In this paper, a hierarchical control system for parallel power electronics interfaces between ac bus and dc bus in a hybrid microgrid is presented. Both standalone and grid-connected operation modes ...in the dc side of the microgrid are analyzed. Concretely, a three-level hierarchical control system is implemented. In the primary control level, the decentralized control is realized by using the droop method. Local ac current proportional-resonant controller and dc voltage proportional-integral controller are employed. When the local load is connected to the dc bus, dc droop control is applied to obtain equal or proportional dc load current sharing. The common secondary control level is designed to eliminate the dc bus voltage deviation produced by the droop control, with dc bus voltage in the hybrid microgrid boosted to an acceptable range. After guaranteeing the performance of the dc side standalone operation by means of the primary and secondary control levels, the tertiary control level is thereafter employed to perform the connection to an external dc system. Meanwhile, the impact of the bandwidth of the secondary and tertiary control levels is discussed. The closed-loop model including all the three control levels is developed in order to adjust the main control parameters and study the system stability. Experimental results of a 2 × 2.2 kW parallel ac-dc converter system have shown satisfactory realization of the designed system.
Solar energy application in a wider spectrum has the potential for high efficiency energy conversion. However, solar cells can only absorb photon energy of the solar spectrum near the solar cell ...band-gap energy, and the remaining energy will be converted into thermal energy. The thermoelectric generator is a good choice to utilize this thermal energy. This paper analyses the feasibility of photovoltaic-thermoelectric (PV-TE), and reviews the current types and performance of PV-TE. Furthermore, it presents the optimization and development of PV-TE. In addition, this paper presents the challenge and efficient improvement of PV-TE in actual application. Therefore, this paper would provide a valuable reference for further research into the field of PV-TE and its applications.
•The performance and recent advances in PV-TE are presented.•The challenge faced in the field of PV-TE and solutions are indicated.•Current state of art in PV-TE for electricity generation is presented.•Optimization and development of PV-TE is demonstrated.
Sodium and potassium ions energy storage systems with low cost and high energy/power densities have recently drawn increasing interest as promising candidates for grid-level applications, while the ...lack of suitable anode materials with fast ion diffusion kinetics highly hinders their development. Herein, we develop a nanoscale confined in situ oxidation polymerization process followed by a conventional carbonization treatment to generate phosphorus and nitrogen dual-doped hollow carbon spheres (PNHCS), which can realize superior sodium and potassium ion storage performance. Importantly, the density functional theory calculation and combined characterizations, e.g., in situ Raman spectroscopy and ex situ X-ray photoelectron spectroscopy, decipher that the P/N doping can enhance the electronic transfer dynamics and ion adsorption capability, which are responsible for enhanced electrochemical performance. Inspiringly, the practicability of the PNHCS anode is demonstrated by assembling the potassium ion hybrid capacitors (KIHCs), where the prominent energy density is 178.80 Wh kg–1 at a power density of 197.65 W kg–1, with excellent cycling stability, can be achieved. This work not only promotes the development of efficient anode material for sodium/potassium ion storage devices but also deciphers the embedded ion storage mechanism.
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•Novel equivalent consumption minimization strategy with three power sources.•A test bench is built to validate the developed energy management strategy.•Online estimation of power ...sources’ state of health by Unscented Kalman Filter.•Modify equivalent factor and fuel cell current change rate with power sources ageing.•Adaptive equivalent consumption minimization strategy with power sources degradation.
The aim of this paper is to present an on-line adaptive equivalent consumption minimum strategy (AECMS) for fuel cell hybrid electric vehicle powered by fuel cell, battery and supercapacitor. In order to design the AECMS, an equivalent consumption minimum strategy (ECMS) without considering power sources degradation is firstly designed to decrease hydrogen consumption and degradation of power sources, which chooses fuel cell as the main power source to supply steady power, battery as the main energy storage source to buffer energy demand by vehicle and supercapacitor as the peak power supplier. A testbench is built to validate the developed ECMS. By contrastive experimental tests on ECMS, Rule Based Control Strategy (RBCS) and a Hybrid ECMS Operating mode control Strategy (HEOS) through the built test bench, hydrogen consumption of ECMS decreases 2.16% and 1.47% respectively and it also has the smoothest fuel cell current. Along with the degradation of fuel cell and battery, the charge sustenance objective of battery cannot be reached. Therefore, AECMS is finally designed to adjust equivalent factors and fuel cell dynamic current change rate along with the state of health (SOH) of fuel cell and battery, to make sure the charge sustenance of battery and prolong the lifetime of fuel cell. The method that on-line estimates their SOHs and the effects of their degradation on ECMS are also analyzed.
