• Journal of Power Electronics
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• 제11권3호
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• pp.375-380
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• 2011

A STATic synchronous COMpensator (STATCOM) is a shunt connected voltage source converter (VSC) based FACTS controller using Gate Turn Off (GTO) power semiconductor devices employed for reactive power control. The operation principal is similar to that of a synchronous condenser. A typical application of a STATCOM is voltage regulation at the midpoint of a long transmission line for the enhancement of power transfer capability and/or reactive power control at the load centre. This paper presents the modeling of STATCOM with twenty four pulse three level VSC and Type-1 controller to regulate the reactive current or the bus voltage. The performance is evaluated by transient simulation. It is observed that, the STATCOM shows excellent transient response to step change in the reactive current reference. While the eigenvalue analysis is based on D-Q model, the transient simulation is based on both D-Q and 3 phase models of STATCOM (which considers switching action of VSC).

• 한국정밀공학회지
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• 제20권4호
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• pp.214-222
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• 2003

Studies on the optimization of machining process can be divided into two different approaches: off-line feedrate scheduling and adaptive control. Each approach possesses its respective strong and weak points compared to each other. That is, each system can be complementary to the other. In this regard, a combined system, which is a feedrate control system fur cutting force optimization, was proposed in this paper to make the best of each approach. Experimental results show that the proposed system could overcome the weak points of the off-line feedrate scheduling system and the adaptive control system. In addition, from the figure, it can be confirmed that the off-line feedrate scheduling technique can improve the machining quality and can fulfill its function in the machine tool which has a adaptive controller.

• 한국지능시스템학회논문지
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• 제14권1호
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• pp.118-124
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• 2004

In this paper, we present a indirect adaptive control method using a wavelet neural network (WNN) for the control of chaotic nonlinear systems without precise mathematical models. The proposed indirect adaptive control method includes the off-line identification and on-line control procedure for chaotic nonlinear systems. In the off-line identification procedure, the WNN based identification model identifies the chaotic nonlinear system by using the serial-parallel identification structure and is trained by the gradient-descent method. And, in the on-line control procedure, a WNN controller is designed by using the off-line identification model and is trained by the error back-propagation algorithm. Finally, the effectiveness and feasibility of the proposed control method is demonstrated with applications to the chaotic nonlinear systems.

• 전기학회논문지
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• 제65권12호
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• pp.2000-2007
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• 2016

Generally, in order to implement the CRM(Critical Conduction Mode), the analog controller is used rather than a digital controller because the control is simple and uses less power. However, according to the semiconductor technology development and various user needs, digital control system based on a DSP is on the rise. Therefore, in this paper, the CRM bridgeless PFC converter based on a digital control is proposed. It is necessary to detect the inductor current when it reaches zero and peak value, for calculating the on time and off time by using the current information. However, in this paper, the on-time and off-time are calculated by using the proposed algorithm without any current information. If the switching-times are calculated through the steady-state analysis of the converter, they do not reflect transient status such as starting-up. Therefore, the calculated frequency is out of range, and the transient current is generated. In order to solve these problems, limitation method of the on-time and off-time is used, and the limitation values are varied according to the voltage reference. In addition, in steady state, depending on the switching frequency, the inductance is varied because of the resonance between the inductor and the parasitic capacitance of the switching elements. In order to solve the problem, inductance are measured depending on the switching frequency. The measured inductance are used to calculate the switching time for preventing the transient current. Simulation and experimental results are presented to verify the proposed method.

• 수산해양기술연구
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• 제50권3호
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• pp.292-300
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• 2014

The Laplace Transform solution is used as a mathematical model to analyse the thermal performance of the building constructed using different wall materials. The solution obtained from Laplace Transform is an analytical solution of an one dimensional, linear, partial differential equation for wall temperature profiles and room air temperatures. The main purpose of the study is showing the detail of obtaining solution process of the Laplace Transform. This study is conducted using weather data from two different locations in Korea: Seoul, Busan for both winter and summer conditions. A comparison is made for the cases of an on-off controller and a proportional controller. The weather data are processed to yield hourly average monthly values. Energy consumption load is well calculated from the solution. The result shows that there is an effect of mass on the thermal performance of heavily constructed house in mild weather conditions such as Busan. Building using proportional control experience a higher comfort level in a comparison of building using on-off control.

• 한국정보통신학회논문지
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• 제18권11호
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• pp.2786-2791
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• 2014

본 논문은 사용자의 장애 환경에 맞추어 장애 환경설정을 이용함으로서 조명 이용의 편의성을 향상시키고 에너지 절약을 위한 지능형 조명시스템에 관한 연구이다. 장애 환경은 조명의 점등이 원활하지 않은 상태를 의미하는 것으로서 이를 해결하기 위한 방법으로 원격제어 방식이 요구된다. 원격제어 방식은 스마트폰, 움직임 센서, 타이머를 이용하여 조명을 점등 한다. 스마트폰과 움직임 센서는 이벤트를 감지하였을 때 원격에서 조명 시스템으로 이벤트 발생을 전송하고 이벤트를 수신한 조명 시스템은 램프를 전등한다. 조명 사용자의 설정 환경에 맞추어 조명을 제어함으로서 사용시간을 조절하고 점등 조작을 감소하여 에너지 절약을 실현한다. 제안 기법을 적용하여 조명시스템을 설계 및 구현하여 실험 결과 편의성이 향상 되었고 최적화된 점등으로 약 13.5w/h 정도 에너지가 절감된다.

