Hasil untuk "Applications of electric power"

Zhaoze LI, Jihong ZHANG, Zhenkui WU et al.

The catalytic synthesis of methanol from hydrogen and carbon dioxide is the key to solving the technical problem of "production, storage, transportation, addition, and utilization" of hydrogen energy. This study highlights a mathematical model of generalized energy storage for methanol synthesis. It focuses on the design of a layered optimization and control scheme for a virtual power plant, focusing on source-network load-storage. The upper layer of the plant encompasses that of generalized energy storage for use with wind power and photovoltaics proposed, which can track several factors. Such factors are generation scheduling, the introduction of virtual power plants to consumers of the master-slave game theory, the use of genetic algorithms to hone the price of electricity at different times of the day, and responses to user demands, thus reducing the net load peak and valley differences. The lower layer is comprised of external power trading as the ultimate guarantee. This shall be combined with generalized energy storage to achieve balance between power supply and power demand, especially the Sinh Cosh optimization algorithm, to enhance the source storage and ensure that the virtual power plant operates under low carbon conditions. Finally, compared to different schemes, the proposed scheme can effectively increase the level of renewable energy consumption and promote regional decarbonization. Also, the proposed scheme can improve the comprehensive operational efficiency of virtual power plants.

P. Sasorov, G. Bagdasarov, N. Bobrova et al.

Plasma discharge in the capillary is used to develop x-ray lasers, waveguides for high power laser pulses, and as active plasma lenses to focus high energy charged particle beams. Capillary discharges in the high repetition rate regime are of interest for applications that require large average values, such as luminosity and/or electric current of laser accelerated particles. In the present paper, we study the capillary discharge in the high repetition rate regime in connection with the ultrashort laser pulse guiding for laser electron acceleration. Using magnetohydrodynamic computer simulations and theoretical scaling, we investigate the filling of the capillary with the gas, the electric discharge development leading to outflow of the plasma from the capillary, and the recovery of gas distribution after the discharge end. In the next cycle, these processes are repeated. As a result, we found the characteristic cycle time, which determines the upper limit on the repetition rate allowed by the capillary parameters. In the case of the capillary discharges used for acceleration of sub-GeV electron beams, e.g., needed for compact free electron lasers, an upper limit on the repetition rate is approximately equal to 10 kHz.

WU Yanjuan, JIN Pengfei, LIU Changcheng et al.

In order to reduce carbon emissions and the impact of source-load uncertainty on system operation, a multi-timescale low-carbon optimization scheduling strategy in day-ahead, intra-day and real-time operations for energy hub (EH) based on a reward-punishment ladder carbon price mechanism and distributed model predictive control (DMPC) is proposed. A reward-punishment ladder carbon price calculation method is introduced and a day-ahead low-carbon optimization scheduling model for EH is constructed. A feedback closed-loop optimization strategy based on DMPC for intra-day rolling and real-time adjustments is formulated. The optimization strategy reduces source-load prediction errors and improves the efficiency of traditional model predictive control (MPC) solving. In the intra-day stage, a rolling optimization model with the objective of minimizing the sum of the ladder carbon price cost, operational cost, and penalty cost for energy storage adjustment is constructed. In the real-time stage, the overall optimization problem is decomposed, and a multi-agent real-time adjustment model based on DMPC is established. The simulation results indicate that the proposed strategy is effective in enhancing the economic efficiency of the system, reducing the uncertainty of source and load, and achieving the low-carbon, economic, stable, and reliable operation for EH.

