control logic and comment

Signed-off-by: Jerry Guo <Jerry.Jinfeng.Guo@alliander.com>

Author: Jerry-Jinfeng-Guo

docs/user_manual/calculations.md

@@ -626,7 +626,7 @@ Power flow calculations that take the behavior of these regulators into account
 
 ##### Control logic for power flow with automatic tap changing
 
-The following control logic is used:
+We provide the control logic used for tap changing. For simplicity, we demonstrate the case where the regulator control side and the transformer tap side are at different sides.
 
 - Regulated transformers are ranked according to how close they are to {hoverxreftooltip}`sources <user_manual/components:source>` in terms of the amount of regulated transformers inbetween.
   - Transformers are regulated in order according to their ranks.
@@ -652,6 +652,7 @@ The following control logic is used:
   - Exploit the neighbourhood of all transformers (see {hoverxreftooltip}`user_manual/calculations:Initialization and exploitation of regulated transformers`)
     - Re-run the iteration in the above if any of the tap positions changed by the exploitation.
 
+In the case where the control side of the regulator and the tap side of the transformer are at the same side, the control logic of taps will be reverted (see `user_manual/calculations:Initialization and exploitation of regulated transformers`). 
 The exploitation of the neighbourhood ensures that the actual optimum is not accidentally missed due to feedback mechanisms in the grid.
 
 ```{note}
@@ -667,7 +668,6 @@ This assumption is reflected in the requirements mentioned in {hoverxreftooltip}
 ```
 
 ```{note}
-The control logic assumes that the (compensated) control voltage decreases when the tap position changes (increases when the control side of the regulator and the tap side of the transformer are at different sides, or decreases they are at the same side).
 If the line drop compensation impedance is high, and the control side has generator-like behavior, then this assumption does not hold, and the calculation may diverge.
 Hence, this assumption is reflected in the requirements mentioned in {hoverxreftooltip}`user_manual/components:Line drop compensation`.
 ```