Variable Induction Research Articles

Single-Receiver Multioutput Inductive Power Transfer System With Independent Regulation and Unity Power Factor

Inductive power transfer (IPT) systems with multiple output voltages are potential to supply a variety of loads simultaneously. This article proposes an IPT system with multiple semiactive rectifier cells (SARCs) connected in series at the receiver (Rx) side. These SARCs are independent of each other and their output voltages can be regulated individually with single receiver coil, which reduces the cost and volume. The proposed IPT configuration has the advantages of high flexibility, simple control, and no cross regulation. Considering that the SARC may cause additional reactance and lead to detuning of the Rx side, variable inductor is introduced to ensure the full tuning condition. Thus, the proposed IPT system can maintain zero phase angle operation with unity power factor in the whole load range, minimizing the reactive power losses. In addition, both primary inverter and the SARCs can achieve zero voltage switching. To verify the feasibility and validity of the proposed IPT system, an experimental prototype with two outputs of 640 W/150 V and 400 W/120 V is built.

A Novel Eddy Current Method for Defect Detection Immune to Lift-Off

Eddy current (EC) sensors have been applied to detect defects in many years. Since both defects and the lift-off variation will lead to measurement signal fluctuation, it is necessary to distinguish the defect response and lift-off variation response. In this work, a novel eddy current method is proposed for defect detection immune to lift-off via a triple-coil structure. Firstly, a simplified theoretical model is built to investigate the relationship between the lift-off and the inductance variation. It is found the lift-off is proportional to the logarithm of inductance variation in real part under high frequency. In terms of sensor design, the triple-coil sensor consists of two pairs of transmitting-receiving coils, from which one of the receiving coils is larger than the other one. With such sensor structure, the small size coil aims to detect the defect, while the larger size coil aims to calibrate lift-off. The proposed method is verified by experiments with the sensor scanning over a Titanium specimen with defects of different sizes. The results indicate the proposed method can achieve efficient and precise defect detection immune to lift-off.

Real Time Simulation of Brushless Doubly Fed Reluctance Generator Driven Wind Turbine Considering Iron Saturation

Brushless doubly fed reluctance generator (BDFRG) provides a good substitute for the doubly fed induction generator for the wind energy applications due to the nonexistence of the slip rings. Real time modelling of the BDFRG is a challenge due to the high leakage inductance of the stator windings. While the magnetic saturation of the iron parts affects the inductances values, therefore studying the effect of magnetic saturation on the BDFRG performance is important. In this paper, a BDFRG model including iron saturation is built. The finite element (FE) analysis using FEMM software is used to generate the relationship between the generator currents and the inductances, the generated data are recorded in a lookup table. A Simulink model of the BDFRG driven wind turbine, with two cases of constant and variable inductances, are developed and verified with FE analyses at range of wind speeds above and below the synchronous speed. The lookup table proposes is verified using finite element analysis at different modes of operation of wind speed and compared with the constant inductance model to show the importance of saturation inclusion in the generator model for accurate generator modelling representation.

Further Improvements in Topological Transformer Model Covering Core Saturation

This paper is devoted to improvements of the low-frequency topological model of a three-legged stacked-core transformer. It is shown that <i>B-H</i> hysteresis loops employed in the transformer model and &#x03C8;&#x2013; <i>i</i> curves measured at transformer terminals are quite different in shape. A distinction is made between transformer modeling at moderate and deep saturations, separated conditionally by the level of technical saturation (near 2 Tesla) typical for grain-oriented steels. In the former case, in addition to the magnetic coupling of different phase windings through the core, an important part is played by air gaps at core joints. It is found that the effective gap length depends on the instantaneous magnetic flux and this dependence is proposed to implement by variable inductances. It is shown that regardless of the core saturation depth, an important role in the transformer modeling belongs to the distribution of the zero-sequence path between all the phases. In addition to accurate replications of the special purpose saturation test, the modeled results are in a close agreement with positive- and zero sequence data measured on a 50 kVA transformer, as well as with the measured inrush currents.

