• Journal of Power Electronics
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• 제14권5호
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• pp.937-945
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• 2014

This paper presents an optimized space vector pulse-width modulation (OSVPWM) technique for a five-level cascaded H-bridge (CHB) inverter. The space vector diagram of the five-level CHB inverter is optimized by resolving it into inner and outer two-level space vector hexagons. Unlike conventional space vector topology, the proposed technique significantly reduces the involved computational time and efforts without compromising the performance of the five-level CHB inverter. A further optimized (FOSVPWM) technique is also presented in this paper, which significantly reduces the complexity and computational efforts. The developed techniques are verified through MATLAB/SIMULINK. Results are compared with sinusoidal pulse-width modulation (SPWM) to prove the validity of the proposed technique. The proposed simulation system is realized by using an XC3S400 field-programmable gate array from Xilinx, Inc. The experiment results are then presented for verification.

• 대한전자공학회논문지SP
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• 제48권2호
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• pp.141-148
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• 2011

Support vector machine (SVM)은 패턴인식 분야에 많이 사용되어지고 있다. 한 예로서 3GPP2 selectable mode vocoder (SMV)와 같은 규격화된 코덱에 쓰여 코덱의 음성/음악 분류 성능을 향상시킬 수 있다. 본 논문에서는 SVM을 개선시켜 음성/음악의 분류성능을 향상시키는 새로운 방법을 제안한다. SVM을 학습시킬 때 적용되는 기존의 기법들과는 달리 제안되는 기법은 SVM이 패턴분류를 행할 때 사용된다. 그렇기 때문에 기존의 기법들과 독립적으로 개발되고 사용될 수 있고, 따라서 패턴분류의 성능을 한층 더 향상시킬 수 있다. 이를 위해 먼저 radial basis function의 커널 width 파라미터가 SVM의 패턴분류에 미치는 영향을 분석해 보았다. 분석한 결과, 커널 width 파라미터를 가지고 SVM의 패턴분류 성향을 미세 조정할 수 있다는 것을 알았다. 또한 음성신호의 각 프레임 간의 상관관계 (correlation)을 확인하고 이를 커널 width 파라미터조절의 길잡이로 삼았다. 실험을 통해, 제안된 기법이 SVM의 성능을 향상시킬 수 있음을 증명하였다.

• 산업경영시스템학회지
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• 제43권4호
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• pp.107-115
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• 2020

Support vector regression (SVR) is devised to solve the regression problem by utilizing the excellent predictive power of Support Vector Machine. In particular, the ⲉ-insensitive loss function, which is a loss function often used in SVR, is a function thatdoes not generate penalties if the difference between the actual value and the estimated regression curve is within ⲉ. In most studies, the ⲉ-insensitive loss function is used symmetrically, and it is of interest to determine the value of ⲉ. In SVQR (Support Vector Quantile Regression), the asymmetry of the width of ⲉ and the slope of the penalty was controlled using the parameter p. However, the slope of the penalty is fixed according to the p value that determines the asymmetry of ⲉ. In this study, a new ε-insensitive loss function with p1 and p2 parameters was proposed. A new asymmetric SVR called GSVQR (Generalized Support Vector Quantile Regression) based on the new ε-insensitive loss function can control the asymmetry of the width of ⲉ and the slope of the penalty using the parameters p1 and p2, respectively. Moreover, the figures show that the asymmetry of the width of ⲉ and the slope of the penalty is controlled. Finally, through an experiment on a function, the accuracy of the existing symmetric Soft Margin, asymmetric SVQR, and asymmetric GSVQR was examined, and the characteristics of each were shown through figures.

• 조명전기설비학회논문지
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• 제12권1호
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• pp.45-50
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• 1998

최근, 유도전동기 회전속도 제어용 구동 전원으로 인버터와 싸이크로컨버터가 널리 사용되고 있다. 싸이크로컨버터에 의한 전동기 구동은 일정 주파수의 교류전원에서 직접 주파수가 다른 교류로 변환함으로 하드웨어 구성이 인버터 보다 간단하다. 본 연구의 목적은 싸이크로컨버터에 의한 유도전동기 벡터제어 시스템의 제어방법 및 하드웨어 설계를 행하는 것이다. 본 연구에서는 교류 전동기 슬립 주파수형 벡터제어 알고리즘을 도출하고 이 원리에 기초하여 싸이크로컨버터를 이용한 벡터제어 시스템을 구성하였다. 싸이크로컨버터는 1차 입력전류 진폭 $li_1l$ 과 각주파수 $\omega_1$을 지령값으로 진폭변조 제어신호를 발생하여 SCR의 게이터를 트리거한다. 본 벡터제어 시스템은 교류 전동기를 구동한 결과 자속이 일정하게 유지되면서 정회전에서 역회전까지 연속적으로 양호한 운전을 할 수 있었다.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1423-1430
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• 2017

Detonation cell width is an important parameter in hydrogen explosion assessments. The experimental data on gas detonation are statistically analyzed to establish a universal method to numerically predict detonation cell widths. It is commonly understood that detonation cell width, ${\lambda}$, is highly correlated with the characteristic reaction zone width, ${\delta}$. Classical parametric regression methods were widely applied in earlier research to build an explicit semiempirical correlation for the ratio of ${\lambda}/{\delta}$. The obtained correlations formulate the dependency of the ratio ${\lambda}/{\delta}$ on a dimensionless effective chemical activation energy and a dimensionless temperature of the gas mixture. In this paper, support vector regression (SVR), which is based on nonparametric machine learning, is applied to achieve functions with better fitness to experimental data and more accurate predictions. Furthermore, a third parameter, dimensionless pressure, is considered as an additional independent variable. It is found that three-parameter SVR can significantly improve the performance of the fitting function. Meanwhile, SVR also provides better adaptability and the model functions can be easily renewed when experimental database is updated or new regression parameters are considered.

