• Title/Summary/Keyword: Restarting strategy

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A Study on Improvement of Genetic Algorithm Operation Using the Restarting Strategy (재시동 조건을 이용한 유전자 알고리즘의 성능향상에 관한 연구)

  • 최정묵;이진식;임오강
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.2
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    • pp.305-313
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    • 2002
  • The genetic algorithm(GA), an optimization technique based on the theory of natural selection, has proven to be relatively robust means to search for global optimum. It is converged near to the global optimum point without auxiliary information such as differentiation of function. When studying some optimization problems with continuous variables, it was found that premature saturation was reached that is no further improvement in the object function could be found over a set of iterations. Also, the general GA oscillates in the region of the new global optimum point so that the speed of convergence is decreased. This paper is to propose the concept of restarting and elitist preserving strategy as a measure to overcome this difficulty. Some benchmark examples are studied involving 3-bar truss and cantilever beam with plane stress elements. The modifications to GA improve the speed of convergence.

A Study on a New Function Optimization Method Using Probabilistic Tabu Search Strategy (확률적 타부 탐색 전략을 이용한 새로운 함수 최적화 방법에 관한 연구)

  • Kim, Hyung-Su;Hwang, Gi-Hyun;Park, June-Ho
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.50 no.11
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    • pp.532-540
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    • 2001
  • In this paper, we propose a probabilistic tabu search strategy for function optimization. It is composed of two procedures, one is Basic search procedure that plays a role in local search, and the other is Restarting procedure that enables to diversify search region. In basic search procedure, we use Belief space and Near region to create neighbors. Belief space is made of high-rank neighbors to effectively restrict searching space, so it can improve searching time and local or global searching capability. When a solution is converged in a local area, Restarting procedure works to search other regions. In this time, we use Probabilistic Tabu Strategy(PTS) to adjust parameters such as a reducing rate, initial searching region etc., which makes enhance the performance of searching ability in various problems. In order to show the usefulness of the proposed method, the PTS is applied to the minimization problems such as De Jong functions, Ackley function, and Griewank functions etc., the results are compared with those of GA or EP.

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Hydro-Thermal Optimal Scheduling Using Probabilistic Tabu Search (확률 타부 탐색법을 이용한 수화력 계통의 경제운용)

  • Kim, Hyung-Su;Park, June-Ho
    • Proceedings of the KIEE Conference
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    • 2002.11b
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    • pp.76-79
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    • 2002
  • In this paper, we propose a Probabilistic Tabu Search(PTS) method for hydro-thermal scheduling. Hydro scheduling has many constraints and very difficult to solve the optimal schedule because it has many local minima. To solve the problem effectively, the proposed method uses two procedures, one is Tabu search procedure that plays a role in local search, and the other is Restarting procedure that enables to diversify its search region. To adjust parameters such as a reducing rate and initial searching region, search strategy is selected according to its probability after Restarting procedure. In order to show the usefulness of the proposed method, the PTS is applied on two cases which have dependent hydro plants and compared to those of other method. The simulation results show it is very efficient and useful algorithm to solve the hydro-thermal scheduling problem.

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Hydro-Thermal Optimal Scheduling Using Probabilistic Tabu Search (확률 타부 탐색법을 이용한 수화력 계통의 경제운용에 관한 연구)

  • Kim, Hyeong-Su;Mun, Gyeong-Jun;Park, Jun-Ho
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.51 no.3
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    • pp.153-161
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    • 2002
  • In this paper, we propose a Probabilistic Tabu Search(PTS) method for hydro-thermal scheduling. Hydro scheduling has many constraints and very difficult to solve the optical schedule because it has many local minima. To solve the problem effectively, the proposed method uses two procedures, one is Tabu search procedure that plays a role in local search, and the other is Restarting procedure that enables to diversify its search region. To adjust Parameters such as a reducing rate and initial searching region, search strategy is selected according to its probability after restarting procedure. Dynamic decoding method was also used to restrict a search region and to handle water balance constraints. In order to show the usefulness of the proposed method, the PTS is applied on two cases which have independent or dependent hydro plants and compared to those of other method. The simulation results show it is very efficient and useful algorithm to solve the hydro-thermal scheduling problem.