Orthogonal-Core-Type Variable Inductor Consisting of Cut Core and Laminated Core

Orthogonal-Core-Type Variable Inductor Consisting of Cut Core and Laminated Core

Phase-Variable Modeling and Comparative Study between a PMa-CPA and a CPA Alternator by Simulation Analysis

This paper presents the phase-variable modeling of a permanent magnet-assisted claw-pole alternator in PSIM simulation software tool with the performance compared with a claw-pole alternator model, which is a special case of the permanent magnet-assisted claw-pole alternator model with the rotor permanent-magnet flux constant setting equal to zero. The constructed model can be simulated as a real alternator directly connected to a diode-bridge rectifier or switch-mode rectifier circuit for the integrated power application system simulation analysis. The proposed model contains two features, one of which is that the stator and rotor windings are circuit-based. The other one feature is that the mechanical torque input is based on a mathematical function. In this model, the rotor position-dependent variable inductor is replaced by a separate voltage source according to the voltage source absorption theorem. The simulation shows that the proposed model has faster torque step response and higher power efficiency than the claw-pole alternator model. The proposed model can be employed to the application of the control design and simulation study of voltage regulation in automobiles. The simulation results with 15-V command and the load sudden change verify the correction of the proposed model.

Wireless Charging Constant Power Output System Based on LCC/S-S Self-Switching

Conventional wireless charging systems cause output power fluctuations during the offset process, and a single topology can cause power reduction or a large impact on the wireless charging network as the coupling mutual inductance changes. For this reason, in this paper, by combining LCC-S and S-S topologies, the high output characteristics of the S-S topology network in the low coupling state and the high output characteristics of the LCC-S topology network in the protection and high coupling in the very low coupling, the power output in the offset state is greatly maintained by combining with the voltage regulation circuit. In this paper, firstly, the theoretical derivation of the working principle of the designed topology is carried out, then the mutual inductance variation range generated by the offset state of the coil is found through finite element simulation, and the accuracy of the theoretical derivation is verified by building a constant power output model of the self-switching system using matlab, and finally, an experimental platform for wireless power transmission is built, and the experimental results confirm that the system power can be maintained within a certain offset range The output fluctuation is within 5%, which verifies the feasibility and realism of the design.

Combined voltage oriented control and direct power control based on backstepping control for four-leg PWM rectifier under unbalanced conditions

The present paper proposes a combined voltage-oriented control and direct power control (VOC-DPC) method associated with the backstepping control technique for a three-phase four-wire grid-connected four-leg rectifier in the synchronous rotating frame without using phase locked loop (PLL) and Parks transformation under balanced and unbalanced load and grid conditions. This control method is proposed in order to remove the drawbacks of the conventional VOC based on the PLL technique .The proposed control method is able to enhance the control performance and dynamic responses of the system when considering slow dynamics and instability issues of the PLL in several cases and can decrease the computational burden due to the absence of PLL and Park transformation. In addition, the performance of the proposed VOC-DPC method is enhanced by using backstepping control (BSC) based on Lyabonov theory for both the input currents and DC-bus voltage loops. As a consequence, constant DC-bus voltage, unit power factor, sinusoidal input currents, and neutral current minimization can be accurately carried out under both DC-bus voltage and load variations. Furthermore, robustness against filter inductance variations can also be achieved. The effectiveness, superiority, and performance of the proposed control method for a four-leg rectifier based on BSC in the dq0-frame are validated by several processor-in-the-loop (PIL) co-simulation tests sing the STM32F407 discovery development board.

A Generalized Analytical Tuning Approach for Model Predictive Controlled Grid-Tied Converters Under Wide Range of Grid Inductance Variation

In medium-high power applications, the LCL is the preferred filter topology to attain efficient power conversion. The filter provides a high damping attenuation of -60 dB/decade above the resonance frequency at the cost of a higher order plant, complex parameter design, and, increased vulnerability to un-modeled disturbances. Recently, model predictive control applied to power electronic converters has experienced great interest from researchers. The technique is tailored to the control of complex MIMO systems such as the LCL filter as it allows simultaneous regulation of several state-variables via a user defined cost function. However, the tuning of weighting factors (WFs) within the cost function is not trivial, and in most cases employs an empirical procedure. This paper presents an analytical procedure for tuning of WFs for indirect model predictive current controlled grid-tied converters. The method is based on using analytical closed-form expressions, that relate closed-loop poles of the filter with WFs via physical plant parameters. The presented expressions generalize the tuning of WFs to any arbitrary LCL design. The proposed method is validated by hardware-in-the-loop simulations conducted on PLECS RTBOX 3. Through experimental testing, it is shown that the controller is robust against a wide range of grid impedance variation.

