Balanced Winding Research Articles

Research on the application of balanced windings in wind farm booster stations

Abstract The 35 kV booster station system is an undisputed main grid in wind farms, and its main transformer wiring and grounding methods directly affect the stable operation of the entire wind farm station. After explaining the important role of balanced windings in transformers, this article uses Matlab/Simulink to build a mathematical model of wind farm stations from the aspects of wind turbines, transmission lines, step-up transformers, grounding transformers, main power grids, loads, etc. From the perspectives of harmonic suppression ability and wind farm operation stability, the applicability of a three-winding transformer with balanced windings as the main transformer of wind farm step-up stations is analyzed in depth. The results show that using a three-winding transformer as the main transformer for the wind farm boosting station has a significant effect on harmonic suppression and can ensure stable operation of the wind farm.

Modeling and Suppression of Conducted Interference in Flyback Power Supplies Based on GaN Devices

The application of GaN power devices has significantly increased the power density of flyback power supplies but has also caused severe electromagnetic interference (EMI) issues. To address the challenge of conducted interference in flyback power supplies, a comprehensive analysis of the transmission mechanism of conducted common-mode noise is undertaken. This analysis involves simplifying the equivalent model of conducted interference and leveraging the circuit characteristics of conducted noise to propose a solution for attenuating common-mode noise. Considering the constraints of external compensation capacitors, a balanced winding is further introduced to mitigate the impact of noise. To enhance the efficacy of conducted interference suppression, it is suggested to change the winding structure of the transformer and incorporate a shielding winding. This configuration aims to minimize the generation and propagation of common-mode noise within the transformer. Finally, experimental verification is carried out using a 150 W GaN flyback power supply prototype. The experimental results demonstrate that the proposed method effectively suppresses common-mode noise in the circuit.

Transformer balancing winding technology with effective shielding for suppressing common mode noise in flyback converters

Transformer balancing winding technology with effective shielding for suppressing common mode noise in flyback converters

Brushless Doubly-Fed Asynchronous Generator Model for Variable Speed Wind Generation Systems.

Because of the raising percentage of the wind energy in the total electrical energy, quality control and regulation of the provided energy will be needed for the electrical grid correct functioning. It is only possible using Variable Speed Wind Generation Systems (VSWGS). In this paper a new electrical generator, Brushless Doubly-Fed Asynchronous Generator (BDFAG) is proposed as a solution for a variable speed wind generation system. The stator of this machine is composed of two balanced three-phase windings with different pole pair number. The rotor is as robust as a conventional squirrel cage, but it has a special design. A steady state model of a BDFAG. is analyzed. Using this model the power balance in the stator windings and the rotor cage is evaluated. The evaluation results will be experimentally verified with a prototype of BDFAG.

A Rewound Five-Phase Synchronous Reluctance Machine: Operating Voltage, Inductance Analysis and Comparison with Conventional Multiphase Machines

In the recent literature, a rewinding approach was proposed to construct a rewound five-phase machine with either star-connected or combined star-pentagon winding using existing off-the-shelf three-phase stator frames. The power per phase drops by a factor of 3/5 in the five-phase machine compared to the three-phase machine. This indicates that either the rated current or voltage must be rescaled. The two options are compared in terms of drive cost and performance. The constant current - reduced voltage option is analytically investigated to determine whether reducing the operating voltage affects the operating speed/output power or not. The second contribution of this work is to determine the optimal slot/pole combinations of the existing off-the-shelf three-phase stators that ensure balanced five-phase star-connected and/or combined star-pentagon windings. This has been done by comparing the harmonic mapping of the rewound machines for different slots/poles combination with the conventional five-phase machines using standard vector-space-decomposition. In addition, the leakage inductance mismatch for different slots/poles combinations of the rewound five-phase machines has been compared to the standard conventional five-phase machines. The last contribution of this paper is to compare the performance of the rewound combined star-pentagon winding with an optimally designed conventional symmetrical one (60-slots/4-poles). This has been done using 2D Ansys Maxwell transient simulation. Finally, experimental results are used to support the theoretical and analytical conclusions.