The Inverter Control Method Using The Voltage Sag Compensation algorithm (순간전압강하 보상 알고리즘을 이용한 인버터 제어에 관한 연구)

  • Yun, Hong-Min;Bae, Jin-Yong;Kim, Yong
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.26 no.12
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    • pp.62-67
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    • 2012
  • In this paper general purpose voltage source inverter drives are equipped with an under-voltage protection mechanism, causing the system to shut down within a few milliseconds after a power interruption in the main input sources. When a power interruption occurs finish, if the system is a large inertia restarting the load a long time is required. This paper suggests modifications in the control algorithm in order to improve the sag ride-through performance of ac inverter. The new proposed strategy recommends maintaining the DC-link voltage constant at the nominal value during a sag control algorithm, experimental results are presented.

A Short Term Hydro-Thermal Scheduling using Tabu Search (Tabu 탐색법을 이용한 수화력 계통의 단기 운용 계획)

  • Kim, Sung-Ki;Kim, Hyung-Su;Mun, Kyeong-Jun;Hwang, Gi-Hyun;Park, J.H.
    • Proceedings of the KIEE Conference
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    • 2000.07a
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    • pp.331-333
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    • 2000
  • This paper propose the method combined Priority and Tabu search (TS) for short term hydro-thermal scheduling. We satisfy various conditions using TS, Restarting method is used as diversification strategy of TS to prevent a local convergence. Also, we use Lagrangian method to solve economic dispatch problems.

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Restarting strategy of medium-voltage inverter with voltage sensor (전압 측정 장치를 사용한 고압 인버터의 재기동 방법)

  • Choe, Seung-Cheol;Hong, Chan-Uk;Yu, An-No
    • Proceedings of the KIPE Conference
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    • 2014.11a
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    • pp.81-82
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    • 2014
  • 산업계에서 많이 사용되는 고압 전동기는 일반적으로 관성이 크므로, 인버터 입력 전원의 고장 또는 정전 사고 후 복전 시, 전동기를 멈추고 재기동하기까지 오랜시간이 걸린다. 이러한 재기동 시간을 줄이기 위해, 고압 전동기를 멈추지 않고, 자유 회전 상태에서 재기동이 가능한 플라잉 스타트(flying start) 기능이 요구된다. 본 논문에서는 전압 측정 장치를 사용한 플라잉 스타트 방법을 제안한다. 제안한 방법은 전압 측정 장치를 통해 측정된 전동기의 잔류 전압 정보를 사용하여 전압의 크기, 주파수, 위상을 보상한다. 자사의 고압 인버터를 사용하여 실험을 통해 그 유효성을 검증하였다.

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Voltage Dip Compensation Algorithm Using Multi-Level Inverter (멀티레벨 인버터의 순간정전 보상알고리즘에 관한 연구)

  • Yun, Hong-Min;Kim, Yong
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.12
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    • pp.133-140
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    • 2013
  • Cascaded H-Bridge multi-level inverters can be implemented through the series connection of single-phase modular power bridges. In recent years, multi-level inverters are becoming increasingly popular for high power applications due to its improved harmonic profile and increased power ratings. This paper presents a control method for balancing the dc-link voltage and ride-through enhancement, a modified pulse width-modulation Compensation algorithm of cascaded H-bridge multi-level inverters. During an under-voltage protection mechanism, causing the system to shut down within a few milliseconds after a power interruption in the main input sources. When a power interruption occurs finish, if the system is a large inertia restarting the load a long time is required. This paper suggests modifications in the control algorithm in order to improve the sag ride-through performance of ac inverter. The new proposed strategy recommends maintaining the DC-link voltage constant at the nominal value during a sag period, experimental results are presented.