Shielding Optimization of IPT System Based on Genetic Algorithm for Efficiency Promotion in EV Wireless Charging Applications

For an inductive power transfer (IPT) system used in electric vehicle (EV) charging, the receiving coil is usually equipped with a shielding structure to reduce iron loss and electromagnetic interference in the chassis. However, the addition of a shielding structure may significantly reduce self-inductance and mutual inductance, and the eddy current on the shielding pad can also produce power loss. To maximize the efficiency of the IPT system used for EV charging and sufficient shielding, this study first analyzed the equivalent circuit model of the IPT system. A 3-D model of an IPT system, with a steel plate and aluminum shielding, is established and investigated in the finite-element analysis (FEA) domain, in which the shielding structure is modeled with some parametric sizes to simplify the modification of the parameters on a shielding structure. The simulation result shows how the ohmic loss on coils and the iron loss on steel plate changes after adding the shielding structure. Afterward, a practical method for optimizing aluminum shielding structure's parameters is proposed to maximize the efficiency of the IPT system, taking iron losses in a steel part and aluminum shielding into account. Furthermore, considering that the optimization procedure becomes complex since the different resonant capacitances are required due to the variable inductances, a new efficiency calculation method by FEA is presented to simplify the optimization procedure. Experimental validation is finally performed on a 3-kW wireless charging prototype; thus, the effectiveness of the proposed method is verified.

Collaborative Optimization Method of Power and Efficiency for LCC-S Wireless Power Transmission System

Dynamic wireless charging enables moving equipment such as electric vehicles, robots to be charged in motion, and thus is a research hotspot. The applications in practice, however, suffer from mutual inductance fluctuation due to unavoidable environmental disturbances. In addition, the load also changes during operation, which makes the problem more complicated. This paper analyzes the impacts of equivalent load and mutual inductances variation over the system by LCC-S topology modeling utilizing two-port theory. The optimal load expression is derived. Moreover, a double-sided control strategy enabling optimal efficiency and power adjustment is proposed. Voltage conducting angles on the inverter and rectifier are introduced. The simulation and experimental results verify the proposed method.

Grey wolf optimizer algorithm for the performance predetermination of variable speed self-excited induction generators

PurposeThis paper aims to apply grey wolf optimizer (GWO) algorithm for steady state analysis of self-excited induction generators (SEIGs) supplying isolated loads.Design/methodology/approachTaking the equivalent circuit of SEIG, the impedances representing the stator, rotor and the connected load are reduced to a single loop impedance in terms of the unknown frequency, magnetizing reactance and core loss resistance for the given rotor speed. This loop impedance is taken as the objective function and minimized using GWO to solve for the unknown parameters. By including the value of the desired voltage as a constraint, the formulated objective function is also extended for estimating the required excitation capacitance.FindingsThe experimental results obtained on a three phase 415 V, 3.5 kW SEIG and the corresponding predetermined performance characteristics agree closely, thereby validating the proposed GWO method. Moreover, a comparative study of GWO with genetic algorithm and particle swarm optimization techniques reveals that GWO exhibits much quicker convergence of the objective function.Originality/valueThe important contributions of this paper are as follows: for the first time, GWO has been introduced for the SEIG performance predetermination and computation of the excitation capacitance for attaining the desired terminal voltage for the given load and speed; the predicted performance accuracy is improved by considering the variable core loss of the SEIG; and GWO does not require derivations of lengthy equations for calculating the SEIG performance.