A novel two-layer winding topology for sub-harmonic synchronous machines

With optimized design and modern brushless operation, wound rotor synchronous machines are resurrecting as a strong contender in many applications presently dominated by permanent magnet machines. Considering the notion, this paper introduces a novel brushless synchronous machine topology that utilizes sub-harmonic magnetomotive force (MMF) of its stator winding for desirable brushless operation. It is significant to state that the sub-harmonic MMF component that is used in this novel topology is one-fourth of the fundamental MMF component, whereas, in previous practices, it was half. Moreover, the stator of the machine uses a new winding arrangement of two sets of balanced three-phase windings wound in two layers to produce the fundamental and the sub-harmonic MMF. To achieve the brushless excitation, the rotor utilizes an additional winding that is used to induce the electromotive force (EMF) by the sub-harmonic MMF component of the stator. This novel two-layer stator winding topology permits the utilization of maximum allowable space in the stator to house conductors in all of its 48 slots, which was not the case in previous papers. To validate the performance, and feasibility, an 8-pole 48-slot brushless wound rotor synchronous motor is designed, and a 2-D finite element analysis simulation is conducted, where the topology shows immense potential in terms of better torque performance.

Особенности применения теоремы вириала для магнитных систем с квазибессиловыми обмотками

The article shows that in a magnetic system with a thin-walled balanced winding close to a force-free one, a significant increase in the parameter θ=WM γ/M σМ , is possible, which, according to the virial theorem, characterizes the ratio of the energy of the magnetic system WM to the weight of equipment with a material density γ, where under the action of electromagnetic forces there appears a mechanical stress σМ. In a quasi-force-free magnetic system, the main part of the winding is in a state of local equilibrium, and only a relatively small part of the equipment is subject to stress. This part determines the weight of the entire system, and this weight can be minimized. The configurations of balanced thin-walled windings are developed, at the boundaries two boundary conditions are fulfilled simultaneously - the absence of the induction component normal to the boundary and the constancy of the product of induction and radius. The authors consider an example of a system consisting of a main part - a sequence of balanced "transverse" modules in the form of flat discs and end parts, consisting of a combination of "transverse" modules and "longitudinal" ones, having the form of rings elongated along the axis with balanced end parts. It is shown that in the system under consideration, the characteristic dimensionless parameter θ with an unlimited increase in the number of elements of the main part can reach a value of about 24, and when the number of these elements changes within 20 - 40, it changes from 6 to 9.

Features of the application of the virial theorem for magnetic systems with quasi-force-free windings

The article shows that in a magnetic system with a thin-walled balanced winding close to a force-free one, a significant increase in the parameter theta=W_Mγ/MsigmaM, is possible, which, according to the virial theorem, characterizes the ratio of the energy of the magnetic system WM to the weight of equipment with a material density γ, where under the action of electromagnetic forces there appears a mechanical stress sigmaM. In a quasi-force-free magnetic system, the main part of the winding is in a state of local equilibrium, and only a relatively small part of the equipment is subject to stress. This part determines the weight of the entire system, and this weight can be minimized. The configurations of balanced thin-walled windings are developed, at the boundaries two boundary conditions are fulfilled simultaneously --- the absence of the induction component normal to the boundary and the constancy of the product of induction and radius. The authors consider an example of a system consisting of a main part - a sequence of balanced "transverse" modules in the form of flat discs and end parts, consisting of a combination of "transverse" modules and "longitudinal" ones, having the form of rings elongated along the axis with balanced end parts. It is shown that in the system under consideration, the characteristic dimensionless parameter theta with an unlimited increase in the number of elements of the main part can reach a value of about 24, and when the number of these elements changes within 20 -40, it changes from 6 to 9. Keywords: Quasi-force-free magnetic field, field energy, mass of a magnetic system, virial theorem, minimization of the ratio of mass to energy.

