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

Abstract

This model implements a synchronous machine (SM) model compatible and designed with SSN and that does not require any parasitic load (like snubbers) to be stable even in open stator conditions. Field terminal is 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 shudown. [Dynamic studies; Electromagnetic Transcient (EMT); Generation; Hydraulic Turbine; Nodal method; State-space representation; Protection:Frequency Control; Metal Oxyde Varistor (MOV) ]

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 later case, du to its large inductance, the field terminal must be shorted with a non-linear resistance (modeled with a SSN iterative MOV) to allow for a smooth decrease of field current and, consequenctly, of machine stator voltage.

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

References

C. Dufour and D. S. Nasrallah, "State-space-nodal rotating machine models with improved numerical stability " accepted at IECON 2016 conference, Firenze, Italia.