This paper proposes an AC-linked hybrid wind/photovoltaic (PV)/fuel cell (FC) alternative energy system for stand-alone applications. Wind and PV are the primary power sources of the system, and an ...FC-electrolyzer combination is used as a backup and a long-term storage system. An overall power management strategy is designed for the proposed system to manage power flows among the different energy sources and the storage unit in the system. A simulation model for the hybrid energy system has been developed using MATLAB/Simulink. The system performance under different scenarios has been verified by carrying out simulation studies using a practical load demand profile and real weather data.
This paper presents a physically based dynamic model for tubular solid oxide fuel cells (SOFCs) based on the electrochemical and thermodynamic characteristics inside SOFC. The diffusion, material ...conservation, electrochemical, and thermodynamic equations are used to develop the SOFC model. The effect of temperature on the steady-state (V-I and P-I) characteristics of the SOFC model has been studied, and the model responses have been obtained for constant fuel flow as well as for constant fuel utilization operating modes. The dynamic characteristics of the model are investigated in small, medium, and large timescales, from milliseconds to minutes. The model has been implemented in MATLAB/Simulink and used to investigate the distributed generation applications of SOFCs.
The integration of distributed generation (DG) sources can cause significant impacts on distribution networks, particularly the changes in magnitudes and directions of short circuit currents that may ...lead to false tripping or fail to trip over-current protection relays in the system. It is expensive and technically challenging to redesign/reconfigure and/or to replace the original protection system for a distribution network. If not appropriately handled, this issue can be a big hurdle before the wide use of DG. Based on the impact analysis of the number of DGs, their locations and capacities upon short circuit currents, this paper presents an optimal DG placement method to maximize the penetration level of DG in distribution networks without changing the original relay protection schemes. Genetic algorithm is used to find the optimal locations and sizes of DG in distribution networks. Simulation studies have been carried out on a three-feeder test distribution network and a widely used 33-node test system to show the effectiveness of the proposed method.
•An optimal sizing scheme and an operating strategy are developed for an island microgrid.•System unit sizing and operating strategy are jointly optimized for the microgrid.•A genetic algorithm-based ...method was used to optimize the microgrid multi-objective solution.•The proposed methods are verified using the operational data obtained from the microgrid developed.•Practical considerations and realistic lessons learned are presented.
An optimal unit sizing method is presented for stand-alone microgrids with practical system and component life-cycle considerations. The proposed method has been applied to the design and development of a real microgrid system on Dongfushan Island, Zhejiang Province, China, consisting of wind turbine generators, solar panels, diesel generators and battery storage units. A genetic algorithm (GA)-based method is used to solve the sizing optimization problem with multiple objectives including the minimization of life-cycle cost, the maximization of renewable energy source penetration and the minimization of pollutant emissions. The actual system configuration and the operating strategy are discussed in detail in this paper, as well as the operational experience regarding the unique microgrid issues observed and lessons learned that may be useful for future microgrid design and development.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper analyzes the reliability of large scale battery storage systems consisting of multiple battery modules. The whole system reliability assessment is based on the reliability evaluation of ...system components including individual battery modules and power electronic converters. In order to evaluate the reliability of a battery module, a reliability model based on the state of health of individual battery cells is introduced. The state of health of a battery cell is calculated based on the capacity fade of the cell using a weighted Ampere-hour throughput method. A universal generating function-based method is then introduced to evaluate the reliability of the battery module. The reliability model of dc/ac power electronic converters is also presented in this paper. The reliability analysis is conducted for battery storage systems with different system configurations and management strategies, and the influence of system configuration on the reliability of battery system is studied. Comparative studies are conducted for a classic battery energy storage system (BESS) and a reconfigurable BESS (RBESS) to demonstrate the advantages of having a reconfigurable system topology. The comparison results show that the proposed RBESS has higher system reliability and more power outputs than the classic BESS.
