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1 – 10 of over 2000Kabra Preeti and Donepudi Sudha Rani
The earlier methods are more resilient to improvements such as load shift and path change. This results in problems such as a voltage drop and a high reactive flux. In addition…
Abstract
Purpose
The earlier methods are more resilient to improvements such as load shift and path change. This results in problems such as a voltage drop and a high reactive flux. In addition, due to the delay, congestion or interruption of the transmission, the system cannot receive all phasor measurement unit (PMU) measurements at the relevant time as well as the presence of noise in the received data.
Design/methodology/approach
With the development of wide area measurement system technologies, it seems to be possible to track voltage stability online via time-stamped PMUs. As the voltage instability causes a voltage decomposition, voltage instability is one of the most important problems when monitoring the power supply.
Findings
This harmonic distortion significantly decreases the data quality in the grid. As a result, instability ascertainment based on PMU has been suggested as a method for detecting voltage instability in power systems monitored with PMU. In addition, a technique called instability amendment via load dropping has been proposed to keep the device from collapsing due to voltage failure.
Originality/value
To improve the power output, the power prominence melioration technique was developed. This proposed system has been implemented in MATLAB Simulink and compared with the recent researches.
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Jose Maria Lopez Pedrosa and Mark Bradley
The purpose of this paper is to develop a high‐throughput approach to optimize printing of pigment‐based formulations.
Abstract
Purpose
The purpose of this paper is to develop a high‐throughput approach to optimize printing of pigment‐based formulations.
Design/methodology/approach
A total of 40 formulations were robotically prepared by varying the concentrations of diethyleneglycol, glycerol and surfynol. In addition, a variety of inkjet printer (process) variables (voltage, pulse width and frequency) was varied. The combined influence of these two sets of variables on printing performance were determined, analysed and optimised using the Statistical Software Package (MODDE 8), which uses multiple linear regression and partial least square analysis.
Findings
The components diethyleneglycol and surfynol were observed to predominantly control viscosity and surface tension of all formulations, which voltage and pulse width were found to be the main factors controlling the spread of the droplet on the substrate.
Practical implications
Optimisation of pigment‐based formulations has typically involved the one‐by‐one systematic variation of components in a stepwise manner. The work reported here allowed the generation of a robust model allowing the properties of any new formulation to be accurately predicted. Importantly, the experimental tools and methods developed can be applied quite generally to the preparation of any new formulation for inkjet printing application.
Originality/value
Experimental design and high‐throughput technology allow new formulations to be accurately predicted for diverse inkjet applications.
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Computers need clean, reliable, electrical power. The various faults of electrical power, such as spikes, sags, outages, noise, frequency variations, and static electricity, are…
Abstract
Computers need clean, reliable, electrical power. The various faults of electrical power, such as spikes, sags, outages, noise, frequency variations, and static electricity, are defined and described. Preventive measures that computer users can employ to reduce the potential of electrical problems are discussed, as are the processes for detecting, diagnosing, and curing electrical problems when they do occur. Sidebars consider: transformers; power distribution units (PDUs); surge currents/ linear and non‐linear loads; and sizing the power conditioning system. The next issue will conclude this series with an article on uninterruptible power supplies and a bibliography.
Alexander S. Tonkoshkur and Alexander V. Ivanchenko
The purpose of this paper is to develop a generalized model of the nonlinear conductivity of varistor ceramic suitable for solving problems of prediction and control of ceramic…
Abstract
Purpose
The purpose of this paper is to develop a generalized model of the nonlinear conductivity of varistor ceramic suitable for solving problems of prediction and control of ceramic nonlinearity, stability of varistor properties.
Design/methodology/approach
The modeling of current-voltage characteristic of the intergranular barrier in metal oxide varistor ceramics is based on the development of the algorithm. It includes all the known mechanisms of electrotransfer in a wide range of voltages and currents of the current-voltage characteristics, and also takes into account the deviation of the barrier form the Schottky barrier.
Findings
The models of double Schottky barrier and double barrier of arbitrary form, as well as the algorithms for calculating the current-voltage characteristics of a single intergranular potential barrier and a separate “microvaristor” with the use of the most well-established understanding of the main mechanisms of electrical are developed. The results of current-voltage characteristics modeling correspond to the existing understanding of the nonlinear electrical conductivity varistor ceramics are based on zinc oxide. The model of double barrier of arbitrary form takes into account the deviation of the barrier form the Schottky barrier which is important in predicting the deformation of the current-voltage characteristics of the varistor products in the process of degradation.