Existence of periodical solutions, i.e. cycles, in the Impulsive Goodwin's Oscillator (IGO) with the continuous part of an arbitrary order m is considered. The original IGO with a third-order ...continuous part is a hybrid model that portrays a chemical or biochemical system composed of three substances represented by their concentrations and arranged in a cascade. The first substance in the chain is introduced via an impulsive feedback where both the impulse frequency and weights are modulated by the measured output of the continuous part. It is shown that, under the standard assumptions on the IGO, a positive periodic solution with one firing of the pulse-modulated feedback in the least period also exists in models with any m >= 1. Furthermore, the uniqueness of this 1-cycle is proved for the IGO with m <= 10 whereas, for m>10, the uniqueness can still be guaranteed under mild assumptions on the frequency modulation function.
This paper proposes multiagent system-based event-triggered hybrid controls for guaranteeing energy supply of a hybrid energy generation system with high security. First, a multiagent system is ...constituted by an upper level central coordinated control agent combined with several lower level unit agents. Each lower level unit agent is responsible for dealing with internal switching control and distributed dynamic regulation for its unit system. The upper level agent implements coordinated switching control to guarantee the power supply of overall system with high security. The internal switching control, distributed dynamic regulation, and coordinated switching control are designed fully dependent on the hybrid behaviors of all distributed energy resources and the logical relationships between them, and interact with each other by means of the multiagent system to form hierarchical hybrid controls. Finally, the validity of the proposed hybrid controls is demonstrated by means of simulation results in different scenarios.
PURPOSE: A literature review is undertaken to understand how well existing studies of the environmental impacts of hybrid and electric vehicles (EV) address the full life cycle of these technologies. ...Results of studies are synthesized to compare the global warming potential (GWP) of different EV and internal combustion engine vehicle (ICEV) options. Other impacts are compared; however, data availability limits the extent to which this could be accomplished. METHOD: We define what should be included in a complete, state-of-the-art environmental assessment of hybrid and electric vehicles considering components and life cycle stages, emission categories, impact categories, and resource use and compare the content of 51 environmental assessments of hybrid and electric vehicles to our definition. Impact assessment results associated with full life cycle inventories (LCI) are compared for GWP as well as emissions of other pollutants. GWP results by life cycle stage and key parameters are extracted and used to perform a meta-analysis quantifying the impacts of vehicle options. RESULTS: Few studies provide a full LCI for EVs together with assessment of multiple impacts. Research has focused on well to wheel studies comparing fossil fuel and electricity use as the use phase has been seen to dominate the life cycle of vehicles. Only very recently have studies begun to better address production impacts. Apart from batteries, very few studies provide transparent LCIs of other key EV drivetrain components. Estimates of EV energy use in the literature span a wide range, 0.10–0.24 kWh/km. Similarly, battery and vehicle lifetime plays an important role in results, yet lifetime assumptions range between 150,000–300,000 km. CO2 and GWP are the most frequently reported results. Compiled results suggest the GWP of EVs powered by coal electricity falls between small and large conventional vehicles while EVs powered by natural gas or low-carbon energy sources perform better than the most efficient ICEVs. EV results in regions dependant on coal electricity demonstrated a trend toward increased SO x emissions compared to fuel use by ICEVs. CONCLUSIONS: Moving forward research should focus on providing consensus around a transparent inventory for production of electric vehicles, appropriate electricity grid mix assumptions, the implications of EV adoption on the existing grid, and means of comparing vehicle on the basis of common driving and charging patterns. Although EVs appear to demonstrate decreases in GWP compared to conventional ICEVs, high efficiency ICEVs and grid-independent hybrid electric vehicles perform better than EVs using coal-fired electricity.