• IEIE Transactions on Smart Processing and Computing
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• 제5권1호
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• pp.35-42
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• 2016

Developments in power electronics have enabled the widespread application of Pulse Width Modulation (PWM) inverters, notably for connecting renewable systems to the grid. This study demonstrates that a high-quality power can be achieved using a stand-alone inverter, whereby the comparison between the power quality of the stand-alone inverter with battery storage (off-grid) and the power quality of the utility network is presented. Multi-loop control techniques for a single phase stand-alone inverter are used. A capacitor current control is used to give active damping and enhance the transient and steady state inverter performance. A capacitor current control is cheaper than the inductor current control, where a small current sensing resistor is used. The output voltage control is used to improve the system performance and also control the output voltage. The inner control loop uses a proportional gain current controller and the outer loop is implemented using internal model control proportional-integral-derivative to ensure stability. The optimal controls are achieved by using the Sisotool tool in MATLAB/Simulink. The outcome of the control scheme of the numerical model of the stand-alone inverter has a smooth and good dynamic performance, but also a strong robustness to load variations. The numerical model of the stand-alone inverter and its power quality are presented, and the power quality is shown to meet the IEEE 519-2014. Furthermore, the power quality of the off-grid system is measured experimentally and compared with the grid power, showing power quality of off-grid system to be better than that of the utility network.

• 한국태양에너지학회 논문집
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• 제31권5호
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• pp.140-145
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• 2011

In this study, the performance and behavior of solar heating system according to the system control scheme, variable flow control (proportional control) and constant flow control (on-off control) was carried out by experiment. The on-off control is used generally for solar thermal system by now. But the proportional control is used for the solar district heating system which is supplied the higher temperature of water than that of desired. The proportional control logic that pump speed is varied in an attempt to maintain a specified outlet temperature of solar heating system was developed and tested for the use widely for the small and medium solar thermal system. The results are as following. First, the proportional controller which is made here could be adopted the characteristics for setting temperature control. Second, the proportional control is better than the on-off control in the side of the performance of thermal stratification in storage tank. Third, the operating energy(electricity consumption by pump) of solar thermal system can be saved more than 60% using the proportional control comparing to the on-off control.

• 전력전자학회논문지
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• 제12권1호
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• pp.98-106
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• 2007

본 논문에서는 개선된 온라인 턴 오프각 제어방식을 이용하여 스위치드 릴럭턴스 전동기의 성능최적화를 위한 온라인 전류제어방식을 제안한다. 성능최적화를 위한 제어방식은 에너지효율의 최대화와 토크리플 저감이라는 두가지 측면에서 접근하며, 두 가지 조건을 모두 만족할 수 있는 최적의 턴 오프 위치각은 제안된 알고리즘의 연산방식을 통해 획득된 턴 오프각 제어기를 통해 구현됨으로서 SRM의 성능최적화를 이룬다. 제안된 제어기는 토크와 전류 특성, 자속변동의 정보와 같은 복잡한 데이터베이스나 SRM이 가지는 고유의 자화곡선을 요구하지 않는다는 장점을 가지며 제안된 연산 제어기를 시뮬레이션과 실험을 통해 실제 적용가능성과 그 타당성을 입증한다.

• 한국전자통신학회논문지
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• 제9권9호
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• pp.1019-1025
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• 2014

최근 무인항공기(UAV : Unmanned Aerial Vehicle)에 대한 연구가 다양한 각도로 진행되어 군사용 비행체에 관한 연구에서 부터 민간용 비행체 및 일반 취미 활동용 비행체에 이르기까지 다양하게 연구가 진행되고 있다. 특히, 무인 소형 비행체에 대한 연구는 수직이착륙(VTOL : Vertical Take-Off and Landing)과 용이한 방향전환 및 정지비행(hovering)에 대하여 연구되고 있으며, 이러한 연구부분에 적합한 무인 소형 비행체가 쿼드로터(quardrotor)형 무인비행체를 중심으로 연구되고 있다. 이러한 무인 비행체에 대한 연구는 공기역학적 힘에 의해 부양되므로 복잡한 동역학 분석과정을 필요로 하고 있으며, 이러한 역학적 분석 및 실험적 모델을 바탕으로 제어기를 설계하고 있다. 본 논문에서는 일반적인 PID 제어기를 바탕으로 기본적인 자세제어를 구현한 후, 제어기 설계에 고려하지 못한 비선형적인 요소를 신경회로망(neural networks)의 강화학습(reinforcement learning) 알고리즘을 이용하여 일반적인 제어기 설계에 고려하지 못한 비선형적인 요소를 보완하여 보다 안정적인 쿼드로터의 자세제어 방안을 제시하고자 한다.