Field weakening with full range torque control for synchronous machines

• US 20040100221A1
• Filed: 11/25/2002
• Published: 05/27/2004
• Est. Priority Date: 11/25/2002
• Status: Abandoned Application

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Fu, Zhenxing
• Application Number:
  US10/304,106
• Publication Number:
  US 20040100221A1
• Time in Patent Office: Days
• US Class Current: 318/700
• CPC Class Codes: H02P 2207/05 Synchronous machines, e.g. with permanent magnets or DC excitation
• CPC Class Codes: H02P 25/03 with brushless excitation

Abstract

A permanent magnet synchronous machine having a base speed is controlled in response to a d-axis current command I_dse*. A torque command T_e* is determined and an angular velocity ω_r of the machine is sensed. A maximum torque per ampere value is calculated for producing the commanded torque T_e* at speeds below the base speed. The angular velocity ω_r is compared with the base speed. If the angular velocity ω_r is less than the base speed, then the maximum torque per ampere value is employed as the d-axis current command I_dse*. If the angular velocity ω_r is greater than the base speed, then the maximum torque per ampere value adjusted by a field-weakening factor proportional to the angular velocity ω_r is employed as the d-axis current command I_dse*.

Claims

1. A method of determining a d-axis current command I_dse* for controlling a permanent magnet synchronous machine having a base speed, said method comprising the steps of:

determining a torque command T_e*;

sensing an angular velocity ω

_r of said machine;

calculating a maximum torque per ampere value for producing said commanded torque T_e* at speeds below said base speed;

comparing said angular velocity ω

_r with said base speed;

if said angular velocity ω

_r is less than said base speed, then employing said maximum torque per ampere value as said d-axis current command I_dse*; and

if said angular velocity ω

_r is greater than said base speed, then employing said maximum torque per ampere value adjusted by a field-weakening factor proportional to said angular velocity ω

_r as said d-axis current command I_dse*.

2. The method of claim 1 wherein said field-weakening factor is substantially defined by

3. A motor controller for a permanent magnet synchronous machine, comprising:

a speed sensor for determining an angular velocity ω

_r of said machine;

a torque controller for providing a torque command T_e*;

a d-axis current calculator for determining a d-axis current command I_dse* in response to said torque command;

a q-axis current calculator for determining a q-axis current command I_qse* in response to said torque command;

a current regulator for determining a d-axis voltage command V_dse* and a q-axis voltage command V_qse* corresponding to said d-axis current command I_dse* and said q-axis current command I_qse*, respectively;

a vector translator for translating said d-axis voltage command V_dse* and said q-axis voltage command V_qse* into stationary reference commands V_a*, V_b*, and V_c*;

a PWM controller for generating pulse-width modulation control signals corresponding to said stationary reference commands V_a*, V_b*, and V_c*; and

an inverter for applying respective voltages to phase windings of said machine in response to said pulse-width modulation control signals;

wherein said d-axis current calculator comprises;

a maximum torque per ampere scheduler for determining a nominal flux current command;

a speed comparator for determining whether said angular velocity ω

_r is above a threshold related to a base speed of said machine;

an adjustment calculator for determining an adjusted flux current command including a field-weakening factor which is proportional to said angular velocity ω

_r; and

a selector for selecting said nominal flux current command when said speed comparator indicates that said angular velocity ω

_r is below said threshold and for selecting said adjusted flux current command when said speed comparator indicates that said angular velocity ω

_r is above said threshold.

4. The motor controller of claim 3 wherein said field-weakening factor is substantially defined by

5. The motor controller of claim 4 wherein said adjusted flux current command is substantially determined in response to the formula: