• 대한전기학회논문지
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• 제41권5호
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• pp.459-467
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• 1992

This paper presents a new algorithm for the countermeasure to alleviate the line overloads due to contingency without shedding loads in a power system. This method for relieving the line overloads by line switching is based on obtaining the kine outage distribution factors-the linear sensitivity factors, which give the amount of change in the power flow of each line due to the removal of a line in a power system. There factors are made up of the elements of sparse bus reactance matrix and brach reactances. In this paper a fast algorithm and program is presented for obtaining only the required bus reactance elements which corresponds to a non-zero elements of bus admittance matrix, and elements of columns which correspond to two terminal buses of the overloaded(monitored) line. The proposed algorithm has been validated in tests on a 6-bus and the 30-bus test system.

• Journal of the Korean Data and Information Science Society
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• 제17권2호
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• pp.609-617
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• 2006

A new fuzzy c-regression algorithm for switching regression analysis is presented, which combines fuzzy c-means clustering and least squares support vector machine. This algorithm can detect outliers in switching regression models while yielding the simultaneous estimates of the associated parameters together with a fuzzy c-partitions of data. It can be employed for the model-free nonlinear regression which does not assume the underlying form of the regression function. We illustrate the new approach with some numerical examples that show how it can be used to fit switching regression models to almost all types of mixed data.

• Journal of Power Electronics
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• 제14권2호
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• pp.282-291
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• 2014

This paper presents a detailed theoretical analysis and performance assessment of the capacitor voltage balancing strategies for staircase modulated modular multilevel converters (MMC) in terms of the algorithm structures, voltage balancing effect, and switching frequency. A constant-frequency redundancy selection (CFRS) method with minimal switching loss is proposed and the function realization of specific modules of the algorithm is given. This method is simple and efficient in both switching frequency and regulation capacity. Laboratory results show very good agreement with the theoretical analysis and numerical simulations.

• Journal of Information Processing Systems
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• 제13권4호
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• pp.987-999
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• 2017

Extraction of influential people from their respective domains has attained the attention of scholastic community during current epoch. This study introduces an innovative interaction strength metric for retrieval of the most influential users in the online social network. The interactive strength is measured by three factors, namely re-tweet strength, commencing intensity and mentioning density. In this article, we design a novel algorithm called IPRank that considers the communications from perspectives of followers and followees in order to mine and rank the most influential people based on proposed interaction strength metric. We conducted extensive experiments to evaluate the strength and rank of each user in the micro-blog network. The comparative analysis validates that IPRank discovered high ranked people in terms of interaction strength. While the prior algorithm placed some low influenced people at high rank. The proposed model uncovers influential people due to inclusion of a novel interaction strength metric that improves results significantly in contrast with prior algorithm.

• 제어로봇시스템학회논문지
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• 제16권3호
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• pp.249-255
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• 2010

The paper proposes a new type of robust speed control strategy for permanent magnet synchronous motor by using PD-sliding mode hybrid control. The PD control has a good performance in the transient region while the sliding mode controller provides the robustness against system uncertainties. Taking advantages of the two control strategies, the proposed control method utilizes the PD control in the approaching region to the sliding surface and the sliding mode control near at the sliding surfaces. The chattering problem of the sliding mode controller is eliminated by applying the saturation function for the switching function of the sliding mode control. The stability of the sliding mode control is verified by using Lyapunov function with the proper selection of variable gains. It is shown that with this simple switching algorithm, stability of the overall hybrid control system is ensured. Through the simulations, the PD-sliding mode algorithm is shown to have a good performance in the transient response as well as being robust against disturbances. The robustness of the PD-sliding mode algorithm is further demonstrated against various external disturbances in the real experiments of SPMSM motor control.

• 전기학회논문지
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• 제62권9호
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• pp.1240-1248
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• 2013

This paper describes a switching-level operation analysis of BTB(Back-To-Back) converter for HVDC(high voltage DC) application based on MMC(modular multi-level converter). A switching-level operation analysis for BTB converter is very important to understand the converter operation in detail and check the voltage and current transients in each components. However, the development of switching-level simulation model for the actual size BTB Converter is very difficult because the MMC normally has more than 150 sub-modules for each arm. So, a switching level simulation model for the 11-level MMC-based BTB converter was developed with PSCAD/EMTDC software, which has 12 sub-modules for the positive arm and another 12 sub-modules for the negative arm. The DC-voltage balance algorithm, the circulating-current reduction algorithm, the harmonic reduction algorithm, and the redundancy operation algorithm were included in this simulation model. The developed simulation model can be utilized to analyze the MMC-based BTB converter for HVDC application in switching level and to develop the protection scheme for the MMC-based BTB converter for HVDC application.

• Journal of Power Electronics
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• 제17권1호
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• pp.115-126
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• 2017

This paper presents a new cascaded asymmetrical single phase multilevel converter with a reduced number of isolated DC sources and power semiconductor switches. The proposed inverter has only two H-bridges connected in cascade, one switching at a high frequency and the other switching at a low frequency. The Low Switching Frequency Inverter (LSFI) generates seven levels whereas the High Switching Frequency Inverter (HSFI) generates only two levels. This paper also presents a solution to the capacitor balancing issues of the LSFI. The proposed inverter has lot of advantages such as reductions in the number of DC sources, switching losses, power electronic devices, size and cost. The proposed inverter with a capacitor voltage balancing algorithm is simulated using MATLAB/SIMULINK. The switching logic of the proposed inverter with a capacitor voltage balancing algorithm is developed using a FPGA SPATRAN 3A DSP board. A laboratory prototype is built to validate the simulation results.

• 전력전자학회논문지
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• 제21권6호
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• pp.514-524
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• 2016

This work suggests a study on 5 kW plasma power supply design and reactor capacitance estimation algorithm for a wide range of linear output control to operate a plasma reactor. The suggested study is designed to use a two-stage circuit and control the full-bridge circuit of the two-stage circuit using the buck converter output voltage of the single-stage circuit. The switching frequency of the full-bridge circuit is designed to operate through high-frequency switching and obtain maximum output using LC parallel resonance. Soft switching technique(ZVS) is used to reduce the loss caused by high-frequency switching, and duty control of the buck converter is applied to control a wide range of linear output. The internal capacitance of the reactor cannot easily be extracted, and thus, the reactor cannot be operated in an optimized resonant state. To address this issue, this work designs the internal capacitance of the reactor such that estimations can be performed with the developed reactor capacitance estimation algorithm applied to the internal capacitance of the reactor. A 5 kW plasma power supply is designed for a wide range of linear output control, and the validity of the study on the reactor capacitance estimation algorithm is verified.

• 한국전자통신학회논문지
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• 제16권1호
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• pp.45-52
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• 2021

3상 PWM 정류기에 대한 공간벡터제어 기반 전압제어방식은 스위칭 구간에 대한 스위칭 패턴을 설계해야하기 때문에 최적한 스위칭 패턴을 설계하는데 많은 노력이 요구된다. 본 연구에서는 3상 6펄스 전압형 PWM 정류기를 위한 D-Q 제어에 기반 한 SPWM 출력전압 제어 알고리즘을 연구하였다. 출력전압제어 알고리즘에서 3상 기준신호들은 공간벡터 표시법에 기반 한 D-Q 변환으로부터 얻어지며 스위칭 패턴 대신에 SPWM 방식을 이용하여 정류기 스위칭 제어 신호들을 생성하도록 하였다. 다음으로, EMTP-RV를 이용하여 D-Q 제어기반 SPWM 방식을 가지는 3상 6펄스 전압형 PWM 정류기를 모델링하였다. 끝으로, EMTP-RV 시뮬레이션을 통해 얻어지는 출력전압파형을 기준 값과 비교, 출력전압이 기준전압을 정확하게 추종함을 확인함으로서 D-Q 제어기반 SPWM 전압제어 알고리즘의 유효성을 확인할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.409-412
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• 1990

Series connection of power switching semiconductor elements is unavoidable when a high voltage convertor is aimed. However, it is important to equalize distribution of turn-off voltage because the switching elements have different characteristics. In this paper optimal switching control algorithm is proposed so that series connected poker switching semiconductor elements can be always switched simultaneous turn-on and turn-off.