17, 95% CI = −0.52 to 1.16; synergy index = 1.27, 95% CI = 0.98–1.66) scales. Similar analyses with cotinine, nicotine, and 2‐hydroxy‐3‐methylbutyric acid also did not show interactions between smoking and alcohol consumption on HCC risk. Smoking and alcohol consumption are strong independent risk factors for HCC and do not appear to synergistically impact its risk, but larger studies are needed.

The transformerless cascaded H-bridge grid-connected inverter (TL-CHB-GCI) is an attractive topology in photovoltaic (PV) systems. However, due to lack of electrical isolation, the leakage current will inevitably appear between the grid and the PV panels, which causes electromagnetic interferences (EMI) and potential safety issues. For the operation of TL-CHB-GCI, another requirement is to maintain power balance between PV modules. Existing methods have not been able to address both issues adequately, therefore, a hybrid multicarrier modulation (HMM) method is proposed in this article. First, the TL-CHB-GCI model with parasitic capacitance is established, and the constraints of the leakage current suppression and power balance are derived respectively, where the intersection of vectors under dual constraint is taken as the candidate vectors. Then, based on the set of candidate vectors, a hybrid carrier is constructed, and a cycling strategy is designed. In HMM, the vector optimization ensures low leakage current, while the carrier cycling achieves intermodule power balancing. Furthermore, the proposed method can be generalized to any even-module TL-CHB-GCI. Finally, the effectiveness of the proposed method is verified by simulations and experimental results.

The energy cost of developing and deploying Generative AI (GenAI) models has exploded with their mass adoption, as has the ensuing carbon emissions. The climate impact of this is currently unknown. In Human-Computer Interaction, GenAI models are rarely trained but often used. Based on detailed review of 282 papers, we estimate this footprint from energy consumption of the total use of GenAI for CHI 2024 research as between 10,769.63 and 10,925.12 kg CO2e - equal to driving a car for more than 100,000 km. We show that in CHI research, GenAI is most often used for Prototyping, Evaluation & User studies, and that Data Collection and Fine-tuning models incurs the highest CO2st.1 We find that CHI submissions are unlikely to report GenAI use transparently, which makes precise calculations difficult. By measuring the usage of a subset of the papers on local hardware, we obtain estimations of the energy consumption and carbon footprint. Based on this evidence, we discuss and demonstrate ways to mitigate the issues of GenAI carbon footprint and lack of transparency.