• 전기학회논문지
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• 제63권4호
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• pp.484-489
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• 2014

Three phase PWM(Pulse Width Modulation) converter of the small-scale wind power system is able to charge battery under the rated wind speed regions. However, it is impossible to control output power of converter at the over win speed region because back-EMF(Electro Motive Force) of PMSG(Permanent Magnet Synchronous Generator) is higher than the battery terminal voltage of PMSG is reduced. However, the cut-off wind speed exists although battery charging algorithm is implemented by flux weakening control method. Therefore, this paper performs analysis of other factors which affects limitation wind speed. The validity of the analysis are verified through simulation.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권4호
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• pp.517-524
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• 2012

The operation of linear oscillating system is complicated, involving system nonlinearities of both actuator and load, and variations of driving frequency in order to track the mechanical resonance. In this paper, both analytical and state-variable modeling techniques are used to investigate the influence of actuator parameters, such as back-emf/thrust force coefficient and cogging force, on the performance of linear oscillating systems. Analytical derivations are validated by simulations, and good agreements are achieved. The findings of the paper can greatly facilitate the design and evaluation processes of permanent magnet linear actuators.

• Journal of Magnetics
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• 제19권1호
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• pp.90-100
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• 2014

Position estimation that uses only active phase voltage and current is presented, to perform high accuracy position sensorless control of a SRM drive. By extracting the amplitude of the first switching harmonic terms of phase voltage and current for a PWM period through Fast Fourier Transform (FFT), the flux-linkage and position are estimated without external hardware circuitry, such as a modulator and demodulator, which result in increased cost, as well as large position estimation error, produced when the motional back EMF is ignored near zero speed. A two-phase SRM drive system, consisting of an asymmetrical converter and a conventional closed-loop PI current controller, is utilized to validate the performance of the proposed position estimation scheme in comprehensive operating conditions. It is shown that the estimated values very closely track the actual values, in dynamic simulations and experiments.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.100-109
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• 2017

This paper proposes performance improvement schemes for sensorless PMSM control drive using a four-switch three-phase inverter (so-called B4 inverter). In the proposed scheme, the back-EMF estimation-based sensorless control algorithm is used to control the brushless PMSM without position sensors. In order to have stable operation, this paper presents a gain adjustment scheme that compensates the reduction of stable sensorless operation range as long as the rotor speed increases. In B4 topology, the center point of dc-link capacitors is connected to 3-phase load, and it is prone to have the load current distortion. Hence, to mitigate this problem, a distortion compensation scheme by modifying voltage commands using measured dc-link potentials is proposed in this paper. The validity of the proposed method is evaluated by simulations and experiments.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.119-120
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• 2016

회전자 자속기준 벡터제어(FOC)의 센서리스의 기법은 다양하지만, 크게 역기전력을 이용하는 방식과 인덕턴스를 기반으로 하는 방식으로 나눌 수 있다. 역기전력을 기반으로 하는 기법은 중속이상의 영역에서는 뛰어난 성능을 보이지만, 저속영역에서 역기전력이 작기 때문에 저속에서 불리함이 있다. 반면, 인덕턴스를 기반으로 하는 기법 중 캐리어 신호를 주입하는 기법은 전동기의 자기적 돌극성(Magnetic saliency)을 이용하므로 저속에서도 사용가능하지만, 고속에서는 전압제한으로 인하여 전압주입에 불리함이 있으며, 고주파잡음의 문제가 있다. 따라서 본 논문은 저속영역에서 사각파 형태의 고주파 주입 센서리스기법을 사용하고, 중속이상의 영역에서 역기전력 센서리스기법으로 절환(Crossover)하는 방식을 제안한다. 기존의 속도추정 기법과 제안하는 기법을 시뮬레이션을 통해 비교한다.

• Journal of Electrical Engineering and Technology
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• 제4권3호
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• pp.370-376
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• 2009

The influence of magnetic saturation on electromagnetic field distribution in both a permanent-magnet direct-current (PMDC) motor and a field-winding (wound-field) direct-current (FWDC) motor, with the same output mechanical power, has been studied. In this paper, an approximate analytical method and time-stepping Finite Element Method (FEM) are used for prediction of Back-EMF and electromagnetic torque. No-load and rotor-lucked conditions, according to experimental measurements, and the FEM and analytical method studies of the motors have been considered. A sensitivity analysis has also been successfully accomplished on the major design parameters that affect motor performance. At last, these two DC motors are compared, in spite of their differences, on the basis of measured output characteristics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.171-174
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• 1991

Among the various PWM methods, the hysteresis-band current control PWM method is popularly used because of its simplicity of implementation, fast response characteristics and inherent peak current limiting capability. However, the current control PWM method with a fixed hysteresis-band has the disadvantage that switching frequency decreases and current ripple is high as the increasing of back-EMF. As a result, load current contains excess harmonics. This paper describes a adaptive hysteresis-bandwidth control algorithm so as to maintain the average switching frequency constant and decrease the current ripple where the hysteresis bandwidth is derived as a relation with the switching frequency. This control algorithm is applied to the surface-type brushless DC motor with separated winding and using the computer simulation, the validity of its algorithm is proved.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.170-172
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• 2006

This paper proposes a design method by varying rotor pole shape to reduce cogging torque, torque ripple and harmonics of back emf in Spoke type brushless DC(BLDC) motor. In the process of design and analysis, Response surface method(RSM) and finite-element method(FEM) are employed to get the rotor geometry and verify the results of new pole shape.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.194-196
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• 2006

This paper deals with design of a small-scaled permanent magnet generator (PMG) for wind power applications. First, this paper determines rated power and rated speed of the PMG from measured characteristics of wind turbines. Second, we derive analytical solutions for the open-circuit field in order to determine optimum magnet thickness and pole pitch/arc ratio. Third, on the basis of open circuit field solutions, stator magnetic circuit is designed. And then, a diameter of stator coil which agree with a required current density is calculated, and its turns are determined from the area of slot. Finally, finite element (FE) method is employed for validity of the designed PMG and, the back-emf measurements are also given to confirm the design.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.124-126
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• 2006

In this paper, a synchronous permanent magnet planar motor (SPMPM) with new permanent magnet array is proposed and the magnetic field distribution is obtained analytically by using magnetic scalar potential. Compared to those of Asakawa, Chitayat and experimental data, the superiority and feasibility of the novel magnet array are verified. The characteristics of the synchronous permanent magnet planar motor with this novel magnet array such as inductance, back-EMF, and force are calculated by analytical method.