This example shows a Machine mechanical coupling of an excitation system using Simscape™ mechanical rotational ports.
Gilbert Sybille, IREQ. Jean-Francois Doyon, ETS.
In large alternators, the excitation system is provided by a small synchronous machine connected to the shaft of the synchronous generator. Current rectification is performed by a rotating diode bridge mounted on the generator shaft, thus avoiding slip rings for providing DC power to the synchronous generator field.
The synchronous generator is driven by a diesel motor with speed regulation. The mechanical coupling of the generator, the exciter system, and the diesel motor is done by using the Simscape mechanical rotational ports of the Synchronous Machine blocks.
This model is very similar to the power_SM_exciter model. The only difference is that the two synchronous Machine blocks and the diesel motor use a mechanical rotational port to connect together and represents the mechanical shaft.
Run the model and compare the simulation results with the ones obtained with power_SM_exciter model. They should be identical.
Note that the inertia and viscous friction are specified for every system (in the mask of the Synchronous Machine blocks, and directly to the mechanical shaft for the diesel motor). This is not the case for the power_SM_Excitation model where the total inertia and viscous friction of the three systems need to be specified in the Synchronous Machine block representing the generator.