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H A Toliyat - One of the best experts on this subject based on the ideXlab platform.
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strategy with smooth transitions and improved torque speed region and stator Copper Loss for two level asymmetrical six phase induction motor drives under switch faults
IEEE Transactions on Power Electronics, 2021Co-Authors: Alejandro G Yepes, Jesus Dovalgandoy, H A ToliyatAbstract:Asymmetrical six-phase drives are very attractive to obtain fault tolerance. Most faults arise in the power electronics. Two conventional methods to handle switch/diode faults in two-level converters are keeping the corresponding phases open (in two-level multiphase drives) or connecting them to the dc-link midpoint (in two-level three-phase drives) through a bidirectional switch (e.g., triac/relay). However, the former yields larger stator Copper Loss (SCL) for given torque and smaller maximum torque, because of current constraints; on the other hand, the latter reduces the maximum speed, due to voltage constraints, and has not been considered for two-level multiphase drives. This article presents several proposals to improve fault-tolerant behavior in two-level asymmetrical six-phase induction motor drives. First, to adequately combine and alternate said two approaches in these particular drives, depending on the speed, neutral-point configuration, and faulty legs. In this manner, the SCL-per-torque decreases and the total torque–speed region of the drive is extended, i.e., the maximum torque and maximum speed rise compared with each of the aforementioned conventional strategies. Second, to also turn on / off a switch between stator neutral points for further improvement in this regard. Third, a pulsewidth modulation procedure to ensure smooth transitions between drive configurations. Experimental results confirm the theory.
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improvement of postfault performance of multiphase drives in terms of operating region and stator Copper Loss
Conference of the Industrial Electronics Society, 2018Co-Authors: Alejandro G Yepes, Jesus Dovalgandoy, H A ToliyatAbstract:Multiphase drives are particularly attractive for safety-critical applications, due to their enhanced fault tolerance. Most of the faults in electric drives occur in the power electronics. Switch faults can be divided into open- and short-circuit ones. The conventional techniques to handle switch faults in two-level converters mainly consist in either keeping the corresponding phases open or connecting the stator terminal to the de-link midpoint through a triode for ac (TRIAC). However, the former results in lower maximum torque and larger stator Copper Loss (SCL), whereas the latter leads to a reduction in the maximum speed and has not been considered in the context of two-level multiphase drives. This paper proposes to adequately combine these approaches in two-level multiphase drives, depending on the speed, the faulted switches and the neutral configuration, so that the total operating region of the drive is extended and the SCL is decreased, when compared to the conventional strategies. It is also shown and exploited that, for multi phase drives based on multiple three-phase winding sets, turning on or off a TRIAC placed between their neutrals as a function of the speed allows further improvement of the postfault performance. Simulation results are provided to confirm the theory.
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postfault strategy for dual three phase machines with minimum Loss in the full torque operation range under two open phases
European Conference on Cognitive Ergonomics, 2018Co-Authors: Alejandro G Yepes, Jesus Dovalgandoy, Fernando Baneira, H A ToliyatAbstract:Dual three-phase machines (D3PMs) are particularly attractive due to their fault-tolerance capability. In general, under open-phase (OP) faults, the current references are adapted following a minimum-Loss strategy (MLS) or a maximum-torque strategy (MTS). The MLS offers lower Copper Loss than the MTS for any given torque, but a smaller torque operation range (TOR). The full-range MLS (FRMLS) has recently been proposed, providing minimum Copper Loss, for each torque value, in the whole TOR (the MTS TOR); however, only one OP was considered. Furthermore, neither the TOR of the MLS nor the Copper Loss of the MLS or MTS have been assessed with two OPs. Consequently, it is difficult to infer a priori the relevance that the FRLMS may have for two OPs. This paper evaluates the extension of the FRMLS to D3PMs with two OPs. First, the procedure to carry out this extension is described. Then, the convenience of the FRMLS for two OPs is studied for different situations. It is concluded that for two OPs in most cases the FRMLS is substantially better than the MTS and MLS in terms of Copper Loss and TOR. Experimental results verify the theory.
