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Abstract The contra‐rotating machine (CRM) has been a preferable selection of the contra‐rotating propulsion system (CRPS) owing to its high efficiency, high compactness, and low noise. However, the conventional CRM with rotating stator has the problem of brush and slip ring, and the conventional brushless CRM has the problem of coordinated control of equal and opposite torque. Aiming at the above problems, this article proposes a transverse‐dislocated magnetic‐field modulated brushless contra‐rotating machine (TDMFM‐BCRM). The proposed TDMFM‐BCRM has some advantages of no rotating winding, no associated brushes and slip rings, and equal and opposite torques at any time, therefore it has good potential for the CRPS. The working principle of the TDMFM‐BCRM including three dimensional magnetic‐field modulated theory, back electromotive force (EMF) generation, and torque relation is studied. Then, the influences of main parameters including magnetic block parameters and PM sizes on torques are investigated. The critical electromagnetic performances of the TDMFM‐BCRM are analysed. A prototype of TDMFM‐BCRM is manufactured and measured to validate the above analysis. Finally, the comparison of the TDMFM‐BCRM and the existing schemes are analysed.

Abstract The brushless doubly‐fed machine (BDFM) utilizes an asymmetric composite rotor featuring salient pole reluctance and magductance to effectively compensate for the phase shift in space, as well as enhance magnetic field modulation effects, and is therefore used as a modulator. This paper evaluates the modulation capability of the modulator from the perspective of the magnetic field conversion mechanism. The theoretical evolutions of the average magnetic field conversion factors and torque contributions of various airgap field harmonics are accomplished. Additionally, multi‐objective optimization is conducted for better performance, using stratified sensitivity analysis on typical 4/2 pole pair BDFMs featuring symmetrical and asymmetric composite rotors. As a result, further improved modulation of the air gap magnetic field is expected, the cross‐coupling efficiency of the rotor is improved, and a lower output torque ripple is also achieved compared to the conventional symmetrical counterpart. Theoretical investigation of the optimized BDFM, including its effectiveness in enhancing performance metrics such as coupling factor, airgap flux density, and phase shift mechanism, is verified through 2D finite element analysis. Furthermore, a proof‐of‐concept prototype for experimentation was manufactured, which achieved good agreement with the theoretical predictions.

Abstract A computationally efficient time‐harmonic finite element model for the steady‐state analysis of a brushless doubly fed induction machine (BDFIM) is proposed. In the model, the electromagnetic couplings of the BDFIM are described by means of the sum of two complex magnetic vector potentials that represent the two fundamental harmonic time components of the magnetic flux density distribution in the rotor frame of reference. As in an ordinary induction motor, the non‐linearity of the magnetisation characteristic is accounted for using an effective magnetic permeability. For the BDFIM, this is derived by considering the features of modulated magnetic flux density waveform. The accuracy of the approach has been validated by comparing the characteristics of a D270 machine operating in the double‐feed mode with ones obtained from the experimentally verified time‐stepping model at various operating conditions. High accuracy of the results coming from the proposed model is demonstrated even under deep saturation conditions within the magnetic circuit.

Abstract Wind energy as the cleanest source of renewable energy requires a highly efficient lightweight generator that provides maximum power density while having the least vibration noise and maintenance. In this study, an axial air gap transverse flux machine is presented, and all excitation sources are located in the stator. This structure provides lower core loss, weight and cost due to the full utilisation of the permanent magnets, SMC‐free structure and short magnetic flux path. In fact, by combining the features of a flux‐switching machine into a transverse flux generator with an axial air gap, it is possible to improve the performance of a direct‐drive wind turbine generator by overcoming traditional structures' challenges. To analyse the axial transverse flux switching permanent magnet generator performance characteristics, 3D finite element simulations have been performed, which have been validated by comparing them to the practical results of a single‐phase prototype. The results are in agreement with an acceptable error that is caused by manufacturing uncertainties.

The contra‐rotating machine (CRM) has been a preferable selection of the contra‐rotating propulsion system (CRPS) owing to its high efficiency, high compactness, and low noise. However, the conventional CRM with rotating stator has the problem of brush and slip ring, and the conventional brushless CRM has the problem of coordinated control of equal and opposite torque. Aiming at the above problems, this article proposes a transverse‐dislocated magnetic‐field modulated brushless contra‐rotating machine (TDMFM‐BCRM). The proposed TDMFM‐BCRM has some advantages of no rotating winding, no associated brushes and slip rings, and equal and opposite torques at any time, therefore it has good potential for the CRPS. The working principle of the TDMFM‐BCRM including three dimensional magnetic‐field modulated theory, back electromotive force (EMF) generation, and torque relation is studied. Then, the influences of main parameters including magnetic block parameters and PM sizes on torques are investigated. The critical electromagnetic performances of the TDMFM‐BCRM are analysed. A prototype of TDMFM‐BCRM is manufactured and measured to validate the above analysis. Finally, the comparison of the TDMFM‐BCRM and the existing schemes are analysed. [ABSTRACT FROM AUTHOR]

