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Electric Machines & Control Application (CN 31-1959/TM, ISSN 1673-6540) was founded in 1959 in title of Technical Information of Small and Medium-sized Electric Machines. The title was changed to Small and Medium-sized Electric Machines in 1977, and then changed to its current title in 2005. The journal is sponsored by Shanghai Electrical Apparatus Research Institute (Group) Co., Ltd., aims to publish cutting-edge achievements in various research fields related to the electrical science. The journal is a source journal of the Comprehensive Evaluation Database of Chinese Academic Journals, and the full text articles are included in Chinese Academic Journals (CD). It has been included in Chinese Core Journals and Key Magazine of China Technology for years. Recently, it has also been included in Scopus, EBSCO, DOAJ, EuroPub, Research4Life, ICI world of Jourmals, ICI Journal Master Lister, Japan Science and Technology Agency database (JST, Japan) and Abstract Journals (AJ, Russia). The impact factor is steadily increasing year by year. Electric Machines and Control Application is published on the 10th of each month and is publicly distributed domestically and internationally. The post issuing code is 4-199.
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2026,53(1):1-11, DOI: 10.12177/emca.2026.105
Abstract:
[Objective] In practical engineering, some asynchronous motors are not equipped with speed sensor and torque measuring instrument, making it difficult to evaluate the energy efficiency of motors, so it is of great significance to study the identification method of speed and torque. This paper proposes an on-line identification method of asynchronous motor operation parameters based on measurable voltage and current. The method has no limitation on voltage and current waveforms, and does not need motor parameters such as stator resistance and reactance, so it is widely applicable and highly practical. [Methods] Firstly, the corresponding rotor slot harmonic frequency was found by fast Fourier transform analysis of stator current, and then the rotor speed was calculated. By constraining the rotor slot harmonic frequency within a certain range through the slip rate, the problem of tooth harmonic aliasing was resolved, enhancing the accuracy of speed identification. Secondly, the stator resistance was calculated by the motor nameplate parameters, and the electromagnetic torque and output torque were calculated by combining the collected voltage and current data. Finally, to further enhance the applicability of the proposed method, the fundamental wave compensation method was introduced to globally scale the filtered signal, accurately restoring the fundamental wave amplitude and further improving identification accuracy. [Results] The direct start and variable frequency drive models of asynchronous motor were built by Matlab to collect output data. Furthermore, experiments were conducted on the Y100L1-4 asynchronous motor to collect voltage and current experimental waveforms. Simulation and experimental results demonstrated that the identification errors for rotor speed and output torque remained within 2% under various operating conditions, thereby validating the feasibility and accuracy of the proposed method. [Conclusion] The proposed method achieves on-line identification of asynchronous motor operation parameters based on measurable electrical quantities, providing a significant reference for real-time identification of asynchronous motor operation parameters in practical engineering applications.
[Objective] In practical engineering, some asynchronous motors are not equipped with speed sensor and torque measuring instrument, making it difficult to evaluate the energy efficiency of motors, so it is of great significance to study the identification method of speed and torque. This paper proposes an on-line identification method of asynchronous motor operation parameters based on measurable voltage and current. The method has no limitation on voltage and current waveforms, and does not need motor parameters such as stator resistance and reactance, so it is widely applicable and highly practical. [Methods] Firstly, the corresponding rotor slot harmonic frequency was found by fast Fourier transform analysis of stator current, and then the rotor speed was calculated. By constraining the rotor slot harmonic frequency within a certain range through the slip rate, the problem of tooth harmonic aliasing was resolved, enhancing the accuracy of speed identification. Secondly, the stator resistance was calculated by the motor nameplate parameters, and the electromagnetic torque and output torque were calculated by combining the collected voltage and current data. Finally, to further enhance the applicability of the proposed method, the fundamental wave compensation method was introduced to globally scale the filtered signal, accurately restoring the fundamental wave amplitude and further improving identification accuracy. [Results] The direct start and variable frequency drive models of asynchronous motor were built by Matlab to collect output data. Furthermore, experiments were conducted on the Y100L1-4 asynchronous motor to collect voltage and current experimental waveforms. Simulation and experimental results demonstrated that the identification errors for rotor speed and output torque remained within 2% under various operating conditions, thereby validating the feasibility and accuracy of the proposed method. [Conclusion] The proposed method achieves on-line identification of asynchronous motor operation parameters based on measurable electrical quantities, providing a significant reference for real-time identification of asynchronous motor operation parameters in practical engineering applications.
