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Metal object detection (MOD) is crucial for the safe operation of ground-assembled wireless electric vehicle charging (WEVC) systems. Electromagnetic sensing by passive coils is a reliable MOD method for high-power applications, such as WEVC. Previous designs of sensing coils are mainly targeted at the systems with unpolarized coils (e.g., circular coils). However, they are not suitable for those with DD-coil-coupling engaged due to the fundamentally different field pattern. To fix this problem, in this article, a field-oriented design of sensing coils is proposed, which mainly aims at blind-zone elimination while maintaining high sensitivity and cost-effectiveness. The blind zone arising from axial symmetry of the field is removed by size-modulated C-shape coil units. And removing the central blind spot relies on an extra patch coil by utilizing the characteristic of parallel magnetic flux generated by DD coils. Tested by 13 positions (central blind spot excluded) where MOs might exist using a 3-kW WEVC prototype, the optimized sensing coils completely remove the axial blind zones when 50 mV is set as the threshold voltage. Moreover, for the central blind spot, the proposed patch coil can stably identify MO intrusion no matter if the prototype operates in light-load or heavy-load conditions. [ABSTRACT FROM AUTHOR]

As asymmetric interior permanent magnet synchronous motor (AIPMSM) has excellent performance but complicated topological structure, a novel high-resolution encoding and edge smoothing method is proposed for topology optimization of the asymmetric rotor of interior permanent magnet synchronous motor (IPMSM) in this study. This method aims to solve complex electromagnetic design problems with time-dependent performance through a multi-objective genetic algorithm (MOGA) integrated with a high-resolution encoding and edge smoothing method. The complex structure is represented by a high-resolution image-like matrix and then vectorized by the edge smoothing method. Therefore, the commonly used discrete binary encoded variables related to the finite element (FE) model are replaced with a vectorized topological structure and other control variables. In this sense, high-resolution matrix and edge smoothing methods are used for the first time to represent the rotor topology of AIPMSMs. Compared with the traditional topology optimization method, the proposed method has the advantage of expressing more complex and vectorized topological structures; meanwhile, the obtained performance is accurate and trustworthy using conventional FE simulation. Numerical results show that a stable convergence is achieved with the avoidance of checkerboards and material overlapping. It is shown that the proposed method can find solutions with better performances, in comparison with the reference model. [ABSTRACT FROM AUTHOR]

In this article, slot-PM-assisted consequent-pole-PM machine (SPMA-CPMM) is proposed. The key is that the consequent-pole ferrite PMs are employed in the stator yoke to reduce the PM material cost largely, while a small amount of tangential magnetized rare-earth PMs is placed in the slot opening to improve the torque production. This proposed hybrid magnet design can greatly enhance the PM utilization ratio and reduce the PM cost while maintaining a relatively large torque density. In this article, the configurations of ferrite-PM machine (FPMM), consequent-pole ferrite-PM machine (CFPMM), and SPMA-CPMM are illustrated, while equivalent magnetic circuits (EMCs) of them are compared. Then, the electromagnetic performances of three machines are investigated and compared, which verifies the validity of the proposed machine. [ABSTRACT FROM AUTHOR]

This article presents a novel slot permanent-magnet-assisted hybrid-magnet memory machine (SPMA-HMMM) with hybrid permanent magnets (PMs) in both stator yoke and slot opening. The key is each pair of yoke PMs is composed of one pole of high coercive force (HCF) PM and one pole of low coercive force (LCF) PM with flexible flux regulation. LCF PMs can be freely magnetized and demagnetized through dc current pulses, which are supplied by dc excitation coils wound on LCF PMs. This design leads to high efficiency of machine due to negligible field excitation loss. In this article, the machine configuration and operation principle are illustrated in detail. An equivalent magnetic circuit is modeled to unveil flux regulation and parallel excitation effect. Then, the electromagnetic performances of SPMA-HMMM under different magnetization states (MSs) are investigated, which verify flux regulation ability of the proposed machine with changeable MSs of LCF yoke PMs. [ABSTRACT FROM AUTHOR]

The transverse flux tubular linear machine (TF-TLM) has merits of high power density and efficiency. However, excited by constant permanent magnet (PM), it is hard for TF-TLM to regulate its flux effectively, which restricts its further application in wave energy conversion (WEC). In contrast, the inherent higher order harmonics existing in the induced voltage may cause the additional loss and produce overvoltage, which should be eliminated to prompt power quality. Therefore, to strengthen the flux regulation capability of TF-TLM and improve the generated power quality, a novel hybrid-excited TF-TLM (HE-TFTLM) with complementary structure is proposed in this article. The key is that a parallel and complementary structure is constructed for hybrid excitations of both dc windings and PMs installed on the stator to enhance the flux regulation capability and eliminate the even-order harmonics in the induced voltage. In addition, the stator consequent-pole design boosts the output thrust density. According to the 3-D finite element analysis (FEA) results, output thrust force reaches 279.14 N, and the power density of the proposed machine can be effectively improved to 154 kW/m3 at rated excitation. [ABSTRACT FROM AUTHOR]

In this article, a novel winding switching control strategy is proposed to extend the speed range of a consequent-pole ferrite-permanent magnet hybrid-excited machine (CPFPM-HEM) for electric vehicle application. The key is that in low-speed range, the ac armature winding and dc field winding are connected in series to achieve large starting torque, while in high-speed range, dc field winding is injected with adjustable dc currents to realize variable speed constant voltage of ac armature winding. Furthermore, consequent-pole rotor is used to reduce the usage of the permanent magnet (PM). In the meantime, ferrite PMs are used to replace rare-earth PMs to reduce the cost with the shortage of rare-earth resources. In this article, the machine configuration, operation principle with dual excitation sources, flux modulation principle, and winding switching strategy are illustrated in detail. Then, the electromagnetic performance of the CPFPM-HEM in different speed ranges is investigated. Finally, the speed range extension with winding switching strategy is verified by the Maxwell/Simplorer co-simulation. [ABSTRACT FROM AUTHOR]

