Doctoral Dissertations

Date of Award

8-2001

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Electrical Engineering

Major Professor

Jack S. Lawler

Committee Members

J. Milton Bradley, Paul B. Crilly, Leon Tolbert, Luiz E. Borges Silva, Tse-Wei Wang

Abstract

The scope of this work is the Permanent Magnet Synchronous Machine (PMSM) operating at Constant Power Speed Range (CPSR). The proposed technique to drive the PMSM at CPSR is the Dual Mode Inverter Control (DMIC) The mam idea behind DMIC is to change the three-phase operation of the PMSM below base speed to hybrid, single-phase and three-phase, operation above the base speed This technique allows driving the PMSM in a wide CPSR The DMIC uses three facts to achieve wide CPSR First, it introduces the idea of the advance angle, which allows driving current into the machine while the back-emf is smaller than the DC link voltage Second, the blanking angle is used to maximize the electrical to mechanical power conversion by increasing the on time of the transistors of the Voltage-Fed Inverter (VFI) and therefore slowing down the decreasing voltage m the outgoing phase Finally, this technique avoids regeneration through the bypass diodes by introducing an ac-voltage controller interfacing the VFI and the PMSM. The analysis of DMIC/PMSM drive system shows that it uses the same principle of Vector Control with Field Weakening (VCFW) i e., the armature current is controlled to have a field component that weakens the air gap field, and therefore opposes the back emf However, the armature current vector must satisfy the voltage and current constraints, which are the maximum current and armature voltage. In VCFW, the voltage limit circle shrinks fast as speed increases because the maximum armature voltage is the maximum output voltage of the VFI, which is limited by the DC link voltage In DMIC, on the other hand, the voltage limit circle shrinks slower, since after the commutation period the machine is operating in single-phase mode The total armature voltage is the contribution of the DC link voltage, the back emf, and the induced voltage provided by the derivative of the on-phase currents In fact, this operation eliminates the voltage constraint, and the machine can operate at any speed, and then the only constraint is the current limit Therefore, it is shown in this work that theoretically there is no speed limit for DMIC driving PMSM over constant power operation range

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