The brushless doubly‐fed machine (BDFM) utilizes an asymmetric composite rotor featuring salient pole reluctance and magductance to effectively compensate for the phase shift in space, as well as enhance magnetic field modulation effects, and is therefore used as a modulator. This paper evaluates the modulation capability of the modulator from the perspective of the magnetic field conversion mechanism. The theoretical evolutions of the average magnetic field conversion factors and torque contributions of various airgap field harmonics are accomplished. Additionally, multi‐objective optimization is conducted for better performance, using stratified sensitivity analysis on typical 4/2 pole pair BDFMs featuring symmetrical and asymmetric composite rotors. As a result, further improved modulation of the air gap magnetic field is expected, the cross‐coupling efficiency of the rotor is improved, and a lower output torque ripple is also achieved compared to the conventional symmetrical counterpart. Theoretical investigation of the optimized BDFM, including its effectiveness in enhancing performance metrics such as coupling factor, airgap flux density, and phase shift mechanism, is verified through 2D finite element analysis. Furthermore, a proof‐of‐concept prototype for experimentation was manufactured, which achieved good agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]

A computationally efficient time‐harmonic finite element model for the steady‐state analysis of a brushless doubly fed induction machine (BDFIM) is proposed. In the model, the electromagnetic couplings of the BDFIM are described by means of the sum of two complex magnetic vector potentials that represent the two fundamental harmonic time components of the magnetic flux density distribution in the rotor frame of reference. As in an ordinary induction motor, the non‐linearity of the magnetisation characteristic is accounted for using an effective magnetic permeability. For the BDFIM, this is derived by considering the features of modulated magnetic flux density waveform. The accuracy of the approach has been validated by comparing the characteristics of a D270 machine operating in the double‐feed mode with ones obtained from the experimentally verified time‐stepping model at various operating conditions. High accuracy of the results coming from the proposed model is demonstrated even under deep saturation conditions within the magnetic circuit. [ABSTRACT FROM AUTHOR]

Rotor position information obtained through a position sensor is crucial for proper field-oriented control (FOC) of permanent magnet synchronous machine-based high dynamic energy conversion applications. In applications such as transportation and industrial, PMSM energy conversion systems are subjected to harsh environmental conditions such as vibration, shock, and thermal shock causing mechanical interfaces holding position sensors to fail, introducing errors to the position measurement. A dynamic position sensor offset error (DPSOE), being such a failure mode has the potential to degrade system torque output or more adversely, reverse machine torque output that may cause catastrophic outcomes. This paper evaluates different DPSOE scenarios, presents an approach to model the failure mode for analysis and proposes two novel, and robust DPSOE detection methods for PMSM drive systems. The proposed detection methods are analytically proven and supported by simulation and experimental results under multiple operating conditions proving robustness.

Wind energy as the cleanest source of renewable energy requires a highly efficient lightweight generator that provides maximum power density while having the least vibration noise and maintenance. In this study, an axial air gap transverse flux machine is presented, and all excitation sources are located in the stator. This structure provides lower core loss, weight and cost due to the full utilisation of the permanent magnets, SMC‐free structure and short magnetic flux path. In fact, by combining the features of a flux‐switching machine into a transverse flux generator with an axial air gap, it is possible to improve the performance of a direct‐drive wind turbine generator by overcoming traditional structures' challenges. To analyse the axial transverse flux switching permanent magnet generator performance characteristics, 3D finite element simulations have been performed, which have been validated by comparing them to the practical results of a single‐phase prototype. The results are in agreement with an acceptable error that is caused by manufacturing uncertainties. [ABSTRACT FROM AUTHOR]

Converters are one of the most sensible components of any power conversion system when it comes to electrical faults. Moreover, if these converters are used in a rotating system, as is the case with rotating rectifiers used in brushless synchronous machines, apart from also being exposed to mechanical effects and thus having a greater likelihood of failure, no access is available directly, causing a lack of available measurements for condition monitoring. This paper applies a model-based method to the online detection of open-diode faults, shorted-diode faults and exciter open-phase faults in the rotating rectifiers of brushless synchronous machines. The applied method relies on the comparison between the measured and the theoretical exciter field currents, the latter computed through a healthy machine model from the machine actual output values. The proposed protection strategy stands out for its computational simplicity and its non-invasiveness, which makes its industrial application straightforward without the need of any further equipment or adaptation. Its applicability has been verified through a double approach, on the one hand, through computer simulations, and, on the other hand, through experimental tests, achieving satisfactory results. The research conducted proves that with the proposed method, given reasonable measurement and model estimation typical errors of less than 5%, positive differences between the measured and the theoretical exciter field currents of more than 13%, 200% and 30% for open-diode faults, shorted-diode faults and exciter open-phase faults, respectively, are detectable with at least a 95% confidence interval. [ABSTRACT FROM AUTHOR]

Permanent Magnet Linear Flux Switching Machines (PMLFSMs) are potential candidates when higher thrust force ( $\boldsymbol {T}_{ \boldsymbol {F}}$ ) and low cost are the primal requirements. However, conventional PMLFSMs shows flux leakages and utilizes high Permanent Magnet (PM) volume ( $\boldsymbol {V}_{ \boldsymbol {PM}}$ ) that increase overall expense. Therefore, this paper proposed novel Segmented PM Consequent Pole Linear Flux Switching Machine (SPMCPLFSM) with flux bridges. In comparison with PMLFSM, the proposed SPMCPLFSM diminish detent force by $\boldsymbol {20.41\%}$ , suppress thrust force ripples by 27.68%, reduces ripple ratio by 1.77 times, improve $\boldsymbol {T}_{ \boldsymbol {F}}$ to 2 times and boost $\boldsymbol {T}_{ \boldsymbol {F}}$ density to 2.64 times utilizing 75% PM volume and reducing PM cost by 24.16%. Moreover, to overcome computational complexity and computation time, analytical model uniting Lumped Parametric Magnetic Equivalent Circuits, vector potential and Maxwell Stress Tensor method are utilized for open circuit flux linkages, magnetic flux density, detent force and thrust force. Finally, analytical model is validated with finite element analysis (FEA) that show good agreement with FEA. Thus, authors are assured to suggest analytical techniques for early design purpose and proposed SPMCPLFSM for roller coaster application.

