User Custom Blocks (UCBs) in SSN are used to simulate an electric subsystem or element inside the SSN solver. They are functionally equivalent to other SSN groups, but are entirely built by the user as opposed to standard SSN groups built automatically from the SimPowerSystems elements.
SSN-UCBs produce what is sometimes called a Discrete Companion Model (DCM), in Norton form, composed of a discrete resistance matrix Ye and a current history vector Ih. Ye and Ih are computed from past nodal voltage solutions and are used to compute the next step voltage solution of the main SSN solver.
The DCM can be computed using a Simulink S-function, with an S-function builder block, or with standard Simulink blocks. The latter method is often preferred because it’s simpler to use. The Simulink block method is used for most of the existing UCB models like SSN Rotating Machine models or OLTC.
Making Your Own SSN-UCB
- Determine the number of electric terminal or phase (nbp) of your UCB
- Select the proper UCB template corresponding to nbp in ARTEMiS/SSN/UCB Templates
- Code your UCB
- Use the UCB