In addition to the classical, dq-based, induction machine (IM) model, RSCAD-RTDS includes the _rtds_INDM, which is a phase-domain (PD) based formulation. The PD model equations are embedded within the network solution by incorporating its differential equations. This approach has been shown to have superior numerical performance compared to the indirect interfacing used with the dq model, allowing the use of a larger simulation time-step. However, in the PD model, the IM inductances vary with changes in rotor position. This characteristic has a negative impact on simulation times. To avoid the time-step limitation of the dq model, while improving on the efficiency of the PD formulation, an IM
model is implemented as a custom component in RSCAD.
The custom IM model combines PD and dq quantities to produce a very efficient formulation, which has similar numerical accuracy to the PD model at large time steps. Furthermore, when magnetic core saturation and zero sequence components are neglected, the custom model exhibits a constant, diagonal conductance matrix, which is very convenient for the efficient solution of the EMTP nodal network.
The custom IM model is subsequently combined with the average UCM to produce an efficient formulation of a flywheel energy storage system (FESS). The main goal on combining the average UCM and the custom IM model is to develop a computationally efficient FESS representation. Such a model is suitable to be used with a hardware-constrained RTDS environment, while enabling the analysis of a central controller when several FESS are present in the network.
Damian Vilchis-Rodriguez | The University of Manchester