인플루엔자 유행의 마르코프 모델 해석

정형환,김관수,박상희 대한전기학회 1984 대한전기학회 학술대회 논문집 Vol.1984 No.7

Pontryagin 최소 원리를 이용한 최적접종에 관한 연구

정형환,주수원,이광우,Jeong, Hyeong-Hwan,Ju, Su-Won,Lee, Gwang-U 대한의용생체공학회 1988 의공학회지 Vol.9 No.1

The optimum control theory has been applied to the problem of finding the most economic use of active and passive immunization controls. Application of Pontryagin's Minimum Principle to this case, involving functions of delayed control has been demonstrated and a procedure has been developed for the numerical solution of the resulting control problem. Using the numerical procedure, optimum control strategies have been obtained for different values of reported case cost.

혼합강도 $H_{\infty}$ 제어기법을 이용한 강인한 부하주파수 제어기 설계

정형환,김상효,이정필,한길만 한국마린엔지니어링학회 2000 한국마린엔지니어링학회지 Vol.24 No.3

In this paper, a robust controller using $H_{\infty}$ control theory has been designed for the load frequency control of interconnected 2-area power system. The main advantage of the proposed $H_{\infty}$ controller is that uncertainties of power system can be included at the stage of controller design. Representation of uncertainties is modeled by multiplicative uncertainly. In the mixed sensitivity problems, disturbance attenuation and uncertainty of the system is treated simultaneously. The robust stability and the performance of model uncertainties are represented by frequency weighted transfer function. The design of load frequency controller for each area was based on state-space approach. The comparative computer simulation results for the proposed controller and the conventional techniques such as the optimal control and the PID one were analyzed at the additions of various disturbances. Their deviation magnitude of frequency and tie line power flow at each area were mainly evaluated. Also the testing results of robustness for the cases that the perturbations of the all parameters of power system were amounted to about 20% were introduced. It was approved that the resultant performances of the proposed $H_{\infty}$ controller with mixed sensitivity were more robust and stable than the one of conventional controllers.

전력 시스템의 동요 억제를 위한 TCSC용 안정화 장치 설계

정형환,허동렬,왕용필,박희철,이동철 한국조명전기설비학회 2002 조명·전기설비학회논문지 Vol.16 No.2

본 논문에서는 FACTS 기기의 일종인 전력조류 극대화 및 제어 기능과 함께 외란에 의한 과도시의 전력계통 안정화 기능을 수행할 수 있는 TCSC용 전력시스템 안정화 장치 설계에 대하여 연구하였다. TCSC용 전력시스템 안정화 장치 설계시 파라미터 선정은 복잡한 수식이 필요 없고 계산시간을 감소시키며 적은 반복횟수로도 최적해를 찾을 수 있는 자연 생태계의 진화를 모의한 유전 알고리즘을 이용하였다. 전력 시스템의 저주파 진동에 강인성을 갖는 TCSC는 TCR(Thyristor Controlled Reactor)과 커패시터의 병렬구조에 의해 용량성과 유도성에 걸친 범위가지 연속적으로 제어할 수 있는 구조로 이루어져 있다. 이러한 제안된 방법의 강인성을 검증하기 위해 여러 가지 운전조건에 대해 전력계통 안정도 및 고유치를 해석하여 기존의 안정화 장치를 적용한 경우와 비교함 으로써 유용성을 입증하였다. In this paper, it is suggested that the selection method of parameter of Power System Stabilizer(PSS) with robustness in low frequency oscillation for Thyristor Controlled Series Capacitor(TCSC) using Geletic Algorithm(GA). A TCSC meddle consists of a stories capacitor and a parallel path with a thyristor valve and a series inductor. Also in in parallel, as is typical with series capacitor applications, is a metal-oxide varistor(MOV) for overvoltage protection. The proposed PSS parameters are optimized using GA in order to maintain optimal operation of TCSC which is expected to be applied in transmission system to achieve a number of benefits under the various operating conditions. In order to verify the robustness of the proposed method, we considered the dynamic response of angular velocity deviation and terminal voltage deviation under a power fluctuation and rotor angle variation.

