TIDUF56 January   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Terminology
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 TMS320F28P65x-Q1
      2. 2.3.2 DRV3255-Q1
      3. 2.3.3 LM25184-Q1
      4. 2.3.4 TCAN1044A-Q1
  9. 3System Design Theory
    1. 3.1 Three-Phase PMSM Drive
      1. 3.1.1 Field-Oriented Control of PM Synchronous Motor
        1. 3.1.1.1 Space Vector Definition and Projection
          1. 3.1.1.1.1 ( a ,   b ) ⇒ ( α , β ) Clarke Transformation
          2. 3.1.1.1.2 α , β ⇒ ( d ,   q ) Park Transformation
        2. 3.1.1.2 Basic Scheme of FOC for AC Motor
        3. 3.1.1.3 Rotor Flux Position
    2. 3.2 Field Weakening (FW) Control
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
      1. 4.1.1 Hardware Board Overview
      2. 4.1.2 Test Conditions
      3. 4.1.3 Test Equipment Required for Board Validation
    2. 4.2 Test Setup
      1. 4.2.1 Hardware Setup
      2. 4.2.2 Software Setup
        1. 4.2.2.1 Code Composer Studio™ Project
        2. 4.2.2.2 Software Structure
    3. 4.3 Test Procedure
      1. 4.3.1 Project Setup
      2. 4.3.2 Running the Application
    4. 4.4 Test Results
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout Recommendations
        1. 5.1.3.1 Layout Prints
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks

3.1.1.3 Rotor Flux Position

Knowledge of the rotor flux position is the core of the FOC. In fact if there is an error in this variable the rotor flux is not aligned with the d-axis and isd and isq are incorrect flux and torque components of the stator current. Figure 3-7 shows the (a, b, c), (α, β) and (d, q) reference frames, and the correct position of the rotor flux, the stator current and stator voltage space vector that rotates with d, q reference at synchronous speed.

GUID-20210326-CA0I-FRBD-TGGV-LXT01LTKDS3S-low.svg Figure 3-7 Current, Voltage and Rotor Flux Space Vectors in the (d, q) Rotating Reference Frame

The measure of the rotor flux position is different when considering the synchronous or asynchronous motor:

  • In the synchronous machine the rotor speed is equal to the rotor flux speed. Then θ (rotor flux position) is directly measured by the position sensor or by integration of rotor speed.
  • In the asynchronous machine, the rotor speed is not equal to the rotor flux speed (there is a slip speed), then a particular method is needed to calculate θ. The basic method is the use of the current model which needs two equations of the motor model in d, q reference frame.

Theoretically, the FOC for the PMSM drive allows the motor torque to be controlled independently with the flux like DC motor operation. In other words, the torque and flux are decoupled from each other. The rotor position is required for variable transformation from stationary reference frame to synchronously rotating reference frame. As a result of this transformation (so called Park transformation), q-axis current is controlling torque while d-axis current is forced to zero.