Analysis and Application of Two-Layer Unconventional Windings for PM-Assisted Synchronous Reluctance Motors

This paper presents a new winding configuration theory of conventional and unconventional slot-pole combinations that can be used to configure windings with any slot-pole combination. First, various two-layer windings can be divided into conventional balanced winding (CBW), unbalanced winding (UBW), unconventional even slot winding (UESW) and unconventional odd slot winding (UOSW). In addition, the winding configuration can be divided into two steps—slot sorting and slot distributions to phases—and the rule of winding distribution and connection of the four kinds of windings is given. Moreover, there are four models established corresponding to the four kinds of windings. The air-gap flux density and harmonic of models with double layer flux-barrier PM-assisted rotor and without flux-barrier rotor are analyzed and compared using two-dimensional transient finite element analysis (FEA). The effect of stator magneto motive force (MMF) on torque performance affected by winding configuration is analyzed by comparing air gap magnetic density under two kinds of rotors. The simulation of torque shows that UBW, UESW, and UOSW have a certain reducing effect on torque ripple in PMASynRM. Meanwhile, a brief comparison is made in terms of radial forces and power losses; the effects produced by UBW, UESW, and UOSW compared to CBW in these two aspects are acceptable.

A New Grid-Connected Constant Frequency Three-Phase Induction Generator System under Unbalanced-Voltage Conditions

This paper presents a new constant frequency, direct grid-connected wind-based induction generator system (IGS). The proposed system includes a six-phase cage rotor with two separate three-phase balanced stator windings and a three-phase SV-PWM inverter which is used as a STATCOM. The first stator winding is connected to the STATCOM and is used to excite the machine. The main frequency of the STATCOM is considered to be constant and equal to the main grid frequency. In the second stator winding, the frequency of the induced emf is equal to the constant frequency, so the generator output frequency is independent of the load power demand and its prime mover speed. The second stator winding is directly connected to the main grid without an intermediate back-to-back converter. In order to regulate the IGS output active and reactive power components, a sliding mode control (SMC) is designed. Assuming unbalanced three-phase voltages for the main grid, a second SMC is developed to remove the machine output’s negative sequence currents. Moreover, a conventional PI controller is used to force the average exchanging active power between the machine and STATCOM to zero. This PI controller generates the reference value of the rotor angular speed. An adjustable speed pitch angle-controlled wind turbine is used as the IGS’s prime mover. The effectiveness and capability of the proposed control scheme have been supported by the simulation results.

Solid-State Transformer Based Fast Charging Station for Various Categories of Electric Vehicles With Batteries of Vastly Different Ratings

This article proposes a solid-state transformer (SST) based power electronic architecture for fast charging three categories of plug-in electric vehicle with batteries of vastly different voltage and power ratings. The SST accomplishes integration to a medium-voltage grid and isolation to the charging ports without the use of an LFT. Delta connected cascaded H-bridge (CHB) is used as the active front-end rectifier and quad active bridges (QABs) are utilized for the isolated dc-dc conversion stage. In the proposed architecture, an additional winding called balancing winding is provided in each of the medium-frequency transformers of the QAB. The balancing winding of the transformers are paralleled such that a circulating current flows among the transformers of the three phases, which eventually reduces the unbalance in the delta-connected clusters. Hence, the magnitude of zero-sequence current required to balance the cluster powers for a certain level of unbalance is also reduced. As a result, the total current in the devices of the CHB decreases and devices with a lesser current rating can be used. The control philosophy and detailed analysis of the system are given in the article. Experimental results with a scaled-down prototype are presented to verify the claims.

Modeling of balancing transformers to determine the effectiveness of their application

One of the urgent problems is providing consumers of distribution electric networks with high-quality electricity. The most important indicators of the quality of electricity are the level and asymmetry of voltage, the deviation of which from the normative indicators leads to disruption of operation and a decrease in the service life of electrical equipment. If the standard indicators of electricity are not met, the consumer has the right to demand compensation from the electricity supply companies. For balance the voltage on the 0.4 kV side of the step-down substations, it is promising to use transformers with a balancing winding both in new construction and in their reconstruction. The problem of determining the effect of the use of transformers with a balancing winding is that the manufacturer does not provide the necessary parameters for them to ensure the calculation of the phase voltage level when connecting an asymmetric load. Also in existing software products, such as, for example, Matlab/Simulink, there are no ready-made mathematical models of the transformers under consideration. As a result, it is impossible to reliably assess the benefits of replacing conventional transformers with a balancing winding, when the task of a feasibility study for the reconstruction of a substation arises in order to ensure standard indicators of the quality of electricity and reduce electricity losses.

