• Journal of Power Electronics
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• v.11 no.4
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• pp.507-511
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• 2011

This paper presents a single-switch buck converter with a ripple-free inductor current. In the proposed converter, the filter inductor current ripple is completely removed by utilizing an auxiliary circuit consisting of an additional winding of the filter inductor, an auxiliary inductor, and an auxiliary capacitor. Moreover, the ripple-free current characteristic is maintained under both light load and full load conditions. The theoretical analysis and performance of the proposed converter were verified with a 110W experimental prototype operating at a 107 kHz switching frequency.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.11
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• pp.1040-1047
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• 2007

This paper presents ripple-free method that can occur in multirate controller design. The conventional multirate input controller has the problem that the ripple occurs in track-following because of chattering phenomenon in control input signal. In order to resolve the problem of rippling, it was proposed to eliminate the ripple phenomenon using feedforward compensator. This paper makes explains problems in conventional ripple-tree multirate controller and introduces a multirate controller design method applying lifting technique based on current estimators in condition space. Using the ripple-tree multirate controller, we show that chattering does not occur in the control input signal through applying the final value theorem from the viewpoint of discrete-time transformation. Also, this study proves that the ripple of the proposed controller decreases with the increase of this sampling frequency and, when sampling frequency is fixed, it decreases with the increase of the control input period.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1293-1302
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• 2018

Multiport power converters have recently become popular to researchers and engineers. However, more improvements are required in terms of their soft-switching operation, bidirectional operation, and integration. In this study, a bidirectional three-port three-switch DC-DC converter is proposed. The converter contains a low-current ripple port and ripple-free current port. Through the integrated structure, utilization of a coupled inductor, and a new switching strategy, the aforementioned specifications are achieved. A modified switching strategy is also utilized in the converter, which has resulted in the bidirectional operation of the converter between ports. Finally, a comprehensive analysis is presented, and the converter characteristics are validated by experimental results.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.273-274
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• 2012

This paper investigates control algorithms for a doubly fed induction generator(DFIG) with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power system under unbalanced grid conditions. Two different control algorithms to compensate for unbalanced conditions are proposed. Evaluation factors of control algorithm are fault ride-through(FRT) capability, efficiency, harmonic distortions and torque pulsation. Zero regulated negative sequence stator current control algorithm has the most effective performance concerning FRT capability and efficiency. Ripple-free control algorithm nullifies oscillation component of active power and reactive power. Ripple-free control algorithm shows the least harmonic distortions and torque pulsation. Combination of zero regulated negative sequence stator current and ripple-free control algorithm control algorithm depending on the operating requirements and depth of grid unbalance presents the most optimized performance factors under the generalized unbalanced operating conditions leading to high performance DFIG wind turbine system.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.7
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• pp.862-867
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• 1999

In general, the realization of high performance brushless permanent magnet motors which are widely used in servo drive is focused on the linear control for ripple-free torque. This is also the main problem that should be solved in all AC motors including induction motor to achieve high performance control, and recent papers deal with this problem. In this paper, the novel optimal excitation scheme of brushless permanent magnet motor producing loss-minimized ripple-free torque based on the d-q-0 reference frame is presented including 3 phase unbalanced condition. The optimized phase current waveforms that are obtained by the proposed method can be a reference values and the motor winding currents are forced to track it by delta modulation technique. As a results, it can be shown that the proposed work can minimize the torque ripple by the optimal excitation current for brushless permanent magnet motor with any arbitrary phase back EMF waveform. Simulation and experimental results prove the validity and practical applications of the proposed control scheme.

• Journal of Power Electronics
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• v.17 no.3
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• pp.590-600
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• 2017

This paper presents a ripple-free input current modified interleaved boost converter for high step-up applications. By integrating dual coupled inductors and voltage multiplier techniques, the proposed converter can reach a high step-up gain without an extremely high turn-ON period. In addition, a very small auxiliary inductor employed in series to the input dc source makes the input current ripple theoretically decreased to zero, which simplifies the design of the electromagnetic interference (EMI) filter. In addition, the voltage stresses on the semiconductor devices of the proposed converter are efficiently reduced, which makes high performance MOSFETs with low voltage rated and low resistance $r_{DS}$(ON) available to reduce the cost and conduction loss. The operating principles and steady-state analyses of the proposed converter are introduced in detail. Finally, a prototype circuit rated at 400W with a 42-50V input voltage and a 400V output voltage is built and tested to verify the effectiveness of theoretical analysis. Experimental results show that an efficiency of 95.3% can be achieved.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.199-205
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• 1998

Brushless DC motors have trapezoidal back-EMF waveform. Theoretically it should be fed with rectangular phase current in order to produce torque ripple free. Because it is drived by a voltage source inverter, perfect rectangular phase current can not available and therefore produce torque ripple. In this paper, the torque ripple due to commutation is analyzed and the practical method that can reduce the torque ripple is proposed. Experimental and simulation results show the effectiveness of the proposed method.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.142-145
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• 2001

In this paper the electromagnetic torque developed in IPMSM(Interior Permanent Magnet Synchronous Motor) is analyzed. If flux distributions in the motor are not sinusoidal, a sinusoidal current produces important torque ripple. Torque ripple causes vibration and noise of motors. The optimized current waveforms for ripple free is able to be obtained by analysis of Back-EMF and torque equation. The method to find the optimal current is based on numerical predetermination. In this paper proposes current waveform which can eliminate the torque ripple, and the validity is verified through the simulation.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.831-838
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• 2001

Torque ripple control of brushless DC motor has long been the main issue of the servo drive systems in which the speed fluctuation, vibration and acoustic noise need to be minimized. The vast majority of the methods for suppressing the torque ripple require the Fourier series analysis and either the iterative or least mean square minimization. In this paper, a novel approach based on the d-q-0 reference frame that achieves ripple-free torque control with maximum efficiency is presented. The proposed method optimizes the reference phase current waveforms including even the case of 3-phase unbalanced condition, and the motor winding currents are controlled to track the optimized current waveforms by the delta modulation technique. As a results, the proposed approach provides a simple and yet effectine means for obtaining the optimal motor excitation currents. The validity and applicability of the proposed control scheme are verified through simulations and experimental investigations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1034-1037
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• 2003

Recently in the field of precision positioning device, the contact-free actuators are gaining focuses with their outstanding performances by eliminating mechanical frictions. Th is paper is about the driving algorithm for contact-free linear actuator. The proposed driving algorithm has similar structure of drives of switched reluctance motor and reduces the normal forces and force ripple. The simulation and experiment are executed to verify the proposed method.