METHOD AND APPARATUS FOR STABILIZATION AND MINIMIZATION OF LOSSES OF A SERIES CONNECTION OF DC/DC-CONVERTERS CONNECTED TO THE OUTPUT-SIDE PARTIAL VOLTAGES OF A THREE-LEVEL PWM RECTIFIER SYSTEM

摘要

A method and an apparatus for active stabilization of the voltage sharing of a series connection of DC/DC converter stages (7, 8), and a method and an apparatus for minimization of the current stress of the input capacitors (5) of DC/DC converters operating at the output of a three level converter. For each DC/DC converter there is one pulse width modulation-stage (57, 58), where at the input side summing elements get control signal defining the power flow to the secondary power circuit from a supervising output voltage controller and/or an output current controller. The symmetry controller creates a positive and negative offset of this control signal in case of an asymmetry of the partial input voltages of the DC/DC-converters. The offset controls the power flow of the DC/DC converters in a way that the DC/DC converter with higher input voltages takes less power from its input capacitor.