Abstract
We apply the multigrid-reduction-in-time (MGRIT) algorithm to an eddy current simulation of a two-dimensional induction machine supplied by a pulse-width-modulation signal. To resolve the fast-switching excitations, small time steps are needed, such that parallelization in time becomes highly relevant for reducing the simulation time. The MGRIT algorithm is an iterative method that allows calculating multiple time steps simultaneously by using a time-grid hierarchy. It is particularly well suited for introducing time parallelism in the simulation of electrical machines using existing application codes, as MGRIT is a non-intrusive approach that essentially uses the same time integrator as a traditional time-stepping algorithm. However, the key difficulty when using time-stepping routines of existing application codes for the MGRIT algorithm is that the cost of the time integrator on coarse time grids must be less expensive than on the fine grid to allow for speedup over sequential time stepping on the fine grid. To overcome this difficulty, we consider reducing the costs of the coarse-level problems by adding spatial coarsening. We investigate effects of spatial coarsening on MGRIT convergence when applied to two numerical models of an induction machine, one with linear material laws and a full nonlinear model. Parallel results demonstrate significant speedup in the simulation time compared to sequential time stepping, even for moderate numbers of processors.
Highlights
Induction motors are electrical machines in which the magnetic field in the rotor is obtained by an asynchronous motion with respect to the field in the stator, e.g. [1]
The MGRIT algorithm is applied to a model of a realistic two-dimensional electrical machine with a pulsed excitation
Using the non-intrusive character of MGRIT for an existing model of an induction machine, performance of MGRIT is dominated by the cost of the time-stepping routine which carries out a nonlinear spatial solve for a given time step
Summary
Induction motors are electrical machines in which the magnetic field in the rotor is obtained by an asynchronous motion with respect to the field in the stator, e.g. [1]. A common approach for defining a time-grid hierarchy is to use different temporal resolutions [7,13,14] Other techniques such as considering time-integration routines of different orders of accuracy have been applied, e.g., in power-grid simulations [15,16]. When using time-stepping routines of existing application codes, the combination of various temporal and spatial resolutions is an attractive approach for defining a time-grid hierarchy, since this allows adding time parallelism non-intrusively and reducing costs on coarse levels at the same time. We demonstrate that spatial coarsening can significantly reduce the runtime of numerical simulations of an induction machine, but it may degrade MGRIT convergence, as observed for the p-Laplacian in [27].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