2026,53(1):12-23, DOI: 10.12177/emca.2026.108
Abstract:
[Objective] In the simulation of grid-forming multi-converter systems, traditional LC equivalent model exhibits insufficient accuracy and significant transient response errors, rendering them struggle to accommodate high-frequency switching characteristics, particularly failing to accurately represent switching transient processes at sub-microsecond simulation time step. To resolve the above challenges, a high-precision modeling method for grid-forming multi-converter system based on state matrix is proposed. [Methods] Firstly, a discretized model for converter switching components under grid-forming virtual synchronous generator control was established, where undetermined parameters were determined by combining discrete circuit with ideal switching characteristic, thereby constructing a generalized fixed-admittance switching (FAS) model based on LC equivalent circuits. Secondly, based on the coupling characteristics of grid-forming multi-converter, an extension method from the single converter state matrix to the multi-converter system was derived, and system-level state-space equations were formulated to efficiently characterize dynamic interactions among converters. Finally, a grid-forming multi-converter system simulation model was established based on the PSCAD/EMTDC platform, and compared the proposed FAS model with the PSCAD ideal model and traditional LC equivalent model. [Results] The simulation results showed that the simulation results of proposed FAS model were closer to the PSCAD ideal model, which effectively reduced the power loss under the sub-microsecond simulation time step and improved the system simulation accuracy and efficiency while maintaining the system stability. [Conclusion] The proposed FAS model exhibits excellent applicability and stability under sub-microsecond simulation time step.
[Objective] In the simulation of grid-forming multi-converter systems, traditional LC equivalent model exhibits insufficient accuracy and significant transient response errors, rendering them struggle to accommodate high-frequency switching characteristics, particularly failing to accurately represent switching transient processes at sub-microsecond simulation time step. To resolve the above challenges, a high-precision modeling method for grid-forming multi-converter system based on state matrix is proposed. [Methods] Firstly, a discretized model for converter switching components under grid-forming virtual synchronous generator control was established, where undetermined parameters were determined by combining discrete circuit with ideal switching characteristic, thereby constructing a generalized fixed-admittance switching (FAS) model based on LC equivalent circuits. Secondly, based on the coupling characteristics of grid-forming multi-converter, an extension method from the single converter state matrix to the multi-converter system was derived, and system-level state-space equations were formulated to efficiently characterize dynamic interactions among converters. Finally, a grid-forming multi-converter system simulation model was established based on the PSCAD/EMTDC platform, and compared the proposed FAS model with the PSCAD ideal model and traditional LC equivalent model. [Results] The simulation results showed that the simulation results of proposed FAS model were closer to the PSCAD ideal model, which effectively reduced the power loss under the sub-microsecond simulation time step and improved the system simulation accuracy and efficiency while maintaining the system stability. [Conclusion] The proposed FAS model exhibits excellent applicability and stability under sub-microsecond simulation time step.
2026,53(1):24-34, DOI: 10.12177/emca.2026.113
Abstract:
[Objective] To enhance the control accuracy of the nonlinear flux observer (NFO)-based sensorless control system for permanent magnet synchronous linear motor (PMSLM), the influence of the inherent end effects in the PMSLM on the motor model parameters is considered and the NFO is redesigned accordingly in this paper. Furthermore, to improve the disturbance rejection capability of the traditional extended state observer (ESO) in PMSLM sensorless control system, a position calculation method employing a variable gain ESO with phase-locked loop (VGESO-PLL) is proposed. [Methods] Firstly, considering the voltage deviation caused by the inherent end effects of the PMSLM during motor operation, a modification to the existing mathematical model was implemented and then the NFO was redesigned. Then, by investigating the impact of ESO bandwidth on position estimation performance, an improved VGESO control method was proposed. This method incorporated a bandwidth variation law driven by the derivative of the estimated speed into the traditional ESO, enabling dynamic adjustment of ESO bandwidth and to enhance the speed observation accuracy under transient conditions. Finally, the characteristic equation of the VGESO was solved by adopting Euler discretization method, and the allowable bandwidth range of the VGESO was determined using the Jury criterion. [Results] Experimental results showed that under operating condition at sudden acceleration from 0.1 m/s to 0.3 m/s, the maximum speed estimation error of the VGESO-PLL was reduced by 8.05% compared to the traditional PLL. Although the maximum speed estimation error was identical to that of ESO-PLL, its speed estimation error exhibited a smaller fluctuation range than ESO-PLL. And under operating condition at sudden deceleration from 0.3 m/s to 0.1 m/s, the maximum speed estimation error of the VGESO-PLL was reduced by 73.1% compared to the traditional PLL and by 37.7% compared to the ESO-PLL. [Conclusion] The restructured NFO in this paper can reflect the influence of the PMSLM end effects. And the proposed VGESO-PLL position calculation method can effectively enhance the speed observation accuracy of the PMSLM under sudden speed change conditions, thereby enhancing the disturbance rejection capability of the VGESO.
