Tutorials: Monday afternoon

Tutorial Objectives

Highly utilized three -phase machines show a highly nonlinear electromagnetic behaviour, making it very challenging or even impossible to control them using standard control-algorithms.

One very appropriate and well-proven method to cope with this nonlinearity is the measurement of multi-dimensional flux linkage maps for each possible operating point of the given machine. During operation a look-up-table is used to adjust the gain of the used control-algorithm to the actual differential inductance in each given operating point. The flux maps are also used in non-linear model predictive control (MPC) schemes to enhance dynamics. And besides machine-control the flux maps are implemented in high accuracy simulations to test new control algorithms. So with this method, the nonlinearities are stored in flux linkage maps and are fed-forward to the controller in each control cycle.

To obtain the flux linkage maps, several methods are described in the literature. One of the most common methods is the steady-state method in which the device-under-test (DUT) is mounted in a hardware test-bench together with a load-machine. The load machine is speed-controlled and guarantees constant rotational speed, whereas the DUT is current controlled, enabling to drive it to every operation point in the dq-current plane. The downside to this method is the need of a real-power hardware test-bench, which is quite a cost factor and general effort. The other well-known method is the locked-rotor test in which the DUT’s rotos is locked and hence the rotational speed is zero. Here no-load machine is necessary but other restrictions apply, for example that no speed-dependent effects can be measured. 2 EPE’25 – Call for Tutorials

In state-of-the-art implementations, the flux maps depend on the rotor-oriented direct and quadrature current components, considering the major nonlinearity-effects of magnetic saturation and cross-coupling. To be able to also consider nonlinearities that are due to the rotor and stator geometry, the dependency on the rotor angle must be considered as well. With these angle-dependent flux linkage maps, the angle-dependent error can be fed-forward e.g. in repetitive control schemes, enhancing control quality significantly.

In this tutorial different methods to obtain multi-dimensional flux maps of permanent magnet synchronous machines (PMSM), synchronous reluctance machines (SynRM), electrically excited synchronous machines (EESM) and induction machines (IM) are presented. This includes steady state-tests, locked-rotor-tests, and a new approach that replaces flux maps with a physics-informed neural network. In addition to the flux-map-identification, also one well-proven control method that makes use of these flux maps and enables for high dynamics is presented. Of course, also hands-on tips from our long-term lab-experience, dealing with several motor test-benches ranging from few hundred Watts (Pedelec/E-Bike motors) to several 100kW (automotive) for over a decade will be given in each of the described topics.