Originality/value
The relation between the form of the current-voltage characteristic and the distribution profile of the donor concentration in the surface regions of the semiconductor crystallites constituting the intergranular potential barrier is established. The accumulation of donors in the space charge region leads to the increase in the current on the prebreakdown region of the current-voltage characteristic and the reduction of voltage corresponding to the breakdown region beginning of the current-voltage characteristic. The significant role of the interlayer in the formation of current-voltage characteristic of the intergranular potential barrier is shown.
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Yaxing Ren, Saqib Jamshed Rind and Lin Jiang
A standalone microgrid (MG) is able to use local renewable resources and reduce the loss in long distance transmission. But the single-phase device in a standalone MG can cause…
Abstract
Purpose
A standalone microgrid (MG) is able to use local renewable resources and reduce the loss in long distance transmission. But the single-phase device in a standalone MG can cause the voltage unbalance condition and additional power loss that reduces the cycle life of battery. This paper proposes an energy management strategy for the battery/supercapacitor (SC) hybrid energy storage system (HESS) to improve the transient performance of bus voltage under unbalanced load condition in a standalone AC microgrid (MG).
Design/methodology/approach
The SC has high power density and much more cycling times than battery and thus to be controlled to absorb the transient and unbalanced active power as well as the reactive power under unbalanced condition. Under the proposed energy management design, the battery only needs to generate balanced power to balance the steady state power demand. The energy management strategy for battery/SC HESS in a standalone AC MG is validated in simulation study using PSCAD/EMTDC.
Findings
The results show that the energy management strategy of HESS maintains the bus voltage and eliminates the unbalance condition under single-phase load. In addition, with the SC to absorb the reactive power and unbalanced active power, the unnecessary power loss in battery is reduced with shown less accumulate depth of discharge and higher average efficiency.
Originality/value
With this technology, the service life of the HESS can be extended and the total cost can be reduced.
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Yih-Lin Cheng and Tzu-Wei Tseng
Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric…
Abstract
Purpose
Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric printhead in MJ would affect droplet formation and performance, but there are very limited studies on it besides patents and know-hows by commercial manufacturers. Therefore, in this research, the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead was studied. Therefore, this research aims to study the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead.
Design/methodology/approach
Ricoh’s Gen4L printhead was adopted. A high-speed camera captured pictures of jetted droplets and droplet velocity was calculated. The waveforms included single-, double- and triple-pulse trapezoidal patterns. The effects of parameters were investigated and the suitable ones were determined based on the avoidance of satellite drops and preference of higher droplet velocity.
Findings
In a single-pulse waveform, an increase of fill time (Tf) decreased the droplet velocity. The maximum velocity happened at the same pulse width, the sum of fill time and hold time (Tf + Th). In double- and triple-pulse, a voltage difference (Vd) above zero in the holding stage was adopted except the last pulse to avoid satellite drops. Suitable parameters for the selected resin were obtained and the time-saving design process was established.
Research limitations/implications
Based on the effects of parameters and observed data trends, suggested procedures to determine suitable parameters were proposed with fewer experiments.
Practical implications
This study has verified the feasibility of suggested design procedures on another resin. The required number of trials was reduced significantly.
Originality/value
This research investigated the process of driving waveform design for the multi-nozzle piezoelectric printhead. The suggested procedures of finding suitable waveform parameters can reduce experimental trials and will be applicable to other MJ 3D printers when new materials are introduced.
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In the event of a DC short-circuit fault in a flexible DC power grid, the high peak value of the fault current puts forward more stringent requirements on the DC circuit breaker…
Abstract
Purpose
In the event of a DC short-circuit fault in a flexible DC power grid, the high peak value of the fault current puts forward more stringent requirements on the DC circuit breaker. The existing fault current cutoff mainly focuses on changing the topology structure. To suppress the development of fault current and reduce the investment cost of the DC grid, this paper aims to propose a dual-loop active current-limiting control based on energy difference.
Design/methodology/approach
Firstly, the equivalent circuit at fault is established, and the parameters related to the fault current are analyzed. Then, the relationship between the output voltage change of the bridge arm and the difference between the AC and DC energy is deduced. Finally, the experimental results are discussed on the real-time simulation platform Opal-RT.