Reluctance machines with dc excitation coils have become a promising solution for electric vehicle propulsion system because of its robust rotor structure and good field-weakening ability. However, these machines usually suffer from relatively low torque density and efficiency. To solve this problem, this article proposes a novel hybrid reluctance machine with improved torque density and efficiency. The key novelty is to introduce skewed permanent magnets (PMs) in slot openings. The tangential component of skewed PMs can be used to relieve the dc saturation in the stator iron core, so that the $B-H$ working range can be extended and relatively high dc excitation can be applied in the proposed machine. Besides, the radial component of skewed PM provides extra torque component under flux modulation effect. Therefore, the proposed skewed PMs can achieve torque boost and core utilization improvement simultaneously. In this article, the dc-saturation-relieving effect of the proposed design is thoroughly investigated and verified by finite element analysis. [ABSTRACT FROM AUTHOR]

The reluctance machine with dc field coils in stator is an emerging brushless candidate for the in-wheel direct drive for its wide speed range and robust mechanical structure, while it suffers from relatively low torque density and efficiency, due to the poor excitation ability of dc field coils and worse extra dc saturation effect in the stator core. To address this issue, a new hybrid reluctance machine is proposed in this article, in which an integrated dual-layer PM source is introduced into stator slots, aiming to relieve dc saturation and, meanwhile, evoke flux modulation effect. In this way, the stator core utilization factor can be boosted due to dc saturation elimination by inner-layer slot permanent magnets (PM). On the other side, extra PM torque is generated by the flux modulation effect of outer-layer slot PMs. Hence, with synthetic assistance from dual-layer slot PMs, the torque density is improved distinctly especially under relatively high current density. Besides, slot PMs share a parallel magnetic circuit with dc field coils, which enables a bidirectional dc magnetization control for speed range extension. In this article, the proposed new topology is fully evaluated by both finite element (FE) analysis and prototype experiments. [ABSTRACT FROM AUTHOR]

This article proposes a novel compact dual-permanent magnet (PM) dual-stator generator for hybrid ac/dc generation system. Two sets of windings are installed in the inner and outer stator separately. It has two electric ports, in which one is used to generate ac voltage and the other electric port that also generates ac voltage is rectified to obtain the dc voltage. The key of the generator is that two stators share one rotor with consequent PM structure, and the output power of the machine is much higher than that of the machine with only one stator. Besides, with two separated stator core and armature windings, the reliability of the proposed generator is improved. The advantage of the proposed dual-stator dual-PM generator is illustrated theoretically, and its slot/pole selection guideline is given. Comprehensive sensitivity analysis of the proposed generator is performed and multilevel design optimization method is adopted. The efficiency, torque ripple, and total harmonic distortion of the inner and outer armature windings of the generator after optimization are calculated to verify the effectiveness of the proposed machine design. [ABSTRACT FROM AUTHOR]

This article proposes a novel model predictive control for a three-phase permanent-magnet synchronous motor (PMSM) with enhanced robustness against parameter variation and higher current control precision. First, the extended set of voltage vectors are adopted to increase the current control precision. Then, the parameter sensitivity problem is avoided in the first stage using an indirect reference vector strategy for the sake of computation time reduction. Subsequently, the inductance disturbance observer is adopted in the current prediction process to enhance the robustness against machine parameter mismatch. The intrinsic connection between the discrete control sets precision and disturbance observer is analyzed. The proposed method improves the robustness against parameter mismatch and current control precision simultaneously. Experimentations are conducted to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a novel direct-drive dual-PM motor for electric automatic guided vehicles (AGV). The proposed motor has split teeth on stator and dual PMs in stator and rotor sides, which contributes to reduced torque ripple, and enhanced torque. The airgap field of the proposed motor is analyzed theoretically, and the slot/pole selection guide line is concluded. The simulation results of the airgap flux density are shown and Fourier Transformation (FFT) analysis results agree well with the theoretically analyses results. Besides, the effects of design parameters of the proposed motor to the performances of the proposed motor are investigated. And it is found that reduced slot open could produce improved efficiency and decreased torque ripple. The efficiency of the proposed motor is relatively high within the operation range. A corresponding prototype is fabricated and the experiment validates the design. [ABSTRACT FROM AUTHOR]

This article aims to propose a new hybrid reluctance machine equipped with relieving-dc-saturation (RDCS) ability for electric vehicle in-wheel drive. The proposed machine uses integrated ac and dc current excitation to eliminate extra dc field coils for the efficient torque generation. Besides, considering the inherent dc saturation in stator core caused by dc current excitation, slot PMs are artificially introduced to provide RDCS effect and thus boost torque density. Moreover, with a modular magnetic field configuration, the proposed topology exhibits excellent fault-tolerant potential at both open-circuit and short-circuit condition, making it suitable for safety-critical in-wheel vehicle propulsion. In this article, the machine configuration and operation principle are introduced, with emphasis on its RDCS effect and corresponding design consideration. Further, performance of this new topology is evaluated by both finite element analysis and prototype experiments. It is revealed that, with this RDCS ability, torque density of the proposed machine can be enhanced by about 25% under relatively high current density. [ABSTRACT FROM AUTHOR]

