• 산업기술연구
• /
• 제32권A호
• /
• pp.115-118
• /
• 2012

Recently, there are a lot of papers in order to replace the electrolytic capacitor into the film capacitor in output of PFC(Power Factor Correction). However, the film capacitor, which has capacitance of low values, causes a large ripple voltage in output of PFC. The LED drivers are connected series in the output of PFC and affected by the magnitude of voltage ripple. In this paper, we have compared the fixed frequency method with the variable frequency for the constant-current control and propose the control method to avoid the sub-harmonic oscillation in the variable input voltage. An 80W PFC, using film capacitors instead of electrolytic capacitors, and LED driver has been built and compared the fixed frequency control method with the variable frequency control method.

• 전력전자학회논문지
• /
• 제16권3호
• /
• pp.258-265
• /
• 2011

본 논문은 다이어프램의 공기압력을 제어하기 위한 가변 주파수 전류 제어기를 제안한다. 제안된 제어기는 기존의 다이어프램의 공기압력을 제어하는 방법과는 달리 단상 인버터를 이용하여 상 전류와 주파수를 제어한다. 한 상의 전류는 다이어프램의 지령 공기 압력을 추종하도록 조절되고, 전류 주파수는 기계적인 진동을 줄이기 위해 변화한다. 일정한 공기압력으로 부드럽게 변화하기 위해서 전류 주파수는 전류 제어기에서 제어전압에 따라 제어되며, 이 때의 상전류가 일정한 공기압력에 만족하게 되면 전류주파수는 다이어프램의 진동을 줄이기 위해 증가된다. 제어 전압에 의한 상 전류가 지령값보다 높게 되면 전류 주파수는 공기압력을 추종하기 위해 감소된다. 제안된 제어방식은 상용 다이어프램을 이용한 실험을 통해 확인하였다.

• Journal of Power Electronics
• /
• 제14권2호
• /
• pp.302-314
• /
• 2014

Due to advancements in power electronics and inverter topologies, the current controlled multilevel voltage-source pulse width modulated (PWM) inverter is usually preferred for accurate control, quick response and high dynamic performance. A multilevel topology approach is found to be best suited for overcoming many problems arising from the use of high power converters. This paper presents a comprehensive review and comparative study of several current control (CC) techniques for multilevel inverters with a special emphasis on various approaches of the hysteresis current controller. Since the hysteresis CC technique poses a problem of variable switching frequency, a ramp-comparator controller and a predictive controller to attain constant switching frequency are described along with its quantitative comparison. Furthermore, various methods have been reviewed to achieve hysteresis current control PWM with constant switching frequency operation. This paper complies various guidelines to choose a particular method suitable for application at a given power level, switching frequency and dynamic response.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 A
• /
• pp.525-527
• /
• 1996

Hysteresis current control is one of the simplest techniques used to control currents for high speed drive systems, because of its simplicity of implementation, fast current control response, and inherent peak current limiting capability. However the conventional fixed-band hysteresis control has a variable switching frequency throughout the fundamental period, and consequently the load current harmonics spreaded on the wide frequency range. In this paper, a simple, novel alterative approach is proposed for a variable-hysteresis band current controller which uses feedback techniques to achieve constant switching frequency with good dynamic response. The method is easily implemented in hardware, the resultant controller is easily tuned to a particular load, and has good immunity to variation in PV parameter and dc supply voltage.

• 조명전기설비학회논문지
• /
• 제29권7호
• /
• pp.38-46
• /
• 2015

This paper propose a variable parameter estimations for variable over current load of five-phase squirrel-cage induction motor(IM) to servo control system. In order to high performance control of AC motor using a field oriented control(FOC) and direct torque control(DTC) algorithm, there are required precise motor parameters for slip calculation, flux observer, controller gain, torque command of current components, rotor position, speed estimation, and so on. We are suggest a analyzed estimation results of the motor parameters that developing five-phase squirrel-cage IM have a stator of concentrated winding for experimental within variable over current load at rated input frequency. There are results of stator winding measurement, no-load test, locked-rotor test, variable over current load test, and estimated parameters of equivalent circuits using manufactured experimental apparatus by IEEE Standard Test Procedure for Polyphase Induction Motors and Generators 112-2004.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
• /
• pp.233-233
• /
• 2000

Direct torque control (DTC) scheme provides a very quick torque response without the complex field-orientation block and inner current regulation loop. DTC is known as an appropriate scheme for high power induction motet drives because it can be used at lower switching frequency. There are two major drawbacks with the application of DTC schemes : one is large current harmonics due to flux drooping in a low speed range, the other is that the inverter switching frequency is varying according to motor parameters and operating speed. Switching devices in the power electronics drives should be supported for relatively high switching frequency. In this paper, a P-type fuzzy controller to realize the variable switching sector scheme and a PID-type fuzzy switching frequency regulator are adopted. A meaningful contribution of this paper is to propose a simple realization scheme of the fuzzy switching frequency regulator. Simulation results show the effectiveness of those propositions.

• 전기의세계
• /
• 제17권3호
• /
• pp.29-38
• /
• 1968

The development of the frequency converter using semiconductor enables to easily control the speed of A.C. motors. It is now technically possible and economically feasible to provide them with power at variable frequency, using silicon-controlled-rectifier (or thyristor) inverters. In such a case, if an induction motor is to be operated efficiently over a wide speed range, it must be supplied from a variable-frequency source whose frequency is adjustable over a range similar to that required for the motor speed. It is desired to observe how several characteristics are changed such as primary current, torque-speed, etc. Although the characteristics could be obtained by means of the conventional method, it requires very complicated calculation. It is assumed that the charateristics above are easily investigated by means of current diagram method from variable circuit constants relating to the motor which is designed in rated frequency. In this paper, the results of the study on the current-diagram method and its application are described as follows; (1) In order to discuss the construction of current diagram, the equation of the stator current with adjustable frequency was derived for applying the Current Diagram Method. (2) The radius, the center of the current circle and current vector locus at any desired frequency could be easily determined with the aid of both above mentioned equation and the standard current diagram at reference frequency. (3) This method could be applicable to the various types of Induction Motors, and this paper has dealt with its application to the capacitor, split-phase and 2-phase types of motors.

• Journal of Advanced Marine Engineering and Technology
• /
• 제29권1호
• /
• pp.132-139
• /
• 2005

This paper describes the application of sliding mode control based on the variable structure control(VSC) concept for high-performance position control of an induction servo motor A design method based on external load parameters has been developed for the robust control of AC induction servo drive. Also, a slip frequency vector control with software current control technique has been adopted to achieve fast response of an induction motor drive The position control scheme is comprised of a variable structure controller and slip frequency vector control for inverter fed induction servo motor. Simulated results are given to verify the proposed design method by adoption of sliding mode and show robust control for a change of shaft inertia, viscous friction and torque disturbance.

• Journal of Electrical Engineering and Technology
• /
• 제10권6호
• /
• pp.2307-2314
• /
• 2015

In this paper, a discontinuous conduction mode (DCM) frequency control algorithm is proposed to reduce the input current ripple of a multi-phase interleaved boost converter. Unlike conventional variable duty and constant frequency control, the proposed algorithm controls the switching frequency to regulate the output voltage. By fixing the duty ratio at 1/N in the N-phase interleaved boost converter, the input current ripple can be minimized by ripple cancellation. Furthermore, the negative effects of the diode reverse recovery current are eliminated because of the DCM characteristic. A frequency controller is designed to employ the proposed algorithm considering the magnetic permeability change. The proposed algorithm is analyzed in the frequency domain and verified by a 600 W three-phase boost converter prototype that achieved 57% ripple current reduction.

• 전력전자학회논문지
• /
• 제21권2호
• /
• pp.168-174
• /
• 2016

In this paper, current control using PI controller in the synchronous reference frame is analyzed through the relationship among bandwidth, resonance frequency, and sampling frequency in the grid-connected inverter with LCL filter. Stability is investigated by using bode plot in frequency domain and root locus in discrete domain. The feedback variable is the grid current, which is regulated by the PI controller in the synchronous reference frame. System delay is modeled as 1.5Ts, which contains computational and PWM modulator delay. Two resonance frequencies are given at 815 Hz and 3.16 kHz from LCL filter parameters. Sufficient phase and gain margins can be obtained to guarantee stable current control, in case that resonance frequency is above one-sixth of the sampling frequency. Unstable current control is performed when resonance frequency is below one-sixth of the sampling frequency. Analysis results of stability from frequency response and discrete response is the same regardless of resonance frequency. Finally, stability of current control based on theoretical analysis is clearly verified through simulation and experiment in grid-connected inverters with LCL filter.