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

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.