Current sharing among inductors is an important issue in both isolated and nonisolated dc-dc converters. In this paper, average current sharing is in-depth modeled and analyzed for both interleaved ...multiphase buck converters and isolated current-doubler dc-dc converters. The features and comparison of various current-sharing techniques used in isolated and nonisolated dc-dc converters are presented, and the corresponding design guidelines are provided based on the theoretical analysis. The analysis reveals that the state-of-the-art current-sharing technique for multiphase buck converters cannot be directly applied to isolated current-doubler rectifier (CDR) dc-dc converters to achieve balanced inductor currents. Passive and active current-sharing methods are proposed for isolated current-doubler dc-dc converters to balance two inductor currents. Experimental results are presented to verify the modeling analysis and the proposed current-sharing techniques for CDRs in isolated dc-dc converters.
This paper presents an integrated inspection and failure model of equipment for asset management. The model combines both repairable and aging failure modes with maintenance activities. Based on this ...model, an optimization approach for determining equipment inspection interval is proposed. The proposed approach can optimize the inspection interval by minimizing the total cost including maintenance, failure loss, repair, replacement, and patrol costs. The proposed method is applied to a mixed set of equipment consisting of breakers and transformers in two regions. The results indicate that the optimal inspection interval for each region can be effectively obtained using the proposed method. Equipment aging failures have significant impacts on the optimal inspection interval. The optimal inspection interval gradually becomes shorter over years due to the equipment aging process. The optimal inspection interval is different for different regions depending on the equipment aging status and other factors in each region. Therefore, it is recommended to have a region-specific inspection strategy for each area.
In this paper, a load transient mitigation technique for stand-alone fuel cell (FC)-battery power generation systems is proposed. The technique can be used not only to improve the output power ...quality of the overall system, but also to mitigate or eliminate the electrical feedback stresses that are caused by load transients upon fuel cells. As a result, the durability of the fuel cell can also be improved. System analysis and controller design procedure for the proposed technique are given in this paper. Simulation studies have been carried out on FC-battery power generation systems using the dynamic models developed for proton exchange membrane fuel cell (PEMFC) and solid-oxide fuel cell (SOFC). Simulation results show the effectiveness of the proposed technique in preventing load transients from affecting the fuel cell performance.
Power outages in urban area carry heavy social and economic costs. Although social cost, especially public sentiment, is concerned by engineers and managers, it has been only qualitatively ...investigated without a rigorous model in the state‐of‐the‐art research and practice of service restoration (SR) for a long time. To fill this gap, this paper investigates a hybrid model which takes public sentiment into consideration by quantifying public sentiment triggered by power outage. Furthermore, conventional SR method focused on the optimization model with ideal conditions, which leaves a large room for improvement in complex environment. To improve the robustness of the model, the authors propose a reinforcement learning framework to analyze emergency management process without prior rules. At each time step, the optimal decision can be made automatically by a learned model. The numerical simulations with modified IEEE 33‐bus and IEEE 123‐bus systems demonstrate the effectiveness of the proposed method.
This paper presents a hybrid model which takes public sentiment into consideration by quantifying public sentiment triggered by power outage. The proposed hybrid model also included a reinforcement learning framework to analyze emergency management process without prior rules.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Electromagnetic waves generated due to partial discharge (PD) can be captured by ultra-high-frequency (UHF) antennas. The size and frequency band of an UHF antenna for PD online monitoring are ...critical factors for practical installation inside a transformer. This paper presents a compact multi-band UHF Hilbert fractal antenna with wide frequency band and suitable size for easy installation. Design criteria of a PD antenna were proposed and the Hilbert fractal antenna was selected as an appropriate candidate for PD detection. Principle of Hilbert fractal antenna was discussed and a fourth order Hilbert fractal antenna was optimized for detecting PD signals. Actual PD experiments have been carried out for two typically artificial insulation defect models while the antenna was used for the PD measurement. More simulation studies and actual PD experiments have been done to further examine the effects of electromagnetic wave refraction and reflection by transformer components. The results show that the proposed UHF antenna is qualified for PD online monitoring.
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