三相電網形成反流器之阻抗估算策略與新型諧波電壓抑制之研製;Development and Implementation of Impedance Estimation Strategy and Harmonic Voltage Suppression for Three-phase Grid-Forming Inverters

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題名:	三相電網形成反流器之阻抗估算策略與新型諧波電壓抑制之研製;Development and Implementation of Impedance Estimation Strategy and Harmonic Voltage Suppression for Three-phase Grid-Forming Inverters
作者:	葉承韋;Yeh, Cheng-Wei
關鍵詞:	三相交流微電網;併網模式;孤島模式;阻抗估算策略;諧波垂降控制;諧波電壓抑制;負虛擬阻抗;Three-phase AC Microgrid;Grid-Connected Mode;Standalone Mode;Impedance Estimation Strategy;Harmonic Droop Control;Voltage Harmonic Mitigation;Negative Virtual Impedance
日期:	2024-08-12
上傳時間:	2024-10-09 17:18:17 (UTC+8)
出版者:	國立中央大學
摘要:	隨著環保意識不斷攀升，再生能源發電的佔比亦逐日增加，本論文主要針對獨立運行的交流孤島微電網系統，著重研究如何於系統在含有非線性負載的情況下，抑制轉換器的輸出電壓諧波成分。現今之儀器設備所屬的類別大多屬於非線性負載，當微電網架構運行於孤島模式中，系統引入非線性負載時，甚至因為轉換器連接至責任分界點的距離增加等情況下，將會造成轉換器的輸出電壓產生諧波，此時使用者端所接受到的電壓信號品質將大幅降低。本文在控制迴路中引入諧波負虛擬阻抗的控制策略，並基於垂降控制架構提出了一種應用於三相諧波抑制的諧波垂降控制策略，減少微電網輸出電壓諧波成分。當電能轉換器輸出功率時，於初級控制中的併網或孤島模式下，估算電能轉換器及責任分界端之間的線路阻抗，並設計諧波負虛擬阻抗以消除線路阻抗對電壓諧波分量產生的影響，使得微電網於孤島模式引入非線性負載的情形下能具備減少微電網電壓諧波輸出的效果。隨後，透過加入所提諧波垂降控制法則於本地控制器中，將進一步抑制垂降控制所輸出的電壓諧波分量，此時於孤島模式運行下的微電網所產生的責任分界點電壓可維持輸出穩定供給，並減少責任分界點的電壓總諧波失真量，以提升整體孤島電能轉換器所輸出的電力品質。本文也提出了一種線路阻抗估算策略，主要可適用於以下類別：於強電網、弱電網、弱電網加入非線性負載以及孤島下加入非線性負載造成電壓電流失真的情形。然而，通常在弱電網和孤島下加入非線性負載的情境下將添增計算困難度，這將使得阻抗估算性能遭到影響。於此本文的估算策略使用了一種基於二階廣義積分正交信號產生器的帶通濾波器，利用基本波實現線路阻抗估算的策略，使得轉換器即便受限於嚴峻的估算情境中，亦不影響整體估算阻抗的能力。;Due to the increasing of environmental awareness, the proportion of renewable energy in power generation is growing. This paper mainly focuses on standalone three-phase AC microgrid systems—specifically studying on how to suppress harmonic distortion for inverter output voltage within nonlinear load. Many modern devices belong to nonlinear load. When such load connected to a microgrid operating in standalone mode, especially when the distance between the inverter and the point of common coupling (PCC) is increased, harmonics may appear in the inverter output voltage, significantly degrading the power quality for users. This thesis introduce a harmonic negative virtual impedance control strategy in the control loop and propose a harmonic droop control scheme tailored for three-phase harmonic suppression, aiming to reduce the output voltage harmonics in the microgrid. During power conversion—whether in grid-connected or standalone mode of primary control—we estimate the line impedance between the inverter and the PCC point in order to design harmonic negative virtual impedance that counteract the line impedances. This allows the microgrid which operate in standalone mode within nonlinear loads effectively reduce output voltage harmonic. We also incorporate the proposed harmonic droop control law into the local controller to further suppress harmonic components produced by harmonic droop controller. As a result, during standalone operation, the PCC voltage remains stably supplied, also the total harmonic distortion (THD) at the PCC can be reduced, which improves the overall power quality in the standalone inverter. This paper also presents a line impedance estimation strategy applicable to various scenarios: strong grid, weak grid, weak grid with nonlinear loads, and standalone mode with nonlinear loads causing voltage/current distortion. However, impedance estimation tends to be more challenging under weak grid or standalone conditions with nonlinear load, which can degrade the performance of proposed method. To mitigate this, the proposed estimation strategy uses a band-pass filter based on a second order generalized integrator (SOGI) signal generator, which extracts the fundamental frequency for line impedance estimation. Even under these difficult conditions, the inverter maintains robust impedance estimation performance.
顯示於類別:	[電機工程研究所] 博碩士論文

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