三相三階式交直流轉換器操作於不同準位電壓與不平衡負載之控制研究

Investigation of the Ability for Three-Phase Three-Level Unity Power Factor Rectifier to Unbalance Loads and Unequal Bus Voltages Requirements

本文主要是研究具高功因特性之三相三開關切換式升壓型整流器，並針對兩直流電容端需要不同準位電壓，或需要不同額定負載時，提出可行的控制方法，並同時探討其允許的電壓準位差異與負載額定差異的範圍，而這些問題在國內外已發表的論文中還未被談及。透過本文所提控制器，當此三開關切換式升壓型整流器的兩直流端電容所接負載不平衡，或需要兩種不同準位電壓輸出時，透過控制三相輸入電流，可使得兩個電容器的電壓在不同準位工作，亦可使其操作在不平衡負載情況，且在有限的不同準位電壓差距與有限的不平衡負載情況下，不需付出輸入三相電流的正負半週準位失去平衡的代價；換言之，在上述情形下仍可控制三相輸入電流之正負半週大小平衡且為正弦，輸入電流不存在直流偏移量，而使此控制可以實用。當然這只能在有限的不同準位電壓與有限的不平衡負載情況下才能保持此形式，而相關可允許不平衡電壓量與不平衡負載量之理論極限推導也將在本文中完成。本文也比較三種脈波寬度調變切換方式之差異，最後實作1 kW 系統以驗證所提理論。

In this paper, the development of high-power three-phase three-switchboost rectifier with different two DC-bus voltage levels or with differenttwo DC-bus load rating issues is presented. The study also explored the impact of the two DC offset voltage control and load unbalanced control,with particularly emphasis on the limits requirements under such situations,which has not been mentioned in the published paper. With the proposedcontroller, it can fit the cases including the two dc-bus load imbalance, andtwo different two dc-bus voltage outputs. That is, the system can still becontrolled with in-phase three-phase input currents even in the above cases.The modulation strategies are compared, and the sensitivity performancedue to the mismatched elements or control parameters is presented.Three-types of PWM switching strategies are compared in this paper, andthe validity of the proposed method is confirmed by simulation andexperimental results through a 1kW prototype.