Time optimal torque control and loss minimization in AC machines using deadbeat direct torque and flux control

Abstract

This paper presents time optimal torque control in overmodulation and switching level loss minimization control of an induction machine (IM) and an interior permanent magnet synchronous machine (IPMSM) via deadbeat, direct torque and flux control (DB-DTFC). Using DB-DTFC, the stator flux linkage can be manipulated each PWM cycle to minimize losses during normal operation. Due to voltage limits during overmodulation it may take a sequence of incremental torque commands over several PWM periods to achieve a desired air-gap torque that is physically infeasible in one step. In that case, the DB control becomes finite settling step (FSS) control in which the steps may be optimized using time optimal strategies. In this paper, a time optimal FSS control using a DB-DTFC solution during overmodulation and a loss minimizing DB-DTFC solution over the full torque-speed operating space are proposed and evaluated for IM and IPMSM drives.

Implementation and evaluation of inverter loss modeling as part of DB-DTFC for loss minimization each switching period

“…The use of the Volt-second (flux linkage) source properties of power electronics, instead of the current regulator, combined with a model inverse digital control method leads to a smooth and fast torque and stator flux response. Consequently, DB-DTFC flux linkage has been used for loss minimizing control (LMC) of IPMSM drives [8] that reduces losses each switching period. The optimal flux commands are estimated by accurate dynamic flux linkage-based loss models of the IPMSM [9].…”