Abstract There is an urgent need to develop a robust capacitor charge power supply (CCPS) system to meet the requirement of pulsed load in all‐weather mobile occasions such as vehicle, ship and aircraft. Brushless doubly fed alternator (BDFA) works through the rotor's pole pairs' transformation to get excitation indirectly, without magnets, brushes and slip rings. Both DC and AC excitation can be used. Therefore, it has high reliability and a good application prospect in the CCPS system. However, the existing research studies lack analysis of the parameters that affect charging performance, and have no experimental analysis of the prototype. To solve this problem, a comprehensive design method and experimental procedure of the pulsed BDFA are proposed and investigated. First, the operation principle of the pulsed BDFA is illustrated. Then, the charging performances under different design schemes are comparatively analysed through the finite element analysis (FEA). Finally, a prototype of the pulsed BDFA is manufactured, and the related experiments are carried out. The results verify the feasibility of the experimental procedure and the accuracy of FEA. The comprehensive design method and experimental procedure in this work provide a straightforward reference for the subsequent applications in the CCPS system.

This article presents a methodology for the development of a promising integrated starter-generator based on a 5 kW Brushless DC Machine with a rotation speed of 6000 rpm for the aviation piston demonstrator engine APD-500 developed for an aircraft with a piston engine and a parallel hybrid electric propulsion system. The developed integrated starter-generator has three modes of operation: in the starter mode, launching the APD-500, in the generator mode, providing electricity generation on board the aircraft and in the electric motor mode for twisting the aircraft propeller shaft in flight (implementation of a parallel hybrid electric propulsion system). Upon completion of the stages of design, construction and calculations, a prototype integrated starter-generator with a DC converter and two control units has been created, which have passed ground tests on an experimental bench as part of an APD-500 aircraft piston engine, showing a 5% discrepancy with the results of computer numerical simulation. The results of ground tests of integrated starter-generator aboard of the aircraft at the airfield have also confirmed the stable operation and the ability to provide the required flight characteristics of presented system. [ABSTRACT FROM AUTHOR]

Brushless doubly‐fed generator (BDFG) is a most promising candidate for the wind turbine due to its simple structure, high reliability, and low converter capacity. To improve space utilization and achieve higher power density, this paper proposes a new dual‐stator BDFG (DS‐BDFG), which provides two separated windings, namely, the power winding (PW) placed in the outer stator and the control winding (CW) placed in the inner stator. A cup‐shaped rotor sandwiched between the inner and outer stators consists of the short‐circuited coil and the salient‐pole core. The coupling between the PW and the CW is realized via the rotor based on the general airgap magnetic field modulation theory for electrical machines. A prototype of the DS‐BDFG with rated PW power of 7.2 kW is designed and optimized. The keys of this paper are the power equation derivation, the determination of pole/slot combinations, and the rotor optimization. The electromagnetic characteristics and unbalanced magnetic force of the DS‐BDFG are analyzed by 2D finite element analysis to verify the reasonableness of the proposed model. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

There is an urgent need to develop a robust capacitor charge power supply (CCPS) system to meet the requirement of pulsed load in all‐weather mobile occasions such as vehicle, ship and aircraft. Brushless doubly fed alternator (BDFA) works through the rotor's pole pairs' transformation to get excitation indirectly, without magnets, brushes and slip rings. Both DC and AC excitation can be used. Therefore, it has high reliability and a good application prospect in the CCPS system. However, the existing research studies lack analysis of the parameters that affect charging performance, and have no experimental analysis of the prototype. To solve this problem, a comprehensive design method and experimental procedure of the pulsed BDFA are proposed and investigated. First, the operation principle of the pulsed BDFA is illustrated. Then, the charging performances under different design schemes are comparatively analysed through the finite element analysis (FEA). Finally, a prototype of the pulsed BDFA is manufactured, and the related experiments are carried out. The results verify the feasibility of the experimental procedure and the accuracy of FEA. The comprehensive design method and experimental procedure in this work provide a straightforward reference for the subsequent applications in the CCPS system. [ABSTRACT FROM AUTHOR]

Converters are one of the most sensible components of any power conversion system when it comes to electrical faults. Moreover, if these converters are used in a rotating system, as is the case with rotating rectifiers used in brushless synchronous machines, apart from also being exposed to mechanical effects and thus having a greater likelihood of failure, no access is available directly, causing a lack of available measurements for condition monitoring. This paper applies a model-based method to the online detection of open-diode faults, shorted-diode faults and exciter open-phase faults in the rotating rectifiers of brushless synchronous machines. The applied method relies on the comparison between the measured and the theoretical exciter field currents, the latter computed through a healthy machine model from the machine actual output values. The proposed protection strategy stands out for its computational simplicity and its non-invasiveness, which makes its industrial application straightforward without the need of any further equipment or adaptation. Its applicability has been verified through a double approach, on the one hand, through computer simulations, and, on the other hand, through experimental tests, achieving satisfactory results. The research conducted proves that with the proposed method, given reasonable measurement and model estimation typical errors of less than 5%, positive differences between the measured and the theoretical exciter field currents of more than 13%, 200% and 30% for open-diode faults, shorted-diode faults and exciter open-phase faults, respectively, are detectable with at least a 95% confidence interval.