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Control Strategy for Dual Three-Phase Machines With Two Open Phases Providing Minimum Loss in the Full Torque Operation Range
IEEE Transactions on Power Electronics, 2018Co-Authors: Alejandro G Yepes, Fernando Baneira, Jesús Doval-gandoy, H A ToliyatAbstract:Dual three-phase machines (D3PMs) are particularly attractive due to their fault-tolerance capability. In general, under open-phase (OP) faults, the current references are adapted following a minimum-Loss strategy (MLS) or a maximum-torque strategy (MTS). The MLS offers lower Copper Loss than the MTS for any given torque, but a smaller torque operation range. The full-range MLS (FRMLS) has recently been proposed, providing minimum Copper Loss, for each torque value, in the whole torque operation range (the MTS torque operation range); however, only one OP was considered. Furthermore, neither the torque operation range of the MLS nor the Copper Loss of the MLS or MTS have been assessed with two OPs. Consequently, it is difficult to infer a priori the relevance that the FRLMS may have for two OPs. This letter evaluates the extension of the FRMLS to D3PMs with two OPs. First, the procedure to carry out this extension is described. Then, the convenience of the FRMLS for two OPs is studied for different situations. It is concluded that for two OPs in most cases, the FRMLS is substantially better than the MTS and MLS in terms of Copper Loss and torque operation range. Experimental results verify the theory.
Ming Cheng - One of the best experts on this subject based on the ideXlab platform.
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fault tolerant control of dual three phase permanent magnet synchronous machine drives under open phase faults
IEEE Transactions on Power Electronics, 2017Co-Authors: Wei Wang, Jinghao Zhang, Ming ChengAbstract:In this paper, a fault-tolerant control is proposed for dual three-phase permanent-magnet synchronous machine (PMSM) drives under open-phase faults. The object of the proposed fault-tolerant control is to maximize the torque capacity while the overcurrent protection is taken into account. Hence, the proposed fault-tolerant control is named as torque mode in this paper. Another existed fault-tolerant control for dual three-phase PMSM drives under open-phase faults is Loss mode, in which the system Copper Loss is minimized. Torque mode is compared with Loss mode, and two important conclusions are given: 1) Loss mode can reduce more Copper Loss; and 2) torque mode can output more torque. The performances of torque mode and Loss mode are verified by experimental results.
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comparison of electromagnetic performance of brushless motors having magnets in stator and rotor
Journal of Applied Physics, 2008Co-Authors: Wei Hua, Z. Q. Zhu, Ming Cheng, Wenxiang Zhao, Xiangxin KongAbstract:The electromagnetic performance of two permanent magnet brushless motors, viz., flux-switching magnet (FSPM) and surface-mounted motors, in which concentrated stator windings are employed but the magnets are located in the stator and the rotor, respectively, is investigated by the finite element analysis. The significant differences in topologies and static characteristics are highlighted. The results show that both motors exhibit sinusoidal back-emf waveform and the FSPM motor exhibits not only larger airgap flux density, higher torque per Copper Loss, but also higher torque ripple due to cogging torque.
Ali Emadi - One of the best experts on this subject based on the ideXlab platform.
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behavior study of permanent magnet synchronous machines based on a new normalized model
IEEE Transactions on Industrial Electronics, 2019Co-Authors: James Weisheng Jiang, Ali EmadiAbstract:Permanent magnet synchronous machines (PMSMs) are widely used in many applications. The performance of the PMSM is highly dependent on the motor parameters. Many research studies have been done to evaluate the PMSM performances in terms of maximum torque capability, power capability, and field-weakening capability. This paper proposes a new normalized PMSM model and uses two parameters, characteristic current and saliency ratio, to uniquely define the motor characteristic. Based on this normalized model, the full map motor behaviors, including torque capability, power capability, torque/power–speed characteristics, and power factor behaviors, are studied parametrically. A new unitless metric, i.e., Copper Loss factor, is introduced to evaluate the Copper Loss variation of PMSMs. The saturation effect on the motor behavior is studied based on the 2004 Prius traction motor, which confirms that the field-weakening characteristic can be well predicted using the linearized model. A new design flow for traction PMSMs, which requires wide-speed operation, is proposed based on the full map motor behavior study, and a prototype machine is designed accordingly. The behavior study and the effectiveness of the traction motor design flow are validated experimentally by the prototype.
