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.
Abstract: Virtual synchronous generator (VSG) technology is the new generation renewable energy power generation technology that transforms it from “passive regulation” to “active support”, that is an effective path to make the renewable energy power generation have the ability to active support the power grid with inertia support, primary frequency regulation and active voltage regulation, and the virtual synchronous generator technology is an exploratory practice for solving the problems of “double-high” power system. The control modes of voltage-controlled and current-controlled of virtual synchronous generator, the operating characteristics of current control, voltage control and improved virtual synchronous generators are summarized, and the comparative advantages and shortcomings are analyzed with the view of technical principles. Focusing on the stability analysis problems and transient control of the grid-connected virtual synchronous generator, the common stability analysis methods are summarized, and the current research on the influence on the power system stability and oscillation of grid-connected improved virtual synchronous generators is summarized. On this basis, the research keys of virtual synchronous generator stability analysis, oscillation suppression and fault voltage ride-through are pointed out. Finally, the interaction mechanism and dynamic stability improvement technology of improved virtual synchronous generators are prospected, and the key problems of follow-up research are pointed out, and the referenced solution paths are proposed.
Abstract: The cost functions of model predictive torque control (MPTC) of permanent magnet synchronous motor (PMSM) need to be weighted and summed because of the different control objective dimensions, but these are difficult to design and adjust the weight coefficients. The objective evaluation methods such as fuzzy decision method, VIKOR method, TOPSIS method, coefficient of variation weighting method and entropy weighting method are applied to the model predictive torque control of permanent magnet synchronous motor to solve the above problems. Examining the model predictive torque control of permanent magnet synchronous motor with flux linkage and torque control, the above methods are feasible and do not need weight coefficients, but the calculation load is increased to a certain extent. There are some differences in the control performance of different strategies, but the overall control performance is basically the same. According to the comprehensive performance comparison, the control performance of TOPSIS method is relatively optimal.
Abstract: The traditional model predictive current control (MPCC) strategy of permanent magnet synchronous motor (PMSM) has poor steady-state performance due to the inability to adjust the amplitude and phase of the output voltage vector. A three-vector model predictive current control strategy based on the reference current slope is proposed. The reference current amplitude slope is compared with the basic voltage vector current amplitude slope. Without using an evaluation function to traverse all voltage vectors, two effective voltage vectors can be selected and combined with the zero voltage vector at a certain duty cycle. The synthesized output voltage vector can cover any amplitude and phase angle within a certain range. This strategy significantly reduces the overall system computation compared to the traditional model control. The simulation results show that compared to traditional model predictive current control strategy, the proposed control strategy can effectively reduce current ripple and improve the steady-state performance of the system.
Abstract: To address the problem of inaccurate parameters in equivalent circuit models of lithium batteries and uncertainty in complex operating noise leading to the low accuracy in state-of-charge (SOC) estimation. An adaptive extended Kalman filtering (AEKF) method incorporating recursive least squares with forgetting factor (FFRLS) is proposed. In each step of the SOC estimation process, the FFRLS algorithm is first used to identify the parameters of the first-order RC equivalent circuit model in real time following the changes of the experimental working environment, which increases the model accuracy and accurately describes the dynamic characteristics of the Li-ion battery when it is in operation. Then the AEKF algorithm is used to update and correct the system noise in real time and estimate the SOC on-line. The experimental platform for power lithium batteries was designed and constructed. Under both the dynamic stress test (DST) and the beijing bus dynamic stress test (BBDST) operating conditions, the maximum absolute error of the method's estimation is lower than 0.15%, the average absolute error is below 0.077, and the root mean square error is below 0.007. Compared with the extended kalman filtering (EKF) method, the estimation effect of the proposed method is greatly improved.
Abstract: The gravity energy storage system has high timeliness requirements for the phase of mass block placement. Addressing the inadequacy of existing grasping devices in terms of timeliness, a control method for a slope gravity energy storage system′s mass block grasping device based on deep neural networks is proposed. Firstly, the overall workflow of the slope gravity energy storage system and the requirements for the mass block grasping device are introduced. Secondly, a method for calculating the instantaneous acceleration of the mass block to determine its travel distance is proposed, and the error sources of this method are analyzed according factors affecting the travel distance of the mass block in the buffer platform. Based on these error sources, a dataset for the mass block′s travel distance is constructed. Finally, a deep neural network is introduced, and the network structure and parameters are determined through training. The Dropout mechanism is employed to enhance the generalization ability of the model, resulting in a predictive model for the mass block′s travel distance. The analysis indicates that the proposed control method can effectively meet the system′s requirements for the timeliness and accuracy of the placement phase. The predicted value of the mass block′s travel distance can be given within 50 ms, with a prediction error within ±0.1 m, Which verifies the feasibility of the method.
Abstract: To address the problem of high peak high frequency common-mode voltage due to high frequency switching action in conventional three-phase inverters. The common mode voltage under space vector pulse width modulation (SVPWM) and tri-state space pulse width modulation (TSPWM) of motor drive system is firstly compared and analyzed, and on this basis, the relationship between the modulating waveform of discontinuous pulse width modulation (DPWM1) and the modulating waveform of TSPWM is investigated, and the method of realizing TSPWM modulation based on carrier wave is given. Then, the relationship between positive and negative polarity carriers is studied, and a way of implementing negative polarity carriers in engineering is given. Finally, the TSPWM modulation implementation proposed is verified by simulation and experiment. The results show that the modulating waveform of TSPWM can be implemented in the same way as the modulating waveform of DPWM1, and the pulse width modulation (PWM) signal under a negative polarity carrier can be generated by a positive polarity carrier instead.
