• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.225-227
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• 2009

The conventional fixed gain PI controller is very sensitive to step change of command speed, parameter variation and load disturbances. The precise speed control of interior permanent magnet synchronous motor(IPMSM) drive becomes a complex issue due to nonlinear coupling among its winding currents and the rotor speed as well as the nonlinear electromagnetic developed torque. Therefore, there exists a need to tune the PI controller parameters on-line to ensure optimum drive performance over a wide range of operating conditions. This paper is proposed artificial intelligent-PI(AIPI) controller of IPMSM drive using adaptive learning mechanism(ALM) and fuzzy neural network(FNN). The proposed controller is developed to ensure accurate speed control of IPMSM drive under system disturbances and estimation of speed using artificial neural network(ANN) controller. The PI controller parameters are optimized by ALM-FNN at all possible operating condition in a closed loop vector control scheme. The validity of the proposed controller is verified by results at different dynamic operating conditions.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.420-423
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• 2009

The conventional fixed gain PI controller is very sensitive to step change of command speed, parameter variation and load disturbances. The precise speed control of interior permanent magnet synchronous motor(IPMSM) drive becomes a complex issue due to nonlinear coupling among its winding currents and the rotor speed as well as the nonlinear electromagnetic developed torque. Therefore, there exists a need to tune the PI controller parameters on-line to ensure optimum drive performance over a wide range of operating conditions. This paper is proposed hybrid intelligent-PI(HIPI) controller of IPMSM drive using adaptive learning mechanism(ALM) and fuzzy neural network(FNN). The proposed controller is developed to ensure accurate speed control of IPMSM drive under system disturbances and estimation of speed using artificial neural network(ANN) controller. The PI controller parameters are optimized by ALM-FNN at all possible operating condition in a closed loop vector control scheme. The validity of the proposed controller is verified by results at different dynamic operating conditions.

• 한국정보통신학회논문지
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• 제6권1호
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• pp.25-29
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• 2002

High speed 신호처리는 통신분야, SC circuit, HDTV, ISDN 등에서 관심이 더욱 승가하고 있으며, high speed 신호처리를 위한 많은 방법들이 있다. 본 논문에서는 CMOS 공정에서 고주파 Op-amp의 실현을 의한 설계를 기술하였다. 아날로그 집적회로를 기초로 하는 high speed op-amp의 기능을 제한하는 요소 중 한가지는 유효 주파수 범위이다. 본 논문에서는 $C_{L}$ =2pF에서 단위이득 주파수가 170MHz인 향상된 대역폭적을 가지는 CMOS op-amp 구조를 계발한다. 공정은 1.2$\mu$디자인 룰을 따른다. 본 논문에서 제시한 CMOS op-amp 고주파 SC filter에서 요구하는 큰 커패시터 부하에서의 넓고 안정된 대역폭을 얻기에 매우 적합하다.

• Journal of Power Electronics
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• 제13권6호
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• pp.975-984
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• 2013

This paper proposes a robust optimal nonlinear control with an observer to reject the offset errors of position tracking for surface mounted permanent magnet synchronous motors. We provide the control method to reject offset errors and load torque for designing field oriented control (FOC) based the alternating current (AC) frame. The proposed method consists of a torque generator, a commutation scheme, an electrical controller, and a load torque observer. The mechanical controller is designed to compensate for load torque and the offset error and generate the desired torque. The commutation scheme is proposed to create the desired currents for the desired torque. The electrical controller is developed to guarantee the desired currents. The observer is designed to estimate both the velocity and the load torque. In order to obtain the robustness to parameter uncertainties and a gain tuning guide, the linear quadratic regulator method is applied to the proposed method. The closed-loop stability is proven. A detailed process for the FOC design and an analysis of the control methods based on the AC frame are presented. The performance of the proposed method was validated via experiments. The proposed method obtains the FOC based on the AC frame. Furthermore, the position tracking performance of the proposed method is superior to that of the conventional method.

• 전력전자학회논문지
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• 제22권2호
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• pp.102-108
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• 2017

Proper design guides are proposed for a practical dual-active bridge (DAB) converter based on the mathematical model on the steady state. The DAB converter is popular in bidirectional application due to its zero-voltage capability and easy bidirectional operation for seamless control, high efficiency, and performance. Some design considerations are taken to overcome the limitation of the DAB converter. The practical design methodology of power stage is discussed to minimize the conduction and switching losses of the DAB converter. Small-signal model and frequency response are derived and analyzed based on the generalized average method, which considers equivalent series resistance, to improve the dynamics, stability, and reliability with voltage regulation of the practical DAB converter. The design of closed-loop control is discussed by the derived small-signal model to obtain the pertinent gain and phase margin in steady-state operation. Experimental results of a 3.3 kW prototype of DAB converter demonstrate the validity and effectiveness of the proposed methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1684-1686
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• 2005