Hybrid Passive Cancelation Method for Reducing Common-Mode Noise in Isolated Power Converters

The shielding technique is an effective method for reducing the common-mode (CM) electromagnetic interference in an isolated power converter. However, the interwinding capacitance between the shielding layer and its adjacent winding provides the path for CM noise current. This CM noise current can be suppressed by making the averaged electric potential (AEP) of the shielding layer and its adjacent winding be equal. In this article, a balancing winding is introduced to be connected with the shielding layer for adjusting the AEP of the shielding layer to be equal to that of its adjacent winding and, thus, canceling the CM noise current. Furthermore, the hybrid passive cancelation (HPC) method is proposed in which the balancing winding is reused as the compensation winding to generate the compensation voltage for canceling the noise current flowing through the parasitic capacitance between the high dv / dt node in the primary circuit and protective earth. The proposed shielding technique with balancing winding and the HPC method are verified by the experimental results.

Development of High-voltage Standard Current Transformer with Three Phases in One Enclosure Based on Shielding and Balanced Winding

When three-phase testing method is applied to test errors of three-phase combined transformers on site, many testing devices are needed while laboratory space is limited. Therefore, narrowing down the space that testing devices occupied appears to be crucial. This article designed and developed the gas-insulated high-voltage standard current transformer with all three phases in one enclosure. Its characteristics is that double shielding and shielding combined with balancing winding are used separately to restrain the influence of leakage current and magnetic field on the error of standard current transformer. Moreover, the article carried out the effect of leakage current and magnetic field on the error of standard current transformer. The results show that the influence of leakage current on the error of standard current transformer is less than 1/10 of the error limit. The influence of adjacent phase current on standard current transformer is less than 1/10 of the error limit. The high voltage standard current transformer with three phases in one enclosure, designed and developed in this article, is capable of testing errors of 10 kV three-phase combined transformers for measurement on the field with three-phase testing method.

Investigation of Different Winding Configurations and Displacements of a Nine-Phase Permanent-Magnet-Synchronous Motor With Unbalanced AC Winding Structure

Integral-slot electrical machines require modifications and optimization of both stator and rotor to maximize the machine performance. In addition, sub-harmonics in magneto-motive force distributions is an important issue in motors with fractional-slot concentrated windings. These additional sub- and super-harmonics increase iron losses, which becomes an even bigger challenge in high speed/frequency applications. A permanent-magnet (PM) motor with unbalanced winding (UBW) and unconventional slot numbers is a good option for applications that require smooth torque output and low back electromotive force voltage harmonics. In this paper, different winding configurations and displacements of an unconventional nine-phase PM motor with both balanced fractional-slot winding and UBW structures have been investigated. The focus has been on 117-slot with 12-pole (for the balanced winding motor) and 36-pole (for the UBW motor) combinations. Motor prototypes with UBW configurations have been manufactured. The finite-element analyses results have been validated with experimental results and it is shown that such unconventional slot/pole combinations can be a good option for some high-power applications.

Unbalanced distributed and balanced concentrated winding comparison in servo motor applications

A comparison between unbalanced distributed winding and balanced concentrated winding is presented in this paper. The application is a torque motor where low speed and high torque are main requirements. Concentrated winding slot/pole combination is selected so that winding factor is maximum and as well as it is equal to the winding factor of the unbalanced winding motor. Stator and rotor Magneto-Motive Force (MMF) functions are obtained for both motor types to model torque ripple components in the frequency spectrum. Finite element analysis (FEA) and experimental results are presented to compare back EMF waveforms, magnetic loading, torque constant and thermal performance of two motors.Two designs have identical stator outer diameter (OD) and active axial length. The detailed comparison shows that two motors have similar torque constant. The behavior of two motors under heavy load differs and concentrated winding design performs better. Thermal performance of the designs is also compared and it is observed that concentrated winding design has also less winding temperature rise.

