Initial Phase Angle Research Articles

Fault Ranging Method for Overhead-Cable Hybrid Distribution Lines Based on CEEDMAN Energy Relative Entropy

According to the parameter characteristics of cable-overhead line and the folding and reflection process of traveling waves when the wave impedance is discontinuous, a traveling wave abrupt change extraction method based on the empirical mode decomposition of fully adaptive noise ensemble (CEEDMAN) energy relative entropy is proposed for the first time. Through the combination of CEEDMAN and energy relative entropy, the transient traveling wave signals are generated when reflection and refraction occur, and the energy value of traveling waves will change abruptly, and the reflected and refracted wave heads will be captured by the change of relative energy. Combined with the magnitude difference of zero sequence current, the fault area can be determined. Traveling waves have different wave speeds in overhead lines and cable lines, and fault ranging is performed by determining the corresponding propagation speed. Finally, simulation verifies that the method can accurately determine the fault zone with high ranging accuracy under the conditions of different fault locations, different transition resistances and different initial phase angles.

深松机振动特性试验与分析

In this paper, the vibration characteristics of the 1ST-460 vibration subsoiler was analyzed. In order to solve the problem of vibration imbalance caused by the vibration component under the action of multiple groups of vibration shovels, the optimal combination mode of the vibration component under the interaction of multiple groups of shovels was obtained. Piezoelectric accelerometers are fixed symmetrically on the frame of the subsoiler to measure the vibration at different positions. TST5910 dynamic signal test and analysis system is used to collect and process the acceleration data. Non-load tests were carried out with different initial eccentric phase angle combination. Results showed that the combination of [0°, 180°, 180°, 0°] (symmetrically up and down staggered vibration) for the eccentric vibration component of four shovels is the optimal initial phase combination, which can lead to the minimum adverse vibration on the frame. Further tests were conducted under different vibrating frequency and amplitude/eccentric with optimal phase combination. The results showed that, when amplitude/eccentricity ratio was 2.0 and 2.5, frequency of vibration was 6.7 and 8.3 Hz, the required traction force of the subsoiler was stable and significantly reduced, which can improve the soil loosening performance and reduce the harmful vibration on the tractor.

Vortex Speckles with Customized Symmetry and Spatial Correlations

A family of optical speckles with propagation-invariant annular morphology are generated via a phase-only mask and free-space evolution, termed vortex speckles, for which phase design is inspired by the vortex beam's helical wave front carrying orbital angular momentum. Vortex beams' graceful symmetry (central and/or axial) can be naturally inherited into vortex speckles by adjusting the parity of the topological value $\ensuremath{\ell}$ and the consistency of the initial phase angle ${\ensuremath{\phi}}_{0}$. By sequentially imprinting such a series of phase profiles onto a spatial light modulator, the resultant stochastically fluctuating vortex speckles naturally constitute an annular pseudothermal light field, and the customized symmetry in intensity profiles leads to spatial correlations, which are exploited for Hanbury Brown and Twiss interferometry and beam-splitter-free lensless ghost imaging and diffraction experiments. Symmetric annular pseudothermal light also has diverse phase correlations, so in a proposed vortex self-interferometer, we can manipulate photon correlations (parity-induced anticorrelation) and observe intriguing correlation states (spatially varying photon correlation oscillations). This work not only presents a flexible light-source option for applications requiring ring-shaped speckle illumination, but it also paves the way for the customization of nontrivial classical correlation modes.

Optimal Projected Circular Orbit for Spacecraft Formation Flying Near a Slowly Rotating Asteroid

In spacecraft formation flying missions, the projected circular (relative) orbit (PCO), which appears circular when viewed along the zenith-nadir direction of the nominal chief spacecraft, is suitable for constructing a synthetic aperture radar. In this paper, the analysis of a PCO for spacecraft formation flying near a slowly rotating asteroid is conducted. By matching the in-plane and out-of-plane relative motion frequency, the critical values of the initial phase angle that characterizes the PCO are identified, resulting in the minimum precession of relative orbit. The analysis is then utilized to develop the fuel-optimal control law for establishing a target PCO. In particular, the fuel-optimal problem is addressed with an indirect method, where a homotopy approach is adopted, and the initial (unknown) costate vector is calculated with a scaling technique, so that the sensitivity to the initial guess problem is mitigated.

