Model Predictive Torque Control for Permanent Magnet Synchronous Motors
Using a Stator-Fixed Harmonic Flux Reference Generator in the Entire
Modulation Range
Abstract
To increase torque and power conversion of permanent magnet synchronous
motors (PMSMs) at high-speed operation, the DC-link voltage of the
inverter must be fully utilized during steady-state and transient
operations. This paper proposes the incorporation of a harmonic
reference generator (HRG) with a pulse clipping (PC) scheme into a model
predictive control framework to achieve highest power output. The HRG
calculates flux references in the stator-fixed coordinate system for an
underlying continuous control set model predictive flux control
(CCS-MPFC). These reference trajectories contain the harmonic flux
component induced by the voltage hexagon in the overmodulation range and
specific switching states (e.g., six-step operation) of the inverter are
ensured by the proposed PC scheme. This enables a seamless transition to
the overmodulation range including six-step operation and increases the
drive’s power conversion to its maximum extent. Since the flux
differential equation in the stator-fixed coordinate system, used as
motor model for the HRG and CCS-MPFC, is able to represent PMSMs with
linear and nonlinear magnetization, the proposed approach is well suited
for the control of PMSMs with nonlinear magnetization. Extensive
transient and steady-state experimental investigations on a highly
utilized PMSM in the entire modulation and speed range prove the
performance of the proposed approach.