This seems to be an easy problem but i cannot figure out how to do it. I have to use switch in my design so that when the voltage across two points excess a fixed amount the switch should be connected to port 1 otherwise port 3. To use that i use control port which is port 2 bu i cannot connect this switch to the rest of the circuit. You can see the design below. 
Electrical – Connecting switch to a resistor in Simulink
batteriesMATLABpowersimulink
Related Solutions
The battery's internal resistance is IN SERIES with the battery. With no load connected, the battery will not deliver any current, and there will be no voltage dropped across the internal resistance.
With a load connected, the battery will deliver current, which will flow through the internal resistance. This current causes some voltage drop in the internal resistance, reducing the effective voltage of the [battery plus internal resistance].
Is there any reason you are mixing SimPowerSystems & SimScape?
With the introduction of SimScape "SimPowerSystems", the legacy method of dealing with electrical simulations has become redundant EXCEPT for some legacy blocks and specialised technologies.
The legacy SimPowerSystems does have a more specialised battery model so I can understand why you would want to use that IF it provides features the simscape battery does not (or that you cannot reproduce...)
you can run with both as long as you provide the needed pre-requisites.
I don't see a SimScape reference block nor a solver block. Do they exist.
The actual problem here is an algebraic loop.
the subsystem highlighted within the 1st post. What EXACTLY is in there? I suspect there is some form of SimPowerSystem voltage sensor to bring a signal into the simulink domain, a Simulink-PS converter block to take it into the SimScape domain. This is where it needs to be solved.
Add a memory block in the simulink domain should break the loop and provided the needed initial condition (if you are running continuous consider adding a TF with a small timeconstant todo the same thing)
Best Answer
you are attempting to connect a SimPowerSystems domain node to a Simulink domain node...
The switch you are using is for simulink signals NOT electrical signals.
For simPowerSystems there is an IdealSwitch which takes a Simulink-domain control signal. This only open-circuits a signal signal & does not act as a double-throw switch. Linking two together & using a logic NOT on one would provide the same affect
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