• 대한조선학회논문집
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• 제54권2호
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• pp.102-112
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• 2017

Many studies on dynamic positioning control algorithms using fixed feedback gains have been carried out to improve station keeping performance of dynamically positioned vessels. However, the control algorithms have disadvantages in that it can not cope with changes in environmental disturbances and response characteristics of vessels motion in real time. In this paper, the Fuzzy Gain Scheduling - PID(FGS - PID) control algorithm that can tune PID gains in real time was proposed. The FGS - PID controller that consists of fuzzy system and a PID controller uses weighted values of PID gains from fuzzy system and fixed PID gains from Ziegler - Nichols method to tune final PID gains in real time. Firstly, FGS - PID controller, control allocation algorithm, FPSO and environmental disturbances were modeled using Matlab/Simulink to evaluate station keeping performance of the proposed control algorithm. In addition, simulations that keep positions and a heading angle of vessel with wind, wave, current disturbances were carried out. From simulation results, the FGS - PID controller was confirmed to have better performances of keeping positions and a heading angle and consuming power than those of the PID controller. As a consequence, the proposed FGS - PID controller in this paper was validated to have more effectiveness to keep position and heading angle than that of PID controller.

• 한국통신학회논문지
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• 제38B권7호
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• pp.572-580
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• 2013

IEEE 802.15.4e은 산업용 네트워크 제어 시스템의 무선 네트워크 적용을 위해 개발된 통신 표준으로서, 기존경쟁 기반의 MAC 프로토콜이 갖는 전송 지연의 문제를 해결하기 위해 비경쟁 기반의 MAC 프로토콜을 제시하고 있다. 이에 본 논문은 IEEE 802.15.4e 기반 무선 네트워크 제어 시스템에 적용 가능한 네트워크 모델과 제어 모델을 제시하고, 성능 평가를 목적으로 한다. 이를 위해 각 모델에 대한 수학적 분석을 토대로 모의실험 환경을 구성하였으며, 무선 네트워크 환경의 주요 환경 요소인 거리, 전송 전력을 변화시켜 패킷 손실에 대한 영향을 분석하였다. 특히 제안하는 모델의 명확성을 입증하기 위해 중복 전송을 고려한 네트워크 모델을 대표적인 비선형 실시간 모델인 역진자 시스템에 도입하여 성능 분석을 수행하였다. 그 결과 본 논문에서 제안하는 네트워크 및 제어기 모델이 사용 가능함을 확인하였고, 각 환경 변화에 따른 성능 추이를 살펴볼 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.168-180
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• 2018

In order to achieve the high quality output voltage of single-phase voltage source inverters, in this paper an Adaptive Complementary Sliding Mode Control (ACSMC) is proposed. Firstly, the dynamics model of the single-phase inverter with lumped uncertainty including parameter variations and external disturbances is derived. Then, the conventional Sliding Mode Control (SMC) and Complementary Sliding Mode Control (CSMC) are introduced separately. However, when system parameters vary or external disturbance occurs, the controlling performance such as tracking error, response speed et al. always could not satisfy the requirements based on the SMC and CSMC methods. Consequently, an ACSMC is developed. The ACSMC is composed of a CSMC term, a compensating control term and a filter parameters estimator. The compensating control term is applied to compensate for the system uncertainties, the filter parameters estimator is used for on-line LC parameter estimation by the proposed adaptive law. The adaptive law is derived using the Lyapunov theorem to guarantee the closed-loop stability. In order to decrease the control system cost, an inductor current estimator is developed. Finally, the effectiveness of the proposed controller is validated through Matlab/Simulink and experiments on a prototype single-phase inverter test bed with a TMS320LF28335 DSP. The simulation and experimental results show that compared to the conventional SMC and CSMC, the proposed ACSMC control strategy achieves more excellent performance such as fast transient response, small steady-state error, and low total harmonic distortion no matter under load step change, nonlinear load with inductor parameter variation or external disturbance.

• Journal of Power Electronics
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• 제16권1호
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• pp.9-17
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• 2016

Maximum power point tracking (MPPT) is necessary for photovoltaic (PV) power system application to extract the maximum possible power under changing irradiation and temperature conditions. The β-parameter-based method has many advantages over conventional MPPT methods; such advantages include fast tracking speed in the transient stage, small oscillations in the steady state, and moderate implementation complexity. However, a problem in the implementation of the conventional beta method is the choice of an appropriate scaling factor N, which greatly affects both the steady-state and transient performance. Therefore, this paper proposes a modified β-parameter-based method, and the determination of the N is discussed in detail. The study shows that the choice of the scaling factor N is determined by the changes of the value of β during changes in irradiation or temperature. The proposed method can respond accurately and quickly during changes in irradiation or temperature. To verify the proposed method, a photovoltaic power system with MPPT function was built in Matlab/Simulink, and an experimental prototype was constructed with a solar array emulator and dSPACE. Simulation and experimental results are illustrated to show the advantages of the improved β-parameter-based method with the optimized scaling factor.

