• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.12-14
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• 1995

It is necessary to analyze exactly the torque ripple components in the harmonics as to decrease the torque ripple. Lower harmonics influence mainly on torque ripple. Among the harmonics, the pairs of 5's, 7's and 11's, 13's are dominant, and the magnitude of each pairs of current harmonics are very significant. Therefore, for decreasing the torque ripple, current harmonic pairs of 6n ${\pm}$1's orders must be simultaneously eliminated. In the case of eliminating one of current harmonic pairs, even though the magnitude of the current harmonics is small, It has great effect on torque ripple.

• 전기학회논문지
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• 제64권8호
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• pp.1217-1223
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• 2015

In this paper, we study the problem of torque ripple minimization in Brushless DC Motors (BLDC) and proposes a disturbance observer (DOB) based controller in order to efficiently reduce the torque ripple. In the DOB based control system, an equivalent disturbance (plant disturbance and effect of modelling error) is cancelled by its estimate. When the DOB controller is applied to BLDC motors, the effect of inverter switching is considered as an equivalent disturbance and to be cancelled by the DOB controller. Through computer simulations, it is shown that the performance of the proposed DOB controller is superior to that of the conventional PI controller. In the case where the numerical values of resistance and inductance are not known exactly, it is shown that the proposed DOB controller achieves better performance than the PI controller.

• 전력전자학회논문지
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• 제20권3호
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• pp.201-208
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• 2015

The effects of dead-time and offset error, which cause output current distortion in single-phase grid-connected inverters are investigated this paper. Offset error is typically generated by measuring phase current, including the voltage unbalance of analog devices and non-ideal characteristics in current measurement paths. Dead-time inevitably occurs during generation of the gate signal for controlling power semiconductor switches. Hence, the performance of the grid-connected inverter is significantly degraded because of the current ripples. The current and voltage, including ripple components on the synchronous reference frame and stationary reference frame, are analyzed in detail. An algorithm, which has the proportional resonant controller, is also proposed to reduce current ripple components in the synchronous PI current regulator. As a result, computational complexity of the proposed algorithm is greatly simplified, and the magnitude of the current ripples is significantly decreased. The simulation and experimental results are presented to verify the usefulness of the proposed current ripple reduction algorithm.

• Journal of Magnetics
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• 제21권4호
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• pp.544-553
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• 2016

Torque ripple minimization without decrease in average torque is a vital attribute in the design of Synchronous Reluctance (SynRel) motor. As the design of SynRel motor is an arduous task, which encompasses many design variables, this work first analyses the significance of the effect of varying the geometrical parameters on average torque and torque ripple and then proposes an extensive optimization procedure to obtain configurations with improved average torque and minimized torque ripple. A hardware prototype is fabricated and tested. The Finite Element Analysis (FEA) software tool used for validating the test results is MagNet 7.6.0.8. Multi Objective Particle Swarm Optimization (MOPSO) is used to determine the various designs meeting the requirements of reduced torque ripple and improved torque performance. The results indicate the efficacy of the proposed methodology and substantiate the utilization of MOPSO as a significant tool for solving design problems related to SynRel motor.

• Journal of Power Electronics
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• 제16권5호
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• pp.1851-1860
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• 2016

The traction motors in electric multiple unit (EMU) trains are powered by AC-DC-AC converters, and the DC link voltage is generated by single phase PWM converters, with a fluctuation component under twice the frequency of the input catenary AC grid, which causes fluctuations in the motor torque and current. Traditionally, heavy and low-efficiency hardware LC resonant filters parallel in the DC side are adopted to reduce the ripple effect. In this paper, an analytical model of the ripple phenomenon is derived and analyzed in the frequency domain, and a ripple control scheme compensating the slip frequency of rotor vector control systems without a hardware filter is applied to reduce the torque and current ripple amplitude. Then a relatively simple discretization method is chosen to discretize the algorithm with a high discrete accuracy. Simulation and experimental results validate the proposed ripple control strategy.

• 전력전자학회논문지
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• 제2권2호
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• pp.49-56
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• 1997

스위치드 리럭턴스 전동기(switched reluctance motor : 이하 SRM 이라 칭함)는 가변 인덕턴스 프로파일의 비선형성과 리플성분이 포함된 펄스전류에 구동되는 본질적인 특성 때문에 토오크는 맥동성분을 포함한다. 본 논문에서는 토오크의 맥동에 영향을 미치는 전류파형 형태를 고찰하고, 속도나 부하에 관계없이 어드밴스 각(advance angle)와 여자전압을 제어함으로써 토오크 맥동을 저감할 수 있는 단일 펄스모드 스위칭 제어방법을 제안하였다. 그리고 설계 제작된 6/4 SRM을 이용하여 제안한 스위칭 제어방법의 타당성을 실험적으로 확인하였다.

• 한국안전학회지
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• 제12권4호
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• pp.63-69
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• 1997

This paper presents a design method for a filter application in a parts-of FA(Factory Automation). Normal equations for ripple voltage and current are derived in terms of dimensionless quantities, and these equations can be used directly to evaluate the values of LC-filter components, taking into consideration the effect of the ripple components on the rms value of the PWM-generated ripple components. Using describing function technique, design equations of the filter are derived. The data needed for the filter evaluation are the amplitude of current ripple and the frequency of square pulses delivered by the HE(Harmonic Elimination) inverter algorithm. Experimental results show that the design of the filter can be based on the method proposed and that the filter can provide a significant reduction of ripple components.

• 한국자동차공학회논문집
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• 제6권4호
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• pp.39-46
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• 1998

For permanent magnet brushless DC motors used for high speed fuel pumps, torque ripple is an important origin of vibration, acoustic noise and speed fluctuation. In this paper, the output torque profile of a PM motor with one phase energized is decomposed into the commutation torque, the reluctance torque and the armature reaction torque according to their source origins. It verifies that the output torque profile is qualitatively equivalent to the BEMF profile for low reluctance motors. This paper discusses the effect of magnet pole shaping and magnet arc length on the output torque and torque ripple. A magnet edge shaping is proposed to design a trapezoidal BEMF motor without torque ripple, with minimal sacrifice of the maximum output torque.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.347-349
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• 2013

This paper describes analysis and calculation of line frequency ripple current according to output capacitor value and effects of LED connection in the single stage flyback converter with high power factor. The low frequency output ripple current delivered from single stage converter has been analyzed in detail and the method evaluating parasitic resistance included in LED has been provided. In order to verify the equation derived in this paper, the single stage flyback converter has been designed with constant output current regulation with DCM operation. Experiments were conducted with different LED load structures to analyze the effect of LED parasitic resistance on output ripple current. As test results, the calculation can provide guide line to select capacitor values depending on output ripple current and LED characteristics.

• 전기학회논문지
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• 제58권9호
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• pp.1720-1727
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• 2009

This paper presents that generation and propagation mechanism of low frequency current ripples generated by a rectification effect of an inverter in fuel cell generation system is analyzed. The ripple reduction methode using hardware components such as capacitors and inductors is examined to reduce low frequency current ripples. A new fast and robust low frequency current ripple elimination algorithm is then proposed to incorporate a single loop current controller, which directly controls fuel cell current, without any extra hardware. The proposed algorithm can completely eliminate this current ripple as well as an overshoot or undershoot is significantly reduced. And the de link voltage and output current are well regulated by inverter controller. The validity of proposed algorithm is verified both computer simulation using PSIM 6.0 and experiment with a 1kW laboratory prototype.