A measurement method for screw rod bending deflection by laser edge detection

The bending deflection of screw rod is an essential factor which affects the transmission accuracy and service life of the screw rod. However, existing researches haven’t proposed an effective and general method for measuring screw rod bending deflection. In this paper, a novel measurement method is proposed by using a laser edge detection sensor. The screw rod profile is approximated as its outer or inner cylinder by an algorithm based on cubic spline interpolation, and a rigorous mathematical model among eccentricity, initial phase angle and cross-section position is built. Then, extensive numerical simulations are conducted to analyze theoretical errors of proposed method, which provides guiding references for practices. Finally, the feasibility and reliability of proposed method are proved by comparing with measuring projector and repeatability and reproducibility analysis. In conclusion, the proposed method can realize continuous non-contact measurement of screw rod bending deflection and has strong practicability and generality.

Protection performance assessments of two types of sheath voltage limiters in 220kV single point bonded cable system

• An effective method about assessing the protection performance is proposed and the overvoltage, current and absorbed energy by limiters are simulated. • Four different factors considering a single-line to ground fault are investigated and variation ranges of overvoltage and energy absorption are achieved. • Protection performance of the two types of limiters is evaluated by comparing the simulation calculation results with the power frequency withstand capability. The growth of the power system contributes to the appearance of large short-circuit currents after a single-line to ground in the 220 kV single-point bonding cable system. The sheath voltage limiters installed may undergo a long-duration overvoltage and the absorbed energy by the limiters may exceed the energy absorption capacity. The sheath voltage limiter may breakdown and the failure poses a threat to the power system equipment and personnel as a result. To provide an effective method about assessing the protection performance when selecting the right sheath voltage limiters for the cable system, two types of limiters are adopted and the overvoltage, current and absorbed energy by limiters are simulated using the software ATP-EMTP in this article. The influences of fault initial phase angle, cable length, short-circuit current, and fault position under a single-line to ground fault are investigated and the variation range of the overvoltage and energy absorption are achieved. On the other hand, the power frequency withstand capability (including voltage withstand capability and energy absorption capability) of sheath voltage limiters, are obtained through laboratory experiments. By comparing the simulation calculation results with the power frequency withstand capability, the protection performance of the two types of limiters is evaluated in the article. The results demonstrate that the transient amplitude of voltage and current as well as absorbed energy of sheath voltage limiters reach the peak values at 0° and 180° for the A phase voltage initial angle. With increase of the cable length, short-circuit current and the distance between the fault point and the sending end of cable, the flowing current and energy absorbed by the type B of limiters rise apparently, whereas the voltage over it shows a slight change. Both the overvoltage and energy absorption of type B of sheath voltage limiter go beyond its power frequency withstand capability, namely evaluated as dangerous under all simulation fault conditions, while the type A is safety, considering the scenarios of the short-circuit currents less than 20 kA and the fault positions of 0 m and 200 m from the sending end of cable.

Realization of Single-Phase Grounding Fault Location and Recovery Technology in Distribution Network

In order to locate the single-phase-to-ground fault in distribution network, a research method of single-phase-to-ground fault location and recovery technology in distribution network is proposed. According to the characteristics of single-phase-to-ground fault in distribution network, the fault characteristics of zero-sequence current and three-phase current transient records are extracted by generalized S transform of correlation coefficient, and multi-source redundant information is formed. Fuzzy C-means clustering analysis method is used to fuse multiple fault features online location strategy. The simulation results show that the fuzzy clustering based on FCM changes continuously with the accumulation of samples, and the sample center changes with the enrichment of the samples. When the arc suppression coil is grounded with different initial phase angle transition resistance and intermittent fault, the state of each measuring point can be correctly identified, and the accurate energization rate is 97%. The test results show that the system can achieve accurate positioning for all sections.