• 전기전자학회논문지
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• 제19권1호
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• pp.73-79
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• 2015

In this paper, maximum boost space vector pulse-width modulation(MBSVPWM) strategy of Z-Source Inverters(ZSIs) is proposed. Conventional space vector pulse-width modulation(SVPWM) method of Voltage Source Inverters(VSIs) is modified to produce unique PWM patterns that realize the maximum boost control of ZSIs. This proposed method minimizes the switching power losses of ZSIs by reducing the numbers of the shoot-through states. Moreover, some switches keep ON state and the switching transitions do not occur during the specific sectors. An experimental system has been built and tested to verify the effectiveness of the proposed strategy.

• Journal of Power Electronics
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• 제16권3호
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• pp.994-1003
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• 2016

Two major obstacles in the utilization of electrical vehicles are their price and range. The collaboration of direct torque control (DTC) with induction motor (IM) is preferred for its low cost, easy implementation, and parameter independency. However, in terms of edges, the method has drawbacks, such as variable switching frequency and undesired current harmonic distortion. These drawbacks result in acoustic noise, reduced efficiency, and electromagnetic interference. A feed-forward approach for stator-flux-oriented DTC with space vector pulse-width modulation is presented in in this paper. The outcome of the proposed method is low current harmonic distortion with fixed switching frequency while preserving the torque performance and simple application feature of basic DTC. The method is applicable to existing and forthcoming IM drive systems via software adaptation. The validity of the proposed method is confirmed by simulation and experimental results.

• Journal of Power Electronics
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• 제17권6호
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• pp.1480-1489
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• 2017

In this study, a carrier-based pulse-width modulation (PWM) method for two-level voltage source inverters in the over-modulation region is proposed. Based on the superposition principle, the reference voltage vectors outside the linear modulation boundary are adjusted to relocate to the vector hexagon, while their fundamental magnitudes are retained. In accordance with the adjusted reference vector, the corresponding modulated waves are respectively deduced in over-modulation mode I and II to generate the gate signals of the power switches, guaranteeing the linearity of the fundamental output phase voltage in the over-modulation region. Moreover, due to the linear relationship between the voltage vector and the duty ratios, the complicated sector identification and holding angle calculation found in previous methods are avoided in the modulated wave synthesis, which provides great simplicity for the proposed carrier-based over-modulation strategy. Experimental results demonstrate the effectiveness and validity of the proposed method.

• 전력전자학회논문지
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• 제20권5호
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• pp.421-428
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• 2015

An advanced direct torque control (DTC) with pulse width modulation (PWM) method is presented in this paper. The duty ratio calculation of the selected voltage vector is based on the voltage functions of the selected voltage vector according to the sector angle. The proposed DTC uses a conventional DTC scheme with six sector divisions and switching rules. However, the winding voltages are supplied by the PWM approach. Furthermore, the duty ratio of the switching voltage vector is determined by the flux, torque error, and motor speed. The base voltage that shall determine the duty ratio can be calculated by approximate voltage functions according to the voltage angle. For the calculation of base voltages, second-order quadratic functions are used to express the output voltage of the selected voltage vector according to voltage angle. The coefficients for the second-order quadratic functions are selected by the voltage vector, which is determined by the switching rules of the DTC. In addition, the voltage functions are calculated by the coefficients and voltage angle between the voltage vector and rotor position. The switching voltages from the calculated duty ratio can supply the proper torque and flux to reduce the ripple and error. The proposed control scheme is verified through practical experimental comparisons.

• 해양환경안전학회지
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• 제25권4호
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• pp.498-503
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• 2019

해양산업분야에서는 극심한 대기오염으로 인하여 전기추진선박에 대한 관심이 높아지고 있다. 이로 인해 선내 전력품질의 저하를 개선하기 위한 연구가 활발히 진행되고 있다. 기존 DFE 정류기의 입력전류 고조파 함유량을 완화시키기 위해 수동형필터, 노치필터, 능동형필터 등을 이용한 다양한 방법이 등장하였다. 그 중에서도 능동필터의 일종인 AFE(Active Front End) 정류장치가 우수한 기술로써 평가받고 있다. 본 논문에서는 공간벡터변조에 의한 AFE정류장치의 전류제어방식을 제안하였다. 기존의 히스테리시스 방식, 삼각파 변조방식 및 공간벡터변조방식을 PSIM을 사용해 시뮬레이션을 수행하여 비교, 분석하였고, 그 결과 공간벡터변조방식이 구조가 간단하고 성능이 가장 우수함을 확인하였다.