As photovoltaic(PV) power generation systems become more common, it will be necessary to investigate islanding detection method for PV systems. Islanding of PV systems can cause a variety of problems and must be prevented. However, if the real and reactive power of load and PV system are closely matched, islanding detection by passive methods becomes difficult. Also, most active methods lose effectiveness when there are several PV systems feeding the same island. The active frequency drift positive feedback method(AFDPF) enables islanding detection by forcing the frequency of the voltage in the island to drift up or down. In this paper the research for the minimum value of chopping fraction gain applied digital phase-locked-loop(DPLL) to AFDPF considering output power quality and islanding prevention performance are performed by simulation and experiment in IEEE Std 929-2000 islanding test.

• 한국지능시스템학회논문지
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• 제18권3호
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• pp.335-340
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• 2008

본 논문은 시간 지연을 가지는 비선형 상호 결합 시스템에 대한 분산 퍼지 출력 궤환 제어기를 제시한다. Takagi-Sugeno (T-S) 퍼지 모델링을 통하여 비선형 상호 결합 시스템을 퍼지 모델로 표현한다. 상호 결합 시스템의 하위 퍼지 시스템을 안정화 시킬 수 있는 분산 출력 궤한 제어기를 설계한다. 폐루프 하위 시스템들의 안정도 조건을 선형 행렬 부등식으로 나타내고, 부등식을 이용하여 제어기의 이득값을 구한다. 모의실험을 통하여 시간 지연이 있는 비선형 상호 결합 시스템에 대한 분산 퍼지 출력 궤한 제어기의 효용성을 평가한다.

• 한국ITS학회 논문지
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• 제7권4호
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• pp.76-85
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• 2008

본 논문에서는 TETRA 단말기용 800 MHz 대역 1 W급 cartesian feedback 선형전력증폭기를 설계 및 제작하였다. 200 kHz 협대역을 갖는 TETRA 신호를 증폭 시, cartesian feedback 선형화기를 통해서 ${\pm}25$ kHz 오프셋 주파수에서 30 dBc 이상의 전력증폭기 선형성을 개선하였다. 선형화의 성능은 I/Q 신호간의 이득과 위상의 불일치 및 DC offset 성분에 의해서 영향을 받음을 알 수 있으며 이러한 문제를 보상 시 선형화를 극대화 할 수 있음을 알 수 있었다. Cartesian feedback 선형화기는 협대역 QAM 신호의 선형화 기술로 적합함을 확인하였으며 이를 이용하여 다른 변조방식을 갖는 신호들의 선형화방법으로도 적용 가능하다.

• Bulletin of the Korean Chemical Society
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• 제22권1호
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• pp.77-83
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• 2001

To gain further insight into the relationship between structure and function of glutathione S-transferase (GST), the four cysteine mutants, C14S, C47S, C101S and C169S, of human GST P1-1 were expressed in Escherichia coli and purified to electrophoretic homogeneity by affinity chromatography on immobilized glutathione (GSH). The catalytic activities of the four mutant enzymes were characterized with five different substrates as well as by their binding to four different inhibitors. Cys14 seems to participate in the catalytic reaction of GST by stabilizing the conformation of the active-site loop, not in the GSH binding directly. The substitution of Cys47 with serine significantly reduces the affinity of GSH binding, although it does not prevent GSH binding. On the other hand, the substitution of Cys101 with serine appears to change the binding affinity of electrophilic substrate by inducing a conformational change of the $\alpha-helix$ D. Cys169 seems to be important for maintaining the stable conformation of the enzyme. In addition, all four cysteine residues are not needed for the steroid isomerase activity of human glutathione S-transferase P1-1.

• Journal of Power Electronics
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• 제19권4호
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• pp.1000-1010
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• 2019

The use of internal-model-based linear controller, such as resonant controller, is a well-established technique for the current control of grid-connected systems. Attractive properties for resonant controllers include their two-sequence tracking ability, the simple control structure, and the reduced computational burden. However, in the case of continuous-designed resonant controller, the transient performance is inevitably degraded at a low switching frequency. Moreover, available design methods for resonant controller is not able to realize the direct design of transient performances, and the anticipated transient performance is mainly achieved through trial and error. To address these problems, the zero-order-hold (ZOH) characteristic and inherent time delay in digital control systems are considered comprehensively in the design, and a corresponding hold-equivalent discrete model of the grid-connected converter is then established. The relationship between the placement of closed-loop poles and the corresponding transient performance is comprehensively investigated to realize the direct mapping relationship between the control gain and the transient response time. For the benefit of automatic tuning and real-time adaption, analytical expressions for controller gains are derived in detail using the required transient response time and system parameters. Simulation and experimental results demonstrate the validity of the proposed method.