Summary: | 博士 === 國立清華大學 === 電機工程學系 === 89 === ABSTRACT
The electrical energy processing technology has gained great progress in the past decade. The main motivation of this research is centered round the study of a high performance three-phase AC/DC converter. The so called high performance means it is desired to achieve (1) sinusoidal line currents without harmonic pollution, (2) clean DC output voltage, (3) the output voltage can be either stepped up or stepped down continuously, (4) bidirectional power flow capability, (5) integrated single stage converter configuration to achieve better efficiency.
Major contributions of this dissertation may be summarized as follows. First, the author proposed an active three-phase step up/down AC/DC converter with bidirectional power flow capability to achieve the previously defined high performance characteristic. Second, based on the generalized zero voltage space vectors concept and the distributed D0 control strategy, the author derived a closed form duty cycle control law and successfully proved the feasibility of the conjecture of constant D0 control strategy. Third, based on the closed form duty cycle control law and the state space averaging technique, the author derived the model of the proposed converter. The DC model and the small signal model may be expressed by both the mathematical equations and the equivalent circuit forms. The transfer functions of the small signal model are also derived for reference. Fourth, due to existence of one degree of freedom, namely choice of D0, of the proposed converter, the author proposed a maximum constant D0 controller for the concerned converter to lower the intermediate capacitor voltage for practical applications. An analog type prototype was also constructed to demonstrate the validity of the proposed theory. Finally, in order to further reduce the switching number of the active switches as well as reduce the switching on/off transient, the author proposed a dead-band controller. It is found that the switching number of each active switch in the bridge is reduced by one sixth and also the intermediate capacitor voltage can be further reduced.
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