Asymmetric Circuit Research Articles

Decomposition of the Voltages in a Three-Phase Asymmetrical Circuit with a Non-Sinusoidal Voltage Source

This article presents the concept of a mathematical description of a three-phase, four-wire asymmetrical electric circuit in decomposition into Voltages’ Physical Components (VPC), associated with distinctive physical phenomena in the load. This is an alternative method of mathematical description to the Currents’ Physical Components (CPC) still being developed since the end of the last century. According to previous studies, the improvement of the power factor in three-phase systems is possible by observing several components. Compensation for the scattered power is possible only by using a reactive compensator connected in series with the load. Thanks to the presented analytical method, it is possible to design compensators connected in series with the load. The VPC power theory opens the possibility of improving the power factor in three-phase networks for loads with asymmetry between phases. Due to the unfavorable impact of high currents on the compensator branches, the method proposed in the article can improve the energy quality in local low-power grids. However, the possibility of its practical use in high-power industrial networks is questionable.

Symmetric Circuit Layout With Decoupled Modular Switching Cells for Multiparalleled SiC mosfets

Parallel connection of silicon carbide (SiC) metal-oxide-semiconductor transistors (MOSFETs) are widely used in large-current-capacity applications or power modules. However, current imbalance caused by the tolerance of device parameters or asymmetric circuit layout is still a challenge for the reliability of the paralleled devices. The asymmetry of power circuit layout is inevitable when more than two devices are paralleled, which will lead to serious dynamic current imbalance. In this paper, an equivalently symmetric power circuit layout based on decoupled paralleled modular switching cells (MSCs) is presented. The current sharing mechanisms of typical asymmetric power circuit layouts are firstly illustrated. The layout with distributed DC decoupling capacitors turns out to have the potential to modify the current paths but requires further optimization. Based on the mechanisms, the construction of the symmetric layout with the concept of MSC is elaborated by mathematical analysis. DC decoupling capacitors are used to decouple the paralleled symmetric MSCs. Thereafter, the key considerations for the decoupling capacitors are discussed. Experiments are finally carried out to validate the analysis. The test results show that the peak current imbalance is reduced to only 4.1% by the equivalently symmetric power circuit layout, which confirms the effect of decoupled MSCs method.

Asymmetric activity of NetrinB controls laterality of the Drosophila brain

Left-Right (LR) asymmetry of the nervous system is widespread across animals and is thought to be important for cognition and behaviour. But in contrast to visceral organ asymmetry, the genetic basis and function of brain laterality remain only poorly characterized. In this study, we performed RNAi screening to identify genes controlling brain asymmetry in Drosophila. We found that the conserved NetrinB (NetB) pathway is required for a small group of bilateral neurons to project asymmetrically into a pair of neuropils (Asymmetrical Bodies, AB) in the central brain in both sexes. While neurons project unilaterally into the right AB in wild-type flies, netB mutants show a bilateral projection phenotype and hence lose asymmetry. Developmental time course analysis reveals an initially bilateral connectivity, eventually resolving into a right asymmetrical circuit during metamorphosis, with the NetB pathway being required just prior symmetry breaking. We show using unilateral clonal analysis that netB activity is required specifically on the right side for neurons to innervate the right AB. We finally show that loss of NetB pathway activity leads to specific alteration of long-term memory, providing a functional link between asymmetrical circuitry determined by NetB and animal cognitive functions.

A distance Protection/Fault location algorithm for Double-Circuit transmission lines with asymmetrical circuits during Cross-Country faults

The impedance-measuring elements and fault locators in distance relays suffer from measuring the correct fault impedance and fault location when facing cross-country faults (CCFs). During such atypical faults, this paper proposes a distance protection along with a fault location algorithm for double-circuit lines with asymmetrical circuits. This is fulfilled through instantaneous fault-branch currents innovatively derived from the line six-phase circuit model analysis on a time-domain basis. The currents derived lead to the relations that are mathematically linear combinations of designated vectors. This makes the possibility of establishing vector-input adaptive linear combiners (VI-ALC) in accordance with the relations derived. Being fed from the vectors of instantaneous measurements at the relaying side, the VI-ALCs with a distinctive capability of online training would swiftly give an accurate estimation of the fault distances during CCFs. The estimations are exploited in a logical procedure for both of the distance protection and fault location functions, taking account of different position status of the CCFs’ comprising LG faults. The proposed algorithm is feasibly implementable and is independent of the system configuration. It operates robustly in high-ground resistance and noisy conditions. Through extensive simulation studies in PSCAD/EMTDC, performance of the proposed algorithm would be investigated and verified in a variety of fault scenarios.

