Current Phase Angle Research Articles

Influence of a new controlled voltage regulator on the current and voltage non-sinusoidality of a power supply system

This work evaluates the influence of a new controlled voltage regulator on the current and voltage non-sinusoidality in different sections of a power supply system during smooth (discrete) voltage regulation on the high-voltage side of a shop transformer. The MatLab software application was used to develop a block-modular model for a transformer substation with the proposed controlled voltage regulator and measurement modules. The developed model was used to investigate the current and voltage non-sinusoidality in different parts of a power supply system when stabilizing the voltage at the consumer end at a given level. The study was carried out using a shop transformer with a capacity of 1 MV∙A and a voltage of 6/0.4 kV under an active-inductive character of the load with the load current phase angle of φ=45 deg. The obtained results confirm that, due to the extended functional capabilities of the proposed technical solution, the voltage at consumers is maintained at a given level under high technical and economic performance. When the network voltage is reduced by 5% and the activeinductive load current is increased by 35%, the proposed device was shown to create voltage non-sinusoidality. The voltage non-sinusoidality value does not exceed the permissible domestic and international norms. In addition, the proposed device is capable of maintaining the voltage at the consumer end at a given level. The obtained integral characteristic of voltage stabilization shows that the application of the proposed technical solution instead of the existing mechanical voltage regulator of the “switching without excitation” type allows the nominal voltage at the busbar of the switchgear to be retained. Further research will investigate voltage stabilization at consumers with simultaneous compensation of reactive power for complex improvement of technical and economic indicators of power supply systems under the conditions of unstable supply voltage and load current.

Design, development and multi-scenario application of portable multifunctional test master based on μM-PMU: The case study of Lingang new City Grid, Shanghai

With the large-scale access of new energy generation and electric vehicle charging piles to the grids, power generation and loads are characterized by random fluctuations and intermittency, which affect the stable operation of the distribution network. μM-PMU is capable of realizing the dynamic process monitoring of the grids. In order to solve the function and performance testing problems of multiple application scenarios of μM-PMU, this thesis develops a portable master station based on synchronous phasor measurement system to realize zero drift, voltage amplitude measurement accuracy, voltage phase angle accuracy, current amplitude measurement accuracy, current phase angle measurement accuracy, frequency measurement accuracy, voltage amplitude change with frequency accuracy, and voltage phase angle change with frequency accuracy, Accuracy of current amplitude with frequency change, accuracy of current phase angle with frequency change, active power accuracy, reactive power accuracy, amplitude step response, phase angle step response, frequency step response, a total of 15 test items. It can automatically calculate test results and generate test reports according to different equipment models, reducing the mistakes and calculation errors that may be caused by manually recording test data and improving the accuracy of test results and calculation precision.

A Section Location Method of Single-Phase Short-Circuit Faults for Distribution Networks Containing Distributed Generators Based on Fusion Fault Confidence of Short-Circuit Current Vectors

A Section Location Method of Single-Phase Short-Circuit Faults for Distribution Networks Containing Distributed Generators Based on Fusion Fault Confidence of Short-Circuit Current Vectors

Analysis and suppression of operational overvoltage and inrush current for high‐speed trains by automatic phase‐switching technique

AbstractWhen a high‐speed train approaches the insulated phase‐splitting section embedded between neighbouring power supply arms, the vacuum circuit breaker (VCB) installed on trains must be disconnected to maintain the traction power supply system as a no‐load condition for completing phase‐switching action, as the train passes through the phase‐splitting section depending on its inertia. However, when operating VCBs, the arc is easily triggered between the mobile contacts inside, accompanied by an overvoltage impulse. Herein, to explore the generating mechanism of inrush current and operational overvoltage, a model describing the ‘substation‐catenary‐train’ traction power supply system is launched based on an equivalent circuit modelling technique. Through the analysis of the transient VCB operational process, the phase of catenary voltage is directly related to the characteristics of the VCB switching‐on overvoltage, as the traction current's phase angle is relevant to the amplitude‐frequency characteristics of the VCB switching‐off overvoltage. Inrush current as a noteworthy element is related to the traction transformer's remanence. The automatic phase‐switching technique is utilised to suppress both operational overvoltage and inrush current, as the optimal combination of VCB switching‐on and switching‐off phases considering the balance between overvoltage and inrush current is achieved based on the particle swarm algorithm.

A Review on the Fault-Tolerant Method of PMSM using Finite Element Method by Modifying Phase Angle for EV Applications

Abstract: The present research reviews a fault-tolerant technique for Permanent Magnet Synchronous Motors (PMSMs) that involves phase angle adjustment. Fault tolerance standards for the motor used in electric vehicles are necessary due to the rapid development of these vehicles. The primary option for electric vehicle drive motors is increasingly being replaced with permanent magnet synchronous motors (PMSM), which have minimal torque ripple, great durability, and other benefits. After comparing a six-phase PMSM to a conventional three-phase PMSM, the performance following a phase open is examined. A fault-tolerant technique for modifying the left phase current's phase angle to reduce torque ripple following a phase open is then described. The finite element simulation indicates that the six-phase PMSM's output torque ripple is reduced, and the fault-tolerant technique that is being described can further reduce the torque ripple.

Design and analysis of PM‐assisted synchronous reluctance machine with shifted magnetic poles

AbstractThe authors present a new design of a PM‐assisted synchronous reluctance motor (PM‐SynRM) with uneven air‐gap length to improve the power factor and enhance the torque production capability. The rotor structure is modified to properly shift rotor magnetic poles and therefore (i) increases the back‐EMF and the electromagnetic torque, (ii) allows electromagnetic torque and reluctance torque components peak near the same current phase angle. The proposed solution is simple, does not require changing the arrangement of magnets and/or flux barriers and is applicable to all types of PM‐SynRMs. Sensitivity analysis is carried out to determine the extent of which the proposed magnetic pole shifting may impact the resultant torque profile. To assess the level of success, the electromagnetic characteristics of the proposed design (e.g. torque, power factor, and back‐EMF) are compared against the baseline structure under the same operating conditions. For verification purposes, Finite Element simulation results are validated via a series of analytical calculations and experimental measurements, and supported with detailed theoretical discussion.

Stator ITSC Fault Diagnosis for EMU Induction Traction Motor Based on Goertzel Algorithm and Random Forest

The stator winding insulation system is the most critical and weakest part of the EMU’s (electric multiple unit’s) traction motor. The effective diagnosis for stator ITSC (inter-turn short-circuit) faults can prevent a fault from expanding into phase-to-phase or ground short-circuits. The TCU (traction control unit) controls the traction inverter to output SPWM (sine pulse width modulation) excitation voltage when the traction motor is at a standstill. Three ITSC fault diagnostic conditions are based on different IGBTs’ control logics. The Goertzel algorithm is used to calculate the fundamental current amplitude difference Δi and phase angle difference Δθ of equivalent parallel windings under the three diagnostic conditions. The six parameters under the three diagnostic conditions are used as features to establish an ITSC fault diagnostic model based on the random forest. The proposed method was validated using a simulation experimental platform for the ITSC fault diagnosis of EMU traction motors. The experimental results indicate that the current amplitude features Δi and phase angle features Δθ change obviously with an increase in the ITSC fault extent if the ITSC fault occurs at the equivalent parallel windings. The accuracy of the ITSC fault diagnosis model based on the random forest for ITSC fault detection and location, both in train and test samples, is 100%.

Permanent Magnet Assisted Synchronous Reluctance Motor with Asymmetric Rotor for High Torque Performance

Permanent magnet assisted synchronous reluctance motor (PMA-SynRM) is a kind of high torque density energy conversion device widely used in modern industry. In this paper, based on the basic topology of PMA-SynRM, a novel PMA-SynRM of asymmetric rotor with position-biased magnet is proposed. The asymmetric rotor design with position-biased magnet realizes the concentration of magnetic field lines in the motor air gap to obtain higher electromagnetic torque, and makes both of magnetic and reluctance torque obtain the peak value at the same current phase angle. The asymmetric rotor configuration is theoretically illustrated by space vector diagram, and the feasibility of high torque performance of the motor is verified. Through the finite element simulation, the effect of the side barrier on output torque and the Mises stress under the rotor asymmetrical design are analyzed. Then the motor characteristics including airgap flux density, back EMF, magnetic torque, reluctance torque, torque ripple, losses, and efficiency are calculated for both the basic and proposed PMA-SynRMs. The results show that the proposed PMA-SynRM has higher torque and efficiency than the basic topology. Moreover, the torque ripple of the proposed PMA-SynRM is reduced by the method with harmonic current injection, and the torque characteristics in the whole current cycle are analyzed. Finally, the endurance to avoid PM demagnetization is confirmed based on the PM remanence calculation.

Distance Protection for Lines Connecting Converter Interfaced Renewable Power Plants: Adaptive to Grid-end Structural Changes

Typical fault current characteristics of converter interfaced renewable power plants have significant impact on the reliability of traditional line distance protection. Large degrees of system non-homogeneity introduce substantial error in the apparent impedance calculation. In this paper, an adaptive distance relaying method for lines connected to converter-interfaced renewable power plants is proposed. A range of fault current phase angles is identified using the local and remote equivalent source impedances, which are calculated using only local measurements. Corresponding to the lower and upper bound of the identified range of fault current phase angle, two apparent impedances are calculated based on priority to dependability and security of protection operation. The trip decision is made based on the weighted sum of the first and second apparent impedances. Tuning of the dependability and security weightage factors based on the calculated remote grid-end source impedance, ensures adaptability and reliability of operation, even after structural changes in the grid. The proposed method is verified using IEEE 39 bus system and validated using field data. Comparative assessment with practically proven distance and modified distance protection method for lines connected with renewables is also provided.

Ground Fault Detection of Small Resistance Grounding System Based on Improved Phase Current Abrupt Variable Method

When a high fault resistance happens in a small resistance ground system, the protection device is simple to be unsuccessful to manage. By analyzing the characteristics of positive, negative currents in the additional state of fault, it is found that the fault detection method constructed only by the phase current increment relationship has risk of misoperation, but relationship among the magnitude of phase current increment can directly reflect the phase of the ground fault. At the same time, the phase location among the fault phase voltage and the current of the unhealthy part and non-fault line is different. Therefore, a ground fault protection method based on the correlation between the phase current increment ratio and the different phase angles of fault phase voltage and current is proposed. We choose the phase with the big phase current mutation as the grounding phase, and affect the fault part by the phase difference between the fault phase voltage and the current of the line. This eliminates the risk of protection maloperation only using the relationship between the size of current increment and protection sensitivity in case of high resistance fault. It can be used for fault phase selection, location, and multi-level protection. The correctness of the way is certificated by simulation.

Non-Contact Measurement Method of Phase Current Based on Magnetic Field Decoupling Calculation for Three-Phase Four-Core Cable

As one of the important parameters characterizing the cable’s operation status, an accurate measurement of the current is particularly important for the cable’s reliable operation and status monitoring. Aiming at the problem that the sum of the current phasors of multiphase cables is 0 when running in a steady state, and that the traditional mutual inductance current measurement method cannot be used for the phase current measurement of such cables, or that the insulation layer needs to be damaged, this paper proposes a non-contact measurement method of three-phase cable current, based on the magnetic field decoupling calculation. When combined with the actual parameters of the three-phase cable, the analytical calculation model of the magnetic field distribution of the three-phase cable is established. The relationship between the output ratio of the sensor and the deflection angle is obtained through theoretical derivation, the magnetic field coupling coefficient matrix is determined, and the transfer relationship between the output of the magnetic sensor and the current of each phase is clarified; an array magnetic field sensor is designed, which can sense the information of the adjacent magnetic field independently and is used for the reconstruction of three-phase currents. The effectiveness of the proposed method was tested on the built three-phase four-core cable current measurement test platform. The experimental results show that under the three-phase current balance, the measurement error of phase A, phase B and phase C is less than 2.8%, and the waveform and phase angle of the three-phase current can be well restored, which verifies the three-phase current measurement method proposed in this paper.

Topology Optimization Framework for Simultaneously Determining the Optimal Structural Design and Current Phase Angle of the IPMSMs for the MTPA Control

Although it is crucial to design the magnetic flux path and the maximum torque per ampere (MTPA) current reference under the current limitation, it is challenging to simultaneously consider these features in developing an interior permanent magnet synchronous motors (IPMSM) due to complicated coupling effects. In this article, to overcome the above issue, the motor-design parameters are estimated by conducting electromagnetic finite element (FE) analysis two times at every iteration of topology optimization. Then, the MTPA current phase angle can be analytically expressed in terms of an elementwise relative density (i.e., design variable in topology optimization). In addition, the structural safety is assessed by conducting the structural FE analysis under design-dependent loads to reflect a high-speed rotation. The proposed two-stage topology optimization enables us to simultaneously optimize both a structural design and current phase angle to achieve the maximum electromagnetic performance. Structural safety and manufacturability are also considered to obtain a practically meaningful design. With two different types of permanent magnets, the optimized IPMSMs are obtained and manufactured to validate the proposed method. Simulation and experimental results demonstrate the validity and potential of this work.