Electrical machines are widely used in home appliances, the performance of which is mostly related to the quality function of the electrical machines. What has been used so far in home appliances brought with themselves a wide assortment of advantages and disadvantages. With the aim to overcome the drawbacks of the previously implemented electrical motors in washing machines, a new configuration of flux switching permanent magnet motor (FSPM) with the segmented outer rotor (SOR‐FSPM) is proposed benefitting from a direct driven drum. To reduce the cogging torque as well as torque ripple and to improve the total harmonic distortion, cutting the stator in a way to lower overlapping between the rotor and stator pole, inserting notches into the poles of the rotor to modify the air gap between the stator teeth and the rotor segments are proposed. The Taguchi method and sensitivity analysis are further applied to find the best combination set of changes in such a way to smoothen the chart showing reluctance between stator and rotor and fix the zero‐point crossing of the flux linkages in different rotor positions. Finally, the proposed SOR‐FSPM is prototyped, and experimental results along with the finite element method results are discussed and compared in order to verify the design process. [ABSTRACT FROM AUTHOR]

One of the types of electrical machines with high specific characteristics and small dimensions is the AFPM motor. These properties determine the interest in this type of electric machines in aviation. The small axial length of the AFPM motors allows them to be directly integrated without the risk of increasing the size of the aircraft. This paper presents the development and the experimental study of an AFPM motor without a stator core and with natural air cooling. The theoretical method for estimating the parameters of the AFPM motor has been presented. The calculated parameters have been used for a more accurate FEM analysis. According to the FEA calculations, the design of the AFPM motor has been developed and experimental studies have been carried out. The presented results of the experimental studies have good convergence with FEA analysis carried out during the design of a AFPM motor. [ABSTRACT FROM AUTHOR]

In this article, a 2-D analytical model is presented for brushless double mechanical port flux-switching permanent magnet machines (BDMPFSPMMs). The BDMPFSPMM is an appropriate candidate to be employed as the electric motor in hybrid electric vehicles (HEVs) due to integrating two rotors and two stators into a compact structure. The radial and tangential components of the magnetic flux density are calculated due to permanent magnets and armature currents in each active region of the machine based on the subdomain method. The effects of the saliency on both the rotor and stator structures as well as their interactions are considered. The approach can be used for the magnetic field calculation in BDMPFSPMMs with any combination of rotor- and stator-pole numbers. Based on the computed magnetic flux density, electromagnetic torque, self and mutual inductances, flux linkage, induced voltage, local traction, and unbalanced magnetic force (UMF) are obtained. To validate the proposed model, the analytical results are compared with those obtained from the finite element method (FEM). [ABSTRACT FROM AUTHOR]

Field-oriented control (FOC) or vector control is a formidable control strategy for permanent magnet synchronous machines (PMSMs) due to high dynamic torque response. However, FOC requires rotor flux orientation information, typically obtained using a position sensor mounted on the motor. The relative displacement between the position sensor and the rotor zero location is a key calibration required to properly orient the stator field based on the rotor magnetic field. A method is proposed herewith that enables the calibration of this relative offset between the position sensor and the rotor zero that reduces the overall manufacturing floor space and manufacturing time. The proposed scheme exploits hardware and software components that are readily available on the motor-drive system for FOC control. The self-calibration scheme generates a slowly rotating stator flux vector to rotate the motor rotor under the no-load condition to collect information about the position sensor alignment. Lack of a need for specialized measurement in comparison to conventional methods saves and space while reducing the calibration time. The novelty lies in the ability to self-calibrate and, in doing so, reduces resource utilization. Analysis, simulation, and experimental results are provided to validate the proposed methodology. [ABSTRACT FROM AUTHOR]

Rotor position sensor signal is a critical signal in a permanent magnet synchronous machine drive system. The alignment between the position sensor zero and the rotor quadrature axis must be accurately quantified for optimal torque generation under field-oriented control. However, the mechanical interfaces used for mounting the sensors are susceptible to failure due to environmental, manufacturing, and operational conditions resulting the position alignment to change from the previously calibrated value. In this article, a theoretical framework is presented that demonstrates the influence of the faulty static offset error in a position sensor of a permanent magnet synchronous machine and accordingly a diagnostic strategy is proposed to detect such failure mode. Both simulation and experimental results are provided to validate the theory and the diagnostic strategy. Theoretical analysis and simulations closely correlate with the experimental results. Furthermore, false positive prevention strategies for the fault diagnostic strategy are also discussed. [ABSTRACT FROM AUTHOR]

In this study, to maximise the performance and efficiency of 48 V integrated electric brake (IEB) system, a system‐level optimal design process is proposed for inverter‐driven brushless AC (BLAC) motor, taking into account the available input voltage that varies depending on the motor operating conditions. To get available input voltages, the voltage drops of battery wiring and inverter are reversely calculated from the motor output power. In the optimal design process, the resistance components in the inverter are separated into DC and AC parts, and these are analysed by including the dq equivalent circuit for motor analysis. The battery currents are obtained using the calculated maximum output performance and the loss between the battery and inverter. The proposed design process is applied to the optimal design of the 48 V motor for IEB systems. Also, to reduce the development cost of the 48 V motor, the manufacturing tools of the previously developed 12 V motor are shared. As an optimal design results, it is confirmed that there is an efficiency improvement effect of ∼5% compared to the conventional design of 12–48 V BLAC motor. [ABSTRACT FROM AUTHOR]