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An Offline Torque Sharing Function for Torque Ripple Reduction in Switched Reluctance Motor Drives
IEEE Transactions on Energy Conversion, 2015Co-Authors: Berker Bilgin, Ali EmadiAbstract:In this paper, an offline torque sharing function (TSF) for torque ripple reduction in switched reluctance motor (SRM) drives over a wide speed range is proposed. The objective function of an offline TSF is composed of two secondary objectives with a Tikhonov factor to minimize the square of the phase current (Copper Loss) and derivatives of current references (rate of change of flux linkage). The proposed TSFs with different Tikhonov factors are compared with the conventional TSFs including linear, cubic, and exponential TSFs in terms of efficiency and torque-speed performance while operating in both magnetic linear and saturation regions. Then, the Tikhonov factor is selected based on a tradeoff between the Copper Loss and torque-speed performance. The maximum torque-ripple-free speed of the selected offline TSF is validated to be seven times as high as the best case in these conventional TSFs. The performance of the offline TSF is verified by simulations and experiments with a 2.3-kW, three-phase 12/8 SRM. Results show that the proposed offline TSF can significantly reduce the torque ripple of SRM without increasing Copper Loss over a wide speed range.
Z. Q. Zhu - One of the best experts on this subject based on the ideXlab platform.
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torque improvement of five phase surface mounted permanent magnet machine using third order harmonic
Power and Energy Society General Meeting, 2016Co-Authors: Kai Wang, Z. Q. Zhu, Grzegorz OmbachAbstract:This paper presents optimal third harmonics in both permanent magnet (PM) shaping and current waveform to improve the output torque of five-phase surface-mounted PM (SPM) machines. The optimal value of third harmonic injected into the sinusoidal PM shape and current waveform for maximum torque improvement is analytically derived and validated by both finite element (FE) analyses and experiments. It is found that the optimal third harmonic is 1/6 of the fundamental one for both PM shape and current waveform. For the five-phase SPM machines having rotors without shaping, Sine shaping, or Sine shaping with third harmonic injected, the electromagnetic performance including the back EMF waveform, cogging torque, average torque, torque ripple, Copper Loss, iron Loss, impact on power inverter, and demagnetization withstand capability are compared. It is demonstrated that, although the Copper Loss and iron Loss increase due to additional third harmonic in the winding current and magnet shape, the average torque with optimal third harmonics injected in PM shaping and current waveform can be improved by >30% while the torque ripple and remains similar to that of the one with Sine shaping. In addition, this will reduce the dc bus voltage while maintaining the machine torque density. Furthermore, the machine with Sine and Sine+3rd rotors presents much better demagnetization withstand capability performance than conventional rotor.
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Integrated Field and Armature Current Control Strategy for Variable Flux Reluctance Machine Using Open Winding
IEEE Transactions on Industry Applications, 2016Co-Authors: Z. Q. Zhu, Beomseok Lee, Xu LiuAbstract:This paper proposes an integrated field and armature current control strategy for a variable flux reluctance machine (VFRM) with an open-winding topology. By using an open-winding inverter, the field and armature currents can be injected into a single coil as a sinusoidal current biased by the dc offset rather than the separated field and armature windings. The integrated current control can reduce the Copper Loss to half and extend the operating speed range owing to the reduction in the winding resistance. In order to utilize the zero-sequence current as a field current, a zero-vector modification technique is proposed, in which the switching-on time of the zero vectors is modified to generate the constant zero-sequence voltage between two inverters. The proposed scheme is implemented in a synchronous $dq0$ -axis frame with space vector modulation. For the validation of the proposed method, a machine model of the VFRM is developed and implemented in MATLAB/Simulink. The simulation and experimental results verify that the proposed strategy can effectively reduce the Copper Loss and extend the operating speed range.