[Objective] To enhance the control accuracy of the nonlinear flux observer (NFO)-based sensorless control system for permanent magnet synchronous linear motor (PMSLM), the influence of the inherent end effects in the PMSLM on the motor model parameters is considered and the NFO is redesigned accordingly in this paper. Furthermore, to improve the disturbance rejection capability of the traditional extended state observer (ESO) in PMSLM sensorless control system, a position calculation method employing a variable gain ESO with phase-locked loop (VGESO-PLL) is proposed. [Methods] Firstly, considering the voltage deviation caused by the inherent end effects of the PMSLM during motor operation, a modification to the existing mathematical model was implemented and then the NFO was redesigned. Then, by investigating the impact of ESO bandwidth on position estimation performance, an improved VGESO control method was proposed. This method incorporated a bandwidth variation law driven by the derivative of the estimated speed into the traditional ESO, enabling dynamic adjustment of ESO bandwidth and to enhance the speed observation accuracy under transient conditions. Finally, the characteristic equation of the VGESO was solved by adopting Euler discretization method, and the allowable bandwidth range of the VGESO was determined using the Jury criterion. [Results] Experimental results showed that under operating condition at sudden acceleration from 0.1 m/s to 0.3 m/s, the maximum speed estimation error of the VGESO-PLL was reduced by 8.05% compared to the traditional PLL. Although the maximum speed estimation error was identical to that of ESO-PLL, its speed estimation error exhibited a smaller fluctuation range than ESO-PLL. And under operating condition at sudden deceleration from 0.3 m/s to 0.1 m/s, the maximum speed estimation error of the VGESO-PLL was reduced by 73.1% compared to the traditional PLL and by 37.7% compared to the ESO-PLL. [Conclusion] The restructured NFO in this paper can reflect the influence of the PMSLM end effects. And the proposed VGESO-PLL position calculation method can effectively enhance the speed observation accuracy of the PMSLM under sudden speed change conditions, thereby enhancing the disturbance rejection capability of the VGESO.
2026,53(1):35-45, DOI: 10.12177/emca.2026.112
Abstract:
[Objective] The extended kalman filter (EKF) is widely used in sensorless brushless DC motor drive systems and can recursively estimate rotor position and speed based on the nonlinear motor model. However, the inherent linearization characteristic of the EKF results in limited approximation accuracy, making the estimator extremely sensitive to parameter uncertainties, model mismatches, and deviations in noise statistics. These limitations can cause the estimated electrical angle and speed to drift over time, leading to commutation errors and significantly reducing motor operating performance. [Methods] To address this issue, this paper proposed a commutation error correction method based on the phase synchronization between the fundamental components of phase back electromotive force and phase current. Firstly, a variable center frequency fundamental extraction filter was employed to extract the fundamental components of both phase current and phase back electromotive force. Secondly, using the vector relationships in the two-phase coordinate system, a commutation error indicator was constructed. When this commutation error indicator was greater than zero, it indicated lagging commutation, when less than zero, it indicated leading commutation. Finally, the commutation error indicator was closed-loop regulated through a proportional integral controller, driving it toward zero and thereby achieving adaptive correction of the commutation timing. [Results] The simulation and experimental results showed good consistency. The proposed method exhibited strong robustness against phase errors induced by various non-ideal factors within the control loop, effectively correcting commutation errors, significantly improving the symmetry of the current waveforms, rendering the commutation process smoother and more stable. Under both lagging and leading commutation conditions, the peak-to-peak values of phase current were reduced by 75% and 67% respectively, and the rotor position error remained within 0.2 rad. [Conclusion] The proposed commutation error correction method based on EKF and phase synchronization of fundamental components between phase current and phase back electromotive force effectively corrects commutation errors, significantly reduces power loss, and enhances both system efficiency and operational stability.
[Objective] The extended kalman filter (EKF) is widely used in sensorless brushless DC motor drive systems and can recursively estimate rotor position and speed based on the nonlinear motor model. However, the inherent linearization characteristic of the EKF results in limited approximation accuracy, making the estimator extremely sensitive to parameter uncertainties, model mismatches, and deviations in noise statistics. These limitations can cause the estimated electrical angle and speed to drift over time, leading to commutation errors and significantly reducing motor operating performance. [Methods] To address this issue, this paper proposed a commutation error correction method based on the phase synchronization between the fundamental components of phase back electromotive force and phase current. Firstly, a variable center frequency fundamental extraction filter was employed to extract the fundamental components of both phase current and phase back electromotive force. Secondly, using the vector relationships in the two-phase coordinate system, a commutation error indicator was constructed. When this commutation error indicator was greater than zero, it indicated lagging commutation, when less than zero, it indicated leading commutation. Finally, the commutation error indicator was closed-loop regulated through a proportional integral controller, driving it toward zero and thereby achieving adaptive correction of the commutation timing. [Results] The simulation and experimental results showed good consistency. The proposed method exhibited strong robustness against phase errors induced by various non-ideal factors within the control loop, effectively correcting commutation errors, significantly improving the symmetry of the current waveforms, rendering the commutation process smoother and more stable. Under both lagging and leading commutation conditions, the peak-to-peak values of phase current were reduced by 75% and 67% respectively, and the rotor position error remained within 0.2 rad. [Conclusion] The proposed commutation error correction method based on EKF and phase synchronization of fundamental components between phase current and phase back electromotive force effectively corrects commutation errors, significantly reduces power loss, and enhances both system efficiency and operational stability.
