Simscape branch current equations

What should be the current equations in branch section while desiging a ssc component which allows the power to flow on either directions. i1, i2 are current of side1 and i3,i4 are the currents at side 2

 nodes
        p1=foundation.electrical.electrical; % + 1:top
        n1=foundation.electrical.electrical; % - 1:top
        p2=foundation.electrical.electrical; % + 2:bottom
        n2=foundation.electrical.electrical; % -2:bottom
        end
  variables
        i1 = { 0, 'A' }; % input Current
        v1 = { 0, 'V' }; % input Voltage
        i2 = { 0, 'A' }; % input Current
        v2 = { 0, 'V' }; % input Voltage1
        v3={0,'V'}; % output Voltage2
        i3= { 0, 'A' }; % output Current
    i4 = {0,'A'};%output current
    v4 = {0,'V'}%output voltage
%         idc = { 0, 'A' }; % output Current
        Pin= { 0, 'W' }; % Input power
        Pout = { 0, 'W' }; % output power
        Losses={ 0, 'W' }; %  power loss

        end
        
        branches
        i1 :p1.i->* ;
        i2 : n1.i->*;
        i3: p2.i->*;
        i4: n2.i->*;
    end

    equations
        v1 == p1.v ;
        v2 == n1.v;
        v3 == p2.v;
        v4 == n2.v;

Answer 1

[Sabin]

The branches section establishes the relationship between the component Through variable and the component nodes (and therefore the domain Through variable). Considering a resistor, the i : p.i -> n.i statement indicates that the current through the resistor flows from node p to node n. For each Through variable, the sum of all its values flowing into a branch point equals the sum of all its values flowing out.

In Simscape power flow in either direction unless there is a mechanism to prevent this. The way we define the branch will dictate the sign convention.