TIDUD61E October   2020  – April 2021

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Input AC Voltage Sensing
      2. 2.2.2 Bus Voltage Sensing
      3. 2.2.3 AC Current Sensing
      4. 2.2.4 Sense Filter
      5. 2.2.5 Protection (CMPSS)
    3. 2.3 Highlighted Products
      1. 2.3.1 C2000™ MCU F28004x
      2. 2.3.2 LMG3410R070
      3. 2.3.3 UCC27714
    4. 2.4 System Design Theory
      1. 2.4.1 PWM
      2. 2.4.2 Current Loop Model (PFC and Inverter mode)
      3. 2.4.3 DC Bus Regulation Loop (for PFC mode only)
      4. 2.4.4 Soft Start Around Zero Crossing for Eliminate or Reduce Current Spike
      5. 2.4.5 AC Drop Test
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
        1. 3.1.1.1 Base Board Settings
        2. 3.1.1.2 Control Card Settings
      2. 3.1.2 Software
        1. 3.1.2.1 Opening Project Inside CCS
        2. 3.1.2.2 Project Structure
        3. 3.1.2.3 Using CLA on C2000 MCU to Alleviate CPU Burden
        4. 3.1.2.4 CPU and CLA Utilization and Memory Allocation
        5. 3.1.2.5 Running the Project
          1. 3.1.2.5.1 Lab 1: Open Loop, DC (PFC Mode)
            1. 3.1.2.5.1.1 Setting Software Options for LAB 1
            2. 3.1.2.5.1.2 Building and Loading Project
            3. 3.1.2.5.1.3 Setup Debug Environment Windows
            4. 3.1.2.5.1.4 Using Real-Time Emulation
            5. 3.1.2.5.1.5 Running Code
          2. 3.1.2.5.2 Lab 2: Closed Current Loop DC (PFC)
            1. 3.1.2.5.2.1 Setting Software Options for Lab 2
            2. 3.1.2.5.2.2 Designing Current Loop Compensator
            3. 3.1.2.5.2.3 Building and Loading Project and Setting up Debug
            4. 3.1.2.5.2.4 Running Code
          3. 3.1.2.5.3 Lab 3: Closed Current Loop, AC (PFC)
            1. 3.1.2.5.3.1 Setting Software Options for Lab 3
            2. 3.1.2.5.3.2 Building and Loading Project and Setting up Debug
            3. 3.1.2.5.3.3 Running Code
          4. 3.1.2.5.4 Lab 4: Closed Voltage and Current Loop (PFC)
            1. 3.1.2.5.4.1 Setting Software Options for Lab 4
            2. 3.1.2.5.4.2 Designing Voltage Loop Compensator
            3. 3.1.2.5.4.3 Building and Loading Project and Setting up Debug
            4. 3.1.2.5.4.4 Running Code
          5. 3.1.2.5.5 Lab 5: Open loop, DC (Inverter)
            1. 3.1.2.5.5.1 Setting Software Options for Lab 5
            2. 3.1.2.5.5.2 Building and Loading Project
            3. 3.1.2.5.5.3 Setup Debug Environment Windows
            4. 3.1.2.5.5.4 Running Code
          6. 3.1.2.5.6 Lab 6: Open loop, AC (Inverter)
            1. 3.1.2.5.6.1 Setting Software Options for Lab 6
            2. 3.1.2.5.6.2 Building and Loading Project and Setting up Debug
            3. 3.1.2.5.6.3 Running Code
          7. 3.1.2.5.7 Lab 7: Closed Current Loop, DC (Inverter with resistive load)
            1. 3.1.2.5.7.1 Setting Software Options for Lab 7
            2. 3.1.2.5.7.2 Designing Current Loop Compensator
            3. 3.1.2.5.7.3 Building and Loading Project and Setting up Debug
            4. 3.1.2.5.7.4 Running Code
          8. 3.1.2.5.8 Lab 8: Closed Current Loop, AC (Inverter with resistive load)
            1. 3.1.2.5.8.1 Setting Software Options for Lab 8
            2. 3.1.2.5.8.2 Building and Loading Project and Setting up Debug
            3. 3.1.2.5.8.3 Running Code
          9. 3.1.2.5.9 Lab 9: Closed Current Loop (Grid Connected Inverter)
            1. 3.1.2.5.9.1 Setting Software Options for Lab 9
            2. 3.1.2.5.9.2 Building and Loading Project and Setting up Debug
            3. 3.1.2.5.9.3 Running Code: Emulated Grid-tied Condition (Verification purpose only)
            4. 3.1.2.5.9.4 Running Code: Grid-tied Condition
        6. 3.1.2.6 Running Code on CLA
        7. 3.1.2.7 Advanced Options
          1. 3.1.2.7.1 Input Cap Compensation for PF Improvement Under Light Load
          2. 3.1.2.7.2 83
          3. 3.1.2.7.3 Adaptive Dead Time for Efficiency Improvements
          4. 3.1.2.7.4 Phase Shedding for Efficiency Improvements
          5. 3.1.2.7.5 Non-Linear Voltage Loop for Transient Reduction
          6. 3.1.2.7.6 Software Phase Locked Loop Methods: SOGI - FLL
    2. 3.2 Testing and Results
      1. 3.2.1 Test Results at Input 120 Vrms, 60 Hz, Output 380-V DC
        1. 3.2.1.1 Startup
        2. 3.2.1.2 Steady State Condition
        3. 3.2.1.3 Transient Test With Step Load Change
          1. 3.2.1.3.1 0% to 50% Load Step Change
          2. 3.2.1.3.2 50% to 100% Load Step Change
          3. 3.2.1.3.3 100% to 50% Load Step Change
          4. 3.2.1.3.4 50% to 100% Load Step Change
      2. 3.2.2 Test Results at Input 230 Vrms, 50 Hz, Output 380 V DC
        1. 3.2.2.1 Startup
        2. 3.2.2.2 Steady State Condition
        3. 3.2.2.3 Transient Test With Step Load Change
          1. 3.2.2.3.1 33% to 100% Load Step Change
          2. 3.2.2.3.2 100% to 33% Load Step Change
      3. 3.2.3 Test Results Graphs
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Software Files
  11. 6Related Documentation
    1. 6.1 Trademarks
  12. 7About the Author
  13. 8Revision History
3.1.2.7.5 Non-Linear Voltage Loop for Transient Reduction

