• Title, Summary, Keyword: synchronous generator

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Dedicated Cutback Control of a Wind Power Plant Based on the Ratio of Command Power to Available Power

  • Thapa, Khagendra;Yoon, Gihwan;Lee, Sang Ho;Suh, Yongsug;Kang, Yong Cheol
    • Journal of Electrical Engineering and Technology
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    • v.9 no.3
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    • pp.835-842
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    • 2014
  • Cutback control in a grid code is one of the functions of a wind power plant (WPP) that is required to support the system protection and frequency stability. When a cutback control command signal is delivered to the WPP from the system operator, the output of a WPP should be decreased to 20% of the rated power within 5 s. In this paper, we propose a dedicated cutback control algorithm of a WPP based on the ratio of the command power to the available power. If a cutback control signal is delivered, the algorithm determines the pitch angle for the cutback control and starts the pitch angle control. The proposed algorithm keeps the rotor speed at the speed before the start of the cutback control to quickly recover the previous output prior to the cutback control. The performance of the algorithm was validated for a 100 MW aggregated WPP based on a permanent magnet synchronous generator under various wind conditions using an EMTP-RV simulator. The results clearly shows that the proposed algorithm not only successfully reduces the output to the command power within 5 s by minimizing the fluctuation of the pitch angle, but also rapidly recovers to the output level before the cutback control.

Modeling and Simulation Techniques for Performance Analysis of High Resolution SAR System (고해상도 영상레이더 성능 분석을 위한 모델링 및 시뮬레이션 기법)

  • Sung, Jin-Bong;Kim, Se-Young;Lee, Hyeon-Ik;Jeon, Byeong-Tae
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.5
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    • pp.558-565
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    • 2013
  • In this paper, modeling and simulation for performance analysis of high resolution SAR system has been carried out in the time, frequency and numeric domain using ADS Ptolemy simulation tool of Agilent corporation. SAR system consists of antenna, controller and transceiver. Error parameters affecting SAR system performances have been defined, modeled and simulated such as phase noise of frequency synthesizer, amplitude and phase characteristic of TWTA, sampling frequency of waveform generator and I/Q imbalance. Finally, the development requirements of SAR system based on the impulse response function have been derived.

Wind Energy Interface to Grid with Load Compensation by Diode Clamped Multilevel Inverters

  • Samuel, Paulson;Naik, M. Kishore;Gupta, Rajesh;Chandra, Dinesh
    • Journal of Power Electronics
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    • v.14 no.2
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    • pp.271-281
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    • 2014
  • Fluctuating wind conditions necessitate the use of a variable speed wind turbine (VSWT) with a AC/DC/AC converter scheme in order to harvest the maximum power from the wind and to decouple the synchronous generator voltage and frequency from the grid voltage and frequency. In this paper, a combination of a three phase diode bridge rectifier (DBR) and a modified topology of the diode clamped multilevel inverter (DCMLI) has been considered as an AC/DC/AC converter. A control strategy has been proposed for the DCMLI to achieve the objective of grid interface of a wind power system together with local load compensation. A novel fixed frequency current control method is proposed for the DCMLI based on the level shifted multi carrier PWM for achieving the required control objectives with equal and uniform switching frequency operation for better control and thermal management with the modified DCMLI. The condition of the controller gain is derived to ensure the operation of the DCMLI at the fixed frequency of the carrier. The converter current injected into the distribution grid is controlled in accordance with the wind power availability. In addition, load compensation is performed as an added facility in order to free the source currents being fed from the grid of harmonic distortion, unbalance and a low power factor even though the load may be unbalanced, non-linear and of a poor power factor. The results are validated using PSCAD/EMTDC simulation studies.