An improved and more robust flux vector orientated control scheme for an emerging doubly‐fed reluctance generator without a shaft angular position or velocity sensor has been proposed, computer‐simulated, and experimentally verified. Whilst retaining the cost and other advantages of using a fractional power electronics converter rating, this promising medium‐speed brushless machine technology has been viewed by research and industrial communities as an appealing economical solution for the compromised reliability and high maintenance requirements associated with the presence of slip rings, brushes, and the failures prone three‐stage gearbox of conventional wound rotor doubly‐fed induction generators, traditionally deployed for commercial wind turbines. The comprehensive comparative simulation and test results obtained have been shown to agree very well undoubtedly demonstrating the good overall performance of the sensorless controller. A precise speed reference tracking with smooth, intrinsically decoupled real and reactive power responses of the grid‐connected winding has been achieved for the typical variable loading profiles and narrow speed ranges (e.g. around 2:1 or so) of a laboratory emulated wind turbine. [ABSTRACT FROM AUTHOR]

The brushless doubly fed induction machine (BDFM) is considered as an alternative to doubly fed induction generators (DFIGs) in wind energy conversion systems. However, BDFMs have a complex machine structure, and their operations are relatively complicated. In this study, the winding function theory is used in the development of a coupled circuit (CC) model for BDFMs with nested loop (NL) and cage+NL rotors, in order to give a robust representation of the electrical operations of BDFMs. The electrical circuit analysis of BDFMs having NL and cage+NL rotors is comprehensively detailed, with the stator and rotor inductances calculated using their winding functions. The interactions of BDFM rotor loops with stator windings are demonstrated in terms of mutual inductances. CC models of different BDFMs are simulated for synchronous doubly fed BDFM operations with an emphasis on generating regions. Also, fresh insight into the torque production in BDFMs is provided, with the rotor loops and stator winding contributions to torque magnitude and ripple examined. [ABSTRACT FROM AUTHOR]

Permanent Magnet Flux Switching Machines (PMFSMs) enclose unique features of permanent magnet (PM) synchronous machine, direct current machine, and switch reluctance machine therefore, applicable for high speed brushless AC applications. However, conventional PMFSMs exhibits demerits of high PM volume VPM, high torque ripples Trip, low average torque Tavg, lower torque density Tden, power density Pden and leakage flux. In this paper, a new topology of 12S‐13P and 6S‐13P E‐Core PM Consequent Pole Flux Switching Machines (PMCPFSM) with flux barrier and partitioned PM is proposed that eliminate leakage flux, enhanced flux modulation effects through flux barriers and reduces the PM volume up to 46.53%. Moreover, due to non‐linear behaviour of PM and complex stator structure alternate analytical sub‐domain model is utilized for initial design and Multi‐Variable Geometric Optimization (MVGO) is opted to investigate influence of design parameters on electromagnetic performances such as Tavg, Trip, Tden and Pden. Analysis and comparison with the existing 12S‐10P E‐Core PMFSM, 6S‐10P E‐Core PMFSM, 6S‐10P C‐Core PMFSM and 12S‐14P C‐Core PMCPFSM reveals that proposed 6S‐13P PMCPFSM produced Tavg higher up to 88.8%, suppress Trip maximum up to 14.72% and offer 2.45 times Tden and Pden capabilities, when compared with the aforesaid state of the art.[AQ ID=Q1] [ABSTRACT FROM AUTHOR]

To accomplish an accurate and fast drive control, model predictive control (MPC) is considered as an effective control strategy nowadays. In MPC, the voltage vectors required for inverter control are evaluated considering the control objectives defined in terms of current or power or torque and flux. The optimal one is selected using an iterative prediction loop and applied in the next control interval. This form of MPC is simple in implementation and shows appreciable dynamic performance but the steady-state performance is compromised due to the limited availability of the number of voltage vectors, especially in the case of a two-level voltage source inverter. The present article explores the viability of the MPC approach for a new candidate such as a brushless doubly fed reluctance machine drive considering its secondary current as the control variable. Moreover, to tackle the steady-state inferiority issue, the duty-cycle control concept is inducted. In comparison to field-oriented control (FOC), the proposed scheme offers a straightforward solution for current control by replacing the inner current proportional–integral controllers and pulsewidth modulator with an optimization-based model predictive current controller. An extensive simulation study in MATLAB, vis-à-vis comparison with FOC scheme, and experimental validations justify the claims of the proposed work. [ABSTRACT FROM AUTHOR]

Signal injection degrades the starting performance of the brushless synchronous starter/generator (BSSG), and reversible magnetic saliency of the main generator (MG) leads to failure for most traditional sensorless methods. A novel full-speed sensorless starting control method of BSSG is proposed to solve these problems. The main exciter (ME), mechanically coupled to MG, is used as a position sensor of MG at low speed. The position of ME is extracted from the hexagonal trajectory of the rotor current space vector and then converted into the rotation angle of MG. At standstill, a fast initial position detection of MG is conducted with the electromotive force (EMF) of MG, induced by the establishment of the field current of MG. Then, the continuous position of MG is the sum of the estimated rotation angle and initial position. At high speed, flux weakening of MG is achieved by changing the structure of ME, invalidating the approach dependent on ME. Thus, estimations at low speed are replaced by ones based on extended EMF of MG gradually before the structure change. Signal injection is not needed and effects of reversible magnetic saliency are avoided in this approach. The effectiveness of this method is verified by experiments. [ABSTRACT FROM AUTHOR]

