- 學位論文
利用閘控串聯電阻改善離岸風場之虛功補償能力
Design of a GTO-thyristor Controlled Series Resistor for Reactive Power Capacity Enhancement of an Offshore Wind Farm
摘要
本論文主要目的在於研究利用閘控串聯電阻改善離岸風場在系統故障時之動態響應。當風機操作在功因控制模式下，探討故障發生時，風機輸出的實虛功配置、轉子的過速問題，和定子端電壓過低造成的影響，使風機在電力系統不穩定時能提供電網虛功和電壓支撐能力，並達到低電壓穿越的法規要求。 本文利用閘控串聯電阻(GCSR)的閘流體投入和切出時間，讓定子側串聯電阻擁有可變電阻的特性，針對不同的故障電壓等級，達到適合的補償效果，並且藉著提升後的電壓加強風機虛功的輸出能力。另一方面，考慮到風機和電網穩定度，選擇適合的電阻值，降低對系統造成的衝擊，也以其串聯電阻吸收轉子的加速能量，平衡風機實功的輸出。 本論文以MATLAB/Simulink軟體進行模擬，建立併網之雙饋式感應發電機模型，模擬結果顯示，當系統發生永久三相短路故障時，閘控串聯電阻可提升風機的定子端電壓、抑制轉子轉速，使風機穩定提供電網最大虛功，提升風機低電壓持續運轉能力。
並列摘要
The main purpose of this thesis is to improve the dynamic performance of grid-connected offshore wind farm under faults using GTO-thyristor Controlled Series Resistor (GCSR). The power dispatch of DFIG and the generator voltage dip in the stator side are studied. Grid regulations require wind farm to remain dynamically stable during faults and to supply active and reactive power into the network. In this thesis, GCSR is proposed to improve generator voltage dip such that the reactive power output can be increased and the active power unbalance of wind turbine can be relieved. In order for GCSR to achieve the goal of variable series resistances under different fault voltages, it is important to determine the size of the inserted resistances so that small signal stability of the wind farm can be ensured. The MATLAB/Simulink simulation software is used to simulate the dynamic performance of the grid-connected DFIG. Simulation results indicate that the DFIG can deliver more reactive power and reduce the voltage drop at the generator by the proposed GCSR. Moreover, rotor speed is significantly reduced to avoid rotor overspeed. As a result, the DFIG can be operated stably during faulted period.