Benefiting from flexible flux control and short-circuit withstand ability, the hybrid excitation machine is an emerging starter generator solution for hybrid electric vehicle propulsion. However, to realize a brushless hybrid design in conventional permanent magnet machines, a three-dimensional magnetic circuit is usually adopted, leading to complicated mechanical structure and torque density sacrifice. To address this issue, a new relieving-dc-saturation hybrid excitation Vernier machine is proposed in this article, which integrates good torque density and bidirectional flux control within a simple and brushless structure. The key is to artificially construct reluctance effect in a consequent-pole Vernier permanent magnet machine (CP-VPMM) by introducing extra dc field excitation equipped with the relieving-dc-saturation ability. In this way, the advantages of bidirectional flux control in stator-dc-excited reluctance machine and good torque density in CP-VPMM are well combined in this topology, making it especially suitable for multimode starter generator application. In this article, the machine structure and its design mechanism are introduced, with its electromagnetic performance evaluated by the finite-element simulation. A prototype is manufactured and tested. Experiment results verify the feasibility of this new topology. [ABSTRACT FROM AUTHOR]

This paper aims to propose a new Vernier reluctance machine (VRM), which integrates the advantages of a robust rotor structure, good torque density, and flexible flux control ability. The key is to establish the excitation field with both stator slot permanent magnets (PMs) and zero-sequence current. Two excitation sources have different pole pair numbers but share a parallel magnetic circuit and contribute to superimposed torque in this machine. Meanwhile, a flexible flux control can be achieved by regulating zero-sequence current, and little demagnetization risk exists for slot PMs during flux control. In this paper, the machine configuration and operation principle are introduced, along with its integrated ac and dc drive method. Electromagnetic performance of this new machine is evaluated by finite-element analysis. Leading design parameters are determined and optimized considering optimal injection ratio of zero-sequence current. A prototype is fabricated, and relevant experiment results demonstrate the feasibility of the proposed solution. [ABSTRACT FROM AUTHOR]

This article proposes a new hybrid-excited dual-permanent-magnet generator with the relieving-dc-saturation (RDCS) structure for stand-alone wind power generation. The proposed generator integrates the stator dc source and rotor permanent-magnet (PM) source in a single brushless structure, which enables coordinated power generation and flexible power adjustment. Moreover, considering the parasitic saturation effect in the stator core caused by the dc field source, a constant PM bias is introduced at the stator side to construct an RDCS structure, so that the core utilization ratio is improved as well as the generator power density. In this article, the generator structure and the operation principle are introduced. Some leading design parameters are determined based on the sensitivity analysis. A finite element and genetic algorithm combined method is further adopted to realize a multi-objective design optimization, and the optimal design of the proposed topology is verified to be a potential generator candidate for stand-alone wind power generation. [ABSTRACT FROM AUTHOR]

This paper proposes a novel modular relieving-dc-saturation Vernier reluctance machine for electric vehicle application, which integrates the merits of a robust structure, controllable excitation field, strong fault-tolerant capacity, and enhanced torque density, benefiting from its special relieving-dc-saturation design. In the proposed machine, zero-sequence current establishes a modular magnetic path and functions as the dominant excitation source for the torque generation. Especially, slot permanent magnets are introduced into each module, which mitigates the saturation effect in stator core caused by dc-biased flux with the zero-sequence current source. Therefore, the proposed machine can achieve enhanced torque density with relatively high current density. In this paper, the machine structure and operation principle are illustrated in detail, with its electromagnetic performance evaluated by time-stepping finite-element analysis. It is revealed that, due to its relieving-dc-saturation ability, torque density of the proposed machine is enhanced by about 20% with high current density. [ABSTRACT FROM AUTHOR]

A novel parallel-hybrid dual permanent magnet (PM) machine topology with both enhanced torque density and improved flux weakening capability is proposed for electric vehicle propulsion in this paper. The key is to artificially construct the harmonics diversity with a single-layer concentrated armature winding in the stator and thus simultaneously couple the armature field with the excitation field produced by slot PM, rotor PM, and stator dc source, respectively. Enhanced torque density is obtained in this new topology due to the symmetrical flux-modulation effect between dual PM sources. Moreover, benefiting from a parallel excitation characteristic of hybrid magnetic circuit, the demagnetization risk is significantly mitigated for slot PM source and thus an extended flux weakening range is obtained. In this paper, the proposed new topology and its design mechanism are investigated, along with its electromagnetic performance evaluated based on finite-element analysis. Further, some leading design parameters are analyzed and determined to provide a design guideline for the proposed new topology. Finally, a prototype is built and fully tested. Relevant experimental results agree well with the finite-element predication. [ABSTRACT FROM AUTHOR]

The transverse flux permanent-magnet (PM) linear machine has attracted much attention in high-performance direct-drive applications because of its high torque density and efficiency. However, due to its inherent large open-circuit flux leakage, the prominent cogging force makes it difficult to obtain a high accuracy in position and speed control, which restricts its potential for precision industrial processing applications. To overcome this problem, a novel transverse flux linear machine is proposed in this paper. The key is by creatively combining a consequent-pole mover design and a stator-segment-interlacing configuration in such a way that a parallel and complementary transverse magnetic circuit is realized for the moving PMs, which can effectively minimize the open-circuit leakage flux and cogging effect. In this paper, the machine structure, operation principle, and theoretical modeling are introduced, with its electromagnetic performance evaluated by using the finite-element method. A prototype is also built for the experimental verification, and relevant test results agree well with the finite-element predications. [ABSTRACT FROM AUTHOR]

