• Journal of Power Electronics
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• 제13권5호
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• pp.854-860
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• 2013

The voltage variation problem at the point of common coupling (PCC) in a grid-connected wind turbine is investigated. The voltage variation problem is one of the most frequent power quality issues for the grid connection of large amounts of input power in a weak grid. Through the simplified modeling of the wind turbine and power network, the magnitude of PCC voltage variation is calculated by using the equivalent circuit parameters and output power of the wind turbine. The required amount of reactive power that can compensate the voltage variation is also presented analytically by using the vector diagram method. The proposed calculation and compensation method of the PCC voltage variation is verified by computer simulations and experiments.

• 전기학회논문지
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• 제56권2호
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• pp.317-324
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• 2007

Most conventional hybrid systems using renewable energy sources have been applied for stand-alone operation, but Utility-interface may be an useful and viable option for hybrid systems. Grid-connected operation may have benefits such as reduced losses in power system distribution, utility support in demand side management, and peak load shaving. This paper addresses power control and dynamic performance of a grid-connected PV/wind/BESS hybrid system. At all times the PV way and the wind turbine are individually controlled to generate the maximum energy from given weather conditions. The battery energy storage system (BESS) charges or discharges the battery depending on energy gap between grid invertger generation and production from the PV and wind system. The BESS should be also controlled without too frequently repeated shifts in operation mode, charging or discharging. The grid inverter regulates the generated power injection into the grid. Different control schemes of the grid inverter are presented for different operation modes, which include normal operation, power dispatching, and power smoothing. Simulation results demonstrate that the effectiveness of the proposed power control schemes for the grid-interactive hybrid system.

• 조명전기설비학회논문지
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• 제27권3호
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• pp.65-78
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• 2013

To analyze influences under open fault conditions in switching devices, an integrated simulation and condition monitoring scheme for a permanent magnet synchronous generator (PMSG) based variable speed grid-connected wind turbine system are presented. Among various faults in power electronics components, the open fault in switching devices may arise when the switches are destructed by an accidental over current, or a fuse for short protection is blown out. Under such a faulty condition, the grid-side inverter as well as the generator-side converter does not operate normally, producing an increase of current harmonics, and a reduction in output and efficiency. As an effective way for a condition monitoring of generation system by online basis without requiring any diagnostic apparatus, the estimation schemes for generated voltage, flux linkage, and stator resistance are proposed and the validity of the proposed scheme is proved through comparative simulations.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권12호
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• pp.609-615
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• 2005

A 30kW electrical power conversion system is developed for a variable speed wind turbine. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and the frequency of the generator output vary according to the wind speed, a 6-bridge diode rectifier and a PWM boost chopper is utilized as an ac-dc converter maintaining the constant dc-link voltage with only single switch control. An input current control algorithm for maximum power generation during the variable speed operation is proposed without any usage of speed sensor. Grid connection type PWM inverter converts dc input power to ac output currents into the grid. The active power to the grid is controlled by q-axis current and the reactive power is controlled by d-axis current with appropriate decoupling. The phase angle of utility voltage is detected using software PLL(Phased Locked Loop) in d-q synchronous reference frame. Experimental results from the test of 30kW prototype wind turbine system show that the generator power can be controlled effectively during the variable speed operation without any speed sensor.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권8호
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• pp.413-419
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• 2003

The paper presents a simulation model and analysis of a grid-connected variable speed wind energy conversion scheme (VSWECS) using the PSCAD/EMTDC software. The modeled system uses a variable speed drive, a fixed pitch angle, a synchronous generator as a wind generator and an AC-DC-AC conversion scheme, which facilitates the wind generation to efficiently operate under varying wind speed while connected to the distribution network. The power output of the WECS is controlled by the AC-DC-AC conversion scheme, the objective of which is to capture the maximum active power under varying wind conditions and to keep the voltage magnitude of the terminal bus at a specific level. Aerodynamic models are applied for a wind turbine model. An simulation analysis of the scheme in terms of its responding to wind variations is also presented.

• 에너지공학
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• 제12권2호
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• pp.154-163
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• 2003

전력계통에 연계하기 위해서 풍력발전시스템은 계속해서 변하는 풍속에 응동하여 적정한 출력을 계통에 공급할 수 있을 뿐만 아니라, 연계되는 전력계통에서 허용될 수 있는 수준의 주파수와 전압크기를 갖는 출력을 제공할 수 있어야 하며, 이를 위해서는 풍력발전의 적절한 출력제어가 필수적으로 요구된다. 본 연구에서는 동기발전기가 전압원인버터로 구성된 AC-DC-AC 변환부를 거쳐 계통에 접속되는 계통연계형 풍력발전시스템의 출력제어 전략을 소개하며, 이를 전자기 과도현상 해석 프로그램인 PSCAD/EMTDC를 이용하여 모의하고 해석하였다. 블레이드를 통해 입력되는 풍속에 대하여 최대 에너지를 공급할 수 있도록 전압원인버터의 유효전력 출력제어가 이루어지며, 출력단 전압을 일정하게 유지하기 위한 무효전력 출력제어가 행해진다. 또한 60 Hz의 주파수 출력 및 고조파 저감을 위해 SPWM 스위칭 방식을 채택하였다. 풍속의 변동 및 부하의 변동에 대한 풍력발전시스템의 응동특성 및 출력변화를 모의하고 해석한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1358-1360
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• 2002

This paper presents a modeling and simulation of a utility-connected wind energy conversion system with a link of a rectifier and an inverter. It discusses the maximum power control algorithm for the wind turbine and presents the relationship of wind turbine output, rotor speed, power coefficient, tip-speed ratio and wind speed when the wind turbine is operated under the maximum power control algorithm. The control objective is to extract maximum power from wind and transfer the power to the utility. This is achieved by controlling the pitch angle of the wind turbine blades. 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 speed, pitch angle, and generator output.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.458_459
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• 2009

This paper analyzes the dynamic characteristics for doubly-fed induction generator(DFIG) in wind turbine system. This paper presents a modeling and simulation of a grid-connected wind turbine generation system for dynamics analysis on MATLAB/Simulink, and analyzes the responses DFIG wind turbine system for stiffness of linked system. Simulation results show the variations of generator's active/reactive output, terminal voltage, fault current, etc.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4494-4499
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• 2014

약한 계통은 단락비가 작고 임피던스가 크므로 과도 안정도 여유도가 매우 낮다. 약한 계통에 사고가 발생하면 보호 시스템은 사고 선로를 개방함으로써 사고를 제거하는데 이것은 시스템의 안정도를 더욱 약하게 만든다. 그러므로 약한 계통의 안정도 여유를 증가시키기 위한 하나의 방법은 시스템에 추가적인 발전기를 연결하는 것이다. 본 논문에서는 약한 계통의 안정도 여유도를 증가시키기 위하여 기존의 동기발전기를 추가하는 경우와 풍력발전기의 를 추가하는 경우의 안정도 여유도를 비교한다. PSSE를 이용한 과도안정도 시뮬레이션 결과 풍력발전기가 충분한 제동력을 제공하고 안정도 여유를 증가시킴을 확인할 수 있었다. 풍력발전기를 추가할 때 안정도 여유도는 CCT 기준으로 5배까지 향상되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 추계학술대회 논문집
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• pp.307-309
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• 2008

This study suggests a modeling of grid-connected wind turbine generation system that has induction generator, and aims to perform simulations for outputs by the variation of actual wind speed and for fault current of wind generation system by the transformer winding connection. This study is implemented by matlab&simulink. The simulation shall be performed by assuming single line to ground fault generated in the system. Generator power, generator rotor speed, generator terminal current and fault current shall be observed following the performance of simulation. The fault current change will be dealt through the simulation results for fault current of wind generation system following the grid-connected transformer winding connection and the simulation result by the transformer neutral ground method.