Introduction to the SSN Solver

The State-Space Nodal (SSN) method is a nodal method, where the main difference is in how the nodal branch or groups are made.

In SSN, the user selects the way the groups are made. These groups are computed by a state-space method while the interface between the groups is solved by a nodal method.

By making large groups, for example, the number of equivalent nodes to be solved by the nodal method can be limited. At the same time, by choosing the groups well, the number of switches per groups can be limited and full-precalculation can be made.

See References for a detailed explanation of the SSN theory.

Within the Simulink/Simscape Electrical Specialized Power Systems (SPS) environment, the SSN presents some challenges for the normal user to achieve real-time simulation. The main challenge is to design the SSN model using SSN Nodal Interface Blocks to make groups of reasonable state and number of switches and to limit the number of total nodal nodes connecting these groups.

The SSN also includes powerful features like:

• Inlined interpolation of thyristor firing

• Inlined interpolation of voltage inverter

• Instantaneous event detection

• An iterative method for MOV and switches

These are explained through a series of examples.