Findings
The proposed current-limiting measures can greatly reduce the fault current, reduce the breaking current of the circuit breaker and increase the capacitor voltage during the fault period, which is beneficial to the stability of the AC system. It is verified that the proposed method is also applicable to a certain high-resistance fault.
Originality/value
This paper applies the method of AC fault to DC fault and deduces the relationship between energy difference and voltage variation corresponding to different step lengths based on digital simulation. In addition, two variables are used as control structure parameters to reduce the probability of system misoperation.
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Vitaliy Bilovol, Claudio Barbon and Bibiana Arcondo
The purpose of this paper is to investigate electrical properties of eutectic In8Sb8Te84 and In10Sb51Te39 as made thin films to evaluate their potential for non-volatile…
Abstract
Purpose
The purpose of this paper is to investigate electrical properties of eutectic In8Sb8Te84 and In10Sb51Te39 as made thin films to evaluate their potential for non-volatile phase-change memories, once the thermal measurements are very optimistic.
Design/methodology/approach
The films were deposited by pulse laser deposition technique. By using a very simple home-made cell, transversal current-voltage curves films were measured involving both voltage controlled-pulses generator and current controlled-pulses generator, employing different pulse shapes: triangular and sine shaped.
Findings
The memory effect, characteristic of a typical phase-change memory material, was observed in both materials under research. For higher tellurium content in the film, lower is the value of threshold voltage.
Research limitations/implications
Further studies on endurance, scaling and SET/RESET operations are needed.
Practical implications
The values of the key parameters, threshold voltage and hold voltage are comparable with those of Ge2Sb2Te5, GeTe and Sb2Te being considered to date as the main compounds for PCM devices.
Originality/value
The conduction mechanism in the amorphous regime is agreed with Poole–Frenkel effect in deep traps.
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M. Jagadesh Kumar and C. Linga Reddy
To develop a silicon lateral Schottky rectifier with low forward voltage drop and low reverse leakage current while its breakdown voltage is significantly larger than that of a…
Abstract
Purpose
To develop a silicon lateral Schottky rectifier with low forward voltage drop and low reverse leakage current while its breakdown voltage is significantly larger than that of a conventional Schottky rectifier.
Design/methodology/approach
A two‐dimensional device simulation has been used, to examine the effect lateral dual sidewall Schottky concept on the current‐voltage characteristics of a lateral Schottky rectifier on silicon‐on‐insulator. The Schottky contact consists of a low‐barrier metal and a high‐barrier metal.
Findings
Results show that, during forward bias, the low‐barrier Schottky (LBS) contact conducts resulting in a low forward voltage drop. During the reverse bias, the LBS contact is shielded by the depletion region of the high‐barrier Schottky contact resulting in a low reverse leakage current.
Practical implications
With this approach, silicon Schottky rectifiers with low power dissipation and improved breakdown voltage can be realized.
Originality/value
The proposed device has a large commercial potential as a low‐power high‐voltage switching device.
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The power electronic converter is used for the satisfaction of reactive power demand of induction generator, when grid-tied. This paper aims to present an application of STATCOM…
Abstract
Purpose
The power electronic converter is used for the satisfaction of reactive power demand of induction generator, when grid-tied. This paper aims to present an application of STATCOM to reduce inrush transient caused by the connection of a squirrel-cage induction generator (SCIG) to the grid.
Design/methodology/approach
The power generation system consists of an uncontrolled prime mover, a SCIG and a power electronic converter connected to the grid. The three-phase Neutral Point Clamped (NPC) converter works as a STATCOM to satisfy a reactive power demand of the generator. A control scheme of STATCOM uses the x-y reference frame rotating synchronously with grid voltage vector and the p-q instantaneous power theory to calculate q component of grid power.
Findings
It is shown that the parallel converter, which works as a reactive power compensator allows decreasing transients during a grid connection of the induction generator.
Research limitations/implications
Transients during a grid connection of the induction generator are only partially decreased.
Practical implications
It is needed to compensate for the reactive power of a SCIG. The NPC converter works as a STATCOM. The converter partially reduces grid transients during generator connection. The laboratory tests are demonstrated by connection 7.5 kW induction generator to 8 kVA transformer.
Originality/value
The paper presents the mitigation of grid transients during connection of induction generator with the power electronic converter working as reactive power compensator.
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