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Reference Number: AA-01343// Views: AA-01343// Created: 2017-11-21 18:15:56// Last Updated: 2017-11-21 20:16:43
Q&A
Why the number of eHS input control signals "U" is larger than the number of sources (fixed and controllable) in my design?

Why the number of eHS input control signals "U" is larger than the number of sources (fixed and controllable) in my design?

When you have an eHS power electronics design, you can include fixed and controllable sources of voltage as shown in Figure 1.This voltage and current sources will EXPLICITLY require "U" input signals whether they are "fixed" or "controlled" type.


Figure 2: Current and voltage sources require EXPLICIT input "U" control signals

There is however another element that will IMPLICITLY  require "U" controlling inputs for eHS: when set to a value different  from zero, the forward voltage (Vf) of devices such as IGBT's, Thyristors and diodes will also require "U" control inputs, as shown in Figure 2, where the "Three level Bridge" mask shows a forward voltage parameter different from zero Vf=0.7. This Vf value will (in a case of a 3-level 3-pahse bridge)  require 18 additional inputs "U" to control the Vf of each switching device.

In order to remove the need of IMPLICIT "U" control inputs, the Vf value of the "Three level bridge" (or whichever power electronic device is being used), should be set to zero: