• Journal of the Korean Solar Energy Society
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• v.32 no.spc3
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• pp.245-254
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• 2012

In photovoltaic system, the characteristics of photovoltaic module such as open circuit voltage and short circuit current will be changed because of cell temperature and solar radiation. Therefore, the boost converter of a PV system connects between the output of photovoltaic system and DC link capacitor of grid connected inverter as controlling duty ratio for maximum power point tracking(MPPT). This paper shows the dynamic characteristics of the boost converter by comparing single-loop and two-loop control algorithm using both analog and digital control. Both proposed compensation methods have been verified with computer simulation to demonstrate the validity of the proposed control schemes.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.1
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• pp.52-60
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• 2005

Generally, a voltage difference or voltage distortion exists between the reference voltage and the practical voltage applied to a motor in a pulse width modulated(PWM) voltage source inverter(VSI). This voltage distortion varies with the operating conditions such as the temperature, DC link voltage, and phase current level. Also the voltage distortion affects the machine current distortion, torque pulsations, and control performance. In this paper, the voltage distortion in a PWM VSI is analyzed and a new on-line estimation method based on the model reference adaptive system(MRAS) is proposed to compensate the time varying voltage distortion, while considering the parameter variations for a permanent magnet synchronous motor (PMSM). The simulation and experimental results show the effectiveness of the proposed voltage difference observer and the compensation method.

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.177-184
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• 2006

In this paper a new dc-link type wind turbine generator system using a shaft generator system, which is widely used for power sources in a ship, is proposed. The basic configuration of the proposed wind turbine generating system is first explained. And the equations expressing the system are derived. Then the steady-state characteristics of the generating system are discussed. We use an experimental system that can simulate the characteristics of a wind turbine in this study, because it is hard to operate an actual wind turbine in a laboratory. In addition, the transient responses of this system are investigated when the velocity of the wind is changed. It is shown that experimental results were very close to the simulated ones, supporting the usefulness of the theory.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.138-145
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• 2015

In this paper, a novel static overmodulation scheme (OVM) for space-vector PWM (SVPWM) is proposed. The proposed static OVM scheme uses the concept of adding offset voltages in linear region as well as overmodulation region to fully utilize DC-link voltage. By employing zero sequence voltage injection, the proposed scheme reduces procedures for achieving SVPWM such as complicated gating time calculation. In addition, this paper proposes a stepwise discontinuous angle movement in high modulation region in order to reduce Total Harmonic Distortion (THD). The validity of the proposed scheme is verified through theoretical analysis and experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1509-1512
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• 2003

The electric power wheelchair needs to control motor torque and speed for responding to variable actions given by handling a joystick. In this paper a DSP-based BLDC motor controller using a single dc-link current sensor is presented for electric power wheelchair. It is composed by a DSP processor and three-phase inverter module. To control torque, high speed current control is achieved by the PI controller and pulse width modulation (PWM) signals with 25 kHz carrier frequency, which is performed by 200 ${\mu}sec$ cycle. The speed controller computes the new direct current reference from the speed error and the PI control equation. The displacement value by handling the joystick is converted to reference speeds of right and left wheel motors using nonholonomic wheelchair kinematics. Experimental results show that the presented control system is enough to implement a speed servo in wheelchair driving.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.297-298
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• 2011

최근 계통연계형 인버터 시스템에서 고 신뢰 운전이 매우 중요한 과제로 대두되고 있다. 특히 인버터의 고장에 관한 많은 연구가 진행되고 있다. 본 논문에서는 계통연계형 인버터에서 직류단 전압 센서의 고장 허용 제어 알고리즘을 제안한다. 직류단 전압의 추정값으로 고장의 발생 시에 허용 제어를 수행한다. 매우 빠른 동특성을 가진 제어기가 요구되는 제안된 알고리즘의 적용을 위해 데드비트 전류제어기를 사용한다. 시뮬레이션을 통해 제안된 알고리즘을 검증한다.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.14-15
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• 2011

본 논문에서는 단상입력을 가지고, 직류단에 소형 캐패시터를 사용하는 인버터를 사용해 3상 전동기 가변속 구동을 한다. 이때 주기적으로 크게 맥동하는 직류단 전압 조건에서 어떻게 전동기를 제어하는가에 대해 언급한다. 평균 전압 제한원을 전류 영역에 표현하고, 새로운 약자속 영역을 정의한다. 이를 바탕으로 전류 지령을 생성하는 제어기를 구성하여 전동기를 제어할 수 있는 기법을 제안하고 이를 실험을 통해 검증한다. 이를 통해 입력 전류의 고조파를 줄여 역율도 개선할 수 있다.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.98-103
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• 2001

In case that electronic ballast employing a valley-fill passive power factor correction (PFC) circuit is used for feeding fluorescent lamps, a new method to reduce crest factor of the lamp current is studied in this paper. In order to reduce crest factor to lower value, a pulse frequency modulation technique based on the waveform of the dc-link voltage which is predetermined by the passive PFC circuit, is taken into the switching control action of the electronic ballast. An equation-based analysis between the crest factor of lamp current and the effect of varying the inverter switching frequency is comprehensively performed.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.291-293
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• 2003

A semiconductor switch-based fast hi-polar high voltage pulse generator is proposed in this paper The proposed pulse system is made of a thyristor based-rectifier, DC link capacitor, a push-pull resonant inverter, a high voltage transformer. secondary capacitor, a high voltage IGBT & diode stacks, and a variable capacitor. The proposed system makes hi-polar high voltage sinusoidal waveform using resonance between leakage inductance of the transformer and secondary capacitor and transfers energy to output load at maximum of the secondary capacitor voltage. Compared to previous hi-polar high voltage pulse power supply using nonlinear transmission line, the proposed pulse power system using only semiconductor switches has simple structure and gives high efficiency

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1392-1393
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• 2011

This paper proposes fuzzy logic control maximum power point tracking(FLC MPPT) of photovoltaic(PV) pump system using IPMSM. Conventional MPPT controller was unstable by reason of the ripple-current of DC link in three phase inverter. Thus in this paper the control algorithm of IPMSM using $i_q$ current is composed to improve the insecurity of conventional MPPT controller. Proposed algorithm is operated by simulation with variation radiation condition. And analyze the response characteristic of IPMSM. The validity of this paper is proved by analyzed data.