A Novel Anti-Offset Interdigital Electrode Capacitive Coupler for Mobile Desktop Charging

This article proposes a novel antioffset interdigital electrode capacitive wireless power transfer system for mobile desktop applications. The coupler consists of two pairs of series connected interdigital electrodes at transmitter side and two copper plates at receiver side, and a detailed generalized design methodology is provided. To realize antioffset at transverse direction, switch array is adopted at series connected interdigital electrodes side, and coupling coefficient can be kept stable at any misalignment distance. When misalignment occurs, changes of switch array are decided by voltage and current phase angle detection at transmitter side, and the system resonance frequency does not need to be tuned with the changes of misalignment distance. No additional position detection sensors are required, which simplifies the system and reduces the production cost. System energy transfer efficiency can be kept stable between 81.18% and 86.77% at any misalignment distance. When rotational misalignment occurs, the receiver can maintain voltage gain of more than 1.95 with stable 5 W output at −45°∼45° offset. Experimental results at 2.28 MHz show great agreement with theoretical analysis.

Residential Harmonic Injection Models Based on Field Measurements

In recent years, harmonic current levels have increased in residential distribution networks due to the growing penetration of nonlinear loads at customer premises. To properly model the harmonic current injection of residences, probabilistic models that account for the stochastic behavior of domestic loads are needed. As a part of the study reported in this paper, a field measurement campaign was performed in 24 dwellings during a one-week period with a one-minute resolution. Harmonic current magnitudes and phase angles of odd harmonic orders up to the 25th as well as the active and reactive power demanded were recorded. By applying two different unsupervised learning techniques (i.e., nonparametric density estimation and Gaussian mixture models) to these measurements, two probabilistic models of harmonic injection of individual residential sites have been derived. Statistical probability distributions have been determined for the magnitude and phase of each harmonic order segmented in different power demand intervals. The developed models are validated on a test feeder by comparing harmonic voltages caused by the injection of the synthetically generated currents with those obtained from measurements. Both field measurement results and the detailed data defining the probabilistic harmonic current models are made public in an Open Science database repository.

A CC-Type IPT System Based on S/S/N Three-Coil Structure to Realize Low-Cost and Compact Receiver

The characteristics of load-independent constant current (CC) output and zero phase angle (ZPA) operation are required in many scenarios of inductive power transfer (IPT) applications. However, the existing topologies with CC output characteristics usually need to introduce additional compensation components on the receiving side to compensate for reactive power and achieve the preset function. This not only increases the occupied space of the receiving side, but also increases the cost and weight. Therefore, this study proposes a new IPT system based on an S/S/N three-coil structure. The proposed system can achieve the CC output function and an operation nearly ZPA and zero-voltage switching (ZVS) through flexible parameter design. Moreover, there are no compensation components on the receiving side of the proposed system, which guarantees a low-cost, lightweight, and compact receiver. Firstly, a comprehensive analysis of the proposed S/S/N three-coil structure IPT system that implements CC output characteristics and ZPA operation is provided. Then, the conditions for realizing ZVS are discussed in terms of parameter design and the sensitivity of CC output characteristics to the changes in compensation capacitance parameters. Furthermore, the proposed S/S/N three-coil structure IPT system is compared with previous related studies to reflect its advantages. Finally, the correctness of the theory is verified by simulation and experiment.

Research on early warning method for pollution flashover based on phase angle of insulator leakage current

Pollution flashover is a systematic disaster of power system. It is significant to early warning insulator pollution flashover in real time and accurately. The phase angle of the insulator leakage current is a critical parameter for insulator pollution flashover early warning. However, in field applications, the operating voltage waveform cannot be obtained so that this characteristic parameter cannot be applied to the insulator pollution flashover early warning system. This paper proposes a method to obtain the phase angle of the leakage current of the online insulator. This method avoids the direct measurement of the operating voltage waveform, but uses the stray capacitance between the signal plate of the early warning device metal shell and the transmission line to obtain the operating voltage signal indirectly. In this paper, the method and the early warning mechanism of pollution flashover are analyzed theoretically, and then the early warning device for pollution flashover is designed. Finally, the effectiveness of the early warning device is verified by experiments.

A comprehensive overview of the ADALINE method applied to rapid voltage sags detection in multi-motors drive systems

Several strategies have been developed for identifying power quality issues, monitoring them, and compensating for relevant disturbances. In this field, online estimate of amplitudes and phase angles of network voltages and currents is commonly used. The adaptive linear neuron (ADALINE)-based voltage sag detection algorithm with least mean square (LMS) adaptation allows for rapid convergence of estimate techniques based on artificial neural networks (ANN). This approach has the advantage of being straightforward to implement on hardware and based on simple calculations (essentially multiply and accumulate "MAC"). This paper gives a comparison of the performance of two ADALINE approaches ("with" and "without" error supervision) for detecting and estimating voltage dips. The described techniques and models of a two-coupled motor system were implemented in MATLAB/Simulink/SimPowerSystems to run simulations under various fault scenarios in order to create the three-phase voltage sag alarm signal. The simulation outcomes are presented and debated.

