I understand that you are trying to convert a physical signal to electrical signal(to be compatible with electrical port).This can be achieved as follows:
Firstly when we are trying to convert a physical signal to a electrical value,there are two types of electrical form from which we have to choose,they are.
After choosing the electrical type, we can opt for the corresponding "Controlled Sources" where they convert the physical signal to the electrical value of chosen form.
These modules can be found in: Library Browser>Simscape>Foundation Library>Electrical Sources.
These modules take the physical signal value and convert them to the chosen form with the value equal to physical signal value.
As you can see in above example the physical signal value is converted to electrical form (i.e current) by controlled current source.
I hope this resolves your query.
Thanks,
Venkat Siddarth V