• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.673-676
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• 2001

The photovoltaic power generation system has a great future as clean energy instead of fossil fuel, which has many environmental problems such as exhausted gas or air pollution. In a utility interactive photovoltaic generation system, a three phase inverter is used for the connection between the photovoltaic array and the utility. This paper presents a three phase inverter for photovoltaic power system with current controller, voltage controller, PLL control system and the phase detector of interactive voltage by using dq transformation. The proposed inverter system provides a sinusoidal ac current for domestic loads and the utility line with unity power factor.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.171-172
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• 2011

The paper proposes a close loop control algorithm for Z-source inverter. The algorithm is realized by PWM duty ratio control in order to improve the output voltage to it's desired level. The controller consist of the output voltage PID controller and DC input voltage P controller. Using the DQ coordinate transformation simplify the controller design. The PSIM simulation results verify the validity by means of comparing the system with or without compensation and estimating if the system has output consistency function when ZSI's load and input voltage value changing.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.573-576
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• 2000

In this paper, analysis of operating characteristics of hybrid cascade multilevel PWM rectifier without bulky and heavy isolation transformers is presented. The multilevel PWM rectifier is analyzed by using the circuit DQ transformation whereby the static and dynamic characteristics and some useful design relationships are obtained. Then, the operating characteristics such as active/reactive power relationships with respect to control variables, DC voltages build up are presented. It will be shown that the DC voltages for the multilevel output generation may be directly built up from AC utility source. Finally, to confirm the validity of the analysis, MATLAB simulations are tarried out.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1664-1672
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• 2015

This paper proposes a series arc fault detection algorithm which incorporates peak voltage and harmonic current detectors for single-phase boost power factor correction (PFC) rectifiers. The series arc fault model is also proposed to analyze the phenomenon of the arc fault and detection algorithm. For arc detection, the virtual dq transformation is utilized to detect the peak input voltage. In addition, multiple combinations of low- and high-pass filters are applied to extract the specific harmonic components which show the characteristics of the series arc fault conditions. The proposed model and the arc detection method are experimentally verified through a boost PFC rectifier prototype operating under the grid-tied condition with an artificial arc generator manufactured under the guidelines for the Underwriters Laboratories (UL) 1699 standard.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.283-286
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• 1988

This paper describes the PWM cycloconverter which can provide step-up ac-ac direct conversion in a wide output frequency range. With input reactor and output capacitor. the input and output ports are exchanged. And sine PWM scheme is applied to the converter. To analyze the converter operation the state equations are derived using dq transformation. Simulated results show that both the output voltage and frequency can be controlled by adjusting the modulating functions.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.231-231
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• 2000

It is proposed that a novel method which can compensate the time delay occurs in overall system, when voltage and current is measured, owing to LPF, hysteresis control inverter and microprocessor program computation time. The Proposed scheme estimates the time delay using the difference between Q-axis stator current command and time delayed Q-axis stator current in synchronous reference frame, and compensates the time delay of voltage and current using angular displacement of DQ transformation. The proposed scheme compensates accurately the time delay occurs in overall system. Therefore performance of vector control system is improved highly and it is verified by simulation and experiment.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.328-335
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• 1999

Three phase full bridge rectifier has been used to obtain dc voltage from three phase ac voltage source. The rectifier system has drawbacks that power factor is low and power flow is unidirectional. Therefore, when dc voltage increases due to regeneration of power the dynamic resister for dissipation of regeneration power must be installed. But three phase PWM converter can be controlled to operate with unity power factor and bidirectional power flow. Therefore when the PWM converter is used as do supply system, the dissipating resistor is not necessary. On this thesis, in order to design a controller having good performance, the hee phase PWM converter is completely modeled by using circuit DQ-transformation and thus a general and simple instructive equivalent circuit is obtained; the inductor set becomes a second order gyrator-coupled system and three phase inverter becomes a transformer as well. Under given phase angle(${\alpha}$) and modulation index(MI) of the three phase inverter, the dc and ac characteristics are obtained by analysis of the transformed equivalent circuit The validity of the equivalent circuit is confirmed through PSPICE simulation. And based on the dc and ac characteristics a controller with unity power factor is proposed.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.79-81
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• 1998

STATCOM can compensate industrial load's reactive power and filter the harmonic of nonlinear load's with the rapid dynamic response. In this paper, STATCOM is modelled to synchronous rotating coordinate by circuit dq transformation, and space vector PWM method is applied for broad voltage modulation. Also predict current controller is used for harmonic current filtering.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1187-1189
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• 2000

This paper presents a high power-hybrid multilevel PWM rectifier with unity power factor. The features and advantages of the proposed PWM rectifier can be summarized as follows; 1) It realizes the high power high voltage AC/DC power conversion. 2) It uses no transformer which is bulky and heavy, 3) It has hybrid structure so that switching devices can be effectively utilized, 4) It produces high quality AC current even in high power high voltage applications, 5) The input power factor remains unity by simple modulation index control. The multilevel rectifier is analyzed by using the circuit DQ transformation whereby the characteristics and control equations are obtained.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.9
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• pp.1239-1246
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• 1995

A forced commutated cycloconverter (FCC) is a direct ac-ac converter capable of providing simultaneous voltage and frequency transformations. In this paper, vector control of an induction motor controlling stator current with forced commutated cycloconverter is presented. The advantage of current control is that the stator dynamics are eliminated and high performance vector control can be achieved. A novel modulation method based on dq transformation techniques is presented. Proposed modulation strategy generates the low frequency modulation function by the instantaneous value of the desired output voltages not by the steady state values of output magnitude and output frequency. PI control and predictive control algorithm for current control are applied, and the validity of proposed method is confirmed through digital simulations. Simulation results of step response and torque distubance and current control are presented.