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.
Tilt photography of unmanned aerial vehicles (UAVs) is widely used in urban management, cadastral mapping, disaster monitoring and other fields, but there are few innovative applications in online ...tourism. In this study, empirical design and usability testing methods were adopted, advanced positioning technology and Cesium engine were used to build a 3D real online travel application based on tilt photography, and the interactive function was realized through JavaScript language dynamic interactive function script. Meanwhile, combined with the questionnaire survey, the mobile application Rating Scale (MARS) was used to evaluate the function and quality of the application. The results show that engagement, functionality and aesthetics have no significant influence on user perception. Information quality and subjective quality of application have significant positive influence on user perception, and the influence of information quality is more significant. This study extends the application of oblique photography in tourism and provides experience for the development of tourism digitization.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This paper investigates a novel leader-following attitude control approach for spacecraft formation under the preassigned two-layer performance with consideration of unknown inertial parameters, ...external disturbance torque, and unmodeled uncertainty. First, two-layer prescribed performance is preselected for both the attitude angular and angular velocity tracking errors. Subsequently, a distributed two-layer performance controller is devised, which can guarantee that all the involved closed-loop signals are uniformly ultimately bounded. In order to tackle the defect of statically two-layer performance controller, learning-based control strategy is introduced to serve as an adaptive supplementary controller based on adaptive dynamic programming technique. This enhances the adaptiveness of the statically two-layer performance controller with respect to unexpected uncertainty dramatically, without any prior knowledge of the inertial information. Furthermore, by employing the robustly positively invariant theory, the input-to-state stability is rigorously proven under the designed learning-based distributed controller. Finally, two groups of simulation examples are organized to validate the feasibility and effectiveness of the proposed distributed control approach.
In this paper we prove the Liouville type theorem for stable solution of the p-Laplace equation (0.1)−Δpu=f(x)|u|q−1u,x∈RN,where f(x) is a continuous and nonnegative function in RN∖{0} such that ...f(x)≥a0|x|a as |x|≥R0>0, where a>−p and a0>0. The results hold true for 1≤p−1<q=qc(p,N,a). Here qc is a new exponent, which is infinity in low dimension and is always larger than the classical critical one.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This article provides a comprehensive analysis for a single-phase double T-type seven-level (SDT-7L) inverter topology with only eight power switches and three series-connected capacitors. Compared ...to the existing single-phase seven-level inverters, the number of power switches and the voltage stresses across them are both reduced. These advantages are achieved by a simple topology configuration without any clamping diodes or flying capacitors. However, this makes it difficult to realize voltage-balance control for the three series-connected capacitors as there are no redundant switching states that can be selected to control and balance the three capacitor voltages. Hence, the capacitor voltage imbalance mechanism of the SDT-7L inverter is studied and revealed that the overdischarge of the middle capacitor is the main cause of the capacitor voltage imbalance issue. To overcome this issue, a variable-carrier-amplitude-based voltage-balance control method and a variable-reference-amplitude based voltage-balance control method are proposed in this article. Both the methods aim at controlling the middle capacitor voltage at the desired 1/3 of the full dc-link voltage, and the other two capacitor voltages are automatically balanced. Furthermore, a theoretical analysis indicates that the proposed two voltage-balance methods are equivalent. Both the simulation and experimental results are presented to verify the SDT-7L topology with the proposed two voltage-balance methods.
Standalone microgrids with renewable sources and battery storage play an important role in solving power supply problems in remote areas such as islands. To achieve reliable and economic operations ...of a standalone microgrid, in addition to the consideration of utilization of renewable resources, the lifetime characteristics of a battery energy storage system also need to be fully investigated. In this paper, in order to realize the economic operation of a recently developed standalone microgrid on Dongfushan Island in China, an optimization model including battery life loss cost, operation and maintenance cost, fuel cost, and environmental cost is established to obtain a set of optimal parameters of operation strategy. Considering the lifetime characteristics of lead-acid batteries, a multiobjective optimization to minimize power generation cost and to maximize the useful life of lead-acid batteries has been achieved via the nondominated sorting genetic algorithm (NSGA-II). The results show that the proposed method can optimize the system operations under different scenarios and help users obtain the optimal operation schemes of the actual microgrid system.
•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
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