• The Transactions of the Korean Institute of Power Electronics
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• v.1 no.1
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• pp.38-46
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• 1996

The commutation operation of the current source converter for switched reluctance motor drives is analyzed in this paper. The commutation operation in the current source converter consists of two modes. At turn-off of phase switch, the phase current decreases sinusoidally, and the sum of two phase currents during commutation period is constant. At this time, the capacitor voltage increases quickly with changing polarity and decreases slowly when another phase switches turn on or off. Frequency of step-down DC chopper in the current source converter is low because of the dump such as BJTs and GTOs are possible as phase switches instead of Power MOSFET and IGBTS. They may result in reductions of conduction losses and manufacturing cost in the current source converter comparing to the voltage source converter of SRM.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.4
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• pp.306-314
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• 2012

In case of the conventional DC-AC inverter using two DC-DC converters with unipolar output capacitor voltages, for generating the AC output voltage, the output capacitor voltages of its each DC-DC converter must be higher than the DC input voltage. To solve this problem, this paper proposes a single-phase DC-AC inverter using two embedded Z-source converters with bipolar output capacitor voltages. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. The AC output voltage is obtained by the difference of the output capacitor voltages of each converter. Though the output capacitor voltage of converter is relatively low compared to the conventional method, it can be obtained the same AC output voltage. Moreover, by controlling asymmetrically the output capacitor voltage, the AC output voltage of the proposed system is higher than the DC input voltage. To verify the validity of the proposed system, a DSP(TMS320F28335) based single-phase embedded Z-source DC-AC inverter was made and the PSIM simulation was performed under the condition of the DC source 38V. As controlled symmetrically and asymmetrically the output capacitor voltages of each converter, the proposed inverter could produce the AC output voltage with sinusoidal waveform. Particularly, in case of asymmetric control, a higher AC output voltage was obtained. Finally, the efficiency of the proposed system was measured as 95% and 97% respectively in case of symmetric and asymmetric control.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.356-362
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• 2015

This paper presents a current control strategy in the synchronous reference frame for a single-phase PWM converter, which ensures sinusoidal input current control under the distorted source voltage and frequency condition. Given that the distorted source voltage distorts the phase angle for PWM converter control, the input current contains the same harmonics as the source voltage. Aside from the distorted voltage, the variation in source frequency reduces the performance of input current control. To achieve sinusoidal input current control under the distorted source voltage and frequency condition, this paper proposes a compensation strategy of current reference with the distortion component extracted from the phase angle and a detection strategy of frequency variation from the output of a synchronous reference frame phase-lock loop. The experimental results confirm the validity of the proposed method under the distorted source voltage and frequency condition.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.79-80
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• 2014

Voltage source multilevel module converter attracts more and more attention recently. The core component of the voltage source multilevel module converter is the valve based on IGBT. So the test circuit for the valve is very important, reliable test method can guarantee the converter valve design meet the operation requirement. This paper analyzes the valve voltage and current stress during the operation, and according to IEC standard test requirement, object, condition, introduces a kind of test circuit. Finally, through the simulation model, to verify the test circuit can provide the proper test condition for the voltage source multilevel module converter valve.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.144-146
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• 1998

In this study Dead time equivalent resistance of Voltage source power converter is very important in current controller design. And Non-linear Modeling method can be applied in Power converter analysis. Using Describing Function method and Non-linear Resistance Modeling. Voltage Source Power Converter Bode diagram and Current controller analysis method are more reality.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.190-196
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• 2013

It presents a unification of buck-boost and flyback converter for driving a cascaded H-bridge multilevel inverter with a single independent DC voltage source. Cascaded H-bridge multilevel inverter is useful to make many output voltage levels for sinusoidal waveform by combining two or more H-bridge modules. However, each H-bridge module needs an independent DC voltage source to generate multi levels in an output voltage. This topological characteristic brings a demerit of increasing the number of independent DC voltage sources when it needs to increase the number of output voltage levels. To solve this problem, we propose a converter combining a buck-boost converter with a flyback converter. The proposed converter provides independent DC voltage sources at back-end two H-bridge modules. After analyzing theoretical operation of the circuit topology, the validity of the proposed approach is verified by computer-aided simulations using PSIM and experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.748-755
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• 2009

This paper proposes a 18-step back-to-back voltage source converter using four sets of 3-Level converter module with auxiliary circuit to increase the number of steps. The proposed back-to-back voltage source converter has an independent control capability of active power and reactive power at the interconnected ac system. The operational feasibility of proposed system was verified through computer simulations with PSCAD/EMTDC software. The feasibility of hardware implementation was verified through experimental results with a scaled hardware model. The proposed back-to-back converter can be widely applied for interconnecting the renewable energy source to the power grid.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.407-408
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• 2015

The existing (q)Z-source PWM AC-AC converters have limited voltage gain because of the equivalent series resistance in the Z-source inductor. In order to obtain higher voltage gain than (q)Z-source AC-AC converters, a coupled inductor (or transformer) based Z-source AC-AC converter is proposed in this paper. By increasing turns ratio of the coupled inductor more than 1, the proposed converter can obtain higher output voltage than (q)Z-source converters with the same duty ratio. A 120 W prototype AC-AC converter is built and tested to verify performances of the proposed converter.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.8
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• pp.836-846
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• 1990

This paper presents a Static Var Compensator (SVC) system compensating the reactive power for power system, which consists of a voltage type Pulse Width Modulation (PWM) converter and a reactance linking the converter to the source. The system drives the four quadrant modes. The system determines the magnitude of the input voltage, and then compares it with the magnitude of the source voltage by regulating the phase of the SVC about the source. Therefore, the system generates leading compensation currents when the input voltage is larger than the source in magnitude, and lagging compensation currents for smaller input voltage. Reactive power about voluntary load in power system is smoothly compensated by those compensation currents, and also power factor of source is improved. Furthermore, the SVC system using PWM method may improve the source current waveforms by eliminating the 5th and 7th harmonic components from the input voltages.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.358-366
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• 2014

This paper proposes a quasi Z-source AC-AC converter with the low DC voltage distribution capability operating as a power electronic transformer. The proposed system has configuration that the input terminals of two quasi Z-source AC-AC converters are connected in parallel, also their output terminal are connected in series. Simple control method of duty ratio was proposed for the in phase buck-boost AC voltage mode and the DC output voltage control. DSP based experiment and PSIM simulation were performed. As a result, the PSIM simulation results were same with the measured results. By controlling the duty ratio under the condition of 100 [${\Omega}$] load, quasi Z-source AC-AC converter could buck and boost the AC output voltage in phase with the AC input voltage, and the same time, the constant DC voltage could be output without affecting the AC output characteristics. And, the DC output voltage 48[V] was constantly controlled in dynamic state in case while the load is suddenly changed ($50[\Omega]{\rightarrow}100[\Omega]$). From the above result, we could know that the quasi Z-source AC-AC converter can act as a power electronic transformer with a low DC voltage distribution capability.