Abstract: A fractional order backstepping control strategy is proposed to enhance the performance of the linear synchronous motor suspension system for magnetic levitation platform. Based on the operating mechanism of the magnetic levitation linear synchronous motor (MLLSM) suspension system, its mathematical model and state space equation are established. Aiming at the strong nonlinearity of the MLLSM suspension system, input output feedback linearization is performed through nonlinear coordinate mapping. And to improve the convergence speed and control accuracy of the suspension system, fractional order theory is introduced to construct fractional order virtual stability functions. Fractional order backstepping controller is designed and Lyapunov function is constructed to prove the stability of the system. Simulation results show that the fractional order backstepping control can improve the response speed of the suspension system and effectively suppress the impact of uncertain disturbances on the suspension system.
Abstract: Permanent magnet synchronous linear motor is one of the most representative advanced motor technologies in the new generation of high-efficient and high-precision electronic equipment, CNC machine tools, and other electromechanical products. A permanent magnet synchronous linear motor model is established. Without considering edge effects, a mathematical model of the tangential electromagnetic force on the primary teeth of the motor is established, and the finite element analysis software is used to simulate and calculate the single tooth tangential electromagnetic force and local cogging electromagnetic force of the motor. Finally, the modal and vibration acceleration of the motor are calculated using the ANSYS Workbench platform to verify the importance of tangential electromagnetic force in vibration analysis. The results indicate that the fluctuation of local cogging electromagnetic force is the important cause of vibration generated by single tooth tangential force. The vibration of the motor can be effectively reduced by reasonably adjusting the distribution of the magnetic field in the primary teeth of the motor, which provides a reference for the design and optimization of this type of motor.
Abstract: The traditional sliding mode observer method is used to obtain the rotor position in the position sensor control of the permanent magnet synchronous motor. The accuracy of rotor position estimation is affected by the factors such as the serious vibration of the sliding mode, the low harmonic interference contained in the estimated reverse potential and the position error of the conventional phase-locked loop when the motor is reversed. The above problems are solved by designing an adaptive sliding mode observer and improving the phase-locked loop. Firstly, a non-singular fast terminal sliding mode surface and an improved exponential approach law are adopted to reduce the sliding mode vibration. Secondly, the traditional phase-locked loop phase detector is improved and the second-order generalized integrator is introduced into the loop filter, which not only enables the accurate extraction of rotor position information when the motor is rotating forward and reversed, but also can filter out the low harmonics in the estimated reverse potential. The simulation results show that the effectiveness of the designed algorithm in reducing the sliding mode vibration, decreasing the delay time of position tracking, and improving the accuracy of position observation.
Abstract: Aiming at the disadvantages of poor heat dissipation condition of cage rotor and easy demagnetization of permanent magnet, an outer squirrel cage rotor magnetic coupler (OSRMC) is proposed. Based on the composition and operation principle of OSRMC, the thermal analysis model and loss principle are given, and it is demonstrated that when the slip of OSRMC is 33.3%, the generated thermal power consumption is the maximum (4/27 times of the rated power). Based on the principle of heat transfer, the two main heat exchange modes and the differential equation of heat conduction of OSRMC are given, and the finite element simulation results of OSRMC are obtained based on the cluster analysis method and the domain partitioning method. The results show that: the main heat exchange mode of OSRMC is thermal convection, and its main temperature rise is located at the coupling between the cage and the permanent magnet and gradually decreases along the axial direction. The calculation accuracy of cluster analysis method is equivalent to that of area division method, but the calculation speed of area division method is fast and the grid division is more difficult.
Abstract: A loading system for performance test of servo systems in robots is designed by using a programmable logic controller S7-1500 and a variable frequency converter Sinamics S120. The compositions of performance test system, hardware and software designs of the loading system are presented. The close-loop control of loading system was modeled, and the torque proportional-integral controller and torque differential negative feedback controller are introduced to eliminate static torque errors and suppress torque overshoots. The practical application results show that the system performance indicators can meet design requirements.
Abstract: In order to solve the problem of high content of non-dominant pole log-harmonic in fractional slot concentrated winding induction machine, a method of suppressing non-dominant pole log-harmonics by setting up compensation windings of fractional slot concentrated windings structure is proposed. Firstly, the distribution law of each harmonic magnetic potential of the fractional slot concentrated winding with different slot-pole coordination is analyzed. Then, according to the different distributions of the dominant pole log-harmonic and the non-dominant pole log-harmonic with higher harmonic content at the axis position, two different compensation winding arrangements are designed. Finally, through theoretical calculations and finite element simulations, it is verified that the method can effectively suppress the non-dominant pole log-harmonics with high harmonic content, and retain the characteristics of high phase independence of the concentrated windings.
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.
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.
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.
Abstract: Aiming at the problem of long solidification time of adhesive for fixing the magnetic tile of brushless DC motor (BLDCM), the minimum bonding strength of the adhesive is obtained by analyzing and calculating the stress of the magnetic tile, and the rapid fixing of the magnetic tile is realized by developing and verifying the thermosetting adhesive. The stability of adhesive after complete solidification is verified by high temperature test, low temperature test, high temperature and humidity test, thermal shock test, and high temperature timely test. The results show that the minimum bonding strength of fixed magnetic tile is 5.81 MPa, and the bonding strength of AC451 glue is 15.6 MPa at 60 ℃/20 min, confirming that the complete fixation of magnetic tile is realized. After dynamic balance test, the glue solidifies at room temperature for 5 h, and its bonding strength reaches 22.2 MPa, which meets the requiments of all type tests. It is safe and reliable, and has wide industrial application prospects.