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integrated field and armature current control strategy for variable flux reluctance machine using open winding
International Conference on Ecological Vehicles and Renewable Energies, 2015Co-Authors: Z. Q. Zhu, Beomseok Lee, Xu LiuAbstract:This paper proposes an integrated field and armature current control strategy for variable flux reluctance machine (VFRM) with open winding topology. By using open winding inverter, the field and armature currents can be injected into a single coil as sinusoidal current biased by dc offset, rather than the separated field and armature windings. With this method, the integrated current control can reduce the Copper Loss to half and extend the operating speed range owing to the reduction of winding resistance. Besides, the voltage utilisation ratio can be also increased with the open winding inverter. The integrated current control scheme is performed in synchronous reference frame with space vector modulation (SVM). The experimental results validate that the proposed strategy can effectively reduce the Copper Loss and extend the operating speed range.
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novel partitioned stator switched flux permanent magnet machines
IEEE Transactions on Magnetics, 2015Co-Authors: David John William Evans, Z. Q. ZhuAbstract:A novel switched flux permanent magnet (PM) machine with a partitioned stator structure is proposed, consisting of a conventional switched flux machine with the PMs removed from the stator teeth and placed on a secondary stator within a salient rotor. This novel machine harnesses two distinct synergies in machine design: magnetically geared and switched flux machines. The machine is optimized and the performance is compared with different numbers of rotor poles and validated by experiment. This machine benefits from reduced Copper Loss, improved torque density, and torque per magnetic volume, compared with conventional switched flux machines.
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comparison of wound field switched flux machines
IEEE Transactions on Industry Applications, 2014Co-Authors: Y J Zhou, Z. Q. ZhuAbstract:This paper proposes a three-phase wound-field switched-flux (WFSF) machine. It is found that this machine has much higher average torque compared with the conventional 12-slot/8-pole machine with a segmented rotor and 12-slot/5-pole WFSF machine under the constraint of the same Copper Loss. All of those machines have been optimized to achieve the maximum torque for comparison. The performances of four machines, including back electromotive force, cogging torque, and static torque, are analyzed and compared by 2-D finite-element analysis and validated by experiments on the prototype machines.
Alejandro G Yepes - One of the best experts on this subject based on the ideXlab platform.
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strategy with smooth transitions and improved torque speed region and stator Copper Loss for two level asymmetrical six phase induction motor drives under switch faults
IEEE Transactions on Power Electronics, 2021Co-Authors: Alejandro G Yepes, Jesus Dovalgandoy, H A ToliyatAbstract:Asymmetrical six-phase drives are very attractive to obtain fault tolerance. Most faults arise in the power electronics. Two conventional methods to handle switch/diode faults in two-level converters are keeping the corresponding phases open (in two-level multiphase drives) or connecting them to the dc-link midpoint (in two-level three-phase drives) through a bidirectional switch (e.g., triac/relay). However, the former yields larger stator Copper Loss (SCL) for given torque and smaller maximum torque, because of current constraints; on the other hand, the latter reduces the maximum speed, due to voltage constraints, and has not been considered for two-level multiphase drives. This article presents several proposals to improve fault-tolerant behavior in two-level asymmetrical six-phase induction motor drives. First, to adequately combine and alternate said two approaches in these particular drives, depending on the speed, neutral-point configuration, and faulty legs. In this manner, the SCL-per-torque decreases and the total torque–speed region of the drive is extended, i.e., the maximum torque and maximum speed rise compared with each of the aforementioned conventional strategies. Second, to also turn on / off a switch between stator neutral points for further improvement in this regard. Third, a pulsewidth modulation procedure to ensure smooth transitions between drive configurations. Experimental results confirm the theory.