A Combined Liquid Cold Plate and Heat Sink Based Hybrid Cooling Approach for the Temperature Control of Integrated Circuit Chips

Abstract The study focuses on the experimental and numerical investigations on the cooling of seven protruding asymmetric integrated circuit (IC) chips arranged optimally at various positions in a switch mode power supply (SMPS) board. The chips are cooled under the laminar forced convection mode using the hybrid cooling technique (liquid cold plate integrated with the heat sinks). Fifteen heat sink cases (combinations) are considered for the analysis with the goal to keep the IC chip’s temperature under the safe limit (less than 100 °C). Variable power (heat) inputs to the IC chips along with a water flow rate of 0.5 kg/s (corresponding to the velocity of 4 m/s) inside the liquid cold plate are considered for the analysis. The heat sinks absorb the heat dissipated from the IC chips and reduce their temperature substantially by enhancing their heat removal rate up to 32%. The convection contribution of the IC chips has also improved by 62% using the heat sinks. Hence, hybrid cooling is found to be an effective technique for the temperature control of the IC chips. Numerical analyses are also carried out using the ansys fluent (v r16) to support the experiments. Both the results agree with each other in the error band of 6–12%.

Layout-Dominated Dynamic Imbalanced Current Analysis and Its Suppression Strategy of Parallel SiC MOSFETs

The multichip power module is a popular application for large-capacity and high-frequency converters. However, the existence of an asymmetric circuit layout has a significant influence on the current sharing among parallel SiC metal-oxide-semiconductor field-effect transistors (MOSFETs). In this paper, the mechanism of the dynamic current imbalance resulting from the asymmetry of signal terminal confluence points (STCPs) is comprehensively investigated by theoretical analyses and simulation validations. It is demonstrated that the infinite norm of the common branch impedance coupling matrix (INC) can be used to characterize the dynamic current sharing performance. With an increase in the infinite norm, the dynamic current imbalance of parallel SiC MOSFETs gradually increases. Moreover, some significant discoveries are obtained. It is concluded that dynamic current imbalance is dominated by the asymmetry of the power source confluence point (PSCP). However, the asymmetry of the drain, gate, and auxiliary source confluence points does not exhibit a great effect on dynamic current sharing. Then, a novel circuit layout with an elliptical structure is proposed to suppress the dynamic current imbalance. Finally, some experimental tests are derived to validate the effectiveness of the designed layout. Compared with the commercial power module, experimental results show that the maximum dynamic imbalanced current with the proposed layout is reduced from 7.39 A to 1.37 A, and the largest dynamic current imbalanced deviation decreases from 28.66% to 5.11%.

Analysis and Research on Power Systems Computer Aided Design for Yindong DC Transmission System

The AC equivalent (Shandong power grid) model of inverter side is established by electromagnetic transient simulation method, and the real data of Yindong transmission frame of HVDC is set in PSCAD model. Shandong power grid has set up different centralized faults. Asymmetric circuit accident are the most serious among them. Based on this analysis, we come to the conclusion that the fault of Shandong electric power AC system has a greater impact on Yindong DC transmission system, which provides important guidance for the reliable operation of Yindong HVDC transmission model in the future. We think it has better theoretical reference value.

Three-phase distribution transformer connections modeling based on matrix operation method by phase-coordinates

This paper proposes a matrix operation method for modeling the three-phase transformer by phase-coordinates. Based on decoupling theory, the 12 × 12 dimension primitive admittance matrix is obtained at first employing the coupling configuration of the windings. Under the condition of asymmetric magnetic circuits, according to the boundary conditions for transformer connections, the transformers in different connections enable to be modeling by the matrix operation method from the primitive admittance matrix. Another purpose of this paper is to explain the differences of the phase-coordinates and the positive sequence parameters in the impedances of the transformers. The numerical testing results in IEEE-4 system show that the proposed method is valid and efficient.