A Variable Inductor Controlled Single-Stage AC/DC Converter for Modular Multi-Channel LED Driver

Light-emitting diodes (LEDs) are widely used in street lighting, landscape lighting, liquid crystal display (LCD) backlighting, healthcare, etc. As an important part of LED lighting products, LED driver plays a vital role in maintenance costs reduction, energy saving and lifetime prolongation. In this paper, a single-stage LED driver is proposed, which is integrated by a totem-pole bridgeless power factor correction (PFC) unit and several modular LCL-T resonant rectifiers. The totem-pole bridgeless PFC unit and the LCL-T resonant rectifiers are integrated by sharing switches, which can simplify the circuit and reduce the system cost. The output current can be regulated by applying the variable inductor control. Constant duty cycle and fixed switching frequency operation can be achieved as well. The operating principle and the performance of the proposed converter are analyzed in this paper. In addition, a precise parameter design method is proposed by considering the high-order harmonics. At last, an experimental prototype is established to validate the proposed parameter design and variable inductor control method.

Adaptive super-twisting sliding mode control for maximum power point tracking of PMSG-based wind energy conversion systems

This paper proposes a super-twisting adaptive sliding mode control law for maximum power point tracking of wind energy conversion systems based on permanent magnet synchronous generators (PMSGs). The employed sliding mode control algorithm can be considered an effective solution, as it retains the robustness properties of classical sliding mode control methods in the presence of disturbances and parameter uncertainties; at the same time, it provides chattering reduction via gain adaptation and generation of second-order sliding modes. In our work, a nonlinear multi-input multi-output tracking control problem is solved to maximize the captured power. Simulation results are presented using real wind speed data, and discussed for the proposed controller and four other sliding mode control solutions for the same problem, in the presence of variations of stator resistance, stator inductance and magnetic flux linkage. The proposed controller achieves the best trade-off between tracking performance and chattering reduction among the five considered solutions: compared to a standard sliding mode control algorithm, it reduces the amount of chattering from two to five orders of magnitude, and the steady-state error on PMSG rotor velocity of one order of magnitude. Also, it reduces the above-mentioned steady-state error of four orders of magnitude with respect to a previously-proposed linear quadratic regulator based integral sliding mode control law for the same system.

Bortezomib for the Management of Relapsed or Refractory Warm Autoimmune Hemolytic Anemia: A Scoping Review

Background:Auto-immune hemolytic anemia (AIHA) may be complicated with a relapsed or refractory course and may lead to life-threatening complications. The management of severe cases refractory to multiple lines of therapy is challenging, and data on the use of subsequent therapeutic agents remains scarce. Plasma cells have been postulated as potential therapeutic targets due to their role in auto-antibody production. Studies on plasma-cell directed therapies, such as bortezomib (BTZ), for the management of AIHA are lacking, and clinical trials remain ongoing.Objectives:To perform a scoping review on existing literature on the use of BTZ in the management of warm AIHA (wAIHA) and its outcomes, and to report an additional case of successful use of BTZ at our institution.Methods:We performed an extensive literature search using MEDLINE (Ovid), Embase, Scopus, and PubMed on all existing reports on BTZ use in wAIHA. Patients with hematopoietic cell transplant-associated AIHA were excluded.We defined complete response (CR) as a hemoglobin (Hb) > 10 g/dL, Hb increase of > 2 g/dL, and a complete cessation of corticosteroids (CS) or other immunosuppression (IS). We defined partial response (PR) as a Hb rise > 2 g/dL, with stable or decreased long-term IS requirements. Onset of response was defined as the time in days after first BTZ dose when a Hb increase of > 2 g/dL was first noted. Duration of response was defined as the time from response onset until relapse or cessation of follow-up. We applied our definitions uniformly across the original data (whenever reported) in the included studies. BTZ used as monotherapy or in addition to prior long-term IS was labeled “single-agent”, and BTZ combined with rituximab (RTX) or cyclophosphamide (CTX) was labeled “combination regimen”.Case Description:A 25-year-old male with Evans syndrome and prior therapy with CS, intravenous immunoglobulin (IVIG), splenectomy, cyclosporine, RTX and vincristine presented with severe thrombocytopenia and recurrent wAIHA. Despite receiving high-dose CS, IVIG, mycophenolate mofetil, RTX, CTX, and danazol, his AIHA persisted severely, while platelets normalized with romiplostim. He was then treated with BTZ 1.3 g/m2 (days 1, 4, 8, 11 every three weeks x 6 cycles) and his Hb improved from 5.8 g/dL to 14.4 g/dL currently, with an onset of response within 19 days and sustained response of 6 months until today. However, he continues to require maintenance BTZ and prednisone.Results:We identified 10 case series/reports (n=29, our patient included) in which BTZ was used to treat wAIHA, with a total of 32 evaluable incidents of BTZ use .The median number of prior therapies was 5 (range: 1-8). BTZ was used in variable regimens and induction durations (Table 1), including single-agent BTZ (n=14), combination regimen (n=16), shorter induction (<30 days) (n=13), and longer induction courses (n=13). 37.5% of responding patients required additional maintenance BTZ.Response rates (Figure 1a):Overall response rate (ORR) of cohort = 78%, CR = 43.8%, PR = 34.4%CR with single-agent BTZ = 20%, combination regimen = 64.7%Median onset of response (Figure 1b):Overall cohort: 21 days [IQR: 13-35]Single-agent BTZ: 21 days [IQR: 19-47]Combination-regimen BTZ: 15 days [IQR: 7-21]Duration of response (Figure 1c):Overall cohort: 150 days [IQR: 120-426]Single-agent BTZ: 272 days [IQR: 129-565]*, Combination-regimen: 150 days [IQR: 90-280]*Short induction: 135 [IQR: 90-228], ongoing response at time of publication = 54%Long induction: 365 [IQR: 132-555], ongoing response = 91%*83% of single-agent arm received longer induction, vs 20% of combination group, potentially confounding results. Controlling for induction duration was not possible due to small numbers.Safety:No serious side effects were reported in our cohort. There were 2 deaths unrelated to BTZ.Conclusion:Limited data suggest that BTZ may be used as a subsequent therapy to treat relapsed or refractory wAIHA, and may offer complete or partial response in cases refractory to multiple therapeutic lines. BTZ combined with RTX or CTX seemed to offer higher rates of CR as well as faster onset of response in comparison to single-agent BTZ. The median time to onset of response was 2 to 3 weeks, and the median response duration was five months. Longer induction (>30 days) was associated with longer durations of response. Our study is limited by publication bias, study heterogeneity, and small numbers. [Display omitted] DisclosuresShah: AstraZeneca: Research Funding; Seattle Genetics: Research Funding; Epizyme: Research Funding. OffLabel Disclosure:bortezomib for autoimmune hemolytic anemia

Evaluation of Transformer Leakage Inductance Using Magnetic Image Method

Leakage inductance is a critical design element of a transformer in a galvanically isolated power converter. For multi-objective optimization-based designs of power converters, analytical leakage inductance models that are computationally efficient and accurate are preferred over the finite element methods (FEMs). In this article, three new analytical models are proposed—triple-2-D, double-2-D, and single-2-D—that are formulated using the magnetic image method. These 2-D models are used to calculate the leakage inductance of a partially filled shell-type transformer having a circular center leg, and the resulting errors are less than 1.25% for each model when compared to the 3-D FEM simulated value of the leakage inductance. Additionally, three different conductor models are considered, and their relative accuracies and computational efficiencies are investigated. Furthermore, a variable inductance transformer (VIT) is designed, whose leakage inductance can be modified by moving one of the windings vertically along the central core leg. The analytically evaluated variable leakage inductances of the VIT are in good agreement with the 3-D FEM simulated and experimentally measured values.

Diversity Analysis in Horse Gram [Macrotyloma uniflorum (Lam.) Verdc.] Mutants

Background: Horse gram is the potential rainfed legume in Indian farming. The major limitation in horse gram breeding is the narrow variability. Variability induction and its estimation would sustain food security. Methods: Variability was induced using gamma rays, electron beam and ethyl methanesulfonate and their combinations. The induced variation for the economic traits, their inheritance and genetic gain were ascertained. Result: The analysis of variance indicated the induction of significant variation for yield attributing traits. The population was grouped into 10 constellations by the virtue of induced variation. The groups I, II and V were the largest comprising of 38, 31 and 19 mutants respectively. The mutants exhibited significant intra and inter group variation. The mutagens induced the maximum variability for plant height (32.24%), 100 seed weight (25.42%) and number of pods per plant (19.18%). The mutants possessed high genotypic and phenotypic coefficients of variation for all the characters except flowering traits and duration. The induced variability for the yield attributing traits possessed significant breeding value as the heritability (86.66%-99.72%) and genetic advance as percent of mean (10.65-81.94) were high and the environmental influence was the minimum.

