Evaluation of a Delta-Connection of Three Single-Phase Unity Power Factor Rectifier Systems (Δ-Rectifier) in Comparison to a Direct Three-Phase Rectifier Realization

摘要

In this paper the delta connection of three single-phase boost unity power factor rectifier units (Δ-rectifier) is analyzed based on an equivalent star connection. As the calculation of the input voltage space vectors which are associated with the combinations of the power transistor switching states of the line-to-line units shows the Δ-rectifier and a direct three-phase unity power factor (VIENNA) rectifier are characterized by equal modulation limits. Furthermore, the Δ-rectifier shows like the VIENNA Rectifier a redundancy of switching states concerning input voltage formation. This redundancy has to be employed for a control and/or suppression of a low frequency zero sequence current component circulating inside the Δ-connection of the line-to-line units. According to a digital simulation the switching frequency ripple of the sinusoidal mains current of the Δ-rectifier shows only a slightly higher normalized RMS value as resulting for the VIENNA rectifier. Therefore, in the course of further research, i.e. Part II of this paper, the stresses on the power components of the Δ-rectifier will be calculated in analytical form in order to provide a basis for a comprehensive comparative evaluation and for the dimensioning and practical realization of the system.