Method for extracting motor impedance characteristics online

Due to increases in switching frequency, the electromagnetic interference of motor drive systems has been receiving more attention. In a motor drive system, the devices in the inverter produce serious electromagnetic interference during high-frequency switching. It is necessary to model the motor drive system to predict the electromagnetic interference level. Extraction of the motor impedance characteristic is necessary for the modeling of a motor drive system. At present, most research only studies the measurement method of a motor in the static state. However, motor impedance characteristics in the static state cannot represent motor impedance characteristics in operation. In this paper, an online measurement method of motor impedance characteristics is proposed. For the three-phase asymmetric circuit caused by modulation, the motor impedance characteristics in operation are calculated by establishing Kirchhoff voltage equations. A precision power scope PX8000 is used to measure the harmonic components of single-phase voltage, single-phase current, and common-mode current. The time-delay difference of the precision power scope PX8000 between different probes is also considered. Experiments prove that the time-delay difference does not affect the measurement results. Through comparing the motor impedance characteristics measured by different filters, the method of extracting the motor impedance characteristics online is validated. Finally, the motor impedance characteristics in the static state and the motor impedance characteristics of online extraction are experimentally compared. The motor impedance characteristics of the online extraction method proposed in this paper have more advantages than traditional methods.

A Design Approach to Wireless High-Power Transfer to Multiple Receivers with Asymmetric Circuit

Wireless Power Transfer (WPT) system commonly compensates by a symmetric pair of inductor and capacitor on the primary-secondary circuits to use the idea of resonance. It should be noticed that an additional component compensation on the common WPT circuit is able to affect the power transferred to the load. Although it is useful to wirelessly transfer power to multiple receivers, the complexity of the system will increase with the number of receivers as well as the system loses symmetry, and then, it would be difficult to design high power transfer system. This study explores the WPT circuit compensated with a single capacitor in the primary side to transfer high power to dual receivers. Using a single capacitor on the primary side makes the circuit asymmetry, so the idea of resonance cannot be used. To find operating points that maximize transferred power, this paper uses a mathematical optimization technique with several design variables. The NSGA-II (Non-dominated Sorting Genetic Algorithm II) is used to optimize the design variables of the mathematical system model. The results show that the proposed system is able to attain high power even though using only a single capacitor compensation without the idea of resonance.

Suppression of Cooking Oil Deterioration by Electromagnetic Field with Harmonics Generated by Asymmetric Circuit

Suppression of Cooking Oil Deterioration by Electromagnetic Field with Harmonics Generated by Asymmetric Circuit

Photosensor Device Based on a 16-Electrode Position-Sensitive Detector with High Temporal Resolution

Abstract—We report the development of a photosensor device based on a position-sensitive detector with a gallium arsenide (GaAs) cathode and a 16-element anode. In the case of asymmetric heterostatic circuit (electrodes combined in fours) its working field was limited by 10 mm (for a 18-mm photocathode). Implementing a scheme of analog coding of the coordinates of the centroids of electron avalanches arriving to the anode in the photosensor device made it possible to increase the field size to 14 mm and achieve a spatial resolution of 50 μm. The resulting photosensor device is used as the principal component of a multimode field photopolarimeter in observations with a microsecond time resolution on the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We report some of the results obtained in the process of this work.

Analysis of the network current in circuits of twenty-four pulse controlled rectifiers

The main part of the electric power is consumed in a transformed form and the use of semiconductor converter circuits for obtaining the specified parameters of the load increases. As part of energy savings, the requirements for the quality of semiconductor converters, their impact on the supply network, the load and related consumers are increasing. To convert AC voltage to DC widely used circuits, made on the basis of single-operation thyristors. Their significant drawback is poor electromagnetic compatibility with the supply network. To improve it and increase its efficiency, multi-pulse rectifier circuits are used. With a high load power, as well as when special requirements are imposed on the harmonic composition of the output voltage and current consumed from the network, twenty-four-pulse controlled rectifier circuits can be used, which can reduce power losses not only in rectifiers, but also in power supply networks and adjacent consumers due to reducing the effect of distortion on the quality characteristics of networks from the non-linear load, which is the rectifier. In proportion to the increase in the pulsation of the rectified voltage, the weight and size and cost parameters of the smoothing filters in DC networks are reduced. In this paper, a computer simulation of the symmetric and asymmetric circuits of twenty-four-pulse controlled rectifiers was performed. Analysis of the simulation results showed that with the same number of ripples in the output voltage and full symmetry of the circuits in terms of load, the shapes of the network current curves are different. When conducting a virtual experiment, it became obvious that for an asymmetric scheme the amplitudes of higher harmonics in the entire range of control angles are consistently lower than the amplitudes of harmonics for a symmetric scheme and the asymmetric scheme is promising for practical use, despite the need to use two different types of transformers.

