TIDUFB1 December   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
      1. 2.2.1 Control System Design Theory
        1. 2.2.1.1 PWM Modulation
        2. 2.2.1.2 Current Loop Model
        3. 2.2.1.3 DC Bus Regulation Loop
        4. 2.2.1.4 DC Voltage Balance Controller
    3. 2.3 Highlighted Products
      1. 2.3.1 TMS320F280013x
      2. 2.3.2 UCC5350
      3. 2.3.3 AMC1350
      4. 2.3.4 TMCS1123
      5. 2.3.5 UCC28750
      6. 2.3.6 LM25180
      7. 2.3.7 ISOTMP35
      8. 2.3.8 TLV76133
      9. 2.3.9 TLV9062
    4. 2.4 Hardware Design
      1. 2.4.1  Inductor Design
      2. 2.4.2  Bus Capacitor Selection
      3. 2.4.3  Input AC Voltage Sensing
      4. 2.4.4  Output DCBUS Voltage Sensing
      5. 2.4.5  Auxiliary Power Supply
      6. 2.4.6  Isolated Power Supply
      7. 2.4.7  Inductor Current Sensing
      8. 2.4.8  Gate Driver
      9. 2.4.9  Isolated Temperature Sensing
      10. 2.4.10 Overcurrent, Overvoltage Protection (CMPSS)
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
      1. 3.1.1 Getting Started Hardware
        1. 3.1.1.1 Board Overview
        2. 3.1.1.2 Test Equipment
    2. 3.2 Software Requirements
      1. 3.2.1 Getting Started GUI
        1. 3.2.1.1 Test Setup
        2. 3.2.1.2 Overview of a GUI Software
        3. 3.2.1.3 Procedures of Test With GUI
      2. 3.2.2 Getting Started Firmware
        1. 3.2.2.1 Opening the Project Inside Code Composer Studio™
        2. 3.2.2.2 Project Structure
        3. 3.2.2.3 Test Setup
        4. 3.2.2.4 Running Project
          1. 3.2.2.4.1 INCR_BUILD 1: Open Loop
            1. 3.2.2.4.1.1 Setting, Building, and Loading the Project
            2. 3.2.2.4.1.2 Setup Debug Environment Windows
            3. 3.2.2.4.1.3 Using Real-Time Emulation
            4. 3.2.2.4.1.4 Running Code (Build 1)
          2. 3.2.2.4.2 INCR_BUILD 2: Closed Current Loop
            1. 3.2.2.4.2.1 Running Code (Build 2)
            2. 3.2.2.4.2.2 Building and Loading the Project and Setting Up Debug
          3. 3.2.2.4.3 INCR_BUILD 3: Closed Voltage and Current Loop
            1. 3.2.2.4.3.1 Building and Loading the Project and Setting Up Debug
            2. 3.2.2.4.3.2 Running Code (Build 3)
          4. 3.2.2.4.4 INCR_BUILD 4: Closed Balance, Voltage, and Current Loop
            1. 3.2.2.4.4.1 Building and Loading the Project and Setting Up Debug
            2. 3.2.2.4.4.2 Running Code (Build 4)
    3. 3.3 Test Results
      1. 3.3.1  IGBT Gate Rising and Falling Time
      2. 3.3.2  Power On Sequence
      3. 3.3.3  PFC Started by GUI
      4. 3.3.4  Zero Crossing Under 380VAC, 9kW
      5. 3.3.5  Current Ripple Under 380VAC,10kW
      6. 3.3.6  10kW Load Test With Grid Power
      7. 3.3.7  9kW Load Test With AC Power Source
      8. 3.3.8  Power Analyzer Results
      9. 3.3.9  Thermal Performance
      10. 3.3.10 Voltage Short Interrupt Test
      11. 3.3.11 Efficiency, iTHD, and Power Factor Results
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 Bill of Material (BOM)
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author

2.4.1 Inductor Design

Input inductor (Li) filters out the switching frequency harmonics. Inductor design, amongst other factors, depends on calculation of the current ripple and choosing a material for the core that can tolerate the calculated current ripple. Figure 2-7 shows one switching cycle waveform of the inverter output voltage vi with respect to the inductor current.

TIDA-010257 Current Ripple Calculation Figure 2-7 Current Ripple Calculation

The voltage across the inductor is given by V = Li(di/dt). For the Vienna rectifier, see Equation 7.

Equation 7. V b u s 2 - V i n = L i × ∆ i p p D ' × T s

where

  • Ts = 1/Fsw is the switching period
  • D’ is the duty cycle for which the switches are ON

For control design, D is assumed to be the voltage at the other terminal of the inductor and is related to D’ by D’ = 1 – D. Rearranging the current ripple at any instant in the AC waveform is given as Equation 8.

Equation 8. ∆ i p p = D ' × T s × V b u s 2 - V i n L i

Now assuming modulation index to be ma the duty cycle can be given as D' = ma*sin(ωt) and assuming that Vin = D' × (Vbus/2), Equation 9 can be derived.

Equation 9. ∆ i p p = V b u s 2 × T s × m a × sin ⁡ ω t × 1 - m a sin ⁡ ω t L i

From Equation 9, it is clear that the peak ripple is a factor where the input AC is in the sinusoidal waveform.

To get the maximum value differentiating the equation with respect to time, use Equation 10.

Equation 10. d ∆ i p p d t = K cos ⁡ ω t 1 - m a sin ⁡ ω t - m a sin ⁡ ω t × cos ⁡ ω t = 0

Which gives the maximum ripple exists at sin(ωt)=1/(2 × ma), Substituting this value, Equation 11 is derived.

Equation 11. ∆ i p p m a x = V b u s 2 × T s 4 × L i ⇒ L i = V b u s 2 4 × F s w × ∆ i p p m a x

With these values in mind, an appropriate core can be selected along with an inductor designed to meet this inductance value.