This paper proposes a new Vernier reluctance machine (VRM) drive for electric vehicle. The key is to incorporate both stator-slot permanent magnets (PMs) and zero-sequence current as the excitation source to establish a parallel magnetic field and interact with armature winding. In this way, two different machines, namely, slot-PM-excited VRM and dc-excited doubly salient machine, are artificially integrated into a single structure, which contributes to enhance the torque density. Moreover, flexible flux control can be realized by regulating zero-sequence current. In this paper, the machine structure and operation principle are introduced, with its feasibility verified by both finite-element analysis and prototype experiments. [ABSTRACT FROM AUTHOR]

A quantitative analysis and design guideline for dual-permanent-magnet Vernier machine (DPMVM) are presented in this paper. First, by winding factor analysis for dominant air-gap harmonics, torque components excited by stator PMs and rotor PMs are quantified, which reveals that, in DPMVM, the rotor PMs essentially have higher torque generation ability than stator PMs, due to the effective utilization of fundamental PM harmonic without flux modulation. Furthermore, mutual influence between dual PM sources is analyzed. It is revealed torque contribution of stator PMs is unilaterally affected by design parameters of rotor PMs. Finally, a design guideline is provided for DPMVM, considering the design priorities of dual-PM sources. Finite element simulation and prototype experiments prove the validity of the theoretical analysis. [ABSTRACT FROM AUTHOR]

A novel bidirectional flux-modulation permanent magnet (BFMPM) machine for stand-alone dc wind power generation is proposed in this paper. The key is to control the inner rotor position with a small servo motor, and with the bidirectional flux-modulation effect, the resultant induced voltages in two sets of stator windings can be adjusted accordingly. Consequently, in a wide wind speed range, the various-speed constant-amplitude-voltage operation is realized. The novel structure has two major merits. First, it has high reliability without the maintenance problems caused by mechanical gearboxes, slip ring assembly, and brushes. Second, the proposed system requires a low-cost uncontrolled diode rectifier, which enhances the reliability and reduces the cost of the system. The analytical model and operation principle of the BFMPM machine are illustrated and the simulation results using a finite-element method is presented. A prototype is optimized and fabricated. The experimental results agree well with the simulation results and verify the correctness of the analytical model and the effectiveness of the proposed structure. Therefore, the novel structure offers a potential solution to provide a stable dc power for the standalone condition, such as remote area and offshore island. [ABSTRACT FROM AUTHOR]

This paper proposes a new slot-permanent-magnet (PM)-assisted variable flux reluctance generator (VFRG) for the hybrid electric vehicles. Compared with the existing dc-excited VFRG, auxiliary PMs are introduced into stator slots, which can fully utilize the redundant harmonics excited by single-layer concentrated armature winding and boost power density significantly. In this paper, the generator structure, operation principle as well as the winding restriction are discussed. Different slot pole combinations are fully compared in terms of both no-load and on-load characteristics. Some important design parameters are redefined for this slot-PM-assisted topology based on a sensitivity analysis. To release cost burden, both rare-earth-magnet and ferrite-magnet-assisted designs are considered into optimization. The feasibility of this new topology is verified by using finite element analysis and prototype testing. [ABSTRACT FROM AUTHOR]

Due to the unique flux distribution, biased flux machines (BFMs) could be driven by biased current to realize flexible flux weakening or strengthening control. In this paper, the electric machines with biased flux are investigated. The key techniques such as constructing biased flux in coils, exploring topologies, developing coil connection patterns, and designing drive circuits are presented. Based on that, the general design guideline for double stator BFMs is concluded. To verify this analysis, one 12/11 (stator teeth/rotor teeth) double stator BFM prototype is built and tested. The proposed double stator BFM has good torque and efficiency performance. Meanwhile, the biased current including dc zero sequence is used to adjust the exciting field. The simulation and experimental results verify the validity and effectiveness of this machine design method and control strategy. The flexible flux modulation characteristic makes this kind of machines suitable for applications with wide speed range. [ABSTRACT FROM AUTHOR]

This paper proposes a novel multi-phase double-winding vernier permanent magnet (DW-VPM) wind power generator applied for hybrid ac/dc microgrid. The key is to employ two sets of windings, namely, ac windings and dc windings in the machine, which serve to produce ac power and dc power for microgrid, respectively. The permanent magnets (PMs) are surface mounted on the rotor, and the stator is designed with open slots. The stator teeth can act as flux modulator for the permeance difference between the stator teeth and the air. Therefore, the field excited by PMs can be effectively modulated. Besides the original harmonic used to induce sinusoidal back electromotive force (EMF) in the ac windings and generate ac power, another low-order harmonic can be generated, which is used to induce square wave EMF in the dc windings and generate dc power through diode-bridge rectifier. Since multi-phase windings can get the square wave EMF more easier, the dc windings are designed with six phases. By using time-stepping finite-element method, the electromagnetic performances of the proposed DW-VPM wind generator are comprehensively investigated and verified. [ABSTRACT FROM AUTHOR]

In this paper, a novel modular linear double-stator biased flux (LDSBF) machine is proposed for wave power generation. The operation principle based on flux path analysis is presented. And stator/rotor pole number combinations are discussed by using coil flux analysis. The modular LDSBF machine has better flux path distribution than its counterpart, namely, linear biased flux permanent magnetic machine. More than that, the topology of the modular LDSBF machine makes it feasible to modular design and easy assembly. The electromagnetic characteristics of four types of linear machines are analyzed and compared by using time-stepping finite-element method. The comparative study shows that modular LDSBF machine with improved performance is a good potential design for wave power generation. [ABSTRACT FROM AUTHOR]