WANG Haitao, YANG Bo

The arc is generated upon contact breaking-off resulting in surface erosion in the terminals and affecting the performance of electrical contact. As there is no natural zero crossing point in the DC power supply system, the erosion caused by arcs is often more severe in DC contactors than that in AC contactors. The arc erosion effect on the contact terminals is analyzed in this paper. Based on the theory of magnetohydrodynamics, a dynamic coupling model of arc and contact terminals considering energy coupling is established. Then, the impacts of the electric current level and breaking speed on the arc erosion in contact terminals are studied by using the model. Simulation results show that the arc temperature near the anode is higher than that near the cathode. It can be noted that the arc temperature and arcing time rise significantly by increasing the current from 20 A to 30 A, which improves the arcing energy by 75.93% and thus worsening the contact erosion. Simulation results also indicate that increasing the breaking-off speed from 0.1 m/s to 0.2 m/s, results in an increase of voltage and current variation rates, an reduction of the arcing time and molten pool volume, a decrease of the arcing energy by 47.83%, and an reduction of the impact of arc erosion on the contact terminal. The experimental results are consistent with the simulations confirming the accuracy of the simulation model.

Javad Tavakoli, Hossein Miri Lavasani, Samad Sheikhaei

A low-power and low-jitter 1.2 GHz Integer-N PLL (INPLL) is designed in a 65 nm standard CMOS process. A novel high-gain sampling phase detector (PD), which takes advantage of a transconductance (Gm) cell to boost the gain, is developed to increase the phase detection gain by ~100× compared to the Phase-Frequency Detectors (PFDs) used in conventional PLLs. Using this high detection gain, the noise contribution of the PFD and Charge Pump (CP), reference clock, and dividers on the PLL output is minimized, enabling low output jitter at low power, even when using low-frequency reference clocks. To provide a sufficient frequency locking range, an auxiliary frequency-locked loop (AFLL) is embedded within the INPLL. An integrated Lock Detector (LD) helps detect the INPLL locked state and disables the AFLL to save on power consumption and minimize its impact on the INPLL jitter. The proposed INPLL layout measures 700 µm × 350 µm, consumes 350 µW, and exhibits an integrated phase noise (IPN) of −37 dBc (from 10 kHz to 10 MHz), equivalent to 2.9 ps rms jitter, while keeping the spur level 64 dBc lower, resulting in jitter figure of Merit (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>F</mi><mi>o</mi><msub><mrow><mi>M</mi></mrow><mrow><mi>j</mi><mi>i</mi><mi>t</mi><mi>t</mi><mi>e</mi><mi>r</mi></mrow></msub></mrow></semantics></math></inline-formula>) ~−236 dB.

Jordi-Roger Riba, Pau Bas-Calopa, Yassin Aziz Qolla et al.

The development of more electric aircrafts (MEA) and all electric aircrafts (AEA) inevitably implies an increase in electric power and a consequent increase in distribution voltage levels. Increased operating voltages coupled with low pressure in some areas of the aircraft greatly increase the chances of premature insulation failure. Insulation failure manifests itself as surface discharges, arc tracking, arcing, and disruptive or breakdown discharges, in order of increasing severity. Unfortunately, on-board electrical protections cannot detect discharges at an early stage, so other strategies must be explored. In their early stage, insulation faults manifest as surface and corona discharges. They generate optical radiation, mainly in the near-ultraviolet (UV) and visible spectral regions. This paper focuses on a method to detect the discharges, locate the discharge sites, and determine their intensity to facilitate predictive maintenance tasks. It is shown that by using small size and low-cost image sensors, it is possible to detect, locate, and quantify the intensity of the discharges. This paper also proposes and evaluates the behavior of a discharge severity indicator, which is based on determining the intensity of digital images of the discharges, so it can be useful to apply predictive maintenance tasks. The behavior and accuracy of this indicator has been tested in the laboratory using a low-pressure chamber operating in the pressure range of 10–100 kPa, which is characteristic of aircraft applications, analyzing a needle-plane air gap geometry and using an image sensor. The proposed method can be extended to other applications where electrical discharges are an issue.

CHEN Siwei, LI Baohong, LIU Tianqi et al.