Research on Deep Defect Detection Method of Cable Lead Sealing Based on Improved Pulsed Eddy Current Excitation

In order to reduce power failures caused by lead sealing defects, it is necessary to carry out nondestructive testing of cable lead sealings. However, previous studies have focused on the detection of surface and near-surface defects of lead sealings. Thus, an improved pulsed eddy current detection (IPECD) method is introduced to detect the deep defects of cable lead sealings (with depths ranging from 6 to 12 mm), and the frequency range selection principle and the optimization method of initial phase angles of different frequency components of IPECD, used to maximize the peak value of the excitation signal, are first explained in detail. Then, the detection sensitivities of the deep defects before and after the optimization are compared and analyzed based on a simulation. Finally, using the IPECD method, experiments are conducted to study the effects of the defect depth on features of the lift-off point of intersection and the zero-crossing time, enhancing the foundation for the prediction or rapid detection of the depth of lead sealing defects.

Analysis and Control of Current Harmonic in IPMSM Field-Oriented Control System

There is a certain amount of current harmonics in interior permanent magnet synchronous motor. In order to accurately control the current harmonic, this article focuses on three aspects: establishing current harmonic calculation model, extracting current harmonic, and designing current harmonic regulator. A current harmonic calculation model, which considers the effect of voltage harmonics induced by current controllers and digital control delay on the initial phase angle of voltage harmonics, is established for the first time. With the help of multiple synchronous rotating frame transformation, a current harmonic extraction method more suitable for motor drive field, which aims to extract the current harmonic characteristics of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis currents, is proposed. On this basis, the controlled quantity and control quantity are unified in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d–q</i> coordinate frame for analyzing the coupling relationship of current harmonic characteristics. And then a PI current harmonic regulator, including current harmonic decoupling and voltage harmonic initial phase angle compensation, is constructed, so as to realize the effective control of current harmonics. Finally, the effectiveness and superiority of the proposed method are verified by simulation and experiments.

A mathematical method for local defects and faults identification of 10 kV three‐core cable based on input impedance spectrum

Due to the strong coupling among the conductors of 10 kV three-core armored cables and the difficulty in identifying its defects and fault types, a method is proposed based on the input impedance spectrum. Firstly, the phase mode transformation matrix of a three-core cable is obtained by combining the multi-conductor transmission line theory with the loop analysis method to realize decoupling between conductors. Secondly, the input impedance matrices of a cable under different situations are derived. Based on this, a method is proposed to identify the local defects and fault types. The capacitive defects and inductive defects are identified according to the left or right offset of the amplitude spectrum; the short circuit and break faults of the cable can be identified according to the number of resonant points in the amplitude spectrum and the initial phase angle of the phase spectrum. Finally, to verify the correctness of the proposed method, a 10 kV three-core cable is taken as an example to carry out PSCAD circuit simulation and practical test. The results show that the proposed method can effectively identify the local defects and fault types of the three-core cable.

Hydrodynamic analysis of the energy dissipation of droplets on vibrating superhydrophobic surfaces

In this paper, experimental and numerical methods are presented to describe the hydrodynamic process of the vibration-induced detachment of a droplet from a superhydrophobic surface. We conduct the investigation of the droplet dynamics under various vibration and impact parameters, from an energy conversion perspective. In particular, the energy dissipation that occurs following the droplet impact is analyzed quantitatively. We identify three viewpoints on vibration-induced droplets. Firstly, the phase angle is the dominant factor in characterizing the droplet morphology evolution and energy dissipation on a vibrating surface. The law governing the initial phase angle is affected by the vibration frequency, while the intensity is affected by the vibration amplitude. Secondly, the energy dissipation is positively correlated with the maximum spreading diameter and impact velocity. A larger initial diameter tends to produce a longer contact time. Finally, the central jet formation depends heavily on the upward velocity of the concave liquid, under the peculiar morphology of a vibration-induced droplet. For all these effects, up to 60% of the total energy is squandered during impact, while the surface energy remains almost constant. Much of the droplet's kinetic energy is lost in resisting the viscous force of the substrate.