Dynamic Droop-based Inertial Control of a Wind Power Plant

  • Hwang, Min;Chun, Yeong-Han;Park, Jung-Wook;Kang, Yong Cheol
    • Journal of Electrical Engineering and Technology
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    • v.10 no.3
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    • pp.1363-1369
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    • 2015
  • The frequency of a power system should be maintained within the allowed limits for stable operation. When a disturbance such as generator tripping occurs in a power system, the frequency is recovered to the nominal value through the inertial, primary, and secondary responses of the operating synchronous generators (SGs). However, for a power system with high wind penetration, the system inertia will decrease significantly because wind generators (WGs) are operating decoupled from the power system. This paper proposes a dynamic droop-based inertial control for a WG. The proposed inertial control determines the dynamic droop depending on the rate of change of frequency (ROCOF). At the initial period of a disturbance, where the ROCOF is large, the droop is set to be small to release a large amount of the kinetic energy (KE) and thus the frequency nadir can be increased significantly. However, as times goes on, the ROCOF will decrease and thus the droop is set to be large to prevent over-deceleration of the rotor speed of a WG. The performance of the proposed inertial control was investigated in a model system, which includes a 200 MW wind power plant (WPP) and five SGs using an EMTP-RV simulator. The test results indicate that the proposed scheme improves the frequency nadir significantly by releasing a large amount of the KE during the initial period of a disturbance.

A 1.8V 2-Gb/s SLVS Transmitter with 4-lane (4-lane을 가지는 1.8V 2-Gb/s SLVS 송신단)

  • Baek, Seung-Wuk;Jang, Young-Chan
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.357-360
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    • 2013
  • A 1.8V 2-Gb/s scalable low voltage signaling (SLVS) transmitter (TX) is designed for mobile applications requiring high speed and low power consumption. It consists of 4-lane TX for data transmission, 1-lane TX for a source synchronous clocking, and a 8-phase clock generator. The proposed SLVS TX has the scaling voltage swing from 50 mV to 650 mV and supports a high speed (HS) mode and a low power (LP) mode. An output impedance calibration scheme for the SVLS TX is proposed to improve the signal integrity. The proposed SLVS TX is implemented by using a $0.18-{\mu}m$ 1-poly 6-metal CMOS with a 1.8V supply. The simulated data jitter of the implemented SLVS TX is about 8.04 ps at the data rate of 2-Gbps. The area and power consumption of the 1-lane of the proposed SLVS TX are $422{\times}474{\mu}m^2$ and 5.35 mW/Gb/s, respectively.

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Design of Power and Load Reduction Controller for a Medium-Capacity Wind Turbine (중형 풍력터빈의 출력 및 타워 하중저감 제어기 설계)

  • Kim, Kwansu;Paek, Insu;Kim, Cheol-Jin;Kim, Hyun-Gyu;Kim, Hyoung-Gil
    • Journal of the Korean Solar Energy Society
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    • v.36 no.6
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    • pp.1-12
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    • 2016
  • A control algorithm for a 100 kW wind turbine is designed in this study. The wind turbine is operating as a variable speed variable pitch (VSVP) status. Also, this wind turbine is a permanent magnet synchronous generator (PMSG) Type. For the medium capacity wind turbine considered in this study, it was found that the optimum tip speed ratios to achieve the maximum power coefficients varied with wind speeds. Therefore a commercial blade element momentum theory and multi-body dynamics based program was implemented to consider the variation of aerodynamic coefficients with respect to Reynolds numbers and to find out the power and thrust coefficients with respect tip speed ratio and blade pitch angles. In the end a basic power controller was designed for below rated, transition and above rated regions, and a load reduction algorithm was designed to reduce tower vibration by the nacelle motion. As a result, damage equivalent Load (DEL) of tower fore-aft has been reduced by 32%. From dynamic simulations in the commercial program, the controller was found to work properly as designed. Experimental validation of the control algorithm will be done in the future.

Development of Small-scale Organic Rankine Cycle System and Study on its Operating Characteristics (소형 유기랭킨사이클 시스템 개발 및 작동특성에 관한 연구)

  • Yun, Eunkoo;Kim, Hyun Dong;Yoon, Sang Youl;Kim, Kyung Chun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.10
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    • pp.919-926
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    • 2013
  • Experiments were conducted to determine the operating characteristics of a small-scale ORC (organic Rankine cycle) system for various low-temperature heat sources. A small-scale ORC power generation system adopting R-245fa as a working fluid was designed and manufactured. Hot water was used as the heat source, and the temperature was controlled using 110-kW electric resistance heaters that provided temperatures of up to $150^{\circ}C$. An open-drive oil-free scroll expander directly connected to a synchronous generator was installed in the ORC unit. Experiments were conducted by varying the rotational speed of the expander under the same heat source temperature conditions. The factors that influence the performance of the small-scale ORC system were analyzed and discussed.