In this study, a new flux‐switching permanent‐magnet (FSPM) motor with two rotors and toroidal coil are introduced. First, the proposed FSPM (PFSPM) motor structure and performance principles are presented. Then, the performance parameters of the PFSPM motor, including flux linkage, back‐electromotive force, air‐gap flux distribution, inductance, eddy current loss, cogging torque and the output electromagnetic torque are compared with a conventional FSPM motor based on finite‐element analysis. Then, the effect of the angle between the two‐rotor poles on the performance parameters of the PFSPM motor is indicated. Finally, the PFSPM motor model is manufactured and the results of the finite‐element test are compared with the results of the experimental test and the accuracy of the finite‐element model is confirmed. [ABSTRACT FROM AUTHOR]

In recent years, consequent‐pole permanent magnet (CPM) machines draw much attention due to their high utilisation ratio of permanent magnet (PM) material. However, they have some disadvantages, such as the even‐order harmonics of airgap flux density, which may cause asymmetric phase back‐EMF and the increase of torque ripple. In this study, a novel hybrid‐pole PM (HPM) machine is proposed, in which the rotor combines consequent‐pole and spoke‐type PM rotors. The working principle of the proposed HPM machine is analysed based on the equivalent magnetic circuit, and validated by the finite‐element method. Then, the electromagnetic performance of the HPM machine is compared with those of the existing CPM and spoke‐type PM machines. It is shown that the HPM machine obtains similar average torque, PM utilisation ratio, torque ripple and efficiency to the spoke‐type PM machine, whilst it has a higher PM utilisation ratio and much lower torque ripple than the conventional CPM machines. Finally, these analyses are validated by the tested results of a 9‐slot/6‐pole HPM machine. [ABSTRACT FROM AUTHOR]

A nonlinear control scheme is proposed for real-time tracking of maximum torque per ampere trajectory of the surface-mounted brushless dc motor with non-sinusoidal back electromotive force (back-EMF). The strategy employs the Lagrange's Theorem to obtain the optimum stator current, at which both torque ripple and corresponding current magnitude become minimized. A new maximum torque per ampere (MTPA) criterion is introduced. Forcing this criterion to zero guarantees MTPA realization. The input–output feedback linearization (IOFL) control scheme is employed to improve tracking of the applied optimum currents. In the suggested approach, the magnitude of the stator current vector is minimized effectively in each instant. The performance of the control system is validated through experimental results. [ABSTRACT FROM AUTHOR]

Often for a closed-loop operation of a brushless direct current (BLDC) motor, Hall-effect sensors are used and recently there have been a number of discussions on Fault-Tolerant Control (FTC) of the BLDC motor for a defective Hall-effect sensor. However, so far, direct redundancy based approach for FTC of BLDC motor for a position sensor fault is not presented. This paper contributes a direct redundancy based method by utilizing redundant Hall-effect sensors for FTC of a BLDC motor. Redundant Hall-effect sensors generate additional transitions resulting in faster fault detection. To verify the proposed idea, MATLAB/Simulink model is developed, and the simulation results are presented by programing a MATLAB function block acting as a fault-tolerant controller. Furthermore, the algorithm is implemented into the MicroLabBox for experimental validation, and the results are discussed. [ABSTRACT FROM AUTHOR]

Flux‐reversal permanent magnet (PM) machines can be considered as stator‐surface‐mounted PM (SSPM) machines, where normally a pair of magnets with reversal magnetization polarities is mounted on the surface of each stator tooth. Hence, the SSPM machines and the conventional rotor surface‐mounted PM (RSPM) machines are rather similar since both machines house the PMs in the air‐gap, and the only difference is the location of magnets in the stator side and rotor side, respectively. In this study, a comparative study between SSPM and RSPM machines is conducted to investigate the difference including topology, operation principle and performance. First of all, the topology of both machines is compared. Then, the operation principle in both machines is analysed based on the air‐gap field modulation theory. Correspondingly, the characteristics of flux density harmonics either due to PMs or armature reaction are obtained. Therefore, the harmonics that make contribution to back‐electromotive force and rated torque are quantified. Besides, other electromagnetic performances, e.g. overload capability, flux weakening ability and loss distribution are also evaluated. Finally, a 12/14 prototyped SSPM machine is manufactured and tested to verify analytical and finite element method‐based prediction. [ABSTRACT FROM AUTHOR]

Permanent magnet flux switching machines (FSPMs) have attracted considerable attention in recent years, due to their outstanding characteristics to operate as brushless AC drives. Since they are relatively new, there are particular challenges not only for their design procedure but also for their operating principle comprehension. This study highlights several issues on FSPMs from the basic operation description to their key design points. After a comprehensive description of FSPMs working principles, a detailed discussion is presented on their armature winding design. In addition, this study reviews various methods for their performance modification, including torque profile, electromotive force, and loss characteristics. This study also surveys field regulation technologies, modelling and design optimisation methods applied to FSPMs along with their fabrication and cost issues. [ABSTRACT FROM AUTHOR]

Persistent signal injection in traditional sensorless methods leads to loss, noise, reduction of the starting torque of the main generator (MG) of the brushless synchronous starter/generator (BSSG), and complicated demodulation methods. Moreover, the reversible magnetic saliency of MG and multiple rectification modes of the rotating rectifier cause errors to most existing sensorless solutions of BSSG. To avoid these drawbacks, this paper proposes a novel method to estimate the rotor position of MG for zero- and low-speed operation. Since MG and the main exciter (ME) are mounted on the same shaft, ME is used as a position sensor, eliminating concerns of the reversible magnetic saliency of MG. With reliable indicators in all rectification modes, the position of ME is extracted from the hexagonal trajectory of the rotor current space vector of ME, which is caused by the rotating rectifier. With the estimated position of ME and signal injection into the stator of MG at standstill, the initial position of MG is detected. Then, signal injection is no longer needed and the continuous position of MG is obtained from the estimated rotation angle of ME and initial position of MG. Finally, the effectiveness of this method is verified by experiments. [ABSTRACT FROM AUTHOR]

This study studies, using experimentally verified finite element (FE) analysis, various performance measures of the brushless doubly fed induction generator (BDFIG) when magnetic wedges are used for closing stator open slots. The BDFIG is an attractive generator solution for offshore wind power and can replace doubly fed slip-ring induction generators. It is shown in this study that the use of magnetic wedges, commonly used in large induction machines, reduces the stator windings magnetising currents in a BDFIG, reflected in the values of magnetising inductances. They also increase the leakage flux in the stator slots, leading to a larger series inductance in the equivalent circuit. The series inductance significantly affects the BDFIG performance as well as the rating of its converter. The effects of magnetic wedges on BDFIG air-gap flux, synchronous torque, and stator tooth top saturation is also investigated. Two-dimensional FE analysis of an experimental 250 kW BDFIG is used in this study, verified by experimental measurements.

This study presents a comparative study of different modular brushless wound rotor synchronous machines (MB-WRSM) using non-overlapping fractional slot double-layer concentrated windings. The goal of the study is to highlight the structure which offers the best fault-tolerance capability and the highest output performance. The fundamental winding factor is calculated by using the method based on voltage phasors as a significant criterion to select the preferred numbers of phases, stator slots, and poles. With the limited number of poles for a small machine (3.67 kW/7000 rpm), 15 different machines for different phase/slot/pole combinations are analysed using two- dimensional (2D) finite element method and compared according to three criteria: torque density, torque ripple, and machine efficiency. The seven-phase/seven-slot/six-pole machine is chosen with the best compromise of high torque density, small torque ripple (3.89%), and high nominal efficiency (95%). This machine is then compared with a reference design surface-mounted permanent magnet synchronous machine (SM-PMSM). The simulation results are discussed and demonstrate that the MB-WRSM presents interesting performance features, such as extended field weakening range, with overall performance closely matching that of an equivalent SM-PMSM.

In this study, a novel partitioned stator hybrid excited machine is proposed, in which the excitation sources including both permanent magnets (PMs) and field windings are allocated on the secondary stator that is separated from the original stator having armature windings. As a result, the available space is boosted to improve the torque density and flux regulation capability. Meanwhile, the rotor is simple without coil or PM. The PMs on the stator is placed on the slot openings between the two neighbour tooth tips, with which the uncontrolled voltage of the proposed machine is limited and it is favoured for safety-critical applications. The machine topology and operating principle are introduced in detail, and the basic electromagnetic performance is evaluated based on finite element method to validate the analysis.

This paper focuses on the comparative analysis of modular spoke-type permanent magnet machines with two magnetization modes, which are referred to as M-I and M-II types. The analytical models of the proposed machines are built based on the simple magneto-motive-force-permeance method. With the help of finite element analysis and the analytical models, magnetic fields in machines with different magnetization modes are compared. Then, taking as a base an existing commercial in-wheel machine used in an electric motorcycle, two proposed machines with different magnetization modes are designed as in-wheel traction machines and compared with respect to electromagnetic torque, flux-weakening performance, over-load capability, etc. The machines are prototyped and experimentally tested to verify the prediction that the M-II machines exhibit a higher torque output whereas the M-I machines have a wider speed range. [ABSTRACT FROM AUTHOR]

This study studies, using experimentally verified finite element (FE) analysis, various performance measures of the brushless doubly fed induction generator (BDFIG) when magnetic wedges are used for closing stator open slots. The BDFIG is an attractive generator solution for offshore wind power and can replace doubly fed slip-ring induction generators. It is shown in this study that the use of magnetic wedges, commonly used in large induction machines, reduces the stator windings magnetising currents in a BDFIG, reflected in the values of magnetising inductances. They also increase the leakage flux in the stator slots, leading to a larger series inductance in the equivalent circuit. The series inductance significantly affects the BDFIG performance as well as the rating of its converter. The effects of magnetic wedges on BDFIG air-gap flux, synchronous torque, and stator tooth top saturation is also investigated. Two-dimensional FE analysis of an experimental 250 kW BDFIG is used in this study, verified by experimental measurements. [ABSTRACT FROM AUTHOR]

This study presents a model predictive virtual power control (MPVPC) method for brushless doubly‐fed induction generator (BDFIG) during the grid synchronisation process. Predictive virtual power model is developed for the first time based on the defined virtual power and state‐space equation of BDFIG. The control characteristics of virtual power are analysed to explain clearly how to realise grid synchronisation condition through the control of virtual power. The MPVPC controller is then designed to unify the control structure during the transition from the grid synchronisation mode to the grid connected mode, and only flux feedback needs to be changed between these two modes. The consistency between theoretical analysis and actual performance is confirmed by the results of both numerical simulation and experimental tests. As demonstrated, the proposed MPVPC controller can achieve fast and smooth grid synchronisation and excellent decoupled control of active power and reactive power. [ABSTRACT FROM AUTHOR]

This article investigates a novel two-converter-based operation of a brushless doubly fed reluctance machine (BDFRM). The BDFRM has a ducted rotor, and the stator is wound with two distributed windings, which are fed from two separate power converters. Operation theory with frequency sharing between the two windings is introduced. The prototype BDFRM design, machine assembly, and the corresponding motor drive implementation processes are discussed. The control strategy for frequency sharing mode of operation with two variable winding frequencies is discussed. Subsequently, the BDFRM drive is tested in frequency sharing mode at varying speed levels and loads. [ABSTRACT FROM AUTHOR]