2026,53(1):46-56, DOI: 10.12177/emca.2026.103
Abstract:
[Objective] Aiming to the problem of design weighting factor in model predictive control, non-dominated sorting genetic algorithm II (NSGA-II) and Bayesian optimization algorithm are used to design weighting factors in this paper. [Methods] Based on model predictive torque control (MPTC) for permanent magnet synchronous motor (PMSM), NSGA-II and Bayesian optimization algorithm were used to design weighting factors in two scenarios, which were without/with considering switching frequency control, respectively. When without considering switching frequency control, only one weighting factor needed to be designed, when with considering switching frequency control, two weighting factors needed to be designed. And based on the weighting factors designed by two algorithms, a comparison of the two algorithms in terms of control performance, execution time and memory occupancy was carried out. [Results] The results showed that both weighting factors design algorithms were feasible for PMSM MPTC system with/without considering switching frequency control. The weight factors obtained by NSGA-II that minimize the fitness function value were essentially equivalent to the optimal weight factors derived from the Bayesian optimization algorithm, and control performances were basically equivalent. The control performance of Bayesian optimization algorithm was relatively superior. [Conclusion] NSGA-II can provide a set of Pareto optimal solutions suitable for diverse application scenarios. Characterized by high computational complexity, extended processing times, and substantial memory requirements, it is well-suited for dynamically evolving operational environments. And the Bayesian optimization algorithm is easy to implement and doesn’t need too much resource, has better optimization effect and higher optimization efficiency in complex scenarios involving multiple control objectives.
[Objective] Aiming to the problem of design weighting factor in model predictive control, non-dominated sorting genetic algorithm II (NSGA-II) and Bayesian optimization algorithm are used to design weighting factors in this paper. [Methods] Based on model predictive torque control (MPTC) for permanent magnet synchronous motor (PMSM), NSGA-II and Bayesian optimization algorithm were used to design weighting factors in two scenarios, which were without/with considering switching frequency control, respectively. When without considering switching frequency control, only one weighting factor needed to be designed, when with considering switching frequency control, two weighting factors needed to be designed. And based on the weighting factors designed by two algorithms, a comparison of the two algorithms in terms of control performance, execution time and memory occupancy was carried out. [Results] The results showed that both weighting factors design algorithms were feasible for PMSM MPTC system with/without considering switching frequency control. The weight factors obtained by NSGA-II that minimize the fitness function value were essentially equivalent to the optimal weight factors derived from the Bayesian optimization algorithm, and control performances were basically equivalent. The control performance of Bayesian optimization algorithm was relatively superior. [Conclusion] NSGA-II can provide a set of Pareto optimal solutions suitable for diverse application scenarios. Characterized by high computational complexity, extended processing times, and substantial memory requirements, it is well-suited for dynamically evolving operational environments. And the Bayesian optimization algorithm is easy to implement and doesn’t need too much resource, has better optimization effect and higher optimization efficiency in complex scenarios involving multiple control objectives.
2026,53(1):57-66, DOI: 10.12177/emca.2026.109
Abstract:
[Objective] The electromagnetic torque of multi-phase self-excited synchronous motor (SESM) is generated by the interaction of the excitation magnetic field and the stator winding magnetic field, with the excitation magnetic field established by the harmonic-excitation windings. However, existing studies have not thoroughly discussed the relationship between the harmonic-excitation windings distribution structure and the excitation winding flux linkage, which limits further improvement of the electromagnetic torque. Therefore, this paper focuses on optimizing the harmonic-excitation windings distribution structure to enhance the electromagnetic torque. [Methods] Firstly, by analyzing the excitation principle of the multi-phase SESM, the influence mechanism of harmonic-excitation windings distribution structure on excitation magnetic flux linkage was studied. Secondly, based on the influence mechanism, an optimization strategy was proposed whereby harmonic winding with identical induced electromotive force phase were connected in series, and multiple series branches were then connected in parallel. Thirdly, the coupling mechanism of the proposed optimization strategy was analyzed, enabling decoupling between the harmonic-excitation windings and the stator winding. Finally, an finite element simulation model of the motor was built based on Ansys Maxwell to compare the traditional scheme and optimized scheme. [Results] The simulation results showed that, at the speed of 100 r/min, the optimized scheme achieved a 74.5% increase in the excitation winding induced electromotive force, a 57.2% increase in excitation current and a 56.9% increase in electromagnetic torque compared to the traditional scheme. [Conclusion] The optimized scheme of harmonic-excitation windings structure designed in this paper effectively improves the electromagnetic torque at zero-low speed domain and enhances the excitation effect.