Fault current limitation control of multiple distributed renewable generations under unbalanced conditions

For multiple distributed generation units (DG unit) parallel system, excessive fault current has adverse effects on the safe and stable operation of the utility grid. As a result, a fault current limitation control of multiple DG units is developed in this paper to limit the fault current of related fault branch and ride through the associated fault conditions. The injection fault current amplitude and phase angle of each DG unit for grid-side converter are controlled through the point of common coupling (PCC) voltage support and fault current limitation to limit the total current amplitude at the corresponding fault location. The validity of the proposed control strategy has been verified by simulation and hardware-in-loop (HIL) experiment results.

Fault-Tolerant Control Methods for Reduced Torque Ripple of Multiphase BLDC Motor Drive System Under Open-Circuit Faults

Multiphase brushless direct current (BLdc) motors with high efficiency and power density are widely used in electric propulsion systems of a wide variety of applications including electric vehicles, submarines, and electric ships. The multiphase motors used in these applications must operate stably without generating large torque ripple in various fault scenarios. In this article, three fault-tolerant control (FTC) methods (minimum double phase, half phase, and multiple phases) are compared with reduce torque ripple by controlling the magnitude and phase angle of healthy phase currents under open-circuit failure. The proposed FTC methods were validated through the hardware-in-the-loop simulation of a 12-phase BLdc motor.

ALERT-RA: an aperture library-enabled real-time respiratory motion adaptive framework for 4D-VMAT.

To develop a framework for robust optimization of real-time respiratory motion adaptive VMAT treatment plans, and to evaluate the robustness of resulting plans to variations in tumor trajectory duringdelivery. The proposed framework is called aperture library-enabled real-time robust adaptation (ALERT-RA). A patient-specific library of optimized MLC apertures is defined for each combination of gantry angle and respiratory phase. The method assumes that the tumor is tracked in real-time throughout delivery, and the aperture corresponding to the current phase and gantry angle will be delivered. The aperture library is optimized by considering all possible tumor trajectories determined by a probabilistic respiratory motionmodel. Plan robustness to trajectory variations was evaluated by sampling a trajectory, and determining the corresponding dose, from the respiratory model for each fraction. The cumulative dose of the full treatment course was simulated 50 times. Percentile dose-volume histograms (PDVHs) were computed from these simulated treatments. The resulting plan quality and robustness of this method were compared to other previously published motion 4D-VMAT methods, including: an optimized tracking approach that assumes reproducible tumor motion, conformal tracking with aperture deformation, and a motion-encompassing method. Two fractionation schemes were tested to determine the possible effect on robustness: a conventional fractionation of 66 Gy in 33 fractions, and an SBRT course with 60 Gy in 5fractions. When considering target coverage, the ALERT-RA method was found to produce a plan which was more robust than those produced using the optimized or conformal tracking methods. Using the PDVH analysis, the 5th and 95th percentiles of the prescription dose volume for the conventionally fractioned plan were found to be (respectively) 79% and 82% for the optimized tracking approach, 81% and 83% for the conformal tracking approach, and 92% and 97% using the new ALERT-RA method. The motion-encompassing plan was slightly more robust than the ALERT-RA plan, with 5th and 95th percentiles at 94% and 95%, respectively. This came at a cost of higher dose to OARs, with the volume of lung receiving 5 Gy or more equal to 48% for the motion-encompassing plan versus 44% for the ALERT-RAplan. For the SBRT plan, the conformal tracking plan was similarly not robust, with 5th and 95th percentiles of the prescription dose volume equal to 88% and 89%. The optimized tracking SBRT plan gave values of 93% and 95%, and the motion-encompassing plan 94% and 95%, while the ALERT-RA gave values of 93% and 96%. The volume of lung receiving 20 Gy or more was slightly higher for the optimized tracking and motion-encompassing plans compared to the ALERT-RA plan, at 15%, 15%, and 14%,respectively. Compared to other motion-adaptive VMAT approaches, the ALERT-RA algorithm is capable of delivering high-quality plans which are robust to variations in tumor motiontrajectories.