• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.309-316
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• 2011

A PLL system has widely used for synchronizing the grid voltage at the grid-connected inverter for supplying power from the PV generation systems. In this paper, a PLL algorithm without both the loop filter and PI controller is suggested for improving the performance of synchronization at the single-phase and three-phase grid connected inverters. In order that the output voltage of a phase detector in the PLL has only a dc voltage, and it approaches to 0 when the synchronization signal is locked to the grid voltage, the feedback signals are determined by using two-phase voltages. After the PLL system with a proportional controller is modelled with the small signal analysis, the stability and steady-state error are investigated. Through the simulation studies and experimental results, the performances of the proposed PLL algorithm are verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.697-702
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• 2016

To control permanent magnet synchronous motors smoothly, it is important to know the exact parameter values of the stator resistance, various inductances, and the flux linkage of the permanent magnet. In practice, these parameters vary due to a variable operating point, temperature change, or a fault. This paper proposes a MRAS (Model Reference Adaptive System) based parameter estimator and adaptive control scheme. Owing to the non-linearity of the system equation with respect to these parameters, although many schemes proposed previously assumed that some parameters are known, all the parameters were assumed to be unknown. The simulation results revealed the effectiveness of the proposed algorithm.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.6
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• pp.57-63
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• 1997

Uninterruptible power supply(UPS) system should provide a good quality and stable power supply no matter what the condition of the raw mains. And when the mains fails, it must provide uninterrupted power to the load for a specified time. In this paper. discrete control system is introduced to improve output waveforms of UPS. This technique can be obtained output voltage by discrete data of synchronous control and voltage control to various loac. And then, the compact and light UPS can be realized by remove of the analog circuit and simulation and ezperinentation were performed with this control algofihtm. The experiment result show the effectiveness of proposed UPS system uwing the discrete control techjique.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.10
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• pp.863-871
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• 2017

LMS (least mean square) algorithm widely used in the AVCS (active vibration control system) of helicopters calculates control input using the forward path transfer function and error signal. If the error signal is sinusoidal, it can be represented as the combination of cosine and sine functions with frequency and phase synchronized with the reference signal. The control input also has the same frequency, therefore control algorithm can be simply implemented if the cosine and the sine amplitudes of the control input are calculated and the frequency and phase of the reference signal are used. Calculation of the control input is implemented as simple matrix operation and the change of the control command is slower than the frequency of the error signal, consequently control algorithm can be operated at lower frequency. The signal processing algorithm extracting cosine and sine components of the error signals are modeled using Simulink and PIL (processor-in-the-loop) mode simulation was executed for real-time performance evaluation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.700-701
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• 2014

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2004.11a
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• pp.123-127
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• 2004

지상파 디지털 TV 방식 중의 하나인 ATSC 8-VSB방식은 전송된 데이터 중 유효 데이터의 비율이 높고 채널이 좋은 경우 동기 및 등화 과정이 간단한 장점이 있지만, 실내수신이나 이동수신 환경에서는 동기 및 등차 과정이 어려운 단점이 있다. 현재 주파수 동기에는 FPLL 알고리즘을 이용하고 있는데, 파일롯의 위치에서의 좌우 스펙트럼의 비대칭 및 채널 환경에 따른 파일롯 신호의 감쇄가 발생하여 양의 주파수 옵셋이 발생했을 때에 비해 음의 주파수 옵셋이 발생했을 때의 동기획득이 어려운 단점이 있다. 본 논문은 파일롯 추출필터와 인접된 필터를 통과한 신호의 파워비율을 이용하여 얻은 제어신호를 이용하여, 기존 FPLL의 동작 범위를 넓힘과 동시에 수렴속도를 빠르게 할 수 있는 방법을 제안하였다.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.235-237
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• 2007

최근 신재생 에너지로 풍력 발전 시스템이 중요시 되고 있다. 이에 본 논문에서는 풍력발전 시스템의 Wind Turbine System을 영구자석형 동기기를 이용하여 시뮬레이션 모델을 구현하였다. 시뮬레이션 모델은 회전자 모델, MPPT 알고리즘, 영구자석형 동기기(PMSM) 등으로 구성되어있다. Wind Blade Rotor의 유체역학적 특성 및 가감속 제어전략을 이용하여 Wind Turbine System의 특성을 시뮬레이션 할 수 있도록 하였다. 본 연구 결과는 이후 영구자석형 동기기를 이용한 풍력발전기의 기초 자료로서 이용될 수 있을 것으로 기대된다.

• Proceedings of the KAIS Fall Conference
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• 2007.11a
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• pp.136-139
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• 2007

최근, 이러한 주변정세는 차세대의 배전계통이 다수의 Micro-grid들로 구성될 것이라고 하는 예상을 전문가들로부터 제기되기에 이르렀다. 그러나 제안된 Micro-grid는 몇몇의 분산전원과 전력품질을 보상하는 기기, 그리고 통신제어설비와 부하들로 구성된다는 기본적인 내용에 지나지 않는다. 본 논문에서는 소형동기발전기(Micro Synchronous Generator), PWM컨버터, 대용량 커패시터, PWM인버터, SSB(Solid State Breaker) 로 구성되는 Micro-grid의 Topology와 모델링 방법, 그 운전 알고리즘을 제안하고, 이를 시뮬레이션을 통하여 제안된 Micro-grid의 기능을 검증하기로 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.820-829
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• 2000

In this paper, DSPA(Dynamic Signalling Period Allocation) algorithm that has been proposed by the authors for MAC(Medium Access Control) protocols in W-ATM(Wireless Asynchronous Transfer Mode) is applied to mixed traffic conditions composed of various service classes. We investigate the bandwidth utilization efficiency and quality of service(QoS) fulfillment by the DSPA algorithm used in W-ATM MAC protocols. Simulation results indicate that the DSPA algorithm significantly increases the throughput of the system with the minimum control overhead. Moreover, QoS of each service class is well satisfied by proper and fair channel allocation to different service classes according to their requirements.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.217-222
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• 2016

This study investigates the design, analysis, and implementation of the square-root extended Kalman filter by using an algorithm derived by combining the Potter or Carlson algorithm with the modified Gram-Schmidt algorithm, for sensorless speed control of a permanent-magnet synchronous motor. The sensitivity of the Kalman filter to round-off errors is a well-known problem. A possible way to address this limitation is by combining the square-root concept and Kalman filter that can improve the numerical performance and solve instability-related problems such as divergence. This paper presents the design and analysis of the implementation of such a square-root extended Kalman filter. To demonstrate the performance of the proposed filter, experimental results under several operating conditions, such as high and low speeds, reversal rotation, detuned parameters and load test, have been analyzed. Further, code sizes and operation times have been compared. Experimental results establish the performance of the proposed square-root extended Kalman filter-based estimation technique for sensorless speed control of a permanent-magnet synchronous motor.