The fault characteristics of direct current (DC) grids can be analyzed by addressing the grid damping characteristics. However,the frequency-dependent characteristics of the transmission line parameters are usually ignored in the conventional grid impedance modeling methods,which cannot accurately reflect the grid damping characteristics. To compare and analyze the fault currents characteristics of the DC grids with cables and overhead lines,an impedance model of DC grid considering the frequency-dependent characteristics of the transmission line parameters based on vector fitting is proposed in this paper. Then,the proposed model is applied to compare and analyze the fault current features including time delays,initial rising rates and amplitudes of the DC grids with cables and overhead lines. Meanwhile,the impacts of the DC grids key parameters on the fault current characteristics of the two DC grids are investigated. Compared with the sweeping results of the frequency-dependent line model,the proposed model performs well in reflecting the damping characteristic of the DC grid,where the root square error is less than 0.6,informing that the proposed model is much more accurate than the simplified model. Finally,the simulation is conducted in a symmetrical monopolar two-terminal DC grid with pole-to-pole fault. The simulation results show that the fault current rising rate of the DC grid with cables is 24.96% higher than that of the DC grid with overhead lines when the arm inductance is increased,which validates that the fault currents of the DC grids with cables are more sensitive to the inductive key parameters than the DC grids with overhead lines.

QIAN Sheng, WANG Qi, YAN Yunsong et al.

The security and stability control system is an important defense line to ensure the reliable operation of the power grid. Serious physical consequences can be caused by cyber attacks against the security and stability control system. In order to quantitatively evaluate the impact of cyber attacks on security and stability control system and solve the problem that the existing risk assessment methods do not fully consider the susceptibility of cyber attacks,a risk assessment method of security and stability control system considering the impact of cyber attacks is proposed. Firstly,the hierarchical structure of the security and stability control system is analyzed. Then,the risk points of cyber attacks on the stability control device body and device's inter-station communication from the three perspectives of attack object,attack methods,and attack consequences are analyzed. Secondly,the susceptibility of cyber attacks is quantified based on the fuzzy analytic hierarchy process,and a successful probability model of cyber attacks for security and stability control system is established combined with the defense unit model of cyber attacks built by Petri nets. Finally,the risk assessment is carried out on the standard and actual systems combined with the physical consequences and the probability of successful attacks. The risk values under two conditions of normal operation and cyber attack are calculated to verify the validity of the proposed model.

XIAO Yao, NIU Wenze, WEI Gaosheng et al.

Solar photovoltaic/thermal (PV/T) technology is the integration of PV modules and solar collectors, which can simultaneously generate electricity and provide thermal energy. The overall efficiency and the space utilization efficiency will be improved simultaneously by the combination of two modules. The types of PV/T technology and related theoretical researches were summarized firstly in this review. By focusing on the heat loss and overtemperature problem of flat-panel PV/T technology, the design progress has been reviewed and analyzed. The state-of-art study on integration of phase change materials with PV/T (PV/T-PCM) technology was comprehensively summarized. The deficiencies in the research and the future development tendency were also prospected in order to provide theoretical guidance for further development of PV/T systems.

Journal of Low Power Electronics and Applications Editorial Office

Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that <i>Journal of Low Power Electronics and Applications</i> maintains its standards for the high quality of its published papers [...]

Gregory Tzermias, Sam Akehurst, Richard Burke et al.

Increasingly stringent emission regulations and environmental concerns have propelled the development of electrification technology in the transport industry. Yet, the greatest hurdle to developing fully electric vehicles is electrochemical energy storage, which struggles to achieve profitable specific power, specific energy and cost targets. Hybrid energy storage systems (HESSs), which combine energy- and power-optimised sources, seem to be the most promising solution for improving the overall performance of energy storage. The potential for gravimetric and volumetric reduction is strictly dependent on the overall power-to-energy ratio (PE ratio) of the application, packaging factors, the minimum and maximum PE ratio achievable for the system’s energy- and power-optimised sources and the performance of power electronics. This paper presents a simple optimisation methodology that considers these factors and identifies the optimal HESS requirements that may present new opportunities for a variety of vehicles where low weight and volume are of high importance. The simplicity of the method means that decisions relating to a HESS can be made earlier in the system design process. This method of analysis showed that a battery HESS has the potential to reduce cell mass and volume by over 30% for applications that are well suited to optimal HESS characteristics.