This study presents a comparative study of different modular brushless wound rotor synchronous machines (MB-WRSM) using non-overlapping fractional slot double-layer concentrated windings. The goal of the study is to highlight the structure which offers the best fault-tolerance capability and the highest output performance. The fundamental winding factor is calculated by using the method based on voltage phasors as a significant criterion to select the preferred numbers of phases, stator slots, and poles. With the limited number of poles for a small machine (3.67 kW/7000 rpm), 15 different machines for different phase/slot/pole combinations are analysed using two- dimensional (2D) finite element method and compared according to three criteria: torque density, torque ripple, and machine efficiency. The seven-phase/seven-slot/six-pole machine is chosen with the best compromise of high torque density, small torque ripple (3.89%), and high nominal efficiency (95%). This machine is then compared with a reference design surface-mounted permanent magnet synchronous machine (SM-PMSM). The simulation results are discussed and demonstrate that the MB-WRSM presents interesting performance features, such as extended field weakening range, with overall performance closely matching that of an equivalent SM-PMSM. [ABSTRACT FROM AUTHOR]

In this study, a novel partitioned stator hybrid excited machine is proposed, in which the excitation sources including both permanent magnets (PMs) and field windings are allocated on the secondary stator that is separated from the original stator having armature windings. As a result, the available space is boosted to improve the torque density and flux regulation capability. Meanwhile, the rotor is simple without coil or PM. The PMs on the stator is placed on the slot openings between the two neighbour tooth tips, with which the uncontrolled voltage of the proposed machine is limited and it is favoured for safety-critical applications. The machine topology and operating principle are introduced in detail, and the basic electromagnetic performance is evaluated based on finite element method to validate the analysis. [ABSTRACT FROM AUTHOR]

The performance of a brushless permanent magnet machine topology equipped with axially and circumferentially magnetized ferrite permanent magnets is presented. Simulation studies show that for smaller ratios of axial length to active length, air-gap flux densities in excess of 1 T can be achieved, resulting in significant improvements in torque production and efficiency. A prototype machine is manufactured, and test results confirm the predictions of the EMF and the static torque. [ABSTRACT FROM AUTHOR]

Brushless doubly fed machine BDFM) is a new type of motor that has bright prospect in industrial application, especially in the field of wind power generation. Here, a wound BDFM based on a rotor with the reluctance effect is proposed, it integrates the flexible connection method of wound rotor winding and the magnetic flux–oriented effect of the reluctance rotor, which restrains higher harmonic and has strong coupling ability. This paper introduces the structure of the new motor and elaborates the magnetic field modulation mechanism, then analyse the performance with the system's output power 6.4 kW using finite element method (FEM). To validate the FEM results, a 30 kW prototype is designed and manufactured. The prototype test verifies the correctness of the simulation results and also manifests the superiority of both steady‐state and dynamic performance of the motor. [ABSTRACT FROM AUTHOR]

This paper investigates different operating points of a ducted rotor brushless doubly fed reluctance machine (BDFRM) in subsynchronous, synchronous, and supersynchronous speed regions. The BDFRM has a ducted rotor and its stator houses two three-phase distributed windings. An example design of the machine is proposed for investigation. A control approach to maximize the torque capability of the given design is introduced. The static structural analysis result of the machine is also presented, which led to the final manufacturing of the machine laminations. Machine assembly and drive implementation steps are discussed. The built machine is experimentally tested in different speed regions. [ABSTRACT FROM AUTHOR]

Doubly fed induction generators and permanent magnet synchronous generators are widely used in wind power generation system in recent years. However, they still have technological and economic penalties, which limit their applications in wind power generation. This study presents a novel brushless doubly fed generator (BDFG) with the hybrid rotor, which has several outstanding advantages, so as to penetrate into large‐scale offshore wind power generation. In this study, the magnetic field modulation of the hybrid rotor is studied in detail. Owing to the decisive role of 'special rotor' on the performance of BDFG, the effect of main rotor structure parameters on coupling capacity is analysed based on Taguchi method, and the effect of assisted cage bars on the coupling capacity is also researched. The simulation models are simulated and analysed to compare the different exciting winding conditions. A 25.8 kW, 8/4 pole prototype BDFG with the hybrid rotor is manufactured to examine the performance of the proposed BDFG. Finally, the simulation and experiment results verify that the optimised rotor has stronger coupling capacity and the few‐pole (i.e. 4‐pole) winding should be used as control winding. [ABSTRACT FROM AUTHOR]

Due to the doubly salient structure, high magnetic flux density in the air gap and low pole number, cogging torque of 6/4 pole flux‐switching permanent magnet (FSPM) machine is seriously high. In some cases, it may cause this machine hard to start up and serious torque ripple. So, reducing the cogging torque of 6/4 pole FSPM machine to a certain low extent is important to keep it work properly. To reduce cogging torque, a chamfering and flange rotor pole shape is proposed to reduce the cogging torque of 6/4 pole FSPM machine without skewing teeth. The key dimensions of the proposed rotor pole shape have been optimised by analytical methods and simulation based on finite‐element analysis. The effectiveness of the proposed method has been verified by experimental results. The effect of the proposed rotor pole shape method on back‐electromagnetic force and average electromagnetic torque has also been investigated. [ABSTRACT FROM AUTHOR]