• 한국태양에너지학회:학술대회논문집
• /
• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
• /
• pp.325-330
• /
• 2012

A single-phase PVPCS(photovoltaic power conditioning system) that contains a single phase dc-ac inverter tends to draw an ac ripple current at twice the out frequency. Such a ripple current may shorten passive elements life span and worsen output current THD. As a result, it may reduce the efficiency of the whole PVPCS system. In this paper, the ripple current propagation is analyzed, and two methods to reduce the ripple current are proposed. Firslyt, this paper presents notch filter with IP voltage controller to reject specific current ripple in single-phase PVPCS. The notch filter can be designed that suppress just only specific frequency component and no phase delay. The proposed notch filter can suppress output command signal in the ripple bandwidth for reducing output current THD. Secondly, for reducing specific current ripple, the other method is feed-forward compensation to incorporate a current control loop in the dc-dc converter. The proposed notch filter and feed-forward compensation method have been verified with computer simulation and simulation results obtained demonstrate the validity of the proposed control scheme.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2000년도 전력전자학술대회 논문집
• /
• pp.317-320
• /
• 2000

This paper proposes a voltage compensation method to improve the control performance of B4 inverter which is studied for low-cost drive systems. The B4 inverter employs only four switches and it has a center-tapped connection in the split dc-link capacitors to one phase of a three-phase motor. In the B4 topology unbalan-cd three-phase voltages will be generated by the dc link voltage ripple. To solve this problem we present a voltage compensation method which adjusts switching times considering dc link voltage ripple. The proposed method is verified by simulation results,

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2005년도 전력전자학술대회 논문집
• /
• pp.572-574
• /
• 2005

In this paper, a compensation scheme for the effect of dc-link ripple voltages on output voltage of two-leg and three-phase PWM inverters is proposed, without which compensation scheme the three-phase output voltage and current are much distorted. The proposed scheme has been verified by experimental results.

• 전력전자학회논문지
• /
• 제9권3호
• /
• pp.195-202
• /
• 2004

본 연구에서는 Brushless DC Motor의 전환구간에서 토크리플 저감을 위한 전류제어 기법을 제안하였다. 전환구간에서 토크리플은 증가하는 전류의 변화율과 감소하는 전류의 변화율이 같지 않음에 주원인이 있고, 실제 역기전력의 모양에 의해서도 영향을 받는다. 이에 제안된 제어기법은 전환하는 전류들의 변화율을 같게 하는 실제 역기전력이 고려된 보상전압을 추하고, 전환구간동안에만 보상전압을 인가함으로써 토크리플을 줄이는 것이다. 시뮬레이션과 실험 결과는 제안된 방법이 토크와 전류의 리플을 현저히 줄일 수 있음을 보여준다.

• 한국정밀공학회지
• /
• 제34권4호
• /
• pp.265-272
• /
• 2017

Velocity ripple in manufacturing processes reduces productivity and limits the precision of the product. In practice, the frequency and phase of velocity ripples always change minutely, which makes it impossible to compensate for the ripple by simply inserting an opposite feed-forward signal in the system. In this study, an active-phase compensation algorithm was developed to enable the velocity-ripple controller to track the phase change of the ripples in real time. The proposed controller can compensate for the velocity ripple whatever its cause, including disturbance by the torque ripple. The algorithm consists of three functional modules: the velocity-ripple extractor, the synchronized integrator, and the phase shifter. Experimental results showed that the proposed controller clearly reduces velocity ripples with phase variation.

• 한국정밀공학회지
• /
• 제22권12호
• /
• pp.51-60
• /
• 2005

This paper describes a robust control scheme for high-speed and long stroke scanning motion of high precision linear motor system consisting of linear motor, air bearing guide and position measurement system using heterodyne interferometer. Nowadays, semiconductor process and inspection of wafer or LCD need high speed and long travel length for their high throughput and extremely small velocity fluctuations or tracking errors. In order to satisfy these conditions, linear motor system are widely used because they have large thrust force and do not need motion conversion mechanisms such as ball screw, rack & pinion or capstan with which the system are burdened. However linear motors have a problem called force ripple. Force ripple deteriorates the tracking performances and makes periodic position errors. So, force ripple must be compensated. To maximize the tracking performance of linear motor system, we propose the control scheme which is composed of a robust control method, Time Delay Controller (TDC) and a feedforward control method, Zero Phase Error Tracking Control (ZPETC) for accurate tracking a given trajectory and an adaptive force ripple compensation (AFC) algorithm fur estimating and compensating force ripple. The adaptive ripple compensation is continuously refined on the basis of tracking error. Computer simulation results based on modeled parameters verify the effectiveness of the proposed control scheme for high-speed, long stroke and high precision scanning motion and show that the proposed control scheme can achieve a sup error tracking performance in comparison to conventional TDC control.

• Journal of Magnetics
• /
• 제22권2호
• /
• pp.266-274
• /
• 2017

In this paper, torques of two motors are compared by Finite Element Analysis (FEA). One has a symmetric rotor structure and the other has an asymmetric rotor structure. The comparison shows that the asymmetric rotor structured motor has reduced torque ripple compared to the symmetric. The torque of the compared motor models was analyzed by separating into magnetic torque and reluctance torque. Through the analysis of torque component separated, it is shown that the magnetic torque and the reluctance torque compensate each other in the motor with the asymmetric structure rotor. Here "compensate" means decrementing the effect of one or more harmonics. It is shown how this compensation appears between the magnetic torque and the reluctance torque by looking into back electro motive force (emf) and the relative permeability distribution of rotor core.

• 조명전기설비학회논문지
• /
• 제27권4호
• /
• pp.8-15
• /
• 2013

This paper proposes a DC-link voltage variation compensation method for a 3-level single phase converter for high-speed trains. Since 3-level NPC(Neutral Point Clamped) type converters have the split DC-link causing the inherent problem of voltage fluctuations in the upper and lower capacitors, reducing the voltage difference between the top and bottom capacitors is required. In this paper, compensation time proportional to the voltage difference is added to PWM switching time to solve the voltage variation. The compensation time is obtained by a PI controller. Simulation results demonstrate the validity of the proposed method.

• 한국정밀공학회지
• /
• 제30권9호
• /
• pp.951-959
• /
• 2013

In order to improve the speed performance of the direct drive mechanical systems, a comprehensive analysis of the velocity ripples of blushless DC motors should be required. Every motor has a certain level of torque ripples when it generates power, and the generated torque ripple also makes the velocity ripples in the final output stage in speed control system. In this paper, a novel algorithm for reducing velocity ripples is proposed based on the modeling of torque ripples for BLDC motors. Various algorithms have been made for torque ripples, but usually they should be installed inside the amplifier logic, result in the difficulties of flexibility for various kinds of torque ripples. The proposed algorithm was developed for being ported in the controller not the amplifier, and it has the capability of the automatic compensation adjustment. The performance of the proposed algorithm was verified by effective simulations and experiments.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.71-73
• /
• 2001

The requirements for higher productivity call for high speed of the machine tool axes. Iron core type linear DC motor is growly accepted for a viable candidate of the high speed machine tool feed unit. LDM, however, has inherent disturbance force components: cogging and force ripple. These disturbance force directly affects the carrage tracking accuracy and must be eliminated or reduced. Reducing motor ripple, this paper adapted the feed forward compensation method. Experiments carried out on the linear motor test setup show that this compensation method is usable in order to reduce the motor ripple.