Xiangling KONG, Jinglun FU

The operational safety and performance of gas turbine is closely related to the health status of its components. Generally, the status of gas turbine components can be evaluated by the morphological characters, such as size, shape, color, etc. Therefore, the method of feature extraction, especially the three- dimensional (3D) feature extraction, has become a key technology for component health status assessment. The existing computer vision based on 3D reconstruction algorithms was reviewed. After that, the research status and development directions of the 3D reconstruction in the gas turbine industry were discussed. In the end, the reconstruction results of a turbine blade using the shape from shading (SFS) algorithm and the Mvsnet were presented and compared.

Xiaoxue AN, Sheng SU, Jun XIANG et al.

The transfer characteristics and removal capability of Hg in ultra-low emission facilities such as selective catalytic reduction (SCR), low temperature electrostatic precipitator, seawater desulfurization and wet electrostatic precipitator in a 300 MW coal-fired boiler of a power plant were studied under different working conditions and different types of coal. The results show that under different working conditions, the total emission concentration of mercury is basically 1.16-2.90 μg/m3. The final release of mercury into the atmosphere is mainly composed of elemental mercury and a small amount of oxidized mercury, the particulate mercury was completely removed. Most mercury is removed in seawater flue gas desulfurization. The overall removal efficiency of mercury of low temperature electric precipitator, a seawater flue gas desulfurization scrubber and wet electric precipitator is 25%, 62% and 37% respectively on average. The proportion of Hg2+ is the key to affect the efficiency of mercury removal in flue gas, and the higher proportion of Hg2+ in flue gas is beneficial to obtain higher efficiency in electrostatic precipitators and seawater flue gas desulfurization devices. In the 300 MW coal-fired boiler of a power plant equipped with a selective catalytic reduction unit, a low temperature electrostatic precipitator, a seawater flue gas desulfurization scrubber, and a wet electrostatic precipitator and other ultra-low emission facilities, the average removal rate of total mercury is about 83%, which can achieve greater levels of mercury removal.

Sheng KUANG, Beibei WANG

The joint operation of the energy storage system and the wind farm can not only track the wind power schedule output, but also participate in ancillary service of the power grid. In order to maximize the total profit of the optimization of wind storage joint operation, the optimal model of wind storage joint operation was established considering the wind energy storage system tracking wind power schedule output and participating in the secondary frequency modulation service of the power grid. The model took into account the energy storage life loss under different state of charge, and the up-frequency modulation power and down-frequency modulation power balance when energy storage participated in frequency modulation. Based on the actual wind farm operation data, an example was designed and the simulation was carried out. The results show that considering the energy storage life loss level not only measure the benefits of energy storage participating in various services, but also give full play to the role of energy storage and improve the benefits of wind storage joint operation.

H. Saunders, K. Schoch

Hao ZHOU, Zhenhuan CHEN, Jiakai ZHANG et al.

The transformation mechanism of minerals in coal ash under different atmospheric conditions affects the melting and slagging process of coal. In order to study the melting characteristics of Zhundong coal under oxygen-rich/H2O-O2 atmosphere, and provide reference for preventing the slagging of Zhundong coal-fired boilers, the charge coupled device (CCD) camera was used to record the deformation process of the pulverized Zhundong coal on the hot stage. By calculating the sampling areas of the pulverized coal at different temperatures, the melting temperatures corresponding to the characteristic change points of the pulverized coal areas were obtained. The temperatures at which Zhundong coal powder began to melt under different oxygen-rich/H2O-O2 atmosphere conditions were compared. The study have shown that as the oxygen concentration increases, the temperature at which the coal powder begins to melt decreases. As the water vapor concentration decreases, the temperature at which the coal powder begins to melt increases. Both water vapor atmosphere and oxygen-rich atmosphere can promote the melting behavior of Zhundong coal.