Current Balancing of Paralleled SiC mosfets for a Resonant Pulsed Power Converter

Paralleling silicon carbide (SiC) mosfets is a cost-effective solution for increasing pulse current rating. However, the device SiC mosfets mismatch and asymmetrical circuit layout would lead to imbalance current of the paralleled SiC mosfets . In this letter, we propose a passive approach, that is, a coupled inductor instead of the conventional resonant inductor, which is used for a resonant pulsed power converter. The coupled inductor enables even current sharing of the parallel SiC mosfet s, and also helps with pulsewidth adjustment, which leads to a simplified system without complex control circuit compared with the active solution. The configuration of the proposed topology, operating principle, imbalance current limitation mechanism, and design guidelines are fully discussed and presented. Additionally, experiments are carried out to verify the analysis and effectiveness of the proposed solution. The proposed method can be extended to the scenario with more than two parallel.

Stator tooth shape optimization for double salient hybrid excitation generator based on asymmetric circuit analysis

PurposeThis paper aims to clarify the relationship between stator tooth shape and DC voltage fluctuation of a double salient hybrid excitation generator (DSHEG). It analyzes the asymmetrical characteristics of the magnetic circuit and inductance between each phase. The study aims to reduce voltage fluctuation by using a stator shape optimization scheme, which helps reducing inductance difference.Design/methodology/approachThis paper opted for a method combined with theoretical analysis, simulation and experimental verification. The stator tooth optimization scheme is given based on theoretical asymmetrical analysis and Taguchi method. A series of two-dimensional finite element analysis simulation of different conditions are conducted. Two prototypes with different stator tooth shape are made and experiments are carried out.FindingsThe paper provides empirical insights into how the stator tooth shape influences the asymmetry of inductance and DC voltage fluctuation. Compensation adjustments to the stator tooth shape can narrow the inductance differences of each phase. It suggests that “LTL” shaped DSHEG has lower voltage ripple than “III” shaped DSHEG without sacrificing output power.Research limitations/implicationsBecause of the chosen research approach, the gap between magnets and stator and end effect are not considered. Errors exist between simulation and experimental results.Practical implicationsThe paper includes implications for other “C” shaped tooth optimization. Study on phase asymmetry of the special machine can further improve quality testing and simplify control strategy.Originality/valueThis paper analyzes the asymmetry of DSHEG and proposes an optimized stator tooth shape to reduce DC voltage fluctuation.

Context-dependent signaling of coincident auditory and visual events in primary visual cortex.

Detecting rapid, coincident changes across sensory modalities is essential for recognition of sudden threats or events. Using two-photon calcium imaging in identified cell types in awake, head-fixed mice, we show that, among the basic features of a sound envelope, loud sound onsets are a dominant feature coded by the auditory cortex neurons projecting to primary visual cortex (V1). In V1, a small number of layer 1 interneurons gates this cross-modal information flow in a context-dependent manner. In dark conditions, auditory cortex inputs lead to suppression of the V1 population. However, when sound input coincides with a visual stimulus, visual responses are boosted in V1, most strongly after loud sound onsets. Thus, a dynamic, asymmetric circuit connecting AC and V1 contributes to the encoding of visual events that are coincident with sounds.

A Novel Arbitrary Terminated Unequal Coupler With Bandwidth-Enhanced Positive and Negative Group Delay Characteristics

A novel and generalized planar coupler with four independent arbitrary terminated resistances, unequal power division, and wideband positive and negative group delays (NGDs) is proposed. The proposed asymmetrical circuit configuration includes six-section of transmission lines (TLs) and two coupled-line sections with series resistors. Six-section TLs have inherited the free impedance-transformation capability of the four independent arbitrarily terminated resistances. The combination of series resistors and short-circuited coupled-line sections enhances the NGD bandwidth and improves the flatness of NGD response. The analytical closed-form equations with reasonable practical ranges of the four terminated resistances are provided and discussed. For experimental demonstration, the proposed theory and predicted performance are verified by two fabricated examples (examples A and B) based on the microstrip technology. The measured results indicate that the coupler is able to realize good matching, excellent isolation, required NGD bandwidth, and acceptable NGD flatness. Example A (B) with different specified terminated impedances achieved an NGD bandwidth of 540 MHz (550 MHz) and 330 MHz (320 MHz) of flat NGD response with a center group delay of −0.48 ns (−0.49 ns) and ±8% NGD fluctuation that is acceptable to be considered as a wideband flat NGD response.

