多相多階市電併聯換流器之動態載波相位調變

隨著工業應用對於功率需求的增大，使用多相多階式換流器不僅可以達到提升電壓與電流的額定值，透過多相電壓耦合還能提升電壓輸出的階層成為近幾年常用的方法，但是多相多階式換流器在線對線電壓的階層會出現三階變動，而導致輸出電壓總諧波失真(Total Harmonic Distortion, THD)表現不太理想。因此本論文提出了一種適用於市電併聯多相多階換流器並針對線對線電壓THD進行改善的動態載波相位調變方法。此調變策略透過不同組態的載波相移，讓線對線電壓階層變動限制在兩階進而達到降低THD的目的，也讓換流器輸出端能使用更小的濾波電感有效降低電感體積增加能量密度。本論文中首先說明多相多階換流器的控制原理，並分別介紹高壓應用的多階換流器和大電流應用的多相換流器兩者使用的調變方法。接續延伸至如何將多階電路與多相電路進行架構與調變方式的整合，提出本文的動態載波相位調變方法並說明其對線對線電壓THD改善效果。接著透過電腦模擬驗證理論的正確性。最終進行模組化的3kVA硬體實現與實際併網測試，實驗結果顯示線對線電壓THD的改善與模擬結果相符，未經過濾波電感之線對線電壓THD由原先的接近20%降至10%，驗證所提出調變策略的有效性。

關鍵字

多相多階換流器；市電併聯換流器；動態載波相移調變；總諧波失真；模組化電路

並列摘要

With the increase of power demand for industrial applications, the use of multiphase- multilevel inverters can not only achieve the need of increasing voltage and current, but also increase the number of voltage for the multilevel inverter through the multiphase voltage coupling. However, the line-to-line voltage of the conventional multiphase-multilevel inverter will change among three voltage levels, resulting in an unsatisfactory total harmonic distortion (THD) performance. Therefore, this study proposes a dynamic carrier phase modulation method to improves the line-line voltage THD for the grid-tied multiphase-multilevel inverters. The proposed dynamic carrier phase modulation method can achieve the two level alternation of reduce the voltage THD. Eventually, a smaller output filter inductor can be used to effectively reduce the volume and increase the power density of the grid-tied inverter. In this study, the control strategy of the multiphase-multilevel inverter will be introduced. Conventional modulation method used for the multilevel inverter for high-voltage applications and the multiphase inverter for high-current applications will be presented, separately. The integration of the multiphase-multilevel inverter with the proposed dynamic carrier phase modulation method will be explained in detail. The operation principle for two voltage level alternation and the line-to-line voltage THD improvement will be presented. Computer simulation results are shown to validate the effectiveness of the proposed control method. A 3kVA modularized multiphase-multilevel grid-tied inverter was built and tested to verify the performance of the proposed control method. Experimental results show that the improvement of the line-to-line voltage THD is consistent with the simulation results. THD can be reduced from 20% to 10%.

並列關鍵字

multiphase-multilevel inverter ； grid-tie inverter ； dynamic carrier phase modulation ； Total Harmonic Distortion,(THD) ； modular circuit design

參考文獻

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