Dc Bias Components Research Articles

A magnetic-mechanical strong coupling FEM model and vibration characteristic analysis of transformer core under DC bias

The vibration of a transformer core induced by magnetostriction is closely related to the environment and safety of devices. The DC bias excitation leads to the over saturation of the transformer core and causes more severe vibration. In this paper, a magnetic-mechanical strong coupling model based on a fixed-point time-periodic 2D finite element method with excitation voltage and DC bias current as the input is established in which the vector magnetic potential A, winding current I, and displacement in the core u are simultaneously taken as solution variables, and the fixed-point reluctivity is introduced to deal with the nonlinear problem of the core. In this model, the magnetic field and mechanical field are associated with the piezomagnetic equations and variational principle, and the circuit and magnetic fields are connected through the law of electromagnetic induction. The equivalent thickness of the core model and the determination of the initial value are discussed. A test transformer with a laminated core is made for experimental measurement. The accuracy and efficiency of the model proposed are verified by comparing the calculated results with the experimental results, and the influence of DC bias components on the magnetic characteristics and vibration of the transformer core is analyzed.

Modeling methodology for the transformer-rectifier flux pump considering electromagnetic and thermal coupling

High-temperature superconducting (HTS) magnets are promising in the application of high-intensity magnetic field. HTS flux pumps are devices that can charge closed HTS magnets without direct electrical contact. Simulation is an effective way to clarify the physical mechanism and provide further insight into the design of the device. In this work, we propose an accurate and efficient modeling methodology to simulate the transformer-rectifier HTS flux pump, which has considered electromagnetic and thermal coupling. The validity of the model has been verified by experimental results and theoretical calculations. The working characteristics of the HTS flux pump are investigated based on the proposed model, including DC bias component in the charging loop, the voltage recovery delay of the dynamic bridge and the temperature distribution in the dynamic bridge. The simulation results clearly depict working details of the device, in terms of electricity, magnetism and heat. The proposed model can serve as a powerful tool to design the HTS flux pump in practical applications.

Thermal Analysis of a Flux-Switching Permanent Magnet Machine for Hybrid Electric Vehicles

This paper investigates the loss and thermal characteristics of a three-phase 10 kW flux-switching permanent magnet (FSPM) machine, which is used as an integrated starter generator (ISG) for hybrid electric vehicles (HEVs). In this paper, an improved method considering both DC-bias component and minor hysteresis loops in iron flux-density distribution is proposed to calculate core loss more precisely. Then, a lumped parameter thermal network (LPTN) model is constructed to predict transient thermal behavior of the FSPM machine, which takes into consideration various losses as heat sources determined from predictions and experiments. Meanwhile, a simplified one-dimensional (1D) steady heat conduction (1D-SHC) model with two heat sources in cylindrical coordinates is also proposed to predict the thermal behavior. To verify the two methods above, transient and steady thermal analyses of the FSPM machine were performed by computational fluid dynamics (CFD) based on the losses mentioned above. Finally, the predicted results from both LPTN and 1D-SHC were verified by the experiments on a prototyped FSPM machine.

Improvement of core loss model under AC–DC hybrid excitation and verification based on TEAM P21 extended model

HVDC (High Voltage Direct Current) transmission equipment generally works under AC–DC hybrid excitation (with both DC-bias components and harmonics), increasing the loss of magnetic components and even causing local overheating. In order to study the influence of AC–DC hybrid excitation on the performance of magnetic materials, the loss properties of electrical silicon steel under AC–DC hybrid excitation are measured and modelled. This paper improves the iron loss model based on the Bertotti loss model by introducing a new term caused by DC bias. In addition, the improved loss model is combined with the transient loss model, and the iron loss calculation is performed based on the results of the TEAM P21 extended model. The comparison between the calculated and measured loss shows that the improved loss model is more accurate than the traditional one.

A Fast Positive-Sequence Component Extraction Method With Multiple Disturbances in Unbalanced Conditions

Fast and accurate acquisition of current components is a key factor for an active power filter to realize transient control under unbalanced conditions. In this letter, a robust real-time algorithm, which rapidly separates the positive-sequence component (PSC) from multiple decaying dc (DDC) components, dc bias component, negative-sequence component, and harmonics, is proposed. To this end, first, the multiple DDC components are detected in the multiple disturbance and unbalanced grid context, by making use of the periodicity of remaining components. The dc bias can be obtained accordingly, followed by the detection of a compound signal encompassing the positive-sequence component, negative-sequence component, and harmonics. Specifically, the compound signal can be extracted precisely, based on the detected DDC and dc bias components, with one grid cycle response time, or approximately, within half grid cycle. A switching logic of the two approaches is designed to shorten the overall convergence time and improve steady-state accuracy. The PSC is then effectively extracted by constructing the virtual orthogonal signal of the compound signal and using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -frame filtering. Compared with the existing transient control techniques, the proposed scheme guarantees one grid cycle response time and simultaneously suppresses multiple disturbances. Finally, experimental results verify the effectiveness of the proposed method.

Grid-Connected Control Strategy of VSG under Complex Grid Voltage Conditions

Under complex grid conditions, the grid voltage usually has an imbalance, low order harmonics, and a small of DC bias. When the grid voltage contains low order harmonics and a small amount of DC bias component, the inverter's output current cannot meet the grid connection requirements, and there is a three-phase current imbalance in the control strategy of common VSG under unbalanced voltage. A theoretical analysis of non-ideal power grids is carried out, and a VSG control strategy under complex operating conditions is proposed. Firstly, the third-order generalized integrator (TOGI) is used to eliminate the influence of the DC component of grid voltage. An improved delay signal cancellation (DSC) method is proposed to control the balance current and power fluctuation under unbalanced voltage based on the method of common VSG positive and negative sequence separation, It also eliminates the harmonic of command current. Then, the improved quasi proportional resonant controller (QPR) cascaded PI is used to suppress the harmonic current further so that the harmonic content of grid-connected current can meet the grid-connected requirements and achieve the three-phase current balance. Finally, the proposed strategy is verified by simulation under the control objectives of the current balance, active power, and reactive power constant.

Partitioned Stator Hybrid Excited Machine With DC-Biased Sinusoidal Current

This article proposes a new partitioned stator hybrid excited (PS-HE) machine with dc-biased sinusoidal current. On the inner stator, the consequent pole permanent magnets (PMs) are employed as the PM excitation. On the outer stator, a set of integrated dual three-phase winding is adopted to produce the wound and armature fields at the same time by injecting the sinusoidal current with dc bias. So, the flexible flux regulation can be realized by controlling the dc bias component. The rotor composed of segmented iron cores is sandwiched between two stators. By employing the air-gap field modulation theory, the air-gap magnetic field harmonics are analyzed to explain the operating and flux regulation principle. Furthermore, a design optimization and the electromagnetic performances of the proposed machine are investigated by finite element analysis. When compared with the existing series and parallel PS-HE machines, the proposed machine can avoid the disadvantage of low torque density of PARALLEL HE machine, and it can solve the problem of the poor flux regulation ability of series HE machine as well, which is mainly contributed by the reasonable space allocation of PMs and field winding excitations. Finally, a prototype is built and tested to verify the theoretical analyses.

Analysis on harmonic characteristics of interleaving paralleled static inverters under asymmetric conditions

With the large number of applications for multi electric aircraft (MEA), the power capacity of the aviation static inverter (ASI) has been continuously improved. Therefore, more and more modular parallel-based topologies are being used in the ASI to achieve power expansion. Combined with carrier phase-shift modulation, the harmonic components of a system can be further reduced. However, due to the parameter asymmetry between paralleled modules and power system disturbances, additional low frequency and DC bias components are superimposed on the control signal. This paper uses exponential function analysis to analyze the harmonic distribution of a modular ASI based on carrier phase-shift modulation under non-ideal conditions. In addition, the distribution characteristics of different paralleled topologies are compared. Finally, the correctness of the theoretical analysis is verified by simulation and experimental results.

Analysis of coupling between two sub‐machines in co‐axis dual‐mechanical‐port flux‐switching PM machine for fuel‐based extended range electric vehicles

The permanent magnet (PM) field coupling between inner and outer machines of co-axis dual-mechanical-port flux-switching PM (CADMP-FSPM) machines is investigated. Firstly, the relationships between the inner and outer stator teeth are analytically evaluated, with three key stator teeth types defined, i.e. series, parallel, and independent teeth. Secondly, the negative effects of PM field coupling, including high even-order electromotive force (EMF) harmonics, three-phase EMFs asymmetry and DC bias component in flux-linkages, are investigated and verified by two CADMP-FSPM machines, namely, 5/6-12/22, and 5/6-18/42 structures. It is found that for avoiding the negative effects of PM field coupling, all inner and outer stator teeth types should be the same, thus, a 10/12-12/22 structure CADMP-FSPM machine is introduced for analysis. Thirdly, the performance of the 10/12-12/22, 5/6-12/22, and 5/6-18/42 structures, featured by PM field distributions, d-axis flux-linkage ripples, cogging torques, electromagnetic torques, losses and efficiencies, are comparatively analysed by finite element (FE) analysis. The results indicate that the 10/12-12/22 structure exhibits the lowest PM field coupling level and the best performance. Moreover, the 10/12-12/22 structure can avoid all the negative effects of PM field couplings. A prototyped 10/12-12/22 CADMP-FSPM machine is built and tested to verify the FE predicted results.

Wide-speed-range sensorless control scheme for IPMSMs based on super-twisting observer and HF signal injection

In this paper, a novel wide-speed-range sensorless control scheme for interior permanent magnet synchronous machines (IPMSMs) is proposed. At mid-high speed range, the super-twisting observer (STO) is designed to estimate the extended electromotive force (EMF). Adoption of sign function ensures the estimation accuracy without compromising the benefits of the standard sliding mode. The improved observation model combining the super-twisting algorithm (STA) alleviates the chattering problem. A new procedure of obtaining the position estimation error is proposed to eliminate the effects due to the change of the rotation direction. At low speed range, position error is obtained directly by extracting the high frequency current from the sample data. The high frequency signal is further improved by introducing a novel adaptive filter to weaken DC bias component. The transition function provides the position error signal for the speed estimator and ensures a smooth switch between the two methods in the transition zone. The effectiveness of the proposed control scheme has been validated by the experimental results.

Characteristics analysis of a new single‐phase π ‐type five‐level inverter

The characteristics analysis of a new single-phase π-type five-level inverter using three-terminal switch-network is proposed in this study. The topology is the variant of three-level T-type topology or multi-level inverter using interleaved pulse width modulation (PWM) in a bridge-leg with coupled inductors. Moreover, the big merit of the new inverter is to apply only four active power switches to achieve five-level operations resulted in high efficiency and low harmonics. Furthermore, double-frequency operation of output inductors and equal division of the current that flows through power switches and filter inductor also can be achieved. These characteristics allow improvement of losses distribution, voltage and volume reduction of output filter inductor. The operation scenario with sinusoidal PWM is described in details. Meanwhile, the magnetic analysis and design, dc bias component evaluation in the magnetising current, stresses analyses and power losses calculation of power switches are studied and discussed. Finally, the simulation and prototype experiment demonstrate the advantages of the proposed topology.

A Fully-Integrated 40–222 GHz InP HBT Distributed Amplifier

This letter presents an ultra-wideband distributed amplifier (DA) implemented in a 250 nm InP HBT technology. Four cascode gain cells are distributed along the input and output microstrip lines to achieve wideband operation. Each cascode cell employs inductive peaking at the output to further enhance the bandwidth and to align the phase delay between the input and output lines. All dc bias components are fully integrated on-chip. The DA exhibits a measured gain of 10 dB with a 3 dB bandwidth extending from 40 to 222 GHz. The maximum output power was measured to be 6.0, 9.2, and 8.5 dBm at 60, 77, and 134 GHz, respectively, which allows the DA to also be used as a medium-power amplifier. To the authors' best knowledge, the DA achieves the highest 3 dB bandwidth of 182 GHz reported thus far, while showing low dc power consumption (105 mW) compared to other state-of-the-art DAs.

60-GHz amplitude shift-keying transceiver LTCC system-on-package module

A highly integrated amplitude shift-keying (ASK) transceiver (TRx) system-on-package (SoP) module is presented for 60-GHz wireless communications applications.The ASK TRx SoP module has been implemented with a six-layer low-temperature co-fired ceramic (LTCC) substrate embedding eight GaAs RF integrated circuit chips, one low-pass filter, a high-isolation via fence, and DC bias components. The fabricated ASK TRx SoP is as small as 17.8 × 17.9 × 0.6 mm3. In the transmitter (Tx) part, an output power of 12.8 dBm is obtained at 62.24 GHz. The receiver (Rx) part reveals a conversion gain of 38 dB, intermediate frequency flatness of below −2 dBm, and good eye pattern of the 1.25 Gb/s data. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:48–51, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27264

Output frequency response characteristics of nonlinear systems. Part II: overlapping effects and commensurate multi-tone excitations

The output response of nonlinear systems is strongly dependent on the extent to which different input frequency combinations/intermodulations overlap one another and contribute to a common output frequency component. This makes it hard to determine the actual number of output frequencies, or to determine which of the many possible combinations contribute to a specified output frequency of interest. Systematic algorithms are presented for resolving these issues in a manner, which is both efficient and straightforward to implement on a computer. Three broad classes of input are considered: multi-tone, but nominally incommensurate sinusoids; multi-tone, harmonically related sinusoids and multi-tone excitations that are equi-spaced in frequency. The considered inputs also admit the possibility of a dc bias component since this can significantly affect the system response. The algorithms are therefore applicable to a broad range of practical inputs, and their use and benefits are illustrated with several examples.

Output frequency response characteristics of nonlinear systems. Part I: general multi-tone inputs

A systematic algorithm for determining the output frequencies generated by a nonlinear system subject to a general multi-tone input, including a bias input, is presented. The algorithm is very efficient, and circumvents many of the difficulties of ‘duplicate frequencies’ that are often generated using previous methods. The inclusion of the dc bias component in the analysis is also important because of the significant effect that non-zero mean inputs can have on nonlinear system response. The algorithm is straightforward to implement on a computer, and the results are illustrated by means of an example.

Ferrite losses of cores with square wave voltage and dc bias

Ferrite material properties may vary depending on the grade and manufacturer: there are differences between batches and also the production process may change in time. On the other hand, in power applications, the usual voltage wave forms are closer to square wave than to sine wave, and moreover they contain a dc bias component that can easily more than double the ferrite losses. Therefore, in loss critical applications it is good to be able to both test and model the losses of the actual ferrite cores under the same conditions as in the actual power application. In this paper, experiments were carried out at different induction levels and dc bias currents. Losses were measured at frequencies of 20, 100, and 500 kHz on a ferrite core with Ferroxcube 3F3 material, a Mn–Zn ferrite. We observe that mainly the lower frequencies are sensitive to dc bias. A model including wide ranges in amplitude, frequency, and also dc bias is proposed. In this model, the losses are separated in three terms: a hysteresis dependent term, an additional loss term depending on dc bias, and a high frequency term.

Inverter plasma discharge system

We have developed a bipolar pulsed dc glow plasma discharge system using an inverter power supply. A target of the developed system is a low-cost surface modification operated in a low background pressure region (10 1–10 3 Pa) obtained with rotary pumps. In this pressure region, breakdown voltages for most gases have minimum values without the help of magnetic fields like a magnetron. Accordingly, we can use simple discharge electrodes such as parallel plates that would be extended for large area processing. These electrodes are driven by the bipolar voltage pulses including dc bias components which would drive both positive ions and electrons. A composition of the developed discharge system is shown. Voltage and current waveforms and emission light signals are measured to demonstrate a discharge operation. Initial applications of the developed system using a bipolar pulse processing technique are proposed.

A non-linear dynamic modelling approach for the characterization and error compensation in sampling oscilloscopes

A mathematical modelling approach is proposed for measurement-based characterization of non-linear dynamic sources of error in the vertical channel of a sampling oscilloscope. The proposed approach has been derived from a recently proposed modified Volterra series expansion which, under particular conditions, provides fast convergence and can be truncated to the first integral term. A possible characterization procedure, based on instrument testing under sinusoidal AC input signals with different frequencies and variable DC bias components, is described and used to evaluate the performances of a commercial oscilloscope. The waveforms obtained by using the identified model are compared with the experimental ones for model validation; successively the model is used for the error compensation of the memory effects.

RF Glow Discharge and Ion Transport: Effects of Applied Frequency, Gas Pressure and Method of Power Coupling

Spatiotemporal structures in a parallel-plate RF glow discharge using argon plasmas have been simulated based on fluid approximation. For unchanged RF and DC bias components of voltage applied at an electrode, ion density, ion flux and mean electric power density increase as frequency f and gas pressure P become higher, whereas sheath length and its variation amplitude are inversely proportional to √f and √P. When two independent RF power supplies having identical frequency and applied voltage to each other are coupled to two electrodes, ion density and ion flux have their maximum values when the phase difference between the two RF power supplies is 180°. Energy and angular distributions of ions striking the electrode are also studied based on the Monte Carlo technique for the simulated parameters of the RF glow discharge. Since the ratio of sheath length to ion mean free path is proportional to √P/f, high-frequency operation under a low-pressure condition is preferable to achieve less attenuated, centered energy and less scattered angular distributions of ions.