Development of Torque simulator for the performance analysis of the 10kW wind turbine system (10kW 풍력발전기의 동작특성 분석을 위한 토크 시뮬레이터 개발)

  • Kim, Se-Yoon;Kim, Sung-Ho;Lee, Jong-Hee;Moon, Jin-Young
    • Journal of Korean Institute of Intelligent Systems
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    • v.24 no.6
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    • pp.579-585
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    • 2014
  • 10kW wind turbine is widely studied in the field of renewable energy for the merits of easy installation to the confined area such as hill, park and urban areas. The performance of various electrical devices such as converter and inverter in the wind turbine system should be systematically analyzed for various wind speeds. However, it is impossible to apply these devices directly to practical wind turbine system for the safety of wind turbine system. Therefore, it is required to develop torque simulator which can generate corresponding torque according to its wind speed. In this work, 10kW torque simulator which consists of three phase torque control inverter, 3 phase induction motor and PMSG(Permanent Magnet Synchronous Generator) is developed.

A design on low-power and small-area EEPROM for UHF RFID tag chips (UHF RFID 태그 칩용 저전력, 저면적 비동기식 EEPROM 설계)

  • Baek, Seung-Myun;Lee, Jae-Hyung;Song, Sung-Young;Kim, Jong-Hee;Park, Mu-Hun;Ha, Pan-Bong;Kim, Young-Hee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.12
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    • pp.2366-2373
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    • 2007
  • In this paper, a low-power and small-area asynchronous 1 kilobit EEPROM for passive UHF RFID tag chips is designed with $0.18{\mu}m$ EEPROM cells. As small area solutions, command and address buffers are removed since we design asynchronous I/O interface and data output buffer is also removed by using separate I/O. To supply stably high voltages VPP and VPPL used in the cell array from low voltage VDD, Dickson charge pump is designed with schottky diodes instead of a PN junction diodes. On that account, we can decrease the number of stages of the charge pump, which can decrease layout area of charge pump. As a low-power solution, we can reduce write current by using the proposed VPPL power switching circuit which selects each needed voltage at either program or write mode. A test chip of asynchronous 1 kilobit EEPROM is fabricated, and its layout area is $554.8{\times}306.9{\mu}m2$., 11% smaller than its synchronous counterpart.

A PN-code Acquisition method Using Array Antenna Systems for CDMA2000 1x (CDMA2000 1x용 배열 안테나 시스템에서 PN 동기 획득 방법)

  • Jo, Hee-Nam;Yun, Yu-Suk;Choi, Seung-Won
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.42 no.8
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    • pp.33-40
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    • 2005
  • This paper presents a structure of the searcher using a diversity in array antenna systems operating in the cdma2000 1x signal environments. The new technique exploits the fact that the In-phase and quadrature components of interferers can respectively be viewed as an independent gaussian noise at each antnna element in most practical cdma signal environments. The proposed PN acquisition scheme is a singles-dwell PN acquisition system consisting of two stages, that is, the searching stage and the verification stage. The searching stage independently correlates the receiver multiple signals with PN generator of each antenna element for obtaining the synchronous energy at the entire region. Then, the searching results of each antenna element are non-coherently combinind. The verification stage compares the searching energy with the optimal threshold, which is predesigned in the lock detector, and decides whether the acquisition is successful or fail. In this paper, we analyzed the effect of tile diversity order to determine the mean acquisition time. In general, it is known that the mean acquisition time significantly decrease as the number of antenna elements increases. But, as the diversity order goes up, the enhancement of the performance is saturated. Therefore, to decrease the mean acquisition time of the searcher, we must design the optimal array antenna systems by considering the operating SNR range of the receiver, the probability of detection $P_D$ and that of false alarm $P_{FA}$ . The Performance of the proposed PN acquisition scheme is analyzed in frequency selective Rayleigh fading channels. In this paper, the effect of the number of antenna elements on PN acquisition scheme is shown according to the probability of detection $P_D$ and that of false alarm $P_{FA}$.