This paper presents a new brushless electrically excited claw-pole generator (EECPG) for vehicle power generation. The proposed design uses a toroidal excitation coil to magnetize all the stator poles and then generate effective power by complementary saliency effect of dual rotors. One salient advantage of this new design is its good excitation ability with minimized excitation copper loss as well as improved energy conversion efficiency. Meanwhile, the brush and slip rings are eliminated compared to the conventional rotor-EECPG. The generator structure is introduced, with its operating principle illustrated by 3-D finite-element predicated flux distribution. Rotor configurations using interlaced and non-interlaced types are both elaborated in terms of back electromotive force harmonic distribution and cogging effect. Load characteristic is predicted by the field-circuit coupled analysis, which proves the proposed brushless claw-pole generator could serve as a high-efficiency cost-effective candidate for vehicle power generation. [ABSTRACT FROM AUTHOR]

In this paper, both the steady-state and dynamic performances of the double-stator permanent magnet brushless (DS-PMB) machines, including the surface-mounted topology (DS-SPMB) and the interior topology (DS-IPMB), are quantitatively compared with that of the traditional single-stator SPMB (SS-SPMB) machine. Based on the same electric loading and magnetic loading, the DS-SPMB and DS-IPMB machines are designed to have the same output power, while the DS-SPMB and SS-SPMB machines are of the same peripheral dimensions. The steady-state and transient characteristics of these machines are simulated by using the circuit-field-torque time-stepping finite element method. Finally, the preferred machine, namely, the DS-SPMB one, is prototyped and tested for experimental verification. [ABSTRACT FROM AUTHOR]

Aiming to improve permanent magnet (PM) utilization factor, suppress cogging torque, and reduce back-EMF harmonics in stator-PM machines, a new type of stator-PM doubly complementary machines (DCMs) are proposed in this paper. These machines employ two complementarities in the structure, as one exists in double rotors and the other exists in the units belonging to same phases. The first complementary characteristic supplies a consecutive switching path for PM exciting flux, so that shorted or open magnetic path could be avoided to reduce cogging torque and improve PM utilization. The second one is designed to reduce back electromotive force (EMF) harmonics and improve the torque density. The topology, operation principle, characteristics, and design methodology for DCMs are presented. Simulation and experiments are conducted for a 12/11(stator teeth/rotor teeth) DCM to evaluate its performance and verify this design methodology. It is revealed that this machine could obtain good sinusoidal back-EMF waveform, small torque ripple, and high PM utilization factor due to the doubly complementary characteristic. [ABSTRACT FROM AUTHOR]

Biased flux machines (BFMs) have biased magnetic flux in the core and allows flexibility to adjust the field with a dc current. The conventional topology exploration methods for BFMs are based on the flux observation. It is time consuming and ineffective since the initial structure searching process is guideless. Meanwhile, BFMs usually work with arbitrary magnetic field harmonics instead of the fundamental one. The torque components of these machines and their essential operation principle have not been fully revealed. To solve these issues, in this paper, a topology exploration method for BFM based on magnetic field modulation mechanism is proposed, and the torque generating principle is analyzed. With this method, some new BFM structures have been developed and their torque components have been developed. It is shown that various space harmonics have contributed to constant torque rather than the fundamental one. To verify the feasibility of this design method, one double stator BFM is selected as a case study. Simulation and experimental results have verified that this design method is feasible and effective since the prototype has good sinusoidal back electromotive force waveforms and well performance. Besides, it is practical to realize flux weakening and strengthening the control with biased current. [ABSTRACT FROM AUTHOR]

This paper proposes a novel hybrid excited generator, which is suitable for a variable-speed wind power generation system. Two sets of excitation sources are employed, which are permanent magnets (PMs) on the rotor and the field windings on the stator. The rotor is design with PM-iron structure, namely the PMs and iron poles are alternatively located in rotor, which can provide PM excitation and flux modulating simultaneously. Meanwhile, the adjacent stator teeth are designed with different height, which enables the stator with flux modulating effect, and, therefore, bidirectional flux modulating can be achieved. Some specific harmonics excited by the rotor PMs can be effectively adjusted by the field current, and the back electromotive force and electromagnetic torque can be regulated accordingly. Therefore, the proposed generator can achieve constant voltage control and maximum power point tracking control by controlling the field current. The design considerations and field regulating principle are analytically investigated. An improved Tabu search algorithm is used to optimize the proposed generator, and finite-element method is used to realize preliminary study of the electromagnetic performances. A prototype is manufactured and experimental tests are conducted to verify the theoretical analysis and control strategies. [ABSTRACT FROM PUBLISHER]

With the increasing popularity of hybrid electric vehicles (HEVs), the demands of improving the fuel economy and energy efficiency of HEVs are enlarged. The technology electrical continuously variable transmission (E-CVT) system provides the opportunity to fulfill this requirement. However, conventional E-CVT with planetary gears suffer from frictional loss, high maintenance, and audible noise. Therefore, a series of gearless E-CVT propulsion systems are developed. Thereinto, a double-rotor single-stator brushless E-CVT having high torque density, reduced stator end winding length, and reduced copper loss was recently proposed. However, only torque of the E-CVT system is optimized by the genetic algorithm in the previous study. This paper adopts a differential evolution algorithm coupled with finite element method to optimize torque, energy efficiency, torque ripples, and multiobjective of the E-CVT system by reconfiguring the height of rotors, the areas of slots, and the height of yoke. It is simulated that by only tuning the weighting factors, the permanent magnetic machine in the E-CVT system can operate in the highest torque mode, highest energy efficiency mode, lowest torque ripples mode, and multiobjective optimization mode. [ABSTRACT FROM PUBLISHER]

