For a new type of toroidal permanent magnet linear motor(TPMLSM), this paper analyzes the thrust fluctuation in the constant acceleration operation of the motor from the Angle of the cogging force of the linear motor. For the motor whose structure has been determined and processed, the structural parameters of the motor cannot be changed, and its performance cannot be improved from the perspective of the motor body. Therefore, this paper tries to consider the influence of the cogging force on the normal operation of the motor from the perspective of control. In this paper, starting from the body structure of motor, first on the annular linear motor of the cogging force characteristics were extracted, and its expression is obtained by Fourier decomposition, then investigated considering the cogging force and does not consider the cogging force control of motor model, it can be seen that the control performance deteriorates significantly after considering cogging force of the motor, and the acceleration fluctuation increases significantly during the operation of the motor. On this basis, disturbance observation algorithm is introduced, and feedforward compensation is carried out by extracting the characteristic values of the disturbance model. The results show that the disturbance observer can suppress the thrust fluctuation caused by the motor cogging force to a large extent, and it can reduce the peak-to-peak value of the thrust fluctuation by more than 85% during the motor acceleration operation.
Multi-terminal flexible DC power grid plays an important role in large-scale new energy integration, which usually requires the installation of multi-terminal DC circuit breaker(MTCB) at the intersection of multiple DC lines. At present, the research on multi-terminal DC circuit breaker is mostly limited to theoretical simulation calculation, and there are few experimental studies and engineering applications. In this paper, a four-terminals DC circuit breaker based on commutating path multiplexing is proposed, which combines with the compact natural commutation scheme of hybrid gap, greatly reducing the cost and volume of the circuit breaker. The commutation characteristics of four-terminals hybrid DC circuit breaker equivalent prototype at 10kV voltage level were tested. On this basis, the equivalent prototype of the circuit breaker test results show that under 10kV voltage level, the four-terminals circuit breaker topology can achieve breaking of 11kA in 2.8ms by natural commutation method.
This paper presents an accurate calculation method to extract parameters of six-phase cylindrical linear induction motor for T type equivalent circuit from finite element analysis of electromagnetic field. The formula for calculating the physical quantities required for parameter extraction is given. According to the electromagnetic power relation and equivalent circuit of the motor, the expression of the thrust is deduced. The asymmetrical distribution of air gap flux density and the asymmetry law of induction potential are analyzed. Therefore, the secondary side parameters are treated symmetrically, then the calculation process of parameter extraction is given according to the principle of secondary thrust and port voltage equivalence. The change regulation of the circuit parameters extracted by this method is in good agreement with the physical process of motor operation. Finally, the accuracy of the proposed method is verified by static experiments.
Five-phase induction motors have the characteristics of high torque density, low torque ripple, and flexible control, making them suitable for medium- and low-voltage power supply situations. However, with the expansion of application scenarios, five-phase motors need to cope with increasingly complex operating conditions. Five-phase motors for propeller propulsion will face various complex sea conditions during actual use, and five-phase motors for electric vehicles will also face various complex road conditions and operating requirements during use. Therefore, as a propulsion motor, its speed control system must have strong robustness and anti-disturbance performance. The use of traditional PI algorithms has problems, such as poor adaptability and inability to adapt to various complex working conditions, but the use of an active disturbance rejection controller (ADRC) can effectively solve these problems. However, due to the significant coupling between the variables of induction motors and the large number of parameters in the ADRC, tuning the parameters of the ADRC is complex. Traditional empirical tuning methods can only obtain a rough range of parameter values and may have significant errors. Therefore, this paper uses ADRC based on genetic algorithm(GAADRC) to tune the parameters of the control and design an objective function based on multi-objective optimization. The parameters to be adjusted were obtained through multiple iterations. The simulation and experimental results indicate that GAADRC has lower startup overshoot, faster adjustment time, and lower load/unload speed changes compared to the empirically tuned PI controller and ADRC. Meanwhile, using a genetic algorithm for motor ADRC parameter tuning can obtain optimal control parameters while the control parameter range is completely uncertain; therefore, the method proposed in this paper has strong practical value.
The six-phase cylindrical linear induction motor has been applied in many fields due to its symmetrical structure, high utilization of the primary winding and no transverse end effect. However, the inverter adopts the sinusoidal pulse width modulation (SPWM) strategy to power the motor, which causes the phase currents to generate harmonic currents at the switching frequency and its double or side-band frequencies, which in turn causes the motor to vibrate at high frequencies. To address the above problem, this paper investigates a carrier phase shifted control for suppressing high frequency vibrations in the six-phase cylindrical linear induction motor. In this paper, by staggering the carriers of the two sets three-phase windings by a certain angle and properly adjusting the carrier phase of two inverters in the motor system, certain side-band harmonics can be cancelled out by each other, which reduces the harmonic magnetomotive force in the air gap, and achieves the purpose of suppressing high frequency vibration of the motor. The simulation analysis and experimental results verify the correctness and effectiveness of the proposed control method.
For the long-primary double-sided linear induction motor (LP-DSLIM) excited by the symmetrical current, there is a double slip frequency ripple in the thrust due to the dynamic longitudinal end effect. The expression of thrust ripple fluctuation caused by the dynamic longitudinal end effect is deduced first. Second, the method of suppressing the injected harmonic current is adopted, the expression of each part of thrust after injection is deduced, and its characteristics are analyzed, from which the feasibility of this method to reduce the thrust ripple is illustrated. Finally, the finite-element simulation and experiment results indicate that the thrust ripple is significantly reduced after the injection of the harmonic current.
Due to high power density, saturation is a common phenomenon in linear motors in the field of electromagnetic launch, and saturation affects both motor performance and motor control. As regard to this problem, the traditional magnetic circuit calculation method is no longer applicable. While the finite element method does not help to deeply understand its physical mechanism on the one hand, and is not applicable in the stage of frequent adjustment of the scheme on the other hand. In this paper, a distributed magnetic circuit method for linear motors is proposed, which is based on the magnetic motive force and Ampere circuit rule, and adopts the idea of nodal division and iterative calculation to achieve an accurate calculation of the flux density of each part of the motor. The method can calculate both the no-load saturation characteristics of the motor and the accurate calculation of the motor electromagnetic force in the case of unknown motor parameters. The correctness of this method is verified by comparing simulation and experiment.
Abstract The ship industry has been developed considerably in the engineering applications of deep-sea energy extraction, and the hydrodynamic performance and noise level of ships have become the focus of research for scholars and industries. In order to study the flow characteristics and acoustic characteristics of the sea suction valve, this paper conducts numerical simulation of the internal flow field and acoustic characteristics of the sea suction valve and the noise elimination trunk structure based on the numerical method of computational fluid dynamics. Through the study and analysis of different sea suction valve structures and different depths of noise elimination trunk on the flow characteristics and acoustic characteristics, it is helpful to provide guidance for engineering optimization design.
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