S.P. Lushchin, A.V. Borkovskih, M.V. Borkovskih

Purpose. Determination of the capacity of wires of overhead power transmission lines based on innovative materials without changing the currently used structures, as well as the possibility of increasing the voltage class of overhead transmission lines when using wires based on aluminum-zirconium materials. Methodology. Analytical method for determining the throughput capacity of overhead power transmission lines. Comparative analysis of electrical characteristics of wires of overhead power transmission lines. Findings. The possibility of increasing the capacity of overhead power transmission lines while maintaining the wire cross-section, using an innovative material based on an aluminum-zirconium alloy, has been proved. The reduction of the weight of the wire based on innovative materials is justified, while maintaining the current throughput. The advantages and disadvantages of European wire structures for overhead power transmission lines are revealed using innovative material based on an aluminum-zirconium alloy. The optimal design of wires based on the innovative material of the aluminum-zirconium alloy for overhead transmission lines, permissible for use on the territory of Ukraine, has been determined. Originality. The expediency of using the traditional designs of the wires of overhead power transmission lines has been proved, in the case of using innovative material. The possibility of increasing the voltage class of overhead power transmission lines using wires based on aluminum-zirconium materials has been substantiated. Practical value. The results are obtained regarding the electrical resistance of overhead power transmission lines to peak loads, taking into account the low costs of modernization with the use of an innovative material based on an alloy of aluminum and zirconium. The use of innovative material creates conditions for increasing the voltage class of overhead power transmission lines, which allows increasing the transmitted power to the consumer. The use of materials based on aluminum-zirconium alloys makes it possible to carry out measures for the reconstruction of electric supply networks without replacement of supports and additional work on land allocation, as in the case of reconstruction without increasing the voltage line class of power lines, and in case of increasing the voltage class.

Lidong ZHANG, Shuo WANG, Weiwei LI et al.

The energy saving and consumption reduction is the main development direction of China's power generation industry. The impinging stream can generate a great relative phase-to-phase velocity at the moment of impact, and form a relatively narrow height turbulence zone, which can greatly improve the heat and mass transfer. This nature of flow can be widely used in the related fields of the power generation industry, especially in the areas of combustion, drying, sewage treatment, desulfurization and denitrification, coal gasification, dust removal, etc. In this paper, based on a brief introduction to the basic principle and classification of impinging stream technology, the research progress of impinging stream technology in recent years is summarized, and the application prospects of impinging stream technology in related fields of power generation industry are discussed, in order to provide reference for further application of impact flow technology in the power generation industry.

D. Bakken, A. Bose, C. Hauser et al.

Kunpeng Feng, Jiwen Cui, Hong Dang et al.

To achieve a narrow bandwidth optical filter with a wide swept range for new generation optical spectrum analysis (OSA) of high performance optical sensors, an optoelectronic equivalent narrowband filter (OENF) was investigated and a swept optical filter with bandwidth of several MHz and sweep range of several tens of nanometers was built using electric filters and a sweep laser as local oscillator (LO). The principle of OENF is introduced and analysis of the OENF system is presented. Two electric filters are optimized to be RBW filters for high and medium spectral resolution applications. Both simulations and experiments are conducted to verify the OENF principle and the results show that the power uncertainty is less than 1.2% and the spectral resolution can reach 6 MHz. Then, a real-time wavelength calibration system consisting of a HCN gas cell and Fabry–Pérot etalon is proposed to guarantee a wavelength accuracy of ±0.4 pm in the C-band and to reduce the influence of phase noise and nonlinear velocity of the LO sweep. Finally, OSA experiments on actual spectra of various optical sensors are conducted using the OENF system. These experimental results indicate that OENF system has an excellent capacity for the analysis of fine spectrum structures.