• Journal of Power Electronics
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• 제15권1호
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• pp.190-201
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• 2015

This paper uses the switching function approach to present a simple state model of the Vienna-type rectifier. The approach introduces the relationship between the DC-link neutral point voltage and the AC side phase currents. A novel direct power control (DPC) strategy, which is based on the sliding mode control (SMC) for Vienna I rectifiers, is developed using the proposed power model in the stationary ${\alpha}-{\beta}$ reference frames. The SMC-based DPC methodology directly regulates instantaneous active and reactive powers without transforming to a synchronous rotating coordinate reference frame or a tracking phase angle of grid voltage. Moreover, the required rectifier control voltages are directly calculated by utilizing the non-linear SMC scheme. Theoretically, active and reactive power flows are controlled without ripple or cross coupling. Furthermore, the fixed-switching frequency is obtained by employing the simplified space vector modulation (SVM). SVM solves the complicated designing problem of the AC harmonic filter. The simplified SVM is based on the simplification of the space vector diagram of a three-level converter into that of a two-level converter. The dwelling time calculation and switching sequence selection are easily implemented like those in the conventional two-level rectifier. Replacing the current control loops with power control loops simplifies the system design and enhances the transient performance. The simulation models in MATLAB/Simulink and the digital signal processor-controlled 1.5 kW Vienna-type rectifier are used to verify the fast responses and robustness of the proposed control scheme.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.963-969
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• 2015

자전거는 환경공해 능력과 웰빙에 대한 관심증가 때문에 가장 유망한 미래 교통수단 중의 하나이다. 실제 자전거에 적용될 무단변속기를 제작하기 전에 신뢰성이 확보된 시뮬레이션 프로그램을 통하여 문제점을 초기에 확인하고, 각 링크의 소재 및 두께 등의 설계인자 최적화와 능력을 평가할 필요가 있다. 이 같은 과정을 통하여 무단 변속기 시스템 설계 과정에서의 소요비용을 줄일 수 있다. 본 논문에서는 설계인자를 확정하기 위해 응력해석을 수행되었으며. 전체 모델링 중에서 각 링크와 조인트 부분을 주요 설계인자로 가정하고 각각의 링크 및 조인트의 영향도 및 작동 시 받은 응력들을 CAE를 통해 확인하였다. 또한, 해석 영역에 대하여 적절한 수학적 모델링을 통해 맥동 현상을 계산할 수 있는 전용 code를 개발하였으며, 이를 Matlab에 적용하여 해석 결과를 graphic화하여 분석하였다.

• 한국산학기술학회논문지
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• 제14권9호
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• pp.4455-4461
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• 2013

본 논문은 전력기기 열화의 주요한 원인으로 알려진 부분방전의 진단을 위해 널리 사용되는 인공신경망의 계층 구조 및 입력벡터의 구성 요소의 변화에 대한 진단 성능을 검토한다. 은닉층이 1개 또는 2개인 인공신경망의 계층구조 변화에 대한 진단 성능을 비교하였으며, 입력벡터는 세라믹 커플러를 이용하여 한주기에 2048번 샘플링한 시계열 신호를 직접 사용하는 경우와 특성벡터를 추출하여 사용하는 경우를 비교하였다. 침${\leftrightarrow}$평판, 구${\leftrightarrow}$구, 침${\leftrightarrow}$침, 평판${\leftrightarrow}$평판, 구${\leftrightarrow}$평판 형태의 5가지 전극조합의 부분방전 실험으로 학습데이타를 수집하고, 시뮬레이션 연구를 수행하여 인공신경망의 진단 성능을 평가하였다.

• 전력전자학회논문지
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• 제12권2호
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• pp.107-114
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• 2007

계통 연계형 태양광 발전 시스템이 정전 혹은 사고 등으로 계통으로부터 분리되었을 때 태양광 발전 시스템이 배전선 부하를 떠맡아 운전을 계속하는 현상을 고립운전이라 하는데 이런 상태가 지속되면 선로 유지보수자의 안전사고를 야기할 수 있으며 전기설비에 나쁜 영향을 줄 수도 있다. 수동 검출법은 연계점(PCC:Point of Common Coupling)의 전압이나 주파수를 측정하여 한계치를 벗어나면 고립운전으로 판단하는데 RLC 부하의 유효전력과 무효전력이 각각 PV 시스템의 유효전력, 무효전력과 서로 비슷하면 검출할 수 없다. 이 경우 고립운전을 검출하기 위한 다양한 능동 검출법이 제안되었으며 가장 효과적인 방법은 미국 샌디아 연구실(Sandia National Lab)에서 제안한 SFS법(Sandia Frequency Shift method)이다. 본 논문에서는 자동 위상 이동을 이용한 새로운 능동 검출기법을 제안하고 Matlab 시뮬레이션과 실험을 통하여 타당성을 검증하였다.

• Journal of Power Electronics
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• 제17권3호
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• pp.821-834
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• 2017

This paper reports on a single-inductor multiple-output step-up converter with digital control. A systematic analog-to-digital-controller design is explained. The number of digital blocks in the feedback path of the proposed converter has been decreased. The simpler digital pulse-width modulation (DPWM) architecture is then utilized to reduce the power consumption. This architecture has several advantages because counters and a complex digital design are not required. An initially designed unit-delay cell is adopted recursively for the construction of coarse, intermediate, and fine delay blocks. A digital limiter is then designed to allow only useful code for the DPWM. The input voltage is 1.8 V, whereas output voltages are 2 V and 2.2 V. A co-simulation was also conducted utilizing PowerSim and Matlab/Simulink, whereby the 55 nm process was employed in the experimental results to evaluate the performance of the architecture.

• Journal of Power Electronics
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• 제18권1호
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• pp.234-250
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• 2018

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.