Bilateral Feedback in Oscillator Model Is Required to Explain the Coupling Dynamics of Hes1 with the Cell Cycle

Biological processes are governed by the expression of proteins, and for some proteins, their level of expression can fluctuate periodically over time (i.e., they oscillate). Many oscillatory proteins (e.g., cell cycle proteins and those from the HES family of transcription factors) are connected in complex ways, often within large networks. This complexity can be elucidated by developing intuitive mathematical models that describe the underlying critical aspects of the relationships between these processes. Here, we provide a mathematical explanation of a recently discovered biological phenomenon: the phasic position of the gene Hes1’s oscillatory expression at the beginning of the cell cycle of an individual human breast cancer stem cell can have a predictive value on how long that cell will take to complete a cell cycle. We use a two-component model of coupled oscillators to represent Hes1 and the cell cycle in the same cell with minimal assumptions. Inputting only the initial phase angles, we show that this model is capable of predicting the dynamic mitosis to mitosis behaviour of Hes1 and predicting cell cycle length patterns as found in real-world experimental data. Moreover, we discover that bidirectional coupling between Hes1 and the cell cycle is critical within the system for the data to be reproduced and that nonfixed asymmetry in the interactions between the oscillators is required. The phase dynamics we present here capture the complex interplay between Hes1 and the cell cycle, helping to explain nongenetic cell cycle variability, which has critical implications in cancer treatment contexts.

Power improvement of a cluster of three Savonius wind turbines using the variable-speed control method

The average power output of multiple Savonius wind turbines optimally arranged in a cluster is improved significantly compared to that of an isolated turbine due to the coupling effect. Previous investigations focused on the influence of the configuration and the initial phase angles of Savonius turbines operating at the same rotational speed in a cluster. This paper proposes to adopt the variable-speed control method to improve the power output of a three-turbine cluster, and simultaneously avoid the requirement for the accurate initial phase angle settings of the turbines. The Taguchi method is used to optimize the configuration of the cluster. The distances between the centers of adjacent turbines (L1-2, L1-3), the configuration angles (θ1-2, θ1-3), and the combination of rotational directions (RD) are taken as Taguchi experimental factors. The optimal configuration of the cluster is determined to be L1-2 = 2.0D, L1-3 = 2.4D, θ1-2 = 110°, θ1-3 = 110°, and RD = (-,+,-). The influence strength of the factors is ranked as configuration angle, RD, and distance between turbines. In addition, the average power coefficient of the turbines in the optimal cluster is 1.425 times that of an isolated turbine and the tip speed ratios of the three turbines are 1.13, 1.14, and 1.09.

