Formulation-Based Model Expressions

[ccoffrin]

Explore the possibility of adding an explicit model-based expression block. For example this can be used to setup different expressions for vm^2 in different formulations. If so many constraint_power_balance constraints could be re-used.

[ccoffrin]

Storage current is also a good item to simplify with an expression. AC models should define an expression while SOC models have a variable.

[ccoffrin]

New NLP interface will make this approach even more effective.