Optimal Torque Control of Synchronous Machines Based on Finite-Element Analysis

Abstract

Synchronous machines that are optimally designed using finite-element (FE) software, and control of such machines using powerful digital signal processors (DSPs), are commonplace today. With field-orientated control, the maximum-torqueper-ampere control strategy for unsaturated voltage conditions (below the base speed) is well known; the field-weakening strategy, however, could be rather complicated. In this paper, a straightforward torque control strategy for the entire speed range is proposed and demonstrated. Practical implementation of the method is very simple since the calculations are done offline in an automated process and are therefore removed from the load of the DSP. The process relies on machine-specific data from FE analysis and therefore includes nonlinear effects such as saturation and cross coupling. Simulation and practical results for a permanentmagnet and a reluctance synchronous machine show that the torque is controlled effectively in the entire speed range using this generic method. Index Terms-Finite-element (FE) analysis, synchronous machines, torque control. NOMENCLATURE u r Stator-voltage vector in the rotating dq reference frame. α r Stator-voltage angle in the rotating dq reference frame. i r Stator-current vector in the rotating dq reference frame. φ r Stator-current angle in the rotating dq reference frame. ψ r Stator-flux-linkage vector in the rotating dq reference frame. δ r Stator-flux-linkage angle in the rotating dq reference frame. ω r Electrical rotational speed. R s Stator resistance. T m Machine torque. p Number of pole pairs. PMSM Permanent-magnet synchronous machine. IPMSM Interior permanent-magnet synchronous machine. RSM Reluctance synchronous machine. 2-D Two-dimensional.

Optimal Torque Control of Saturated Synchronous Motors: Plug-and-Play Method

“…If only three points are available due to the vicinity of the MTPV limit, (19) is applied instead of (18). The value of the q-axis flux component ψ q could y 1 ), (x 1 , y 2 ), (x 2 , y 1 ), and (x 2 , y 2 ) used for interpolating the value at (x, y).…”

“…Instead, the q-axis flux component is first calculated using the Pythagorean theorem at all the three or four points used in the interpolation algorithm for ψ d . To get the interpolated ψ q , either (18) or (19) is used, depending on the number of the points.…”

“…The magnetic saturation can be included properly in these methods, but the off-line data processing is difficult and time-consuming, even though some open-source post-processing algorithms are available [21]. Feedforward methods based on the finite-element method (FEM) rely on the knowledge of the motor geometry [16], [18]. Furthermore, the feedforward methods can be augmented with an additional voltage controller in order to be able to dynamically adjust the voltage margin [19], [20].…”

Efficient State Reference Generation for Torque Control in Externally Excited Synchronous Machines

“…For an overview, the interested reader is referred to Refs. [10][11][12], and the references therein. As such, a possible approach is to adapt the existing state reference generation strategies developed for PMSM torque control.…”

Behavior modeling of permanent magnet synchronous motors using flux linkages for coupling with circuit simulation

“…Especially Interior PMSMs (IPMSMs) deliver the great performance at the high-efficiency over wide speed and torque ranges. Therefore various control motor models have been proposed to achieve the high-performance [1][2][3].…”