Dynamic Characteristic Master Curve and Parameters of Different Asphalt Mixtures

Using an AMPT tester and based on laboratory tests, this paper performed a comparative study on the dynamic characteristics of different asphalt mixtures, analyzed the influence of different asphalt binders on the characteristic parameters of the dynamic modulus master curve and the phase angle master curve of asphalt mixture, and expounds the evaluation function of the phase angle master curve for mixture relaxation characteristics. The results show that the modulus master curve parameters of the asphalt mixture are closely related to voids in the mineral aggregate, mixture density, and asphalt content of the asphalt mixture. For the same kind of asphalt mixture, because the gradation of mineral aggregate is fixed and the volume parameters are almost the same, the ultimate modulus of the mixture at different temperatures is unique; when the temperature changes or the asphalt changes, the shape parameter β of the modulus master curve changes regularly, which brings different dynamic responses, and the lower β will show the characteristics of a higher modulus. Asphalt is the source of the viscoelasticity of the asphalt mixture. Although the influence of particle gradation of the mixture will bring about the change of modulus, the phase angle of the mixture depends on the viscoelastic properties of asphalt, and the initial phase angle in the main curve is positively correlated with asphalt penetration and negatively correlated with the softening point and viscosity, while the peak phase angle A is negatively correlated with penetration, and the softening point viscosity is positively correlated. The viscoelastic interval, represented by ω, is negatively correlated with penetration but positively correlated with the softening point and viscosity. The peak position, parameter ωc, of the phase angle master curve can evaluate the relaxation characteristics of the mixture, and the crack resistance of different mixtures can be compared without complex model calculation. In the comparison of the relaxation time of asphalt mixture, the relaxation time of foam cold-recycled mixture is the largest, which is significantly higher than that of other forms of cement mixture; the emulsified asphalt cold-recycled mixture is equivalent to AC20 and LSPM30 mixtures; the SBS-modified asphalt mixture has the best relaxation characteristics.

Analysis of Current Differential Protection Considering Rated Capacity of Inverter-Interfaced Renewable Plant

With the increasing capacity of grid-connected renewable energy power plants (REPPs), the fault current characteristics are remarkably altered. The limited amplitude and controlled initial phase angle of REPPs’ short-circuit current become highlighted. As a result, the differential current is no longer greater than restraint current on both sides of the protected devices when a fault occurs. It may lead to mal-operation of the current differential protection, which is used widely. It is necessary to demonstrate the cause-and-effect relationship between REPPs’ rated capacity and the protection adaptability. To solve this problem, the relationship between the rated capacity of inverter-interfaced REPP (IIREPP) and fault current amplitude, as well as its initial phase angle, is deduced first based on the IIREPPs’ fault behaviors. Further, by analyzing the influence of different rated capacity of REPPs on the ratio of operate to restraint current, the analytical expression of the IIREPP’s maximum rated capacity is deduced, which is suitable for analyzing the adaptability of differential protection. Finally, the simulation tests were carried out based on PSCAD/EMTDC. The test results show that the aforementioned expression is effective for evaluating the adaptability of current differential protection.

Systematic Geolocation Errors of FengYun-3D MERSI-II

Geolocation accuracy is a critical issue for remote sensing applications. To achieve subpixel accuracy, geolocation errors need to be systematically identified and corrected. In this study, we propose a geometric sensor model for FengYun-3D (FY-3D) MERSI-II, a second-generation visible (VIS)/infrared (IR) spectroradiometer, to generate the geolocation lookup table (GLT). The geometric sensor model retrieves the imaging rays from the focal plane to the K-mirrors, 45&#x00B0; scanning mirrors, the platform, and the earth&#x2019;s surface. After refining the attitude errors with ground control points (GCPs), the rigorous sensor model can achieve subpixel geolocation accuracy. However, significant systematic geolocation errors were identified from the residuals, especially for the area with large view angles. To study the errors of MERSI-II, we proposed a homogenous coordinate in the focal plane. As proven by both theory and experiments, the attitudes were adjusted to a wrong value and introduced systematic errors when there were principal point errors. The pitch angle error of K-mirrors caused the oscillation in the flight direction. The principal distance error introduced line coordinate-related error in the flight direction. Meanwhile, the initial phase angle error between the K-mirror and 45&#x00B0; scanning mirrors caused the line coordinate-related errors in the scanning direction. After correcting all the above-mentioned errors, the systematic geolocation errors of MERSI-II were removed. With 23 independent datasets, the root mean square errors (RMSEs) of 250 m bands were approximately 0.4 pixels, 100 m at nadir.

