Advanced Materials Research Vols. 960-961

Abstract: This paper shows the modeling and the effectiveness of wind turbine for voltage improvement of power systems. The wind turbine is based on a doubly-fed induction generator (DFIG). A field-oriented control is used to control of the power flow exchanged between the DFIG and the power system. A simplified wind turbine model based on independent control of active and reactive powers is used in this paper. The proposed methodology is tested in the single machine power system connected to a wind farms in the case of sudden voltage variations.

Abstract: This paper will introduce the sensorless vector control system of permanent magnet synchronous motor,it adopts the PLL structure to correct motor back electromotive force for the motor rotor speed/position estimation and vector control algorithm to realize speed and current loop control of PMSM.This paper established a mathematical model of the PMSM,design of system software and hardware,the principle of speed/position estimation method and simulation of system in Matlab/Simulink.Finally,it introduces the experiment of whole system in TMS320F2808-based PMSM experiment platform,the simulation and experimental result verify feasibility,fast response and practicability of the system.

Abstract: The multifunctional stepper motor is built on the basis of ordinary stepper motor, combined with single chip microcomputer control system, dedicated driver chip STK672-040 and chip ULN2003A function, it can not only do the actual stepping motor testing but also can set out the particular function of stepper motor. In addition, the system can link an external circuit and cooperate with the external circuit to complete the work required.

Abstract: In this thesis, fault characteristic frequency can not be accurately detected if they are drowned by noise. A novel method which is Multiple Signal Classification (MUSIC) based on four-order cumulate is provided to diagnose motor broken rotor bars and stator winding inter-turn short circuit. Because four-order accumulation is able to depress noise meanwhile fault information can be obtained accurately through this way presented even with small samples. Simulation results shown that the method were higher in resolution of frequency, more accurately in fault detection and less in computational complexity.

Abstract: In view of the research in the existing forecast model and transformer DGA methods, this paper presents the collaborative model of intelligent concentration forecast of dissolved gases in transformer oil based on multi-Agent system, for improving the predictability of transformer fault. It presents the main function of each Agent, blackboard and JADE bus in this model, discusses the collaborative process of intelligent concentration forecast of dissolved gases in transformer oil based on multi-Agent system, and designs a combination forecasting architecture and a method of composition forecasting. Finally it indicates the feasibility and effectiveness of the intelligent concentration forecast model of dissolved gases in transformer oil based on multi-Agent system according to the application examples.

Abstract: Aimed at the problem of speed identification for the asynthetic motor speed-less sensor vector control system, based on basic equations of vector control and centered by the current model and voltage model of rotor flux linkage, after the establishment of the rotor speed identification module by module reference self-adaptation theory (MRAS), this paper builds the MRAS speed-less sensor vector control system and establishes the system simulation model in Simulink software environment. Simulation results show that: the system has good dynamic and static characteristics and stability. Key words: speed-less sensor; vector control; MRAS; simulation CLC: TM343.2 Document Code:A

Abstract: The extraction method of induction motor’s fault character based on coordinate transformation could restrain the influence of fundamental component leakage by translating fundamental component into DC component. The amplitude of the fault character frequency component was inaccurate by spectrum analysis taking no account of the leakage of itself. So rotor fault diagnosis method of induction motor based on discrete spectrum correction technology is proposed. This method which did not depend on spectral function of the window function improved the traditional phase difference correction method, and the stator current signal analysis by means of an appropriate window function is performed to reduce the interference between each frequency. The proposed method could detect the existence of fault character frequency component and its frequency and amplitude. The simulation and experimental results indicated that using this method could get better precision of frequency and amplitude of the fault character frequency component.

Abstract: Parameters of induction motors have crucial effects on power system simulation. This paper proposes a dynamic aggregation method of induction motors. In this method, firstly, starting off the electromechanical models of induction motors, taking the coefficients of the electromechanical equations and steady state slips of motors as the characteristic vectors, motors are grouped with fuzzy C-means clustering method. Then, electromechanical equations of the equivalent motor are obtained by averaging that of the individual motors in the same group. Finally, parameters of equivalent motors are calculated based on the relationship of transient impedance before and after aggregation, and the principle that active and reactive power loads are equal before and after aggregation. Simulation results show that the proposed method can improve the precision of simulation

Abstract: The paper proposes a AC and DC mixed output VPS(vehicle power supply). It is composed of a two-stage circuit with the input stage and the output stage. The input stage contains a single-phase PWM inverter, a HFT (high-frequency transformer) and an uncontrolled rectifier. The single-phase PWM inverter adopts the open-loop control strategy to convert the low DC voltage into a high-frequency one with square wave. The HFT enhances the voltage and insulates the low-voltage side from the high-voltage side. The uncontrolled rectifier transforms the square voltage into DC voltage. In the output stage, one output uses single-phase PWM inverter and the other uses a DC chopper, both of which adopt the double-loop PWM control mode. The mode consists of an outer voltage loop and an inner current loop to produce desirable voltage and power. With the two-stage control strategy, ideal output currents and the output voltages are obtained, and the input power factor is controllable. The VPS model is established on MATLAB/SIMULINK, and this system is also implemented in laboratory based on DSP TMS320F28335. The results of simulation and experiment verify the proposed VPS system.

Abstract: This paper describes the speed regulation of a magnetic gear integrated permanent magnet synchronous motor. The operating principle of the motor is discussed and the torque transmission is analyzed using finite element method; hence the motor model is established. The speed regulation is analyzed under vector control, and the simulated results verify the feasibility of speed regulation control.