This is the first part of an exciting three-part Model Monday post series highlighting RSCAD’s phase domain synchronous machine model and how it can be used for the closed-loop testing of a generator protection relay. Tune in next week – Monday, August 22, for part two!
The RSCAD library includes a phase domain synchronous machine (PDSM) model with a stator-ground fault option as well as direct access to the field winding. The RTDS Simulator is the only real time simulation tool that includes a model of this nature. The advanced features and capabilities of the PDSM model included in RSCAD make it ideal for testing of generator protection, including 100% stator-ground fault detection.
The new values of machine inductances are calculated each timestep as the rotor position and possibly the saturation changes. The effect of the changing PDSM inductances is embedded and solved as part of the main network solution. The embedded phase domain approach shows superior numerical performance compared to the conventional interfaced approach of a DQ0 based model. The PDSM model computes the self and mutual inductances of machine windings (including faulted windings) as functions of rotor position and saturation in order to simulate internal faults.
The faulted PDSM model (_rtds_PDSM_FLT_v2) has two options for providing field excitation to the model: the user can select to use “Control System Input” or “Power System Node”. If “Control System Input” is selected, the value of the field voltage is determined by an input control signal, where an input of 1 causes the machine to generate 1 per unit terminal voltage in open circuit in linear steady-stage conditions. The user has the option to send per unit voltage out and connecting the machine to one of the many exciter models available in the RSCAD library. If the “Power System Node” option is selected, two power system nodes will appear which can be used to energize the field winding using actual power system components, such as a DC source model or power electronics. In this case, the user must provide the field current in kA required for 1 per unit unsaturated open-circuit terminal voltage at rated speed. After compile the circuit, the required field voltage for 1 pu unsaturated open-circuit terminal voltage at rated speed, as well as the required field voltage for initialization of the machine, will both be written to the .map file which is automatically created after compiling. The .map file for a simple case containing a PDSM which uses control components for field excitation is shown below.
Tune in to next week’s Model Monday for a detailed look at how the PDSM model can be used to perform the closed-loop testing of a generator protection relay using the RTDS Simulator.