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The effect of power supply and/or motor asymmetry on the phase-load distribution and the ripple of electromagnetic torque in a polyphase drive is studied by the method of symmetrical components. It is shown that the presence of asymmetry causes the mapping of all harmonics in the supply voltage into all planes of symmetrical components and eliminates the possibility of independent control of harmonics. The dynamic model of a five-phase squirrel-cage induction motor demonstrates that even minor phase or amplitude asymmetry causes asymmetry in the phase load and ripple of the electromagnetic torque. Their level eliminates the possibility of continuous operation of the motor in this mode and requires the use of control systems that provide load balance in the intact phases. [ABSTRACT FROM AUTHOR]

For the last few years, predictive torque control (PTC) has attracted the attention of the researchers due to its simplicity and effectiveness. In PTC, flux-weighting factor needs to be wisely adjusted since it affects greatly the performance of the drive system. Many research trials were devoted to select this weighting factor or even eliminate it. Each of these trials illustrates a method to overcome this problem and presents a solution to the conventional weighting factor calculation method. This paper presents a critical evaluation of the performance of recently proposed methods for weighting factor selection for finite control set PTC. Based on the way the weighting factor is calculated, the methods are classified to offline and online methods. In this study, more focus will be directed to the evaluation of the online methods since they can update the weighting factor automatically if the operating point changes. Specifically, four recently developed methods along with the conventional method are considered in this study. Flux ripple, torque ripple, current total harmonic distortion, and average switching frequency are adopted as the judging criteria for this comparison. Simulations at different operating points are used to assess the performance of each method, and the characteristics of each method are compared according to the performance indices suggested. The strengths and weaknesses of each method are highlighted. Therefore, the suitable method can be identified according to different application requirements. [ABSTRACT FROM AUTHOR]

The generated torque ripples from the BLDC motor is the main issue that affects the drive performance of the BLDC drive system. In this paper, a new switching technique to minimize the torque ripples due to current commutation is proposed. The presented scheme has been implemented using a commercial and low-cost mid-range PIC microcontroller to generate the modified pulse width modulation (PWM) control signals. An analysis of phase current during commutation time is carried out. Experimental results verify the effectiveness of proposed method. Results had shown a smoother output torque and current produced in comparison with that using conventional PWM control technique with an average of 50 % reduction in the generated torque ripples. [ABSTRACT FROM AUTHOR]

This paper presents an effective scheme to minimize the torque ripples for direct torque control (DTC) of induction motor drives. The switching strategy compares the torque error from a PI torque controller with two triangular waveforms, and then produces a constant switching frequency, which is determined by the frequency of the triangular waveforms and is almost independent of the speed. The gains of PI torque controller are designed based on root-locus plot to guarantee a good convergence of the torque error. In order to examine the performance of the proposed DTC scheme for an induction motor drive, a complete simulation model is developed using MATLAB/Simulink and validated under a wide speed range. The proposed DTC drive is also implemented and tested in real-time using a DSP-DS1102 control board for a prototype 1 KW induction motor. Simulation and experimental results show that the proposed DTC drive exhibits a good dynamic and steady state performances with low torque ripples over a wide speed control range. [ABSTRACT FROM AUTHOR]

This paper describes an active filter topology to improve the performance of hysteresis direct torque control (HDTC) of interior permanent magnet synchronous motor (IPMSM). The filter topology consists of an active filter and two RLC filters, and is connected to the main power circuit through a 1:1 transformer. The active filter is characterized by detecting the harmonics in the motor phase voltages and injecting equivalent harmonic voltages to produce almost sinusoidal voltage waveform to the motor terminals. The active filter uses hysteresis voltage controller while the motor main circuit uses hysteresis direct torque control. The simulation results of this combined control structure show considerable torque ripple reduction in the steady state range and adequate dynamic torque performance as well as considerable harmonic voltage and EMI noise reduction. [ABSTRACT FROM AUTHOR]