以正負序虛功電流控制為基礎之市電併聯轉換器低電壓渡過策略的研究

Research of Low Voltage Ride-Through Strategies for Grid-Connected Converters Based on Positive Sequence and Negative Sequence Reactive Current Control

許哲瑋(Che-Wei Hsu)

指導教授 ： 鄭博泰

國立清華大學/電機資訊學院/電機工程學系/碩士(2010年)

摘要

隨著越來越多分散式能源透過市電併聯轉換器連接到交流電力系統，電力公司為了確保故障發生時電力系統運轉的穩定，制定低電壓渡過規範要求分散式發電系統在規定的時間內必須持續與電力系統維持連接的狀態。除了維持與電力系統連接，電力公司制定的低電壓渡過規範還要求分散式發電系統必須提供虛功率支撐交流電壓。傳統的虛功補償方法可以提供虛功電流以滿足低電壓渡過規範，但是在市電電壓驟降的情況下，傳統方法提供的虛功電流有可能超過市電併聯轉換器本身的電流額定，因此有觸發市電併聯轉換器過電流保護的風險。當電源轉換器的過電流保護被啟動，轉換器停止運轉，而分散式發電系統與電力系統解聯，便無法滿足低電壓渡過規範。因此，在市電電壓不平衡的情況下，如何產生不超過轉換器額定的電流是非常重要的。本篇論文為了滿足低電壓渡過規範以及確保市電併聯轉換器的安全操作提出正負序虛功電流控制方法，此方法分別產生正負序虛功電流命令並且使得三相電流不會超過市電併聯轉換器的電流額定。因為在電源轉換器的安全操作中，使得三相電流不超過轉換器的交流電流額定是非常重要的。本論文針對正負序虛功電流命令的產生以及市電併聯轉換器控制方法進行理論分析與解釋，並且使用電腦模擬和硬體實驗驗證本文所提出的正負序虛功電流控制方法。另外，針對本論文提出的虛功電流控制方法和其它文獻上已提出的低電壓渡過方法進行分析與比較。

關鍵字

市電併聯轉換器 ； 低電壓渡過 ； 虛功率 ； 虛功電流

並列摘要

With more and more distributed energy resources (DERs) being connected to the grid through interface converters, the utility requires the DER generation system to remain grid-connected during grid voltage imbalance to ensure the operating stability of the AC power system. These low voltage ride-through requirements also suggest that the DER generation system injects reactive power to support grid voltages. Traditional reactive power compensation methods can provide request reactive current to meet the low voltage ride-through requirements. However, the resulting peak phase current may exceed the peak rated current of the converter during voltage sag, thus facing the risk of over-current protection tripping of itself. In this thesis, a positive sequence and negative sequence reactive current injection method is proposed to meet the low voltage ride-through requirement. The proposed method can generate the positive sequence and negative sequence reactive current commands so the resulting phase current does not exceed the ampere constraint of the converter，which is very critical for the safe operation of the converter. Its operation principle and control method are explained and analyzed. Simulation and laboratory test results are presented to validate the effectiveness of the proposed method. Comparisons of the proposed method and other low voltage ride-through techniques are also presented.

並列關鍵字

grid-connected converter ； low voltage ride-through ； reactive power ； reactive current

參考文獻

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