• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.85-86
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• 2019

본 논문에서는 DQ 변환을 적용한 직렬-병렬 공진형 무선 전력 전송 시스템의 동기 좌표계 모델을 제안한다. 무선 전력 전송 시스템은 일반적으로 급전 측과 집전 측에 단상 전류가 흐르기 때문에 제어에 어려움이 있다. 따라서 정상 상태의 전압 및 전류의 수식을 이용하여 부하에 전달되는 전압 및 전류의 크기를 제어하는 경우가 많다. 따라서 과도 상태의 전압 및 전류의 동특성이 원하는 특성과 다르게 나타날 수 있다. 본 논문에서는 직렬-병렬 공진형 무선 전력 전송 시스템의 단상 전압 및 전류를 DQ 변환하여 과도 상태 및 정상 상태의 전압 및 전류의 동특성을 해석할 수 있는 등가 회로 모델을 제시한다.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.23-24
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• 2007

Most of modern wind turbines employs a doubly-fed induction generator (DFIG) system because it has many advantages due to variable-speed operation, relatively high efficiency and it small converter size. The DFIG system uses a wound rotor induction machine so that the magnetizing current of the generator can be fed from both the stator and the rotor. This paper presents a protection relaying algorism for DFIG using the DQ equivalent circuits. The induced voltages calculated from the stator and rotor sides are nearly the same in the steady state. They become different in the DQ equivalent circuits during an internal fault. The proposed algorithm compares the inducted voltages estimated from the stator and the rotor circuit converted into the stationary reference frame. If the difference between the induced voltages exceeds the threshold, the proposed algorithm detects an turn-to-turn fault.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.145-146
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• 2019

본 논문에서는 DQ 변환을 적용한 직렬-직렬 공진형 무선 전력 전송 시스템의 동기 좌표계 모델을 제안한다. 일반적으로 무선 전력 전송 시스템의 경우 급전 측과 집전 측에 단상 전류가 흐르기 때문에 제어에 어려움이 있다. 따라서 정상 상태의 전압 및 전류의 수식을 이용하여 부하에 전달되는 전압 및 전류의 크기를 제어하는 경우가 많다. 따라서 과도 상태의 전압 및 전류의 동특성이 원하는 특성과 다르게 나타날 수 있다. 본 논문에서는 직렬-직렬 공진형 무선 전력 전송 시스템의 단상 전압 및 전류를 DQ 변환하여 과도 상태 및 정상 상태의 전압 및 전류의 동특성을 해석할 수 있는 등가 회로 모델을 제시한다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.181-183
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• 2020

본 논문에서는 DQ 변환을 적용한 직렬-병렬 공진형 무선전력 전송 시스템의 동기 좌표계 모델과 이를 이용한 전류제어기 시스템을 제안한다. 무선 전력 전송 시스템은 일반적으로 급전 측과 집전 측에 단상 전류가 흐르기 때문에 제어에 어려움이 있다. 따라서 정상 상태의 전압 및 전류의 수식을 이용하여 부하에 전달되는 전압 및 전류의 크기를 제어하는 경우가 많다. 따라서 과도 상태의 전압 및 전류의 동특성이 원하는 특성과 다르게 나타날 수 있다. 본 논문에서는 직렬-병렬 공진형 무선전력 전송 시스템의 단상 전압 및 전류를 DQ 변환하여 과도 상태 및 정상 상태의 전압 및 전류의 동특성을 해석할 수 있는 등가 회로 모델을 제시하고 이를 이용하여 과도 상태 제어를 위한 고성능 전류 제어기를 제안한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.367-375
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• 2013

The mechanical vibration of a PM synchronous motor at low speeds due to the back emf harmonics may be serious problems in some application such as MDPS(Motor driven power steering), electric vehicles. In this paper, torque ripple reduction for an interior PM synchronous motor including back emf harmonics is proposed. The dq flux linkage harmonics of the permanent magnet are estimated on real time by using the dq currents of the real system and the model of the MRAS observer. Based on the estimated flux linkage harmonics, the dq harmonic currents for reducing the torque ripples are compensated on the dq reference currents. The estimation of the flux linkage harmonics by the MRAS observer and the torque ripple reduction of the proposed algorithm was verified by the simulation and experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.49-58
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• 2009

This paper presents the vector control of single phase induction motor(SPIM) to operate water pumping system using PV system with a maximum power point tracking(MPPT). The water pumping system uses a variable speed SPIM driven a centrifugal pump by field oriented control(FOC) inverter. The MPPT using a DC-DC converter controlled the duty cycle to track maximum power from PV under different insolation conditions. The duty cycle directly relate with a flux producing current control($i_{ds}$). The FOC inverter uses a current control voltage source inverter(CC-VSI). The simulation results are shown that the characteristics and performance of drive system, which varies as each conditions of light by expresses in voltage($V_{dq}$), current($I_{dq}$), speed of motor and torque.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.18 no.2
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• pp.63-74
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• 2014

Objectives The purpose of this study was to survey the current status of use of questionnaires for evaluating Yin Deficiency Syndrome and analyze the comparison with questionnaires. Methods We searched online medical databases to find domestic/international articles using questionnaires for evaluating intensity of Yin Deficiency Syndrome. Finally 18 articles were collected to be reviewed and they were classified according to their subjects and type of the Questionnaires. Results Out of 18 articles, 11 were based on the Yin-Deficiency Questionnaire (Yin-DQ) and the others used various questionnaires, except the Yin-DQ, for assessing Yin Deficiency Syndrome. In Korea the Yin-DQ was used widely but in foreign countries, for instance, China, Taiwan, a variety of questionnaires were used. Conclusion The Yin-DQ had a wider use in assessing Yin Deficiency Syndrome, but cut-off score for diagnostic criteria was not defined. Therefore, we decided that the YDS (Yin Deficiency Scale) with cut-off score was more suitable for screening patients with Yin Deficiency Syndrome. Moreover, we suggested that additional studies on using the YDS and developing more appropriate diagnostic tool should be conducted to improve diagnostic objectivity.

• 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.

• Steel and Composite Structures
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• v.28 no.4
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• pp.509-516
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• 2018

The differential quadrature (DQ) and teaching-learning based optimization (TLBO) methods are coupled to introduce a hybrid numerical method for maximizing fundamental natural frequency of laminated composite skew plates. The fiber(s) orientations are selected as design variable(s). The first-order shear deformation theory (FSDT) is used to obtain the governing equations of the plate. The equations of motion and the related boundary conditions are discretized in space domain by employing the DQ method. The discretized equations are transferred from the time domain into the frequency domain to obtain the fundamental natural frequency. Then, the DQ solution is coupled with the TLBO method to find the maximum frequency of the plate and its related optimum stacking sequences of the laminate. Convergence and applicability of the proposed method are shown and the optimum fundamental frequency parameter of the plates with different skew angle, boundary conditions, number of layers and aspect ratio are obtained. The obtained results can be used as a benchmark for further studies.

• 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.