Electric Machines & Control Application (CN 31-1959/TM, ISSN 1673-6540), founded in 1959 and 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 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. More
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    2024,51(5):1-11, DOI: 10.12177/emca.2024.033
    Abstract:
    In the highway DC microgrid, the time characteristics and charging mode characteristics of electric vehicle charging behavior may cause varying degrees of impact on the DC bus voltage, and the high-penetration rate of electric vehicle loads presents new challenges to the coordination control of the “source-load-storage” system. By analyzing the traffic load characteristics and micro-source characteristics of the highway DC microgrid, a multi-source coordinated control strategy based on DC bus voltage bias for electro-hydrogen coupling system is proposed. This control strategy uses the battery as the core component of voltage regulation to achieve coordinated and self-consistent operation by detecting the fluctuation of the DC bus voltage at the inverter port, without the need for communication to achieve power balance of the system. To avoid the battery exiting operation due to the crossing of the state of charge (SOC), a multi-source adaptive droop controller is designed, enabling the hydrogen unit to actively respond to SOC changes, reduce the unbalanced power caused by battery SOC management, suppress the speed of SOC approaching the boundary value, and achieve dynamic balance of SOC. Finally, the effectiveness of the proposed control strategy is verified in Matlab/Simulink.
    2024,51(5):12-20, DOI: 10.12177/emca.2024.026
    Abstract:
    To solve the problem of output power fluctuation in gravity energy storage systems due to discrete mass block switching, a power smoothing control strategy based on instantaneous power mirror compensation is proposed. Firstly, the working principle of the slope gravity energy storage system is introduced to analyze the causes of power fluctuation of the system. Secondly, the system structure for suppressing power fluctuation as well as the power smoothing control strategy are designed, and the theoretical calculation of the system structure parameters is carried out by taking the example of a 11 kW slope gravity energy storage system. Finally, a simulation model for slope gravity energy storage system is established, and the transient fluctuation characteristics of the system during the mass block alternation process are analyzed. The results show that by applying the proposed method, the mass block can provide continuous and stable mechanical power during the alternating process, which can better smooth the output power of the gravity energy storage system, verifies the effectiveness of the method.
    2024,51(5):21-29, DOI: 10.12177/emca.2024.030
    Abstract:
    For the problem of large chattering and difficult parameter tuning of traditional exponential reaching law sliding mode variable structure control, a new sliding mode reaching law is designed and fuzzy control is used to realize parameter tuning. In the double closed-loop DC speed regulation system, a speed regulator is designed based on the new reaching law. At the same time, in order to improve the efficiency of reaching law parameter tuning, an online tuning method of reaching law parameters is designed by using fuzzy control. The sliding mode parameters of the new reaching law are adjusted online by fuzzy control to improve the speed regulation performance of the system. The simulation model of DC speed regulation system is built in Matlab/Simulink, the results show that the new reaching law is superior to the traditional exponential reaching law in suppressing chattering and fast convergence, and the fuzzy control online tuning reaching law parameters is more efficient and performs better than the trial and error method.
    2024,51(5):30-38, DOI: 10.12177/emca.2024.023
    Abstract:
    Aiming at the problem of poor torque performance of dual three phase permanent magnet synchronous motor (DTP-PMSM) traditional model predictive torque control strategy, a model predictive torque control without cost function strategy based on virtual voltage vectors is proposed. Firstly, the mathematical modeling method of vector space decomposition (VSD) is investigated, and the DTP-PMSM mathematical model is establish based on VSD. Secondly, a set of 12 virtual voltage vectors without vector replacement are constructed, and the angular position and magnitude information of the reference vector are predicted by dead-beat direct torque and flux control, and the optimal virtual vector with the angular position closest to the reference vector is filtered out, which avoids traversal of virtual voltage vectors to seek for the optimal and thus reduces the computational burden significantly. And at the same time, a simplified vector magnitude adjustment method is used to make the magnitude of the optimal vector infinitely close to the magnitude of the reference vector, which effectively reduces the torque pulsation. Finally, an experimental test platform is built to compare the proposed strategy with the traditional strategy. The results show that the proposed strategy effectively reduces the current harmonics and torque pulsations.