The PFC stage control is composed of an inner current loop, which tries to follow the input voltage and an outer voltage loop that tries to maintain a constant DC bus voltage at the output. The voltage loop is thus in conflict with the current loop and hence must be designed to be very low bandwidth (approximately 10 Hz) in order to achieve good power factor. The slow voltage loop results in significant overshoot and undershoot under transients (see Figure 3-59).

GUID-EC589EB1-5EE6-4B99-8231-5BE3A85C27C5-low.gifFigure 3-59 Non-Linear Voltage Loop with Hysteresis

To improve voltage overshoot and undershoot, while maintaining good power factor a non-linear voltage control loop is implemented as shown in Figure 3-60. A hysteresis band is added in the non-linear voltage loop to avoid oscillation between high-gain and low-gain mode. Furthermore the gain change is slewed to avoid any sudden changes. Figure 3-61 shows the result with non-linear voltage loop.

GUID-E46494DF-CDC8-4332-93F3-22533E812E70-low.gifFigure 3-60 Voltage Transient Without Non-Linear Voltage Loop, Vin 120 Vrms, 880 W to 0 W Transient, Overshoot 51.2 V
GUID-96582D4D-DAC0-4D19-969E-2CC6E7061463-low.gifFigure 3-61 Voltage Transient With Non-Linear Voltage Loop, Vin 120 Vrms, 880 W to 0 W Transient, Overshoot 16.8 V

To enable non-linear voltage loop, select the drop down box under Project Options on the powerSUITE page of the solution. Default value of five times the gain is applied for the proportional term under transient condition. This value can be adjusted under the <solution>_user_settings.h file by modifying the NON_LINEAR_V_LOOP_KP_MULTIPLIER define. The project must be saved, re-compiled, and loaded on the controller when this option is changed. Hardware setup and software instructions for the lab 4 can be followed to see the behavior of the board under transients.