Influenza 流行모델의 改善에 관한 硏究

鄭亨煥,司空鍵,李光雨 동아대학교 공과대학 부설 한국자원개발연구소 1981 硏究報告 Vol.5 No.2

A mathematical model, which can be used for the study of an influenza epidemic, was derived by using the property of incubation period. The main results are as follows. 1) The new-model shows more exactly the curve of response. 2) The standard deviation of normal distribution curve of the incubation period is about 1.5. The Authors believe that the method to study the influenza model in this paper will be helpful to study the characteristics of other epidemics. It will also contribute to the influenza-control model.

전력시스템의 부하주파수 제어를 위한 IA-PID 제어기 특성에 관한 연구

정형환,김창현,이정필,정문규 동아대학교 정보기술연구소 2001 情報通信硏究所論文誌 Vol.9 No.1

In this paper, the robust PID controller using immune algorithm(IA) for load frequency control(LFC) is designed. In proposed method, objective function is represented as antigens. An affinity calculation is embedded within the algorithm for determining the promotion or suppression of antibody. Simulation results show that the proposed robust load frequency controller can achieve good performance even in the presence of generation rate constraints

DC 링크의 분명한 수식화에 의한 AC-DC 조류계산

정형환,안병철,허동렬 동아대학교 공과대학부설 생산기술연구소 1997 生産技術硏究所硏究論文集 Vol.2 No.2

This report has been suggested a calculation method include the DC-Link equations into process of power flow repetition of AC system, on to use the fast decoupled method. The DC link model which consisted of thirteen non-linear equations could be expressed using nine non-linear equations in accordance with the consideration of system configuration and functional characteristic. In recognition of the advantage for DC transmission on a side of elevation upon an economical transmission through a lower loss and a stability enhancement, the estabishment of real system and this study are doing to activate in the world. Also in our land, the DC transmission between the shore and Jae-Ju Province is going to expedite in actual fact. Such as fact in today, it has been done to think that is meaningful to exhibit the effective power flow for advactage fo a memory capacity, a calculatot's speed, and can be known the electric power distributions of integrated AC-DC system.

최적 변조 제어기를 이용한 교류-직류계통의 안정화에 관한 연구

정형환,허동렬 동아대학교 공과대학부설 생산기술연구소 1997 生産技術硏究所硏究論文集 Vol.2 No.1

In this paper, optimal modulation controller is designed to improve the stability of A.C. and A.C.-D.C. power system, and optimal theory is applied to select optimal modulation controller input signal. Optimal modulation controller for speed govemor and exiter controller system is constructed in A.C. power system, considering ACR-AVR, APR-AR as the control method of direct current system. It is considered that the stability of A.C. power system only and A.C.-D.C. power system against load fluctuationa and disturbance under case of optimal modulation control.

밀폐된 계층인구에 있어서 유행병 모델

정형환,주수원,이광우,Jeong, Hyeong-Hwan,Ju, Su-Won,Lee, Gwang-U 대한의용생체공학회 1993 의공학회지 Vol.14 No.4

Of the assumptions commonly used in continuous infection model, the least likely to be even approximately true in large population, is that of homogeneous mixing. In this paper, We investigate a model for the spread of infection amongst a population which is divided into classes, such that the individuals of each class mix homogeneously amongst themselves, but mix to a lesser degree with individuals of other class. The stochastic model in this form is intractable and approximations are made, yielding results in reasonable agreement with simulation trials.

HIV 감염과 AIDS의 전파 특성에 관한 기초적 연구

정형환,이광우 대한의용생체공학회 1994 의공학회지 Vol.15 No.3

This paper describes some preliminary attempts to formulate simple mathematical models of the transmission dynamics of HIV infection in homosexual communities. In conjunction with a survey of the available epidemiological data on HIV infection and the incidence of AIDS, the model is used to assess how various processes influence the course of the initial epidemic following the introduction of the virus. Models of the early stages of viral spread provide crude methods for estimating the basic reproductive rate of the virus, given a knowledge of the incubation period of AIDS and the initial doubling time of the epidemic. More complex models are formulated to assess the influence of heterogeneity in sexual activity. This latter factor is shown to have a major effect on the predicted pattern of the epidemic.