Current regulation for a field weakening motor control system and method
View Patent ↗A control system and method for an electric machine includes a first calculation module that receives a modified torque command and a calculated stator flux command and that generates first and second current commands and first and second voltage commands. A voltage magnitude calculation module generates a voltage magnitude based the first and second voltage commands. A reference voltage calculator module generates a reference voltage based on a DC link voltage, an angular stator velocity and the first and second current commands. A flux weakening module generates the calculated flux command based on the angular stator velocity, the reference voltage and the voltage magnitude.
1. A control system for an electric machine, comprising:
a first calculation module that receives a modified torque command and a calculated stator flux command and that generates first and second current commands and first and second voltage commands;
a voltage magnitude calculation module that generates a voltage magnitude based said first and second voltage commands;
a reference voltage calculator module that generates a reference voltage based on a DC link voltage, an angular stator velocity and said first and second current commands; and
a flux weakening module that generates said calculated flux command based on said angular stator velocity, said reference voltage and said voltage magnitude.
2. The control system of claim 1 further comprising a torque limiting module that generates said modified torque command by limiting an input torque command.
3. The control system of claim 1 wherein said first calculation module includes a current command calculation module that generates said first and second current commands based on said calculated stator flux command and said modified torque command.
4. The control system of claim 3 further comprising a synchronous current regulator module that generates said first and second command voltages based on said first and second command currents.
5. The control system of claim 1 further comprising a transformation module that generates first and second stationary output voltages from said first and second command voltages.
6. The control system of claim 1 wherein a square of said reference voltage is equal to a square of said voltage magnitude minus a square of a transient stator voltage.
7. The control system of claim 6 wherein said square of said transient stator voltage is equal to a first current transient minus a first cross coupling term plus a square of second current transient minus a second cross coupling term.
8. A method for operating an electric machine, comprising:
calculating first and second current commands based on a modified torque command and a calculated stator flux command;
generating first and second voltage commands based on said first and second current commands;
calculating a voltage magnitude based said first and second voltage commands;
generating a reference voltage based on a DC link voltage, an angular stator velocity and said first and second current commands; and
generating said calculated flux command based on said angular stator velocity, said reference voltage and said voltage magnitude.
9. The method of claim 8 further comprising limiting an input torque command to said modified torque command.
10. The method of claim 8 further comprising transforming said first and second command voltages into first and second stationary output voltages.
11. The method of claim 8 wherein a square of said reference voltage is equal to a square of said voltage magnitude minus a square of a transient stator voltage.
12. The method of claim 11 wherein said square of said transient stator voltage is equal to a first current transient minus a first cross coupling term plus a square of second current transient minus a second cross coupling term.