A Novel Inductor for Stabilizing the DC Link of Adjustable Speed Drive

The DC-link filter which includes a magnetic inductor and a storage capacitor is one of the key parts of adjustable speed drives in the market. It significantly affects the stability, reliability, and power density of the motor-drive system. This paper proposes a novel, variable active inductor to improve the performance of DC links in terms of stability, reliability, size, and cost. In contrast to conventional DC-link magnetic inductors, the variable active inductor is made of power electronic circuits, including active switches, passive filters, and smart controllers, which no longer rely on magnetic material. The demonstration shows that the inductor can emulate the electrical characteristics of the magnetic inductor for filtering harmonics and stabilizing the DC link, meanwhile representing a smaller size, lighter weight, and lower cost compared with a conventional one. Furthermore, this paper proposes a variable inductance control method which is able to adaptively tune the inductance value with the operating conditions of the drive system. The DC link can be stabilized, and high performance can be maintained in both balanced and unbalanced grid voltage conditions. A case study of the proposed variable inductor in a motor drive with a three-phase diode-bridge rectifier as the front end is discussed. Experimental results are given to verify the functionality and effectiveness of the proposed variable inductor.

An Explicit Discrete-Time Large- and Small-Signal Modeling of the Dual Active Bridge DC–DC Converter Based on the Time Scale Methodology

The conventional method to model a dc–dc converter is by averaging its state variable over a switching period. However, due to the dc–ac–dc structure of the dual active bridge converter (DABC), the average value of the inductor current over a switching cycle is zero. Therefore, the conventional methodology cannot be applied to the DABC. The time-scale discrete-time modeling of the DABC is proposed to mitigate the zero average state variable problem. The time-scale methodology simplifies the analysis of the DABC by segregating the fast state variable inductor current and slow state variable output voltage. The proposed model has the advantage of the explicit large signal in terms of the circuit parameter, like the average value model. The explicit steady-state circuit expression from the large-signal model helps in the study of the soft-switching range of the DABC. Moreover, the small-signal model from the proposed method results in an explicit small-signal model. The model incorporates semiconductor <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -resistance, inductor equivalent series resistance, transformer resistance, and leakage inductance. The effect of the converter net equivalent resistance on the small-signal model is thoroughly studied. Finally, the model accuracy in the steady-state, open-loop, and the small-signal are verified in both the switching simulation model and experimental setup.

Transient voltages and energy balance in REBCO insulated magnet: experimental and numerical studies

Different means are investigated today to protect a rare earth–barium–copper oxide (REBCO) coil against local thermal runaway, what is commonly called a ‘Quench’. Metal Insulated Coil or No-Insulated coil have been successfully introduced. However, these protections method may show other issues and are limited in terms of dynamics, making them impractical for fast applications. We successfully tested early detection of dissipative voltage followed by current dumping as a method to protect REBCO insulated test coils, even with engineering current density in the kA mm−2 range. Pick up coils can be used to compensate inductive coil voltage. In previous works we highlighted the presence of transient voltage due to the hysteretic current distribution in REBCO tape width, which can complicate the detection. We then developed a numerical electromagnetic model that reproduce the transient behavior of REBCO coils. Here we study a small REBCO coil instrumented with three different pick-up coils, including a co-wound pick-up whose coupling is close to perfect. The post processing and analysis of the simulation results makes it possible to identify in the transient coil voltage the contribution due to transient losses and coil inductance variation. The resulting evaluation of the REBCO coil inductance and its variations is validated by analysis of the pick-up coil signals. From a practical point of view, this work shows the possibility to have very sensitive early detection of thermal runaway if the threshold is adjusted based on the expected coil compensated voltage drift. The interest of using isolated high-strength co-wound reinforcement tape as pick-up coil is also highlighted.