Analysis and Design of Solar Power System Interface Utility Using ZVS Converter

The solar power generation system with minimal losses, high simplicity and easy control is attempted in this work , by developing a grid-tied zero-voltage switching ( ZVS) inverter with a less number of power conversion stages and the least count of passive components, for single-phase applications that are suitable for conversion from low-voltage DC (40-60 V) to line voltage AC ( 230 VAC; RMS) at average power levels of 175 W and below. The ZVS full-bridge inverter fed from a PV panel is working on higher frequency with an asymmetric auxiliary circuit , which guarantees ZVS at the switching instants of the metal-oxide-semiconductor field-effect transistors (MOSFETs) by supplying the reactive current to these full-bridge semiconductor switches and reducing the switching losses. Checking of the constructional workability and analytical feasibility of the proposed topology with the highest efficiency and the simplest control was the target of this work, which was set on the basis of the results obtained in the MATLAB Simulink environment. The control strategies were planned for the optimum value of the reactive current injected by the auxiliary circuit to guarantee ZVS and use of phase shifted pulsewidth modulation (PWM) with varying frequencies for the full-bridge inverter and half-bridge cyclo-converter. The hybrid maximum power point tracking (MPPT) was part of this plan used to set the power at its maximum value against the environmental changes. Citation: Deshbhratar, R. G., and Renge, M. M. (2018). Analysis and Design of Solar Power System Interface Utility Using ZVS Converter. Trends in Renewable Energy, 4, 83-101. DOI: 10.17737/tre.2018.4.3.0052

Direct intertectal inputs are an integral component of the bilateral sensorimotor circuit for behavior in Xenopus tadpoles.

The circuit controlling visually guided behavior in nonmammalian vertebrates, such as Xenopus tadpoles, includes retinal projections to the contralateral optic tectum, where visual information is processed, and tectal motor outputs projecting ipsilaterally to hindbrain and spinal cord. Tadpoles have an intertectal commissure whose function is unknown, but it might transfer information between the tectal lobes. Differences in visual experience between the two eyes have profound effects on the development and function of visual circuits in animals with binocular vision, but the effects on animals with fully crossed retinal projections are not clear. We tested the effect of monocular visual experience on the visuomotor circuit in Xenopus tadpoles. We show that cutting the intertectal commissure or providing visual experience to one eye (monocular visual experience) is sufficient to disrupt tectally mediated visual avoidance behavior. Monocular visual experience induces asymmetry in tectal circuit activity across the midline. Repeated exposure to monocular visual experience drives maturation of the stimulated retinotectal synapses, seen as increased AMPA-to-NMDA ratios, induces synaptic plasticity in intertectal synaptic connections, and induces bilaterally asymmetric changes in the tectal excitation-to-inhibition ratio (E/I). We show that unilateral expression of peptides that interfere with AMPA or GABAA receptor trafficking alters E/I in the transfected tectum and is sufficient to degrade visuomotor behavior. Our study demonstrates that monocular visual experience in animals with fully crossed visual systems produces asymmetric circuit function across the midline and degrades visuomotor behavior. The data further suggest that intertectal inputs are an integral component of a bilateral visuomotor circuit critical for behavior. NEW & NOTEWORTHY The developing optic tectum of Xenopus tadpoles represents a unique circuit in which laterally positioned eyes provide sensory input to a circuit that is transiently monocular, but which will be binocular in the animal's adulthood. We challenge the idea that the two lobes of tadpole optic tectum function independently by testing the requirement of interhemispheric communication and demonstrate that unbalanced sensory input can induce structural and functional plasticity in the tectum sufficient to disrupt function.

A Modified Phase Disposition Pulse Width Modulation to Suppress the Leakage Current for the Transformerless Cascaded H-Bridge Inverters

Transformerless cascaded H-bridge inverters have the advantages of low cost and high efficiency in low-power applications. However, the leakage currents resulting from the parasitic capacitors may increase system losses, electromagnetic interference, and safety concerns. To reduce the leakage current, this paper first establishes the equivalent common-mode circuit of the inverter with the parasitic capacitance and analyzes the characteristics of leakage current in the symmetrical and asymmetrical filter inductance circuit, respectively. The analysis shows that the traditional phase disposition pulse width modulation or phase-shift pulse width modulation cannot solve the leakage current issues, but modifying the modulation methods can eliminate the system leakage current in the symmetrical circuit, and it has a little effect in the asymmetrical circuit. For this reason, a modified phase disposition pulse width modulation for the symmetrical circuit, which can eliminate the leakage current effectively with simple implementation, is proposed. Simulation and experimental results are reported, along with evaluation and comparison results, against a conventional carrier-based pulse width modulation method.