Single-Turn Magnet With an Additional Balanced Winding and Flux Concentrators

The balanced winding displaced in the cavity, the magnet provides the possibility for obtaining the stronger magnet field without enhancing mechanical stresses in the conductors. The model of such a system is the single-turn magnet with an additional triple-thread spiral winding. The equilibrium condition with respect to the radial force takes place at definite values of the axial current and pitch of the turns. In order to decrease the transverse field provoking the azimuthal force, the correction system in the form of cylindrical conductors with slits has been used. The discharging of the end part of the additional winding from the axial force is achieved using the flat concentrators of the flux.

Influence of Rotor-Pole Number on Electromagnetic Performance in 12-Phase Redundant Switched Flux Permanent Magnet Machines for Wind Power Generation

In this paper, electromagnetic performances of 12-phase 24-stator-pole redundant switched flux permanent magnet (SFPM) machines with 20-, 22-, 26-, and 28-rotor-pole rotors designed for wind power generation are comparatively analyzed. The influence of key design parameters on the open-circuit phase electromotive force and cogging torque is comparatively evaluated by a 2-D finite-element analysis (FEA). FEA results show that the 24-/26-pole SFPM machine exhibits the highest electromagnetic torque and efficiency than the other three, while the 24-/22-pole one has the smallest cogging torque and torque ripple as well as relatively good voltage regulation and efficiency, which are essential for a wind generator. Furthermore, the investigation on redundancy performance shows that cross coupling among the four sets of three-phase balanced windings and the saturation effect can be neglected when the generator operates with relative light loads. Finally, the 12-phase 24-/22-pole SFPM machine is built and tested to validate the simulations.

Inductive voltage divider modeling in Matlab

Inductive voltage dividers have the most appropriate metrological characteristics on alternative current and are widely used for converting physical signals. The model of a double-decade inductive voltage divider was designed with the help of Matlab/Simulink. The first decade is an inductive voltage divider with balanced winding, the second decade is a single-stage inductive voltage divider. In the paper, a new transfer function algorithm was given. The study shows errors and differences that appeared between the third degree reduced model and a twenty degree unreduced model. The obtained results of amplitude error differ no more than by 7 % between the reduced and unreduced model.

Prediction of Structural Behavior of FRP Pressure Vessel by Using Shear Deformation Theories

Traditionally, pressure vessels were constructed from isotropic materials such as steel and aluminum. Structures made of isotropic materials are less efficient since the longitudinal stresses use only half that of the structure capabilities but now, with the advent of composites, the material can be tailored so that more fibers are laid in the direction where the stresses are high. The versatility of filament winding saves weight by tailoring the winding patterns to carry the loads. The determination of proper filament winding angle and thickness is very important aspect to improve the structural efficiency. A composite pressure vessel with a geodesic fiber trajectory for the entire shell is considered. The composite pressure vessel comprises of Low Density Poly Ethylene (LDPE) liner and E-Glass/Epoxy composite shell layers with variable thickness and orientation of the fiber. Netting Analysis is used for the calculation of the hoop and helical thickness of the shell when subjected to uniform internal pressure and balanced symmetry winding pattern are adopted. Composite pressure vessel is fabricated by filament winding technology. Hydraulic test is performed on the composite pressure vessel till burst pressure. Strains were noted at different internal pressures applied on the composite pressure vessel by using Strain gauges.A software code SHELL Analyzer is developed using Classical Lamination theory, First Order Shear Deformation theory and Third Order Shear Deformation theory to predict the strains on a Composite Pressure vessel. Hence theoretical results were validated with experimental results. The results shows that the TOSDST is more accurate than CLST &FOSDT to predict the stresses and strains.