• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.534-537
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• 1997

Solar power systems have become popular in the modem electric energy system. In order to supply the DC power, generated by solar cells, to the electric power system, the solar power system requires DC-to-AC power conversion. A line-commutated inverter or a forced-commutated inverter can be used in the DC-to-AC power conversion. Because of the nonlinear V-I characteristics of the solar cells, multiple operating points determined by the control mode of the inverter exist in the DC V-I state plane of the solar power system. In this paper, the stability of utility-interactive solar power system with a line-commutated inverter is analyzed at various operating points, using the eigenvalue method and the state-plane analysis technique. The stability of a forced-commutated inverter case is also anaiyzed and compared to that of the line-commutated inverter case.

• 전력전자학회논문지
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• 제22권3호
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• pp.256-262
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• 2017

This paper presents the control algorithm of a single-phase AC/DC/AC PWM converter for the linear compressor of a refrigerator. The AC/DC/AC converter consists of a full-bridge PWM converter for the control of the input power factor and a half-bridge PWM inverter for the control of the single-phase linear compressor. At the DC-link of this topology, two capacitors are connected in series. These DC-link voltages must be balanced for safe operation. Thus, a new control method of DC voltage balancing for the half-bridge PWM inverter is proposed. The balancing algorithm uses the Integral-Proportional controller and inserts the DC-offset current at the Proportional-Resonant current controller of the inverter to solve the DC-link unbalanced voltages between the two capacitors. The proposed algorithm can be easily implemented without much computation and additional hardware circuit. The usefulness of the proposed algorithm is verified through several experiments.

• 조명전기설비학회논문지
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• 제28권8호
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• pp.82-89
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• 2014

The industrial products to use single phase inverter are raised the necessity of power quality improvement, such as AC Motor Driver, Lighting, Renewable energy power converter. Also, it is increasing that applied the single phase multilevel inverter for high quality power at renewable energy power converter. Especially, the photovoltaic multilevel inverters have at least more than two DC_Link and more than one DC/DC Converter. This paper proposes a triple output DC/DC Converter with one switch for photovoltaic multilevel inverter. The proposed converter has advantages of low cost and volume because it has one switch. The operation principle of the converter is analyzed and verified. A prototype is implemented to verify of the proposed converter.

• 전력전자학회논문지
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• 제19권5호
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• pp.422-430
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• 2014

This study proposes a small-signal model and control design for a two-stage DC-DC-AC converter to investigate its dynamic characteristics in relation to battery energy storage system. When the circuit analysis of the two-stage DC-DC-AC converter is attempted simultaneously, the mathematical procedure of deriving the dynamic equation is complex and difficult. The main idea of modeling the two-stage DC-DC-AC converter states that this topology is separated into a bidirectional DC-DC converter and a single-phase inverter with an equivalent current source corresponding to that of the inverter or converter. The dynamic equations for the separated converter and inverter are then derived using the state-space averaging technique. The procedures of building the small-signal model of the two-stage DC-DC-AC converter are described in detail. Based on the derived small-signal model, the individual controllers are designed through a frequency-domain analysis. The simulation and experimental results verify the validity of the proposed modeling approach and controller design.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.19-21
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• 2006

This paper presents the control method that inverter output keeps to linear to reference voltage of Synchronous Reluctance Motor using DC Link voltage Synthesis. The Inverter output voltage cannot be displayed to linear about inverter reference voltage if Real DC Link voltage is different from DC Link voltage of PWM amplitude. Also, the overmodulation that there is linearity broken if reference voltage is out of range that inverter can output voltage. Torque ripple generates the vibration and noise of a motor. This paper proposes the control method so that torque ripple decreases and the linearity of inverter output keeps using the DC Link voltage Synthesis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1161-1165
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• 2004

The fundamental digital control of utility-connected PV inverter are presented with detailed analysis and simulation and experimental results. PLL controller using virtual two phase detector, current controller of DC-DC converter, dc link voltage controller and inverter current controller are discussed. The novel PLL controller using virtual two phase detector can detect the information of utility voltage instantaneously and is not sensitive to the noise. Current controller of DC-DC converter, dc link voltage controller and inverter current controller are the conventional methods. We have constructed utility-Connected PV Inverter and applied to those controllers. The simulation and experimental results demonstrate an excellent performance in the single-phase grid-connected operation.

• 전기학회논문지
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• 제60권6호
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• pp.1152-1162
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• 2011

In this paper, a single-phase DC-AC inverter using two embedded Z-source converters is proposed. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. The output AC voltage of the inverter is obtained by the difference of output capacitor voltages of each converter. The output voltage of each converter take shape of the asymmetrical AC waveform centering zero voltage. Therefore, the proposed inverter can generate the same output voltage despite low VA rating L-C elements, compared to the conventional inverter using high DC voltage with AC ripple. To verify the validity of the proposed system, the PSIM simulation was achieved under the condition of rapid increase of DC source (110[V]${\rightarrow}$150[V]) and R-load (50[${\Omega}$]${\rightarrow}$300[${\Omega}$]). For controlling the voltage of the inverter system, the one-cycle controller was adopted. As results, the proposed inverter output the constant AC voltage (220[V]rms/60[Hz]) for all conditions. Also, the R-L load and nonlinear diode load were adopted for the proposed inverter loads, and we could know that the its output voltage characteristics were as good as the pure R-load. Finally, the RMS and THD of output AC voltage were examined for the different loads, input DC voltages and reference voltage signals.

• Journal of Power Electronics
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• 제18권4호
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• pp.1067-1074
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• 2018

This paper presents a control method for variable-speed motor drives that do not use a DC-link electrolytic capacitor. The proposed circuit consists of a power factor correction converter for boosting the DC-link voltage, an inverter for driving the motor, and a small DC-link film capacitor. By employing a small DC-link capacitor, the proposed circuit that is small, and a low cost and weight are achieved. However, because the DC-link voltage varies periodically, the control of the circuit is more difficult than that of the conventional method. Using the proposed control method, an inverter can be controlled reliably even when the capacitance of the DC-link capacitor is very small. Experiments are performed using a 1.5-kW inverter with a $20-{\mu}F$ DC-link capacitor, and the experimental results are analyzed thoroughly.

• 전력전자학회논문지
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• 제5권2호
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• pp.170-175
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• 2000

삼상 소프트 스위칭 응용을 위한 새로운 유사병렬 공진형 DC-link 인버터를 제안한다. 제안된 인버터의 기존의 공진형 인버터의 단점인 전압 Stress와 PWM 제한 문제를 단지 하나의 추가 스위칭 소자를 사용하여 해결할 수 있다. 본 논문에서는 제안된 인버터의 동작모드 분석을 통하여 회로의 동작을 자세히 설명하고 공진소자의 설계방법을 제안한다. 마지막으로 실험을 통하여 제안된 인버터의 타당성을 검증한다.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.216-225
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• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.