Transmission Line Fault Location Based on Improved Algorithm of Electromagnetic Time Reversal

For most traditional fault location methods, the fault type needs to be known in advance or there may be dead zones using the decoupled modulus. To solve the problems, an improved algorithm based on electromagnetic time reversal is proposed. The improved algorithm can realize fault location by using the coupling signal in the non-fault phase of the transmission line, so fault location can be realized effectively even when the fault phase is unknown. The feasibility of using non-fault phase coupled signals to locate faults is theoretically verified. A 750kV overhead transmission line model is established by ATP-EMTP to obtain the fault signal at the observation point. The fault signal is time reversed and then connected to the observation point as an injection source. Each hypothetical fault location is traversed and its current is calculated by the BLT super-matrix equation. The 2-norm based on current energy is proposed as the criterion, and the position with the largest norm is the fault location. The simulation results show that the algorithm is not affected by the fault types, transition resistance and the initial phase angles of the power sources on both sides, and has high accuracy.

Design Optimization of Linear-Rotary Motion Permanent Magnet Generator With E-Shaped Stator

A linear-rotary motion permanent magnet (PM) generator is investigated with six axial modular E-shaped stator sections arranged circumferentially, which can meet the requirement of wave and tidal energies generation. The PM pole is magnetized in radial direction, and the adjacent PM poles with opposite magnetized directions are interlaced by half mover pole pitch both in circumferential and axial directions, which are located on the mover surface. The rotational and rectilinear motions are achieved by one magnetic circuit structure according to the transverse flux principle and electromagnetic induction principle. The optimization design and electromagnetic properties of the proposed motor are calculated by 3-D finite element simulation. Then the optimal structural parameters are obtained. The back electromotive force (back EMF) and harmonics, the amplitudes of the cogging torque and detent force are decreased than those of the initial topology. Since three phases of the nine phase windings generate same initial phase angle of back EMF whether it works in rotational or rectilinear motion, the traditional three phase energy storage system can be used to realize the energy storage of the nine phase windings, which reduces the difficulty of electrical energy storage. The variation of the amplitude of back EMF is hardly affected with different mover positions, which is conducive to improve the efficiency of marine energy power generation.

Surface Topography Prediction Model for Free-form Surface Milling under a Dynamic System Response

At present, numerous studies on surface topography prediction models for plane workpieces have been performed at home and abroad. Given the complexity of curved surface models (especially free-form surfaces that cannot be expressed in analytic formulas), prediction models for the surface topography of free-form surfaces are rarely studied. This paper aims to establish and simulate a 3D surface topography model of ball-end milling for all types of curved surfaces, including simple surfaces and free-form surfaces. The dynamic factors influencing the surface topography, such as the spindle runout initial phase angle, runout amplitude, axial drift initial phase angle, and axial drift amplitude are considered in this model. Moreover, some processing parameters influencing the surface topography, such as cutter tooth number, machining inclination, radial cutting depth, feeding frequency and feed per tooth are also considered in this model. The simulation results can be used to optimize the milling process of the actual free-form surface to improve workpiece surface quality or to predict the surface topography of the given machining parameters.

Integration of Interturn Fault Diagnosis and Torque Ripple Minimization Control for Direct-Torque-Controlled SPMSM Drive System

This article proposes an integration method for interturn fault diagnosis and torque ripple minimization control of direct-torque-controlled surface-mounted permanent magnet synchronous machine (SPMSM) drive system without requiring the specific fault severity (short-circuited turn ratio, current). In this method, the interturn fault is detected and located based on the amplitude and initial phase angle of the zero-sequence voltage component (ZSVC). Both the torque injection and the improved flux observer are applied to reduce the torque ripple caused by the interturn fault. Furthermore, the torque injection and the improved flux observer are directly calculated by using the already obtained amplitude and initial phase angle of the ZSVC during the fault diagnosis process, without requiring the specific values of short-circuited turn ratio and fault current. The experimental results validate the effectiveness of the proposed integration method for the direct-torque-controlled SPMSM drive system.