SBAA541 December   2022 AMC1202 , AMC1302 , AMC1306M05 , AMC22C11 , AMC22C12 , AMC23C10 , AMC23C11 , AMC23C12 , AMC23C14 , AMC23C15 , AMC3302 , AMC3306M05

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 DC Charging Station for Electric Vehicles
    2. 1.2 Current-Sensing Technology Selection and Equivalent Model
      1. 1.2.1 Sensing of the Current With Shunt-Based Solution
      2. 1.2.2 Equivalent Model of the Sensing Technology
  4. 2Current Sensing in AC/DC Converters
    1. 2.1 Basic Hardware and Control Description of AC/DC
      1. 2.1.1 AC Current Control Loops
      2. 2.1.2 DC Voltage Control Loop
    2. 2.2 Point A and B – AC/DC AC Phase-Current Sensing
      1. 2.2.1 Impact of Bandwidth
        1. 2.2.1.1 Steady State Analysis: Fundamental and Zero Crossing Currents
        2. 2.2.1.2 Transient Analysis: Step Power and Voltage Sag Response
      2. 2.2.2 Impact of Latency
        1. 2.2.2.1 Fault Analysis: Grid Short-Circuit
      3. 2.2.3 Impact of Gain Error
        1. 2.2.3.1 Power Disturbance in AC/DC Caused by Gain Error
        2. 2.2.3.2 AC/DC Response to Power Disturbance Caused by Gain Error
      4. 2.2.4 Impact of Offset
    3. 2.3 Point C and D – AC/DC DC Link Current Sensing
      1. 2.3.1 Impact of Bandwidth on Feedforward Performance
      2. 2.3.2 Impact of Latency on Power Switch Protection
      3. 2.3.3 Impact of Gain Error on Power Measurement
        1. 2.3.3.1 Transient Analysis: Feedforward in Point D
      4. 2.3.4 Impact of Offset
    4. 2.4 Summary of Positives and Negatives at Point A, B, C1/2 and D1/2 and Product Suggestions
  5. 3Current Sensing in DC/DC Converters
    1. 3.1 Basic Operation Principle of Isolated DC/DC Converter With Phase-Shift Control
    2. 3.2 Point E, F - DC/DC Current Sensing
      1. 3.2.1 Impact of Bandwidth
      2. 3.2.2 Impact of Gain Error
      3. 3.2.3 Impact of Offset Error
    3. 3.3 Point G - DC/DC Tank Current Sensing
    4. 3.4 Summary of Sensing Points E, F, and G and Product Suggestions
  6. 4Conclusion
  7. 5References

3.1 Basic Operation Principle of Isolated DC/DC Converter With Phase-Shift Control

Figure 3-1 shows a typical control loop of a phase-shift dual active bridge (DAB) DC/ DC converter. There are two control loops in this system: (a) an outer voltage loop and (b) an inner current loop.

For the voltage loop, the output voltage is fed into an ADC of a MCU (denoted as Vfb) in Figure 3-1. Vfb is compared with a reference voltage (denoted as Vref). The error between the measured voltage and reference voltage is fed to a compensator, which can be realized as a PID controller. The output of the voltage loop is used as reference (Iref) