Finite-Settling-Steps Direct Torque and Flux Control for Torque-Controlled Interior PM Motors at Voltage Limits

Abstract

This paper proposes a voltage-limited finite-settlingstep direct torque and flux control (FSS-DTFC) method with a constant switching frequency for torque-controlled interior permanent-magnet synchronous motors (IPMSMs). The proposed control law dynamically scales the voltage vectors on the hexagonal voltage boundary to ensure the maximum torque capabilities under the given operating conditions while simultaneously regulating the stator flux linkage magnitude under flux-weakening operation. Instead of relying on classical overmodulation methods at voltage limits, this paper developed two independent voltage truncation rules to facilitate the possible voltage vector choices. The analytical solution led to the dynamic voltage modification at each time step with respect to the available inverter voltage. The voltage-limited FSS-DTFC approach has potential advantages in achieving a fast transient torque trajectory and direct manipulation of the stator flux linkage while exploiting the maximum voltage excitation. Index Terms-Dynamic voltage vector choices, maximum voltage excitation, torque-controlled interior permanent-magnet synchronous motors (IPMSMs), voltage-limited finite-settling-step deadbeat-direct torque and flux control (FSS-DTFC).

An Enhanced Finite-Settling-Step Direct Torque and Flux Control (FSS-DTFC) for IPMSM Drives

“…8 shows an overall block diagram of the control system with the proposed enhanced FSS-DTFC algorithm. A discrete time Gopinath-style stator flux linkage observer is integrated into the enhanced FSS-DTFC system and is an important part for estimating the stator flux linkage [4]- [6]. For the stator flux linkage observer, the cross-coupling is decoupled when the stator current observer is developed.…”

“…The DB-DTFCs apply the principle of deadbeat control to achieve a desired value in one inverter switching period. DB-DTFC methods have been implemented for IM drives [1], [2] and IPMSM drives [4]- [6]. However, in these studies, insufficient information was available to determine the stator voltage vector during a wide range of operation at elevated speeds.…”

“…Recently, a finite-settling-step DTFC (FSS-DTFC) method associated with the inverter voltage and current constraints for IPMSMs has been proposed [5], [6]. The FSS-DTFC is an exact counterpart of the DB-DTFC, in terms of the physical constraints, in discrete time.…”

Hexagon Voltage Manipulating Control (HVMC) for AC Motor Drives Operating at Voltage Limit

“…Although it is excellent in the maximum-torque-per-ampere (MTPA) operation, the performance requirements are satisfied with the help of multiple-objective sub-control actions at voltage limit, such as the maximum-torque-per-voltage (MTPV) or flux weakening (FW) control, anti-windup control, and over-modulation scheme. As a result, one major difficulty under the voltage-limited region arises from the fact that sub-control actions conflict in subtle ways [11]. In addition, there are certain current limitations or load angle constraints that must be considered when designing a MTPV tracking controller.…”

“…Recently, a finite-settling-step DTFC (FSS-DTFC) method associated with the inverter voltage and current constraints for interior permanent-magnet synchronous motors (IPMSMs) was proposed [11][12] law dynamically scales the voltage vectors on the hexagonal voltage boundary to ensure the maximum torque capabilities under a given operating condition, while simultaneously regulating the stator flux linkage magnitude to meet the flux weakening requirements. The automatic transition to the FW mode was achieved with a single voltage selection rule.…”