Advanced Materials Research Vols. 614-615

Abstract: The inverter switch state is based on the torque error and the stator flux amplitude error in the hysteretic controller which is adopted on the traditional direct torque control for the brushless doubly-fed machine, in this way, current and flux are distorted that results torque ripple in low speed range, even more influents control effect of the whole system. According to this problem, a new direct torque control method with fuzzy-PI regulator for the brushless doubly-fed machine is presented in this paper, applying the fuzzy theory to design controller parameters. The simulation results show that the method is effective to improve the dynamic characteristics of the motor, reduce the torque ripple, improve the speed and the torque control precision, and expand the direct torque control system of speed range.

Abstract: Zero-crossing detection with voltage comparator in position detection method based on the AC component of Supposing Neutral Point(SNP) induced sensitivity to noise. In this paper, it is proposed that the ASIC ML4425 should integrate AC component instead of the terminal voltage and phase-locked loop(PLL) was used to determine the proper commutation sequence for the BLDC motor. Basic principle and implementation of the ASIC-based sensorless controller will be presented and experiments will be given to verify the control strategy.

Abstract: A siding mode control (SMC) strategy with a new-style disturbance observer is proposed for the permanent magnet synchronous motor (PMSM), which has vibration problems of rotating speed and electromagnetic torque in low speed range. In the paper the mathematical model of a PMSM composed of parameter uncertainty and disturbance is established, a SMC which can effectively improve system robustness and response is designed, a novel disturbance observer to estimate the disturbance caused by the model parameter and load changes is used, the estimated value to build a feed-forward compensation added to a SMC input is employed, and finally the stability of the scheme is analyzed. Simulation results show that the algorithm has a faster response, less stabilization error compared with the traditional SMC, and the vibration is restrained effectively.

Abstract: The undervoltage tripper is a protection accessory of the low voltage apparatus and can turn off the circuit-breaker automatically when the power occurs lowering out off the given range. As a result of electrical network quality and manufacture procedure and so on, the failure rate of the circuit-breaker’s undervoltage tripper is high and always solved difficultly. This paper proposes one kind of adaptive undervoltage tripper with overvoltage protection function. It can adapt the supply voltage change automatically, absorb overvoltage, block the undervoltage tripper’s coil voltage, cause the operating region of the undervoltage tripper without high voltage dead area and improve the circuit-breaker work’s reliability.

Abstract: The cylindrical permanent-magnet linear motor (PMLSM), as a linear driving device, produces the electromagnetic force to cause linear motion through the electricity directly and does not need additional mechanical conversion devices to transform rotation to linear motion. This paper calculates the electromagnetic distribution and force of two kinds of cylindrical PMLSM by ANSYS, and compares and analyzes their thrust performance. It is concluded that a radially magnetized cylindrical PMLSM is suitable for the applications requiring smaller speed variation while an axially magnetized one possesses a bigger thrust and thrust variation yet.

Abstract: Based on finite element theory, the computer-aided design technique was used to simulate the main magnetic field of a single-phase three-column and yoke-pressing transformer, and the voltage source is excited onto the coil windings taking the field-circuit coupling method into account. The distribution of the main magnetic field in iron and the excitation current waveform in the winding were presented to provide a scientific basis for further practical application and optimization in the use of single-phase three-column yoke-pressing transformer.

Abstract: To solve the problem of electromagnetic coupling of the main winding and the inner feedback winding, this paper built a 2D finite model of the inner feedback motor and simulated the magnetic field on rated load. Distribution of flux density and flux line is obtained, which provides the reference for optimization, controlling and fault analysis for these motors.

Abstract: With the rapid development of economy and construction of large-scale hydropower, thermal power and nuclear power base, the demand of long-distance, high-capacity transmission of UHV (ultra high voltage) is increasing in China. This paper presents the application of finite element method (FEM), software ANSYS in the magnetic field of core about single-phase three-winding 750KV autotransformer with the next column excitation regulator device. As most driving sources applied to transformers are voltage sources, field-circuit coupling method is generally used in solving electromagnetic field of transformers, so this paper is written to verify if the simulation results are similar to the qualification and to prove the correctness of the method and the practical value.

Abstract: Stand-alone PMSG has to face voltage fluctuation problems. This paper proposes a kind of voltage stabilizing method based on series resonance in the armature loop and analyses the principle of stabilizing voltage and expounds on the calculation method of series capacitance. Taking a 5kVA three-phase PMSG as an example, we have done the model calculation and simulation, and steady-state analysis results verify the effectiveness of this method. Transient analysis results show that the reasonable selection of capacitance in series has good effects both on limiting short circuit current and avoiding demagnetization of the permanent magnet materials.

Abstract: In consideration of low power density of electric excitation claw-pole alternator (EECA) and some difficulties in magnetic field regulation of permanent magnet claw-pole alternator (PMCA), a novel hybrid excitation brushless claw-pole alternator (HEBCA) is proposed in this paper. Its structure and field control principle are described. Three dimensional finite element analysis is used to obtain the no-load magnetic field distributions and field control capability under different field currents. The result shows that the flux of the prototype machine can be adjusted over a wide range with a relatively low field current