• 한국정밀공학회지
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• 제30권12호
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• pp.1287-1293
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• 2013

In this paper, we consider variable speed wind turbine systems containing uncertain elements. Though PI controller is generally used for pitch control, it cannot guarantee a stability and performance of the complicated wind turbine systems. A robust pitch control scheme is proposed to regulate the electric power output above the rated wind speed. The pitch controller is designed in order to guarantee uniform boundedness and uniform ultimate boundedness based on the bound values of the set where the uncertainties are laid or moves. In order to verify the proposed control scheme, we present stability analysis and simulation results using Matlab/Simulink.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.963-970
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• 1994

In speech signal processing, it is very important to detect the pitch exactly. The algorithms for pitch extraction that have been proposed until now are not enough to detect the fine pitch in speech signal. Thus we propose the new algorithm which takes advantage of the G-peak extraction. It is the method to find MZCI(maximum zer-crossing interval) which is defined as cut-off bandwidth rate of LPF (low pass filter)and detect the pitch period of the voiced signals. This algorithm performs robustly with a gross error rate of 3.63% even in 0 dB SNR environment. The gross error rate for clean speech is only 0.18%. Also it is able to process all course with speed.

• 한국지능시스템학회논문지
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• 제23권1호
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• pp.1-6
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• 2013

정격풍속이상에서 발전기의 출력을 일정하게 유지하기 위하여 PID에 기초한 다양한 종류의 방법들이 발표되었다. 그러나 고정된 PID 이득을 이용한 이러한 방법에서는 전 영역에서 동작하리라는 보장이 없다. 이 논문에서는 전 영역에서 동작하는 시스템을 설계하기 위하여 풍속의 강도에 따라 PID 이득이 변하는 방법을 제안하였다. 풍속의 강도에 따라 피치각에 따른 전력의 민감도는 계속 변하는데, PID 이득을 민감도의 함수로 유도하였다.

• Journal of Power Electronics
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• 제15권1호
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• pp.246-255
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• 2015

This paper presents experimental results and its assessment of a variable-speed wind power generation system (VSWPGS) using permanent magnet synchronous generator (PMSG) and boost chopper circuit (BCC). Experimental results are obtained by a test bench with a wind turbine emulator (WTE). WTE reproduces the behaviors of a windmill by using servo motor drives. The mechanical torque references to drive the servo motor are calculated from the windmill wing profile, wind velocity, and windmill rotational speed. VSWPGS using PMSG and BCC has three speed control modes for the level of wind velocity to control the rotational speed of the wind turbine. The control mode for low wind velocity regulates an armature current of generator with BCC. The control mode for middle wind velocity regulates a DC link voltage with a vector-controlled inverter. The control mode for high wind velocity regulates a pitch angle of the wind turbine with a pitch angle control system. The hybrid of three control modes extends the variable-speed range. BCC simplifies the maintenance of VSWPGS while improving reliability. In addition, VSWPGS using PMSG and BCC saves cost compared with VSWPGS using a PWM converter.

• 드라이브 ㆍ 컨트롤
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• 제15권1호
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• pp.28-37
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• 2018

When the wind speed rises above the rated wind speed, the produced power of the wind turbines exceeds the rated power. Even more, the excessive power results in the undesirable mechanical load and fatigue. A solution to this problem is pitch control of the wind turbines. This paper presents a systematic design method of a collective pitch controller for the wind turbines using a discrete fuzzy Proportional-Integral (PI) controller. Unlike conventional PI controllers, the fuzzy PI controller has variable gains according to its input variables. Generally, tuning the parameters of fuzzy PI controller is complex due to the presence of too many parameters strongly coupled. In this paper, a systematic method for the fuzzy PI controller is presented. First, we show the fact that the fuzzy PI controller is a superset of the PI controller in the discrete-time domain and the initial parameters of the fuzzy PI controller is selected by using this relationship. Second, for simplicity of the design, we use only four rules to construct nonlinear fuzzy control surface. The tuning parameters of the proposed fuzzy PI controller are also obtained by the aforementioned relationship between the PI controller and the fuzzy PI controller. As a result, unlike the PI controller, the proposed fuzzy PI controller has variable gains which allow the pitch control system to operate in broader operating regions. The effectiveness of the proposed controller is verified with computer simulations using FAST, a NREL's primary computer-aided engineering tool for horizontal axis wind turbines.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.285-286
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• 2011

Wind turbine system is converting wind energy into electric energy. In nature, torque of the blade is nonlinear function. To get a high quality electric power, system needs control of blade angle. The control of a blade is divided into a stall regulation type and a pitch control type. Pitch control type is more expensive and complicated, but it can make torque of the blade in accordance with variable wind. This paper shows 2MW pitch control system's hardware and electric part.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권11호
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• pp.753-759
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• 2004

This paper presents a modeling and simulation of a fuzzy controller for maximum power extraction of a grid-connected wind energy conversion system with a link of a rectifier and an inverter. It discusses the maximum power control algorithm for a wind turbine and proposes, in a graphical form, the relationships of wind turbine output, rotor speed, power coefficient, tip-speed ratio with wind speed when the wind turbine is operated under the maximum power control. The control objective is to always extract maximum power from wind and transfer the power to the utility by controlling both the pitch angle of the wind turbine blades and the inverter firing angle. Pitch control method is mechanically complicated, but the control performance is better than that of the stall regulation method. The simulation results performed on MATLAB will show the variation of generator's rotor angle and rotor speed, pitch angle, and generator output.

• Journal of Power Electronics
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• 제11권3호
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• pp.342-349
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• 2011

We propose a torque and pitch control scheme for variable speed wind turbines with permanent magnet synchronous generator (PMSG). A torque controller is designed to maximize the power below the rated wind speed and a pitch controller is designed to regulate the output power above the rated wind speed. The controllers exploit the sliding mode control scheme considering the variation of wind speed. Since the aerodynamic torque and rotor acceleration are difficult to measure in practice, a finite time convergent observer is designed which estimates them. In order to verify the proposed control strategy, we present stability analysis as well as simulation results.

• 한국산학기술학회논문지
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• 제14권7호
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• pp.3170-3176
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• 2013

본 연구에서는 피치각 가변형 축류팬의 성능(정압별 풍량, 소비전력)과 소음특성을 실험으로 구하였다. 피치각은 $20^{\circ}{\sim}45^{\circ}$로 $5^{\circ}$ 간격으로 6개의 각도를 변화시켜 가면서 측정 하였고 팬 날개는 동일한 에어포일 형상으로 길이는 80 mm, 90 mm, 100 mm, 110 mm, 120 mm로 변경하여 실험을 수행하였다.

• 한국음향학회지
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• 제13권5호
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• pp.77-82
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• 1994

음성신호 처리에서, 피치를 정확하게 찾아내는 것이 매우 중요하다. 현재까지 많은 피치 검출 방법들이 제안되어 왔지만, 광범위한 화자와 다양한 음성 데이터로부터 정확한 피치를 찾는 것은 어렵다. 따라서 본 논문에서는 G-peak 검출을 이용한 새로운 피치 검출 알고리즘을 제안한다. 이 방법은 G-peak 의 MZCI (최대 영교차 간격) 을 LPF (low-pass filter)의 차단대역폭으로 결정하여 음성신호의 피치를 검출하는 방법이다. 본 알고리즘은 0dB SNR 환경 하에서 3.36%의 그로스 에러를 나타내는 잡음에 강인한 방법이다. 또한 잡음이 없는 음성의 그로스 에러는 0.18%였고, 모든 과정은 고속 처리가 가능하다.