• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.341-342
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• 2010

본 논문에서는 종전의 3상 H-브리지 PWM 인버터와 다른 토폴로지를 갖는 3상 벅-부스트 DC-AC 인버터를 위한 제어 기법을 제안하였다. 이를 위하여 공간벡터 변조 방식(SVM : Space Vector Modulation) 및 PI 제어기를 벅-부스터 DC-AC 인버터에 적용하고 이를 PSIM 시뮬레이션 통하여 타당성을 검증하였다.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2018-2030
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• 2015

A two stage ac drive configuration consisting of a single-phase line commutated rectifier and a three-phase voltage source inverter (VSI) is very common in low and medium power applications. The deterministic pulse width modulation (PWM) methods like sinusoidal PWM (SPWM) could not be considered as an ideal choice for modern drives since they result mechanical vibration and acoustic noise, and limit the application scope. This is due to the incapability of the deterministic PWM strategies in sprawling the harmonic power. The random PWM (RPWM) approaches could solve this issue by creating continuous harmonic profile instead of discrete clusters of dominant harmonics. Insufficient filtering at dc link results in the amplitude distortion of the input dc voltage to the VSI and has the most significant impact on the spectral errors (difference between theoretical and practical spectra). It is obvious that the sprawling effect of RPWM undoubtedly influenced by input fluctuation and the discrete harmonic clusters may reappear. The influence of dc link fluctuation on harmonics and their spreading effect in the VSI remains invalidated. A case study is done with four different filter capacitor values in this paper and results are compared with the constant dc input operation. This paper also proposes an ingenious RPWM, a ripple dosed sinusoidal reference-random carrier PWM (RDSRRCPWM), which has the innate capacity of suppressing the effect of input fluctuation in the output than the other modern PWM methods. MATLAB based simulation study reveals the fundamental component, total harmonic distortion (THD) and harmonic spread factor (HSF) for various modulation indices. The non-ideal dc link is managed well with the developed RDSRRCPWM applied to the VSI and tested in a proto type VSI using the field programmable gate array (FPGA).

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.131-137
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• 1998

The solar cells should be operated at the maximum power point because its output characteristics are greatly fluctuated on the variation of insolation, temperature and load. Photovoltaic system needs an inverter which can interface the dc output power of solar cell with the residential ac load. The inverter has to supply a sinusoidal current and voltage to the load and the utility line with a high power factor. This paper proposes an utility interactive photovoltaic system designed with a step-up chopper and a PWM voltage source inverter. The step-up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power points of solar cell without any influence on the variation of insolation and temperature. The voltage source inverter operates in a manner that its output voltage is in phase with the utility voltage. The inverter supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.196-198
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• 2007

In the substations for traction systems and the large-scale discharging system of secondary batteries, the voltage of DC bus line goes up by the regenerated energy and the energy is usually wasted in resistor for system stability. This paper proposes the DC power regenerating system using a three phase PWM inverter. The proposed system can regenerate the excessive DC power from DC bus line to AC supply and control the power factor of AC supply to unity. To implement unity power factor, the magnitude of the inverter output voltage should be higher than that of AC supply and therefore SVPWM technique is adopted. Computer simulations are carried out to verify the validity of the proposed system.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1207-1208
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• 2006

Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage 380[VDC] and a PWM inverter with LC filter to convent the DC voltage to single-phase 220[VAC]. Expressly, a tapped inductor filter with freewheeling diode is newly implemented in the output filter of the proposed high frequency isolated ZVZCS PWM DC-DC converter to suppress circulating current under the wide output voltage regulation range, thus to eliminate the switching and transformer turn-on/off over-short voltage or transient phenomena. Besides the efficiency of 93-97[%] is obtained over the wide output voltage regulation ranges and load variations.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.549-553
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• 1999

This paper describes a design method of grid-connected photovoltaic power generation systems with three phase inverter. A 3-phase 50kW photovoltaic power generation system including a DC/AC inverter is designed and made in order to investigate the system performance for grid connection. Also the control scheme of a three phase current-controlled PWM inverter is presented by using d-q transformation. The experimental waveforms show that the proposed system has stable behavior with an unit power factor in utility-interactive operation.

• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.746-748
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• 1987

A volocity and an efficiency of an induction motor are lower than those of a DC motor. But in the control, the utility of an AC motor is more enlarged with the development of inverter. But unfortunately, in using the induction motor, it include a lot of harmonics because of switching of semi-conductor devices(SCR or Tr) in the inverter. In PCR, as the change of a firing angle $\alpha$, harmonics are changed. Hence, in this thesis analyze the harmonics and provide the region of it's application when PWM and 6-step applied to inverter. Of course, frequencies of inverter changed. Especially, in PWM a carrier ratio is changed.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.365-366
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• 2010

본 논문에서는 양방향성 Z-소스 DC-DC 컨버터 2대를 이용한 단상 Z-소스 부스트 인버터를 설계하고 분석하였다. 두 대의 컨버터를 이용한 인버터 시스템은 종전의 PWM 인버터 시스템과 달리 두 컨버터에서 출력되는 두 교류 출력을 이용한 것으로 전체 시스템의 교류 출력전압에 포함된 고조파가 낮다. 또한, 컨버터 내부를 구성하는 L-C로 인해 추가적인 출력필터 설계가 불필요 하다는 장점이 있다. 본 연구에서는 종전의 부스트 컨버터 또는 벅-부스트 컨버터 방식이 아닌 두 대의 Z-소스 DC-DC 컨버터를 입력 DC전원과 출력 부하를 공통으로 하는 단상 인버터 시스템을 구성하고, 교류 출력파형 및 제어방법과 동작특성을 분석하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.2
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• pp.131-138
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• 2007

In this paper, a novel nonlinear control method of the CVCF(constant voltage and constant frequency) output voltage for the three-phase PWM inverter with LC output filters is proposed. A nonlinear modeling including the output LC filters is linearized by feedback linearization theory, the controllers of which can be designed based on a linear control theory. It is applied to the DC/AC power conversion of the PWM inverter for stand-alone wind power generation system. It has been verified by the experimental results that the proposed control scheme gives high dynamic responses at load variation as well as a zero steady-state error.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.408-421
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• 2008

In this paper, the parallel operation for a FC generation system is introduced and designed in order to increase the capacity for the distributed generation of a proton exchange membrane fuel cell (PEMFC) system. The equipment is the type that is used by parallel operated PEMFC generation systems which have two PEMFC systems, two dc/dc boost converters with shared dc link, and a grid-connected dc/ac inverter for embedded generation. The system requirement for the purpose of parallel operated generation using PEMFC system is also described. Aspects related to the mechanical (MBOP) and electrical (EBOP) component, size, and system complexity of the distributed generation system, it is explained in order to design an optimal distributed generation system using PEMFC. The optimal controller design for the parallel operation of the converter is suggested and informative simulations and experimental results are provided.