Well, you have 4 total variables: V and i inherited from the branch, and your additional custom variables q and w.
By inheriting from the electrical branch, you have also inherited 1 equation defining the sign convention of V ... it's something like V == P.v - N.v; .
That leaves you with 3 equations to properly define the system, but you seem to have 4 in your component (Assuming that you plan on leaving that one part commented out).
Without knowing much about your model, it seems like both phi and its initial value phi_0 are in the parameters section. It therefore seems like this could be a dynamical state. If you move phi to the variables section, that should round off your number of variables vs. number of equations.
Also, if you are using R2014a or later, all variables will show up in the "Variables" tab of your block, so you could specify the initial phi value directly there without the need to make it an explicit parameter in the .ssc file.
- Sebastian