This paper presents a novel scale-down hybrid-excited dual permanent magnet (PM) generator for direct-drive wind power application. Two sets of consequent-pole PMs are used in the proposed design, with one on the outer stator and the other on the middle rotor. PMs are separated by iron poles one by one, to form the magnet-iron sequences, which can provide PM excitation and flux modulating simultaneously. Since both the outer stator and middle rotor have flux modulating effect, bi-directional flux modulating can be achieved. Besides the fundamental field components, some other major field harmonics are also synchronous due to the bi-directional flux modulating effect, and these harmonics can contribute to the electromagnetic generation. Therefore, the proposed machine can achieve high torque density and suitable for direct-drive applications. Field windings are employed on the outer stator, so the air-gap field can be easily regulated by controlling the dc current. Hence, the proposed generator can maintain constant output voltage when the wind speed varies. Finite-element method coupled with genetic algorithm is used to optimize a scale-down design of the proposed generator, and its electromagnetic performances are studied in detail. [ABSTRACT FROM AUTHOR]

This paper presents an optimal design methodology of a dual-mechanical-port bidirectional flux-modulated machine for electric continuously variable transmission in hybrid electrical vehicles. The machine utilizes bidirectional flux modulation effect to combine two rotors and one stator together, aiming to realize electrical and mechanical power flexible split and combination. Due to the complexity of the machine structure, conventional optimization methods using analytical model are inapplicable. Therefore, an effective and practical method that combines the genetic algorithm and finite-element method (GA-FEM) is proposed to optimize the design of the machine in this paper. Since the computational cost increases exponentially with the increasing of number of design parameters, to reduce the computational cost in the optimization process, the design parameters are divided into two levels basing on a sensitivity analysis. And, then, the sensitive parameters are optimized using the GA-FEM coupled method. Finally, a prototype is fabricated to verify the effectiveness of the optimal design. [ABSTRACT FROM PUBLISHER]

This paper presents a new magnetic-gear pole-changing hybrid excitation machine (MG-PCHEM), which can provide high torque density and improved flux-weakening ability. The key is to flexibly change the pole-pair number of inner excitation sources by injecting variable dc field currents, and, hence, regulate the dominant pole-pair flux components to realize an effective magnetic field adjustment. In the following paper, the machine configuration and its operation principle of flux control are introduced first. Then, the influences of some leading design parameters are analyzed including the slot-pole combination and other dimension parameters, and after which a comparative study is carried out with traditional single-stator topology. Based on the optimal design, electromagnetic performance of the MG-PCHEM is further evaluated by using the finite-element method. Finally, a prototype is designed, manufactured, and fully tested. Relevant experimental results verify the feasibility of this new hybrid solution as well as the finite-element predictions. [ABSTRACT FROM AUTHOR]

This paper systematically studies a new kind of PM machines with both stator and rotor PM excitations, namely, dual-PM excited machines. The key is to rely on the PM-iron structure in the machine to provide both PM excitation and flux modulation. Besides the fundamental field component in the air-gap, some other predominant harmonics introduced by the flux modulating effect can also contribute to the electromagnetic torque production. Therefore, this kind of machines can be designed with high torque density. Four dual-PM excited machine concepts with the same rotor configuration but different stator structures are comparatively studied, which include double-stator PM machine, stator multitooth-PM machine, stator slot-PM machine, and stator tooth-PM machine (STPM). Based on the flux modulating effect, the general design principle of the dual-PM machines is proposed in this paper. Through analytically investigating the air-gap field harmonics, the physical insight of the dual-PM machines is brought forward. All the four machines are optimized using an improved Tabu search coupled with finite element method, and their electromagnetic performances are comprehensively studied and compared. A prototype of STPM is manufactured. Experimental tests are conducted and the results well verify the electromagnetic design. [ABSTRACT FROM AUTHOR]

Severe leakage flux is a long-existed drawback in the transverse-flux permanent magnet machines (TFPMs), which results in a low permanent magnet (PM) utilization rate and prominent cogging torque in TFPMs. Aiming to solve this problem, this paper presents a novel consequent-pole transverse-flux machine (CP-TFM). The key is to artificially shift the upper and lower salient-pole rotors with a half-pole pitch and connect them with a ring-shaped core. Therefore, a complementary magnetic circuit is constructed to reduce the flux leakage between the adjacent poles as well as improve the PM utilization rate. To verify the feasibility of design, a 3-D finite-element model is established and its electromagnetic performance is evaluated. With the same peripheral dimension and copper loss, a quantitative comparison is carried out between the proposed CP-TFM and conventional TFPM. Finite-element simulation results reveal that compared to its contrast, the proposed solution can almost double the PM utilization ratio and effectively reduce the cogging torque. [ABSTRACT FROM AUTHOR]

From a new stator-flux perspective, a comparative study between the series and parallel hybrid excitation machine (PHEM) is conducted and it is revealed that in PHEMs there still exist distinct stator-flux harmonic components during high-speed flux weakening operation, which could be further utilized to improve the torque capability at high-speed range. Inspired by this idea, an auxiliary winding is creatively introduced into PHEMs to recycle and utilize the magnetic field energy generated during the field regulation. A new design case is presented in this paper, in which two sets of armature windings with different pole pair numbers are arranged to realize the function of flux weakening operation and energy recycling, respectively. The feasibility of this new hybrid solution is evaluated by using the finite-element analysis. Furthermore, a prototype is manufactured and relevant experiments are performed. The experimental results agree well with the theoretical analysis and simulation results, which verify that the recycled energy can be effectively used to boost the output torque and power of PHEMs in the high-speed region. [ABSTRACT FROM AUTHOR]