    2024,51(5):39-49, DOI: 10.12177/emca.2024.029
    Abstract:
    In order to solve the problem that induction machines generate time harmonics in the windings when supplied at variable frequency, which leads to the increase of electromagnetic vibration and noise, an improved sine pulse width modulation control strategy using hybrid harmonic injection is proposed. A 1 120 kW submersible induction machine is taken as the research object, by injecting 3rd and 9th hybrid harmonics into the machine, the modulation wave of voltage, carrier harmonics and their side harmonics components are weakened, thus reducing the vibration noise of the machine. The harmonic ratio coefficients in the 3rd and 9th hybrid harmonics injection methods are optimized to further strengthen the weakening of sideband harmonics and reduce the machine noise overall. Finally, by comparing the performance of the machine with hybrid harmonic injection method and the conventional machine before optimization in terms of iron consumption and copper consumption, it is verified that the proposed strategy effectively attenuates the electromagnetic noise of the machine without affecting the basic performance of the machine.
    2024,51(5):50-60, DOI: 10.12177/emca.2024.037
    Abstract:
    Aiming at the problems of limited image scale and low recognition accuracy in the field of substation equipment inspection image recognition, an image classification and recognition method based on improved ResNet34 network is proposed. The Seam Carving algorithm is employed to compress the low energy areas in the image for the preservation of key features. Additionally, six types of image enhancement techniques such as elastic transformation and Gaussian noise are utilized to increase the diversity of the images. The basic ResNet34 network is integrated with the convolutional block attention module to enhance the model′s ability to extract key features from equipment inspection images. A model pre-trained on the ImageNet dataset is utilized as a feature extractor for transfer learning to address the issue of insufficient sample quantity. A cosine annealing strategy is introduced in the Adam optimizer to dynamically adjust the learning rate, to make the improved ResNet34 network converge to the optimal solution faster. Experimental results show that the proposed method improves accuracy by 0.073 3 and reduces the loss rate by 0.201 9 compared to the basic ResNet34 network, which provides a reliable solution for the field of substation equipment inspection image recognition.
    2024,51(5):61-71, DOI: 10.12177/emca.2024.035
    Abstract:
    A primary segmented discontinuous linear motor applied to the annular line transportation system is taken as the research object. The merits of the segmented discontinuous primary structure include cost savings, reduced losses, and a more flexible motor system, but this structure results in a large end force on the mover switching between segments , which results in large thrust fluctuations during motor operation. To solve this problem, an optimization method combining the secondary auxiliary pole and primary end teeth is proposed. The detent force of the motor during no-load operation is emulated and analyzed, and the detent force on the mover in the two cases of primary coupling and switching between segments are compared. Firstly, the main structural parameters of the motor are optimized, the multi-objective response surface model is established by combining the response surface method. Secondly, optimization is performed by genetic algorithm, and the detent forces before and after optimization are compared by simulation; Finally, a test verification based on the prototype is carried out, and the results show that the motor model with an auxiliary structure can effectively suppress the detent force and thrust fluctuation.
    2024,51(5):72-80, DOI: 10.12177/emca.2024.027
    Abstract:
    Aiming at the problems of high rotor temperature and difficult heat dissipation during the operation of the drive motor for vacuum pump, a negative salient pole permanent magnet synchronous motor and a conventional permanent magnet synchronous motor are designed according to the actual requirements of the driving conditions of vacuum pump. Firstly, the impact of the size of the rotor magnetic barrier on the motor torque and the impact of the number of magnetic barrier layers on the inductance are analyzed using finite element software, so the suitable values of the rotor magnetic barrier size and the number of magnetic barrier layers are obtained. Secondly, the electromagnetic performances of the two motors, such as the air gap magnetic density waveforms, no-load back electromotive force and losses are comparatively analyzed. Finally, the temperature fields of the two motors as well as the temperature rises at the rotors and shafts of the two motors are analyzed by simulation comparison. The results show that compared with the conventional permanent magnet synchronous motor, the negative salient pole permanent magnet synchronous motor has better torque performance, smaller rotor loss and rotor temperature rise, which provides a scientific reference for the development of new products.
    2024,51(5):81-89, DOI: 10.12177/emca.2024.034
    Abstract:
    Harmonic currents in active magnetic bearing systems are caused by rotor imbalance and sensor runout, which consequently result in harmonic vibrations. Repetitive controller can suppress both same frequency and multiply frequency harmonics, but traditional repetitive controller must satisfy that the control system sampling frequency is an integer multiple of the actual rotor speed, which severely limits their applicability. To solve this problem, an improved dual mode fractional order repetitive controller is designed. The Lagrange interpolation method is utilized to convert the fractional order to an integer, addressing the non-integer delay issue in repetitive control. Even and odd harmonics are independently suppressed through dual channels, the 1st, 2nd, 3rd, 4th and 5th harmonics are respectively reduced by 87.9%, 61.3%, 86.9%, 36.9% and 85.3%. Simulation and experimental results verify the accuracy and effectiveness of the improved repetitive controller for harmonic current suppression.
    2024,51(5):90-99, DOI: 10.12177/emca.2024.031
    Abstract:
    Based on fluid dynamics, a simulation model of transformer oil containing bubbles streamer discharge under the action of impulse voltage is established. The variation laws of electric field intensity and space charge density of transformer oil containing bubbles are studied by changing the position, size and number of bubbles. The simulation results show that when the breakdown voltage reaches a certain value, an electric field gradient is formed inside the bubble due to the accumulation of gas inside the bubble, resulting in an internal discharge phenomenon. The closer the bubble is to the high-voltage electrode the faster it is broken down, and the discharge proceeds in a relatively shorter time. The larger the size of the bubble, the slower the transformer oil streamer discharge. And the more the number of bubbles , the more intense the electric field during the streamer discharge, the longer the discharge lasts, and the greater the damage caused to the transformer.
    2024,51(5):100-110, DOI: 0.12177/emca.2024.025
    Abstract:
    To suppress the permanent magnet eddy current losses in tangential permanent magnet synchronous motors, an estimated model for permanent magnet eddy current losses is constructed based on Maxwell equation and constitutive equation with approximate assumptions on the shape of the permanent magnet. A magnetic conductance function based on Carter coefficient concept is employed to estimate the change in magnetic flux density under the slot due to stator slotting. The conclusions of the theoretical analysis are verified based on five motor designs with slot-pole ratios of 1.05, 1.20, 1.30, 2.40, and 3.60, respectively. The permanent magnet losses are analyzed at load current and double load current to obtain the radial air-gap magnetic flux density curve and its harmonic content for each motor. Considering the weakening effect of increasing the slot-pole ratio on stator iron losses and permanent magnet eddy current losses, a motor slot-pole ratio selection strategy is proposed. The results show that increasing the slot-pole ratio can decrease the variation in magnetic flux density stator slot, thus suppressing low-order harmonic content in the air-gap magnetic field and reducing permanent magnet eddy current losses, enhancing the motor's operational reliability, but it also introduces more high-order harmonics, which increases the stator iron consumption.
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    2019,46(9):85-94, 110, DOI:
    [Abstract] (428) [HTML] (0) [PDF 923.86 K] (14281)
    Abstract:
    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.
    2017,44(6):8-12, DOI:
    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.
    2020,47(3):17-22, DOI: 10.12177/emca.2019.172
    Abstract:
    In the permanent magnet synchronous motor (PMSM) drive system, the system current inner loop controller based on the finite control set model predictive current control (FCS-MPCC) algorithm is affected by the variation of motor parameters. The prediction model of PMSM is derived. The cost function is reconstructed with the voltage vector as the constraint, and the current ripple problem caused by the digital delay is compensated. A robust FCS-MPCC algorithm is proposed, which reduces the sensitivity of the algorithm to the parameters by introducing weight coefficients and quantitative adjustments in the prediction model. The simulation results show that the proposed algorithm is effective and can make the system have good dynamic performance and steady state accuracy.
    2017,44(6):1-7, 18, DOI:
    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.
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