SSN Synchronous Machine with Field Terminal and no Minimum Parasitic Load or Snubber Requirement

This model implements a synchronous machine (SM) model compatible and designed with SSN and does not require any parasitic load (e.g.: RC snubbers) to be stable even in open stator conditions.

Field terminals are accessible electrically as an SSN node in this model and fed by a thyristor rectifier with non-linear dumping resistance, which is active only during machine emergency shutdown.

The SSN Synchronous Machine model implements two types of saturation (global and differential) based on the total flux and includes the zero-sequence impedance of the machine.

The SSN Synchronous Machine saturation can be applied to both d-q axes, making it suitable to simulate round-rotor synchronous machines undersaturation.

Demonstration

In this simulation, the SM is first driven to nominal power with current controller acting on the field current, as well as a turbine power and frequency control.

A fault is then made close to the SM stator terminal which activates protection measures: SM stator breaker is opened, as well as field terminals. In the latter case, due to its large inductance, the field terminal must be shorted with a non-linear resistance (modeled with an SSN iterative MOV) to allow for a smooth decrease of field current and, consequently, of machine stator voltages.

References

C.Dufour, 'Highly stable rotating machine models using the state-space-nodal real-time solver', COMPENG-2018 conference, Oct. 10-12 2018, Florence, Italia