Current Loop Stability Analysis of a VIENNA-type Three-phase Rectifier for an Imaging System Power Supply Application

Matthieu Darnet, Emmanuel Godoy, Daniel Sadarnac, Stephane Gautrais

Abstract

High power supply for imaging systems needs to meet increasing demand in speed, power and voltage control. A Vienna-type three-phase rectifier prototype has been developed by GE Healthcare to handle it. This power supply has a significant stability issue because its load has a pulsed profile, and the ranges of power demand, input voltage, and grid impedance are wide. First, a model of the rectifier and its control has been made. Second, a current loop stability analysis has been investigated. Stability margins have been drawn for all the range of output power, input voltage and grid inductance for the current loop. Stability has been shown for all the operating points. However, a poorly damped input filter brings potential oscillations and reduces stability margins. Delay margins are also particularly low. Finally, a validation of the rectifier model has been made with measurements on the prototype.

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