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improvement of postfault performance of multiphase drives in terms of operating region and stator Copper Loss
Conference of the Industrial Electronics Society, 2018Co-Authors: Alejandro G Yepes, Jesus Dovalgandoy, H A ToliyatAbstract:Multiphase drives are particularly attractive for safety-critical applications, due to their enhanced fault tolerance. Most of the faults in electric drives occur in the power electronics. Switch faults can be divided into open- and short-circuit ones. The conventional techniques to handle switch faults in two-level converters mainly consist in either keeping the corresponding phases open or connecting the stator terminal to the de-link midpoint through a triode for ac (TRIAC). However, the former results in lower maximum torque and larger stator Copper Loss (SCL), whereas the latter leads to a reduction in the maximum speed and has not been considered in the context of two-level multiphase drives. This paper proposes to adequately combine these approaches in two-level multiphase drives, depending on the speed, the faulted switches and the neutral configuration, so that the total operating region of the drive is extended and the SCL is decreased, when compared to the conventional strategies. It is also shown and exploited that, for multi phase drives based on multiple three-phase winding sets, turning on or off a TRIAC placed between their neutrals as a function of the speed allows further improvement of the postfault performance. Simulation results are provided to confirm the theory.
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postfault strategy for dual three phase machines with minimum Loss in the full torque operation range under two open phases
European Conference on Cognitive Ergonomics, 2018Co-Authors: Alejandro G Yepes, Jesus Dovalgandoy, Fernando Baneira, H A ToliyatAbstract:Dual three-phase machines (D3PMs) are particularly attractive due to their fault-tolerance capability. In general, under open-phase (OP) faults, the current references are adapted following a minimum-Loss strategy (MLS) or a maximum-torque strategy (MTS). The MLS offers lower Copper Loss than the MTS for any given torque, but a smaller torque operation range (TOR). The full-range MLS (FRMLS) has recently been proposed, providing minimum Copper Loss, for each torque value, in the whole TOR (the MTS TOR); however, only one OP was considered. Furthermore, neither the TOR of the MLS nor the Copper Loss of the MLS or MTS have been assessed with two OPs. Consequently, it is difficult to infer a priori the relevance that the FRLMS may have for two OPs. This paper evaluates the extension of the FRMLS to D3PMs with two OPs. First, the procedure to carry out this extension is described. Then, the convenience of the FRMLS for two OPs is studied for different situations. It is concluded that for two OPs in most cases the FRMLS is substantially better than the MTS and MLS in terms of Copper Loss and TOR. Experimental results verify the theory.
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Control Strategy for Dual Three-Phase Machines With Two Open Phases Providing Minimum Loss in the Full Torque Operation Range
IEEE Transactions on Power Electronics, 2018Co-Authors: Alejandro G Yepes, Fernando Baneira, Jesús Doval-gandoy, H A ToliyatAbstract:Dual three-phase machines (D3PMs) are particularly attractive due to their fault-tolerance capability. In general, under open-phase (OP) faults, the current references are adapted following a minimum-Loss strategy (MLS) or a maximum-torque strategy (MTS). The MLS offers lower Copper Loss than the MTS for any given torque, but a smaller torque operation range. The full-range MLS (FRMLS) has recently been proposed, providing minimum Copper Loss, for each torque value, in the whole torque operation range (the MTS torque operation range); however, only one OP was considered. Furthermore, neither the torque operation range of the MLS nor the Copper Loss of the MLS or MTS have been assessed with two OPs. Consequently, it is difficult to infer a priori the relevance that the FRLMS may have for two OPs. This letter evaluates the extension of the FRMLS to D3PMs with two OPs. First, the procedure to carry out this extension is described. Then, the convenience of the FRMLS for two OPs is studied for different situations. It is concluded that for two OPs in most cases, the FRMLS is substantially better than the MTS and MLS in terms of Copper Loss and torque operation range. Experimental results verify the theory.