Control of a Permanent Magnet Synchronous Motor (PMSM) with constraints

Abstract

The aim of the thesis is to design and implement a controller that controls the PMSM without violating the given constraints. This is especially with respect to the battery current.

Two approaches has been implemented in this paper, where both of themhave shown to satisfy the given constraints. This was however on expense on the performance of some of the responses, especially id (t ). As a Surface PMSM (SPMSM) has been used, a nonzero value on id (t ) only contributes in heat increase in the motor. The approaches have shown different overall performance of these responses. The simulations in this paper was carried for a given test case where an angular position reference was followed. Both approaches have utilized a cascade of P- and PI-controllers, where one replaced the current controllers with a predictive controller, while the other utilized saturation blocks.

The predictive controller has been realized by using a Nonlinear Model Predictive Control (NMPC) structure, as the constraint for the battery current was found to be nonlinear. In this paper two versions of the NMPC has been looked at, where one considered constant angular velocity in the prediction horizon and the other did not. Thiswas motivated by the assumption that a constant velocity in the controller might have significant reduction on the computational time. Based on the results however, this paper has shown that including angular velocity in the prediction horizon might be a better choice. This is in terms of the performance and computational time presented in the results. However as a framework that does not support c-code generation has been used, this paper cannot give any direct results on the computational effort the predictive controllers induce.

The work of this paper should therefore be regarded as an introductory on future work. This is if it is of interest to use the NMPC presented here for controlling the motor. The results alone are not of very big significance as the control structure currently

is not deploy-able. However for further work, the results give insights in what to expect when utilizing a framework that supports c-code generation. The other approach that have utilized saturation blocks can be used directly. However some additional tuning might be required if the performance is not sufficient.