The fuel economy and battery charge sustaining capability are two key criteria for the energy management of a full-power fuel cell hybrid vehicle equipped with small-capacity battery pack. In order ...to achieve stable battery charge sustenance and near-optimal fuel consumption, this study proposes an optimization-oriented adaptive equivalent consumption minimization strategy (A-ECMS) based on demand power prediction achieved via an iterative predictor. The proposed strategy updates the optimal equivalent factor periodically via local optimization process according to the predicted power to converge the state of charge (SOC) and guarantee fuel economy. The simulation results show that the iterative predictor has considerable accuracy, and the correlation between the predicted data and the real data reaches up to 0.987. The proposed strategy can quickly recover the battery SOC within 40 s in a 500-s driving cycle, which is shorter than existing feedback-oriented A-ECMS. At charge sustaining stage, the proposed strategy maintains the battery SOC around the reference value with an extremely low fluctuation degree of 0.36. The equivalent fossil-fuel consumption of the proposed strategy is 8.003 L/100 km, which is lower than that of existing A-ECMS. Besides, further investigation reveals that the proposed strategy has robust performance against the disturbance of power prediction errors.
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•An optimization-oriented predictive adaptive equivalent consumption minimization strategy is developed.•A short-term demand power predictor is designed based on iterative learning framework.•A local optimization method is proposed to update near-future optimal equivalent factor periodically.•Better battery charge sustaining capability is achieved while guaranteeing fuel economy.
Aims Periprosthetic fracture and implant loosening are two of the major reasons for revision surgery of cementless implants. Optimal implant fixation with minimal bone damage is challenging in this ...procedure. This pilot study investigates whether vibratory implant insertion is gentler compared to consecutive single blows for acetabular component implantation in a surrogate polyurethane (PU) model. Methods Acetabular components (cups) were implanted into 1 mm nominal under-sized cavities in PU foams (15 and 30 per cubic foot (PCF)) using a vibratory implant insertion device and an automated impaction device for single blows. The impaction force, remaining polar gap, and lever-out moment were measured and compared between the impaction methods. Results Impaction force was reduced by 89% and 53% for vibratory insertion in 15 and 30 PCF foams, respectively. Both methods positioned the component with polar gaps under 2 mm in 15 PCF foam. However, in 30 PCF foam, the vibratory insertion resulted in a clinically undesirable polar gap of over 2 mm. A higher lever-out moment was achieved with the consecutive single blow insertion by 42% in 15 PCF and 2.7 times higher in 30 PCF foam. Conclusion Vibratory implant insertion may lower periprosthetic fracture risk by reducing impaction forces, particularly in low-quality bone. Achieving implant seating using vibratory insertion requires adjustment of the nominal press-fit, especially in denser bone. Further preclinical testing on real bone tissue is necessary to assess whether its viscoelasticity in combination with an adjusted press-fit can compensate for the reduced primary stability after vibratory insertion observed in this study. Cite this article: Bone Joint Res 2024;13(6):272–278.
By adding glass fibres to carbon fibre composites, the apparent failure strain of the carbon fibres can be increased. A strength model for unidirectional hybrid composites was developed under very ...local load sharing assumptions to study this hybrid effect. Firstly, it was shown that adding more glass fibres leads to higher hybrid effects. The hybrid effect was up to 32% for a hybrid composite with a 10/90 ratio of carbon/glass fibres. The development of clusters of broken fibres helped to explain differences in the performance of these hybrid composites. For 50/50 carbon/glass hybrids, a fine bundle-by-bundle dispersion led to a slightly smaller hybrid effect than for randomly dispersed hybrids. The highest hybrid effect for a 50/50 ratio, however, was 16% and was achieved in a composite with alternating single fibre layers. The results demonstrate that thin ply hybrids may have more potential for improved mechanical properties than comingled hybrids.
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