[Objective] The electromagnetic torque of multi-phase self-excited synchronous motor (SESM) is generated by the interaction of the excitation magnetic field and the stator winding magnetic field, with the excitation magnetic field established by the harmonic-excitation windings. However, existing studies have not thoroughly discussed the relationship between the harmonic-excitation windings distribution structure and the excitation winding flux linkage, which limits further improvement of the electromagnetic torque. Therefore, this paper focuses on optimizing the harmonic-excitation windings distribution structure to enhance the electromagnetic torque. [Methods] Firstly, by analyzing the excitation principle of the multi-phase SESM, the influence mechanism of harmonic-excitation windings distribution structure on excitation magnetic flux linkage was studied. Secondly, based on the influence mechanism, an optimization strategy was proposed whereby harmonic winding with identical induced electromotive force phase were connected in series, and multiple series branches were then connected in parallel. Thirdly, the coupling mechanism of the proposed optimization strategy was analyzed, enabling decoupling between the harmonic-excitation windings and the stator winding. Finally, an finite element simulation model of the motor was built based on Ansys Maxwell to compare the traditional scheme and optimized scheme. [Results] The simulation results showed that, at the speed of 100 r/min, the optimized scheme achieved a 74.5% increase in the excitation winding induced electromotive force, a 57.2% increase in excitation current and a 56.9% increase in electromagnetic torque compared to the traditional scheme. [Conclusion] The optimized scheme of harmonic-excitation windings structure designed in this paper effectively improves the electromagnetic torque at zero-low speed domain and enhances the excitation effect.
2026,53(1):67-76, DOI: 10.12177/emca.2026.107
Abstract:
[Objective] With the development of electric vehicles, the VIENNA rectifier, as a key component of new energy vehicle charging stations, has also been widely applied. However, when connected to the grid, the VIENNA rectifier injects harmonics into the grid. To address the unclear mechanism of harmonic coupling between its AC and DC sides, this paper establishes a harmonic state space (HSS) model of the VIENNA rectifier. [Methods] Firstly, based on the HSS theory, the VIENNA rectifier was modelled, and the harmonic coupling impedance matrix was derived. Secondly, based on the coupling impedance distribution diagram and the coupling impedance amplitude diagram, the harmonic coupling and transmission relationships between different variables were visualized. Finally, simulations were conducted based on Matlab/Simulink to compare the computational results of the HSS model with the simulation results of the Simulink model, thereby validating the accuracy of the HSS model. [Results] The harmonic coupling and transmission characteristics of the VIENNA rectifier exhibited a cross-frequency transmission relationship whereby the kth harmonic in the AC-side voltage coupled out the k±2th harmonics in the AC-side input current, and the k±1th harmonic in the DC-side voltage. A 10V/6th harmonic disturbance was injected into both the HSS model and the Simulink simulation model, the results indicated that all key variables were affected. However, the small-signal waveforms of these key variables in both models were largely consistent, with minimal discrepancies. This validated the accuracy of the HSS model established in this paper. [Conclusion] The model established in this paper can accurately reflect the harmonic coupling and transmission laws between the AC and DC sides of the VIENNA rectifier, providing a theoretical basis for the parameter design of the converter and the formulation of effective measures to suppress frequency coupling phenomena.
[Objective] With the development of electric vehicles, the VIENNA rectifier, as a key component of new energy vehicle charging stations, has also been widely applied. However, when connected to the grid, the VIENNA rectifier injects harmonics into the grid. To address the unclear mechanism of harmonic coupling between its AC and DC sides, this paper establishes a harmonic state space (HSS) model of the VIENNA rectifier. [Methods] Firstly, based on the HSS theory, the VIENNA rectifier was modelled, and the harmonic coupling impedance matrix was derived. Secondly, based on the coupling impedance distribution diagram and the coupling impedance amplitude diagram, the harmonic coupling and transmission relationships between different variables were visualized. Finally, simulations were conducted based on Matlab/Simulink to compare the computational results of the HSS model with the simulation results of the Simulink model, thereby validating the accuracy of the HSS model. [Results] The harmonic coupling and transmission characteristics of the VIENNA rectifier exhibited a cross-frequency transmission relationship whereby the kth harmonic in the AC-side voltage coupled out the k±2th harmonics in the AC-side input current, and the k±1th harmonic in the DC-side voltage. A 10V/6th harmonic disturbance was injected into both the HSS model and the Simulink simulation model, the results indicated that all key variables were affected. However, the small-signal waveforms of these key variables in both models were largely consistent, with minimal discrepancies. This validated the accuracy of the HSS model established in this paper. [Conclusion] The model established in this paper can accurately reflect the harmonic coupling and transmission laws between the AC and DC sides of the VIENNA rectifier, providing a theoretical basis for the parameter design of the converter and the formulation of effective measures to suppress frequency coupling phenomena.
2026,53(1):77-86, DOI: 10.12177/emca.2026.115
Abstract:
[Objective] To enhance the torque density of permanent magnet adjustable speed drive (PMASD), this paper proposes a composite flux PMASD with squirrel-cage structure, and conducts its electromagnetic design and electromagnetic characteristic analysis. [Methods] Firstly, a brief introduction to the structure and principle of the proposed PMASD was provided, and the theoretical model of PMASD was established based on the equivalent magnetic circuit method. Secondly, the PMASD simulation model was established based on the finite element method. The influence of key structural parameters such as the pole-arc coefficient, thickness and the pole-pairs of permanent magnets on the air-gap magnetic field, torque and torque ripple of the PMASD were studied. And the influence of the cross-sectional area of L-shaped conductor on the loss and torque characteristics of the PMASD were also analyzed. Finally, the torque characteristic and speed regulation characteristic at different shifting distances of the squirrel-cage rotor were analyzed. [Results] When the pole-arc coefficient was 0.8, the air gap flux density waveform of the PMASD was closer to a sine wave, and the torque ripple was relatively small. As the thickness of the permanent magnet increases, the amplitude of the fundamental wave of the air gap flux density was increased, with the growth rate gradually decreasing. A reasonable combination of permanent magnet thickness and pole-arc coefficient could improve the fundamental wave proportion. As the number of pole-pairs increased, within the low slip speed range, the PMASD torque output capacity was first enhanced and then decreased. Meanwhile, the slip speed corresponding to the maximum torque showed a trend of first increasing and then decreasing. As the cross-sectional area of the conductor bar increased, the resistance of the conductor bar was reduced, and the copper loss of the squirrel-cage rotor was decreased. With the increased of shifting distances, the torque and copper loss were generally reduced, but the reduction rate was gradually decreased. [Conclusion] The proposed composite flux squirrel-cage structure enhances the torque output capability and torque density of the PMASD, offering excellent speed regulation characteristics and thermal conductivity.
[Objective] To enhance the torque density of permanent magnet adjustable speed drive (PMASD), this paper proposes a composite flux PMASD with squirrel-cage structure, and conducts its electromagnetic design and electromagnetic characteristic analysis. [Methods] Firstly, a brief introduction to the structure and principle of the proposed PMASD was provided, and the theoretical model of PMASD was established based on the equivalent magnetic circuit method. Secondly, the PMASD simulation model was established based on the finite element method. The influence of key structural parameters such as the pole-arc coefficient, thickness and the pole-pairs of permanent magnets on the air-gap magnetic field, torque and torque ripple of the PMASD were studied. And the influence of the cross-sectional area of L-shaped conductor on the loss and torque characteristics of the PMASD were also analyzed. Finally, the torque characteristic and speed regulation characteristic at different shifting distances of the squirrel-cage rotor were analyzed. [Results] When the pole-arc coefficient was 0.8, the air gap flux density waveform of the PMASD was closer to a sine wave, and the torque ripple was relatively small. As the thickness of the permanent magnet increases, the amplitude of the fundamental wave of the air gap flux density was increased, with the growth rate gradually decreasing. A reasonable combination of permanent magnet thickness and pole-arc coefficient could improve the fundamental wave proportion. As the number of pole-pairs increased, within the low slip speed range, the PMASD torque output capacity was first enhanced and then decreased. Meanwhile, the slip speed corresponding to the maximum torque showed a trend of first increasing and then decreasing. As the cross-sectional area of the conductor bar increased, the resistance of the conductor bar was reduced, and the copper loss of the squirrel-cage rotor was decreased. With the increased of shifting distances, the torque and copper loss were generally reduced, but the reduction rate was gradually decreased. [Conclusion] The proposed composite flux squirrel-cage structure enhances the torque output capability and torque density of the PMASD, offering excellent speed regulation characteristics and thermal conductivity.
2026,53(1):87-100, DOI: 10.12177/emca.2026.111
Abstract:
[Objective] The initial feature of single-phase grounding faults in distribution networks is weak, with a low signal-to-noise ratio. Traditional fault detection methods suffer from low detection accuracy and insufficient generalization capability when labeled data samples are limited. To address this issue, this paper proposes a TransTCN semi-supervised collaborative learning framework that integrates Transformer and temporal convolutional network (TCN). [Methods] Firstly, the improved complementary ensemble empirical mode decomposition (ICEEMD) method was employed to perform adaptive mode decomposition on fault zero-sequence current signal, thereby selecting the optimal feature components. Secondly, model training was initialized with a small number of labelled data sample, and the unlabeled dataset expanded through a high-confidence pseudo-label generation mechanism, and combined with a loss function featuring weight-adaptive allocation to achieve iterative optimization of model parameters. Finally, a single-phase grounding fault model for a 10 kV distribution network was constructed using PSCAD. The detection performance of the proposed TransTCN semi-supervised model was validated under varying grounding resistances, initial fault angles, and operational conditions. [Results] Under conditions where labeled data constituted merely 15% of the dataset, the proposed TransTCN semi-supervised model achieved an identification accuracy of 95.31% for weak feature single-phase grounding fault. [Conclusion] TransTCN semi-supervised model has significant advantages in weak feature extraction and few-sample learning scenarios. It performs well in terms of fault identification accuracy, convergence stability, and cross-condition generalization ability, and has certain engineering application value.
[Objective] The initial feature of single-phase grounding faults in distribution networks is weak, with a low signal-to-noise ratio. Traditional fault detection methods suffer from low detection accuracy and insufficient generalization capability when labeled data samples are limited. To address this issue, this paper proposes a TransTCN semi-supervised collaborative learning framework that integrates Transformer and temporal convolutional network (TCN). [Methods] Firstly, the improved complementary ensemble empirical mode decomposition (ICEEMD) method was employed to perform adaptive mode decomposition on fault zero-sequence current signal, thereby selecting the optimal feature components. Secondly, model training was initialized with a small number of labelled data sample, and the unlabeled dataset expanded through a high-confidence pseudo-label generation mechanism, and combined with a loss function featuring weight-adaptive allocation to achieve iterative optimization of model parameters. Finally, a single-phase grounding fault model for a 10 kV distribution network was constructed using PSCAD. The detection performance of the proposed TransTCN semi-supervised model was validated under varying grounding resistances, initial fault angles, and operational conditions. [Results] Under conditions where labeled data constituted merely 15% of the dataset, the proposed TransTCN semi-supervised model achieved an identification accuracy of 95.31% for weak feature single-phase grounding fault. [Conclusion] TransTCN semi-supervised model has significant advantages in weak feature extraction and few-sample learning scenarios. It performs well in terms of fault identification accuracy, convergence stability, and cross-condition generalization ability, and has certain engineering application value.
2026,53(1):101-109, DOI: 10.12177/emca.2026.104
Abstract:
[Objective] During the operation of bilateral permanent magnet linear motor, only a small portion of the terminal voltage is allocated to the resistive voltage drop and back electromotive force across the motor windings, while the majority is applied to the inductance voltage drop across the motor windings. Thus, the accuracy of inductance parameters directly affects the rationality of the converter system capacity design. Significant deviations in inductance calculations may result in either capacity redundancy, leading to unnecessary cost wastage, or insufficient capacity, preventing the motor from achieving its specified output performance. Consequently, precise calculation holds significant engineering importance. Therefore, this paper proposes an inductance parameter calculation method. [Methods] Firstly, based on electromagnetic field theory, an analytical mathematical model for bilateral permanent magnet linear motor was established. Secondly, the expressions for the air gap magnetic flux density of a single current-carrying conductor and a single-phase excited winding of bilateral permanent magnet linear motor were derived, as well as the expressions for the self-inductance and mutual inductance of the windings. Finally, the results obtained from the analytical method were compared with the finite element simulation results to verify the effectiveness of the proposed method. [Results] The error between the calculated and simulated values of the air gap magnetic flux density was 1%, and the error between the calculated and simulated inductance was less than 2%, verifying the accuracy of the proposed method. Furthermore, operational experiments spanning light-load to heavy-load conditions were conducted on a dynamic experimental platform. The measured inductance values obtained from experiments exhibited an error of 4.6% when compared to the analytical calculation values. Additionally, the terminal voltage values derived from the inductance calculations were found to be essentially consistent with the measured terminal voltage values, thereby further validating the effectiveness and engineering applicability of the proposed inductance parameter calculation method. [Conclusion] This research provides a reliable theoretical basis and technical support for parameter optimization design and power supply system configuration of bilateral permanent magnet linear motors.
[Objective] During the operation of bilateral permanent magnet linear motor, only a small portion of the terminal voltage is allocated to the resistive voltage drop and back electromotive force across the motor windings, while the majority is applied to the inductance voltage drop across the motor windings. Thus, the accuracy of inductance parameters directly affects the rationality of the converter system capacity design. Significant deviations in inductance calculations may result in either capacity redundancy, leading to unnecessary cost wastage, or insufficient capacity, preventing the motor from achieving its specified output performance. Consequently, precise calculation holds significant engineering importance. Therefore, this paper proposes an inductance parameter calculation method. [Methods] Firstly, based on electromagnetic field theory, an analytical mathematical model for bilateral permanent magnet linear motor was established. Secondly, the expressions for the air gap magnetic flux density of a single current-carrying conductor and a single-phase excited winding of bilateral permanent magnet linear motor were derived, as well as the expressions for the self-inductance and mutual inductance of the windings. Finally, the results obtained from the analytical method were compared with the finite element simulation results to verify the effectiveness of the proposed method. [Results] The error between the calculated and simulated values of the air gap magnetic flux density was 1%, and the error between the calculated and simulated inductance was less than 2%, verifying the accuracy of the proposed method. Furthermore, operational experiments spanning light-load to heavy-load conditions were conducted on a dynamic experimental platform. The measured inductance values obtained from experiments exhibited an error of 4.6% when compared to the analytical calculation values. Additionally, the terminal voltage values derived from the inductance calculations were found to be essentially consistent with the measured terminal voltage values, thereby further validating the effectiveness and engineering applicability of the proposed inductance parameter calculation method. [Conclusion] This research provides a reliable theoretical basis and technical support for parameter optimization design and power supply system configuration of bilateral permanent magnet linear motors.
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The impact of largescale access of wind farms on the transient stability of power grids could not be ignored. Taking the extended twomachine system with doublyfed wind turbines as an example, the equivalent model of doublyfed induction generator was established, and the twomachine system could be equivalent to a singlemachine infinity system. Based on the law of equal area, the analytic formula of critical clearing angle of the system was deduced in detail after wind power accessed. The analytic formula was used to quantitatively analyze the variation trends of the critical clearing angle with wind power ratio, wind turbine grid connection position, fault location and load access position. The influence laws of the above four factors on the stability of transient power angle were summarized. The simulation models of the extended twomachine system with doublyfed induction generator was established in BPA and FASTEST, and the accuracy of the theoretical analysis was verified.
The impact of largescale access of wind farms on the transient stability of power grids could not be ignored. Taking the extended twomachine system with doublyfed wind turbines as an example, the equivalent model of doublyfed induction generator was established, and the twomachine system could be equivalent to a singlemachine infinity system. Based on the law of equal area, the analytic formula of critical clearing angle of the system was deduced in detail after wind power accessed. The analytic formula was used to quantitatively analyze the variation trends of the critical clearing angle with wind power ratio, wind turbine grid connection position, fault location and load access position. The influence laws of the above four factors on the stability of transient power angle were summarized. The simulation models of the extended twomachine system with doublyfed induction generator was established in BPA and FASTEST, and the accuracy of the theoretical analysis was verified.
Abstract:
Multimotor synchronous and coordinate system was widely used in the field of motor control. The control strategy played a important role in the performance of multimotor synchronization system. Domestic and foreign scholars had conducted deep research, who aimed at the problem of multimotor synchronization.They put forward a variety of synchronization control strategies. The control strategies proposed at home and abroad were reviewed. The accuracy of tracking, robustness and capacity of antiload of the control object were analyzed. The new prospect of multimotor synchronization control was proposed.
Multimotor synchronous and coordinate system was widely used in the field of motor control. The control strategy played a important role in the performance of multimotor synchronization system. Domestic and foreign scholars had conducted deep research, who aimed at the problem of multimotor synchronization.They put forward a variety of synchronization control strategies. The control strategies proposed at home and abroad were reviewed. The accuracy of tracking, robustness and capacity of antiload of the control object were analyzed. The new prospect of multimotor synchronization control was proposed.
Abstract:
Inwheel motor drive technology represents an essential development direction in new energy vehicle drive system. The technical requirements and drive form were introduced. The technical requirements and drive form of inwheel motor drive were summarized. Current research situation of inwheel motor drive technology was compared and analyzed briefly. The key technique problems of inwheel motor technology were proposed. The essential technologies in descreasing unsprung mass, restraining vertical vibration effect and reducing torque ripple of inwheel motor were discussed, which were supposed to be solved urgently. The development trend of inwheel motor drive technology was predicted.
Inwheel motor drive technology represents an essential development direction in new energy vehicle drive system. The technical requirements and drive form were introduced. The technical requirements and drive form of inwheel motor drive were summarized. Current research situation of inwheel motor drive technology was compared and analyzed briefly. The key technique problems of inwheel motor technology were proposed. The essential technologies in descreasing unsprung mass, restraining vertical vibration effect and reducing torque ripple of inwheel motor were discussed, which were supposed to be solved urgently. The development trend of inwheel motor drive technology was predicted.
2024,51(9):70-79, DOI: 10.12177/emca.2024.090
Abstract:
To address the issue of high torque ripple in permanent magnet assisted synchronous reluctance motor (PMA-SynRM), a multi-objective optimization design method based on the non-dominated sorting genetic algorithm II (NSGA-II) was proposed. First, the basic structure and working principle of the PMA-SynRM were introduced. Next, the rotor structure of the PMA-SynRM was improved by constructing air barriers and designing asymmetric auxiliary slots. Then, sensitivity analysis was conducted to identify the parameters that had the most significant impact on the optimization objectives of the PMA-SynRM, and multi-objective optimization was performed using NSGA-II. The optimal topology was selected from the generated Pareto front. Finally, the torque performance of the optimized motor was compared with that of the initial motor using finite element analysis software. Simulation results showed that the performance of the PMA-SynRM optimized through NSGA-II was significantly improved.
To address the issue of high torque ripple in permanent magnet assisted synchronous reluctance motor (PMA-SynRM), a multi-objective optimization design method based on the non-dominated sorting genetic algorithm II (NSGA-II) was proposed. First, the basic structure and working principle of the PMA-SynRM were introduced. Next, the rotor structure of the PMA-SynRM was improved by constructing air barriers and designing asymmetric auxiliary slots. Then, sensitivity analysis was conducted to identify the parameters that had the most significant impact on the optimization objectives of the PMA-SynRM, and multi-objective optimization was performed using NSGA-II. The optimal topology was selected from the generated Pareto front. Finally, the torque performance of the optimized motor was compared with that of the initial motor using finite element analysis software. Simulation results showed that the performance of the PMA-SynRM optimized through NSGA-II was significantly improved.
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Electric Machines & Control Application ® 2026
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Electric Machines & Control Application ® 2026
Supported by:Beijing E-Tiller Technology Development Co., Ltd.
