• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.924-925
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• 2008

There are many types of grid-connected inverter controllers, PI controller based is the most popular methods. But, a common PI control is produced zero-steady state error and phase delay in sinusoidal reference. Synchronous reference frame or DQ transform based controller is capable for reducing both of zero-steady state error and phase delay is. But DQ transform based controller has cross-coupling component which difficult to analyze the system in single phase model. In this paper, to obtained single phase model of the system, DQ transform based controller is analyzed in two techniques. The first is by neglecting cross-coupling. The second is eliminated cross-coupling component by decoupling method. By these two techniques, single phase model is obtained. Then, the single phase model is analyzed to evaluate its performance in stability and frequency response, through Root Locus and Bode diagram, respectively. MATLAB and PSIM simulation is used to verify the analysis. Simulation result is shown; cross-coupling component has no significant influent to the controller.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1027-1029
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• 2002

UPFC(Unified Power Flow Controller)는 계통의 선로로 전송되는 무효전력과 유효전력을 독립적으로 보상해줄 수 있는 유연송전시스템 기기로, 전력계통 전압 안정화와 위상제어 둥의 목적으로 실용성과 적용성이 뛰어나므로 최근 들어 국내외에서 활발하게 연구 되고 있다. 본 논문에서는 회로 DQ 변환 기법을 적용하여 UPFC를 모델링하고 동작특성 해석한다. 회로 DQ 변환의 결과 정특성 및 동특성을 나타낸는 등가회로를 구할 수 있으며 이로부터 각종 특성식과 설계식을 도출해 낸다. 또한, 제안된 모델링 및 동작특성 해석의 결과의 타당성은 PSIM 시뮬레이션을 통하여 검증한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.517-520
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• 2004

In this paper, a PWM Cuk AC-AC converter is modelled by using complex circuit DQ transformation whereby the equivalent model is obtained which has the complete information of the Cuk converter. Using the model, the dynamicc characteristics equations such as state equations is analytically obtained. Finally, the PSIM simulation show the validity of the modelling and analysis.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.513-516
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• 2004

In this paper, a PWM Cuk AC-AC converter for power quality improvement of custom power is presented. The PWM Cuk AC-AC converter that is used in VVCF applications such as AC line conditioner, phase shifter is modelled by using complex circuit DQ transformation whereby the static characteristics equations such as voltage gain and power factor is analytically obtained. Finally, the PSIM simulation show the validity of the modelling and analysis.

• Structural Engineering and Mechanics
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• v.25 no.2
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• pp.161-180
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• 2007

A first endeavor is made to exploit the differential quadrature method (DQM) as a simple, accurate, and computationally efficient numerical tool for the large deformation analysis of thin laminated composite skew plates, which has very strong singularity at the obtuse vertex. The geometrical nonlinearity is modeled by using Green's strain and von Karman assumption. A recently developed DQ methodology is used to exactly implement the multiple boundary conditions at the edges of skew plates, which is a major draw back of conventional DQM. Using oblique coordinate system and the DQ methodology, a mapping-DQ discretization rule is developed to simultaneously transform and discretize the equilibrium equations and the related boundary conditions. The effects of skew angle, aspect ratio and different types of boundary conditions on the convergence and accuracy of the presented method are studied. Comparing the results with the available results from other numerical or analytical methods, it is shown that accurate results are obtained even when using only small number of grid points. Finally, numerical results for large deflection behavior of antisymmetric cross ply skew plates with different geometrical parameters and boundary conditions are presented.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.1
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• pp.27-32
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• 2006

In this paper, a new scheme of current programmed control for three phase PWM AC-AC converter is presented. Compared to duty-ratio voltage control, current programmed control has several advantages such as reduction of system order, inherent current protection and robust output. By considering only the magnitude components, a similar scheme in the DC-DC converter can be extended to the three phase PWM AC-AC converter. The proposed current programmed control will be well adopted into various converter topologies though three phase PWM AC-AC boost converter is treated as an example. The converter analysis is carried out by applying the vector DQ transformation to obtain physical insight into the converter operation and to establish some important characteristic equations for control purpose. The experiment results show the validity of the proposed scheme.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.820-821
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• 2011

본 논문은 단상 line-start permanent- magnet (LSPM) 전동기가 가지는 비동기 운전영역에서 나타나는 다양한 토크성분을 해석적 방법으로 분석한다. 비 동기속도에서의 정상상태 전류를 DQ 등가회로를 이용하여 유도하였으며, 이를 이용하여 유도전류와 제동전류의 주파수를 확인하였다. 마지막으로 시간차분 해석을 이용하여 비동기 운전영역의 특정 속도에 대한 토크와 전류를 분석하였으며, 주파수 변환을 이용하여 각 전류의 주파수 성분을 확인하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.121-127
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• 2016

We propose a algorithm to calculate power factor of fundamental waveform in an environment where the voltage and current have been distorted by harmonics. In the proposed power factor computation algorithm, voltage and current are converted to rotating DQ reference frame, and power factor is calculated from active power and reactive power. We compare the proposed method with the conventional power factor measurement method as mathematically. In a condition that voltage and current are distorted by harmonics, the proposed method accurately measure the power factor of fundamental wave, and it is confirmed by simulation using MATLAB. If the proposed power factor measurement method is applied to an automatic power factor control system, a power factor compensation performance can be maximized in harmonic distortion environment. As a result, it is possible to reduce electricity prices, reduce line loss, increase load capacity, ensure the transmission margin capacity, and reduce the amount of power generation.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1707-1713
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• 2016

This paper proposes a dc error compensation algorithm using dq-synchronous coordinate transform digital phase-locked-loop in single-phase grid-connected converters. The dc errors are caused by analog to digital conversion and grid voltage during measurement. If the dc offset error is included in the phase-locked-loop system, it can cause distortion in the grid angle estimation with phase-locked-loop. Accordingly, recent study has dealt with the integral technique using the synchronous reference frame phase-locked-loop method. However, dynamic response is slow because it requires to monitor one period of grid voltage. In this paper, the dc offset error compensation algorithm of the improved response characteristic is proposed by using the synchronous reference frame phase-locked-loop. The simulation and the experimental results are presented to demonstrate the effectiveness of the proposed dc offset error compensation algorithm.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.42-45
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• 1997

A synchronous solid-state var compensator(SSVC) system which employs a three-phase neutral-point-darned (NPC) inverter is presented and analyzed for high voltage and high power applications. The proposed SSVC system can compensate for leading and lagging displacement factor. An optimal pulse-width-modulation (PWM) is used as a means of reducing the size of reactive components. A equivalent model is obtained using DQ-transform, and the characteristic of open-loop system are archived from DC and AC analyzes. A $\alpha$ phase-shift control is suggested using a self-controlled dc bus.