Single sensor current control of a multiple phase AC machine

• US 5,274,317 A
• Filed: 11/12/1992
• Issued: 12/28/1993
• Est. Priority Date: 11/12/1992
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: Delco Electronics Corporation (General Motors Company), General Motors Corporation (General Motors Company)
• Inventors: Cheever, Gordon D. Jr., Deasy, Kevin M., Utley, Daniel E.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Cabeca, John W.
• Application Number:
  US07/974,761
• Time in Patent Office: 411 Days
• Field of Search: 318/767, 318/432, 318/798, 318/811, 318/799, 318/802, 318/806, 318/810
• US Class Current: 318/802
• CPC Class Codes: H02M 7/53873 with digital control
• CPC Class Codes: H02P 6/28 Arrangements for controlling current H02P6/10 takes precedence

Abstract

An improved digital PWM closed-loop current control for a multiple phase winding AC machine which requires only a single sensor for monitoring the current in one of the phase windings of the machine. The PWM on-time values for the various phase windings of the machine are stored in a single look-up table as a function of stator position and requested current amplitude, and the on-times used to schedule phase winding energization are periodically updated using a two-part look-up procedure. Initially, the stored on-time value for a single phase winding is retrieved from the table as a function of stator position and the requested current amplitude. The retrieved value is then compared with a measure of the actual current in the respective phase winding to form an error signal, which is used to adjust the requested current amplitude. The requested current amplitude, as adjusted, is then used, along with the stator position, as a table look-up parameter to retrieve PWM on-times for all three phase windings, thereby automatically adjusting multiple phase winding currents in a balanced fashion.

Claims

1. In a control system for a multiple phase winding AC machine including a control unit having a table of stored instantaneous current commands for each of said multiple phase windings based on an amplitude signal indicative of a desired current amplitude for said machine, a method of operation for said control unit comprising the steps of:

obtaining from said table an instantaneous current command for one of sad phase windings based on said amplitude signal;

forming an error signal based on a comparison of the instantaneous current command obtained from said table with a measure of instantaneous current in said one phase winding;

modifying said amplitude signal in accordance with said error signal to form a closed-loop amplitude signal;

obtaining from said table a set of instantaneous current commands for each of said phase windings, based on said closed-loop amplitude signal; and

applying a source of direct current to said phase windings in accordance with conduction control signals based on said set of instantaneous current commands.

2. Control apparatus for a multiple phase winding AC machine, comprising:

a look-up table of instantaneous current commands for each of said multiple phase windings stored as a function of an amplitude signal indicative of a desired current amplitude for said machine;

inverter means for controlling application of a source of direct current to said phase windings in accordance with conduction control signals;

means for obtaining from said look-up table an instantaneous current command for one of said phase windings based on said amplitude signal;

means for measuring instantaneous current in said one phase winding;

means for forming an error signal based on a comparison of the instantaneous current command obtained from said look-up table with said measured instantaneous current;

means for modifying said amplitude signal in accordance with said error signal;

means for obtaining from said look-up table a set of instantaneous current commands for each of said phase windings based on said modified amplitude signal; and

means for developing the conduction control signals for said inverter means based on said set of instantaneous current commands.

3. Control apparatus for a multiple phase winding AC machine, comprising:

a look-up table of pulse-width-modulation (PWM) on-times for each of said phase windings stored as a function of an amplitude signal indicative of a desired current amplitude for said machine and a stator angle signal indicative of a desired magnetic field orientation of said phase windings, the on-times being chosen to produce a predetermined current waveform having the desired current amplitude in the respective phase windings;

inverter means for modulating the application of a DC source to said phase windings in accordance with conduction control signals;

means for retrieving from said look-up table a PWM on-time for one of said phase windings based on said amplitude and stator angle signals to form a current command signal;

means for measuring a phase winding current in said one phase winding and scaling said measured current for comparison with said current command signal;

means for forming an error signal based on a comparison of the current command signal with the scaled measured current;

means for modifying said amplitude signal in accordance with said error signal;

means for retrieving from said look-up table PWM on-times for each of said phase windings based on said stator angle signal and the modified amplitude signal, and for developing the conduction control signals for said inverter means based on such retrieved PWM on-times.