- 學位論文
以固態轉供開關與不斷電系統為基礎之電壓驟降渡過策略
Voltage sag ride-through solutions based on solid-state transfer switches and uninterruptible power supplies
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摘要
本論文針對固態轉供開關系統(STS)與不斷電系統(UPS)，提出了一個新型的磁通控制技術，以實現快速的負載轉移並同時抑制湧浪電流。以閘流體元件為基礎的傳統的固態轉供開關系統已經被廣泛的應用於電力網路以提升電力品質與供電可靠度。然而，傳統的固態轉供開關系統所需之負載轉供時間經常需要超過四分之ㄧ個市電週期，同時負載轉供的過程也會引起嚴重的湧浪電流。在本論文中，一個具備強制換相電路之改良式固態轉供開關被提出，用於大幅減少線路轉移時間，並為敏感性負載提供更快速的電壓驟降渡過能力。以強制換相能力為基礎，當固態轉供開關搭配負載變壓器被用於保護敏感性負載時，一磁通估測技術與一閘流體之切換策略被提出用於抑制饋線轉移時之湧浪電流。實驗室之測試結果與電路設計上之考量均被提出討論，以驗證本論文所提出之固態轉供開關系統之效能。 不斷電系統之湧浪電流議題與解決方案同樣在本論文被提出。當不斷電系統被使用作為電壓驟降渡過策略時，負載從故障的市電電壓轉換到不斷電系統之過程經常伴隨著湧浪電流現象。為了抑制湧浪電流，一閉迴路之磁通補償器被提出，並被整合於傳統之電壓與電流控制器。本論文所提出之磁通補償器能追蹤變壓器之磁通變化，並能在不犧牲任何輸出電力品質之狀態下立即修正驟降電壓所引起之磁通偏移。因此能完全避免湧浪電流。除此之外，本文所提出之磁通控制設計被延伸至抑制多具負載變壓器於不斷電系統中所引起的湧浪電流問題。有關於磁通控制策略之設計考量與磁通估測技術之誤差分析均在本論文中被詳細探討。
並列摘要
This dissertation presents a new flux control scheme for a solid-state transfer switch (STS) system and an uninterruptible power supply (UPS) system to accomplish fast load transfer and to mitigate the inrush current. Conventional STS system based on thyristors has been widely used in medium-voltage applications to enhance the power quality and reliability. However, conventional STS system often requires more than a quarter of cycle to complete the load transfer and its line transfer action also causes a considerable inrush current. In this dissertation, an improved STS with forced commutated circuit is presented to greatly reduce the transfer time and provide a better voltage sag ride-through capability for the critical loads. Based on this forced commutation capability, moreover, a flux estimation scheme and a thyristor gating scheme are presented to suppress the inrush current during the load transition process when the combination of the STS system and the transformer is used to serve the critical loads. Laboratory test results and design considerations are presented to validate the performance of proposed STS system. The inrush current issues associated with the solution for the UPS system are also presented in the dissertation. When the UPS systems are used for the voltage sag ride-through, the inrush current phenomenon often exists in the load transition process from a deformed grid voltage to battery power. To mitigate the inrush current, a closed-loop flux compensator is proposed and integrated with the voltage and current controllers. The proposed flux compensator can track the transformer flux and corrects the flux deviation in real time without sacrificing any voltage quality, thus completely avoiding the inrush current. Furthermore, the proposed flux control design is also extended to alleviate the inrush current when multiple transformers are energized by the UPS system. Detail description of the design issues and investigation of flux estimation error are given.
參考文獻
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