This paper proposes a novel hybrid-excited dual-PM machine for electric vehicle propulsion. The key is to use an integrated stator winding to replace the armature winding and the field winding in the conventional hybrid-excited machine. The stator winding is excited by ac current with dc bias, in which the ac component is used to produce the rotating armature field, while the dc bias current is used for the flux regulation. Therefore, the function of the ac and dc windings can be incorporated and realized by using just one set of winding. The torque density and flux regulating capability can be improved, and the winding configuration is also simplified. In addition, dual-PM excitation structure combines the advantage of stator-PM doubly salient machine and rotor-PM magnetic-geared machine, which can further enhance the torque capability. The operating principle and control strategy of the proposed machine are discussed. The electromagnetic performances are studied using the time-stepping finite-element method. A machine prototype is manufactured and experimental tests are conducted to verify the effectiveness of the machine design. [ABSTRACT FROM PUBLISHER]

This paper proposes a new brushless contra-rotating power split transmission (CR-PST) system for the direct-drive wind power generation. The core element of this system is a doubly fed dual-rotor flux-modulation permanent magnet machine, which has two contra-rotating rotors connected with two wind blades to absorb the wind energy, and two sets of stator windings to realize torque split between the two shafts. This proposed CR-PST system has compact structure and bidirectional flux-modulation design, as well as increased wind power conversion efficiency. Compared with the conventional wind turbine system, which can only work with single maximum power point tracking (MPPT) control strategy, the proposed CR-PST system can collect increased wind energy with dual MPPT method for the given wind speed. Time-stepping finite-element method is used to analyze the steady and dynamic performance of the proposed system and the control strategy is verified by experiments and simulation results. [ABSTRACT FROM PUBLISHER]

Doubly salient electromagnetic machine (DSEM) can constitute a competitive rugged starter generator (SG) system. But under the traditional startup control method, the field current is set to the rated value regardless of speed or load torque conditions, and the phase currents are controlled with standard angle commutation, bringing in large power loss as well as non‐negligible torque ripple. To overcome these shortcomings, based on the established DSEM power loss calculation model, a currents distribution strategy is proposed according to the obtained quantitative relationship between DSEM power loss and field current under multiple speed and load torque conditions. Then, to identify the load torque for practical implementation, a novel torque observer is designed based on back propagation (BP) neural network algorithm. Afterwards, to further improve the startup torque performance, currents distribution with advanced angle commutation (AAC) strategy is put forward, where the optimal advanced angle is selected from a 3‐D lookup table to achieve the minimal commutation torque ripple. Under the proposed control strategies, DSEM power loss as well as the output torque ripple are desired to be decreased, the simulation and experimental results on a 12/8‐pole DSEM prototype verify the correctness and feasibility of the proposed strategies under multiple operating conditions. [ABSTRACT FROM AUTHOR]

Recently, the interest in consequent-pole flux-switching permanent magnet (CP-FSPM) machines has been increasing because of the flux-focusing PM arrangements and the removal of the flux-barrier effect. A simple and rigid outer-rotor salient pole rotor structure can be adopted in CP-FSPM machines, making them applicable for in-wheel direct-drive applications. In this study, three CP-FSPM machines with II-shaped (II-PM), V-shaped (V-PM), and straight U-shaped PM (SU-PM) arrays are analyzed and compared. Moreover, a CP-FSPM machine with inclined U-shaped PM (IU-PM) arrays is proposed to improve the flux-focusing effect and stator slot utilization. The working principles of CP-FSPM machines are analyzed by adopting a semi-analytical model. Combining the finite element analysis (FEA) results of air gap flux density and the analytical model of phase back electromotive force (EMF), the contributions of multiple working harmonics to the back EMF are quantitatively analyzed. Additionally, 6/16 and 6/17 CP-FSPM machines with different PM arrangements are globally optimized. Both the no-load and on-load performance of the optimized machines are included in the performance comparison. The results illustrate that the 6/16 and 6/17 machines exhibit their respective merits, and the IU-PM machine shows the best torque production ability in these CP-FSPM machines with the same design criteria. [ABSTRACT FROM AUTHOR]

This paper presents a novel magnetic-geared permanent magnet (MGPM) machine with dual-layer PM excitations, referred as dual-layer MGPM (DL-MGPM) machine. The key is to employ both the outer rotor and the modulation ring with PM-iron sequences, in which the PMs are separated by iron segments one by one, and can provide PM excitation and flux modulation simultaneously. Both the outer rotor and the modulation ring can achieve flux modulating, namely, bidirectional flux modulating, which can couple the magnetic fields excited by the two sets of PMs and armature currents effectively. The proposed DL-MGPM machine, as well as its existing counterpart which employing all the PMs on the outer rotor and referred as single-layer MGPM (SL-MGPM) machine, are optimal designed using finite element method coupled with genetic algorithm. The electromagnetic performances of the DL-MGPM machine and the SL-MGPM machine are investigated in detail and quantitatively compared. The results show that the proposed DL-MGPM machine can achieve higher torque density than the SL-MGPM machine, and is more suitable for low-speed high-torque direct-drive applications. [ABSTRACT FROM AUTHOR]

A novel design method for electrical machines with biased dc excitation flux linkage, named biased flux machines (BFMs) is proposed in this paper. The biased current including dc and ac components is applied to drive these machines, in which dc current is used to generate or modulate the exciting magnetic field and ac current is used to generate armature field. To demonstrate this design and control method, a new double salient BFM is proposed. The feasibility of this design is verified by simulations and experiments. The major advantages for this design method could be summarized as: 1) for permanent magnet exciting BFMs, the biased current can be combined with negative $d$ -axis current to realize flexible flux weakening or strengthening control; 2) for hybrid exciting or electrical exciting machines, the biased current can function as the dc windings, which helps to save more space for armature windings and further reduce cost and improve efficiency; and 3) this method is universal, which can be used in all BFMs. [ABSTRACT FROM AUTHOR]

This paper presents a novel hybrid-excited dual permanent magnet (PM) brushless machine with bidirectional flux-modulating effect. Two sets of windings are housed in the stator slots, in which the armature windings are used to produce the rotating magnetic field, and dc field windings are used to generate the excitation field. The air-gap flux can be regulated effectively by controlling the direction and magnitude of the dc currents, and hence the constant power operating region can be expanded efficiently. Meanwhile, both the rotor and the stator have PM excitations, and dual field modulating effect is artfully incorporated into the machine design to ensure an effective magnetic coupling among the magnetic fields excited by the armature windings, dc field windings and the two sets of PMs. The torque capability of the proposed machine can be improved. Through analytically studying the air-gap field harmonics, the working principle of the proposed machine is discussed. The electromagnetic performances are investigated using finite element method and verified by experimental results. [ABSTRACT FROM PUBLISHER]

Flux-controllable machines have attracted much attention in modern industry, especially in electric vehicle propulsion and wind power generation, as they can ensure a wide constant power speed range when working at motoring mode, while maintain constant induced voltage when working at generating mode. This paper reviews the current research work about flux-controllable machines, mainly focused on electrically excited machines, hybrid excited machines and memory machines. The latest novel machine concepts with the potential of good flux controllability are particularly investigated. The working principle, advantages and drawbacks, and future trends of different flux-controllable machines are discussed, compared and summarized in detail. [ABSTRACT FROM AUTHOR]

The electrical continuously variable transmission system is a very promising concept for variable-speed constant-frequency wind power generation due to its ability of seamless speed adjustment. In this paper, a novel wind energy conversion system based on electrical continuously variable transmission is proposed. This system combines the merits of two popular wind generation concepts: It enjoys high torque density like the permanent-magnet synchronous generator system and, also, it needs only a partial-scale converter like a doubly fed induction generator system. With a special doubly fed dual rotor structure, the system realizes both speed variation and power generation within one single machine, which makes it very compact. Besides introducing its structure and working principle, the design and performance analysis of the machine are presented in this paper. A prototype is made and tested for validation. [ABSTRACT FROM AUTHOR]

A novel brushless electric continuous variable transmission (E-CVT) system is presented and optimized. The proposed system offers an alternative solution for a variable-speed constant-frequency operation of the wind turbine application. The key is to eliminate the gearbox and brushes in the machine and this E-CVT system comprises of two rotors and two stators within one machine. This design inherits and integrates the merits of the direct-drive permanent magnet generator and the doubly fed induction generator with the additional benefit of the improved torque density and the need for a low-cost partial-scale converter. The structure, operation principle, and performance are analyzed. Genetic algorithm is employed to optimize the parameters for maximizing its power density. Time-stepping finite-element method is used to analyze the dynamic performance of the proposed system. [ABSTRACT FROM AUTHOR]

A novel gearless and brushless power-split transmission system is proposed for a variable speed constant frequency wind power generation application. The key is to design a special hybrid axial–radial flux focusing structure, which has an improved utilization of permanent magnet (PM) materials. This design integrates the merits of two popular concepts—the direct-drive PM generator and the doubly fed induction generator. It is direct driven, with high torque density and in the meanwhile, it needs only a partial-scale converter. To improve the stability of the system, five phase currents are used for the control winding. A time stepping finite-element method is used to analyze the dynamic performance of the proposed system. [ABSTRACT FROM AUTHOR]

This paper proposes and implements a new single-phase magnetless flux switching machine (FSM) for rooftop wind power generation. The key is to integrate an outer-rotor FSM and an inner-rotor FSM with shared stator yoke and stator drum windings. In such a way, this proposed machine can not only realize flux switching function to regulate magnetic flux effectively, but also incorporate the field and armature windings within one stator to reduce the copper losses and improve the overall machine efficiency. Meanwhile, the structure is compact and rotors can be directly driven by blades to capture the wind power. The machine design guidelines from both magnetic and electric aspects are illustrated, the machine characteristics are analyzed by using time-stepping finite-element method, and the system performances are evaluated based on mathematical modeling. Both simulation and prototyping test are conducted to verify the validity of the proposed machine and system. [ABSTRACT FROM AUTHOR]

In this paper, an efficient and effective magnetic circuit model is developed for the analysis of a magnetless double-rotor flux switching motor. First, a magnetic circuit network for the proposed machine is built, and formulas for the calculation of the magnetic components in the circuit, including the permeances of teeth, yokes, slots, leakage permeances, and air-gap permeances, are derived. Then, by applying Kirchhoff’s current law to each node in the network, nodal analysis is used to solve the matrix equation. All the circuit variables, and hence the complete motor magnetic characteristics are being considered. When the rotor rotates, the air-gap permeances are adjusted accordingly, and the above calculations are repeated, so as to find the complete static performance of the motor. Last, the validity and the effectiveness of the proposed method are verified using both the experimental results and the simulation results obtained from the time-stepping finite-element method. [ABSTRACT FROM AUTHOR]