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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).

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This paper proposes a hexagon voltage manipulating control (HVMC) method for ac motor drives operating at voltage limit. The command output voltage can be determined simply by the torque command and the hexagon voltage boundary in the absence of motor current-regulating proportional-integral (PI) control gains, additional flux weakening (FW) controllers, and observers for closed-loop control. These attributes reduce the time and effort needed for calibration of the controller in the nonlinear voltage-limited region. The proposed HVMC accomplishes the "true" maximum available voltage utilization, allowing for higher efficiency than that of the current vector controller (CVC) alone in the FW domain. In addition, a voltage selection rule was proposed to determine the unique HVMC solution between two possible voltage vectors. The successful application of the control approach was corroborated by a graphical and analytical analysis. The proposed control approach is potentially applicable to a wide range of control designs for ac drives.Index Terms-Ac motor drives operating at voltage limit, hexagon voltage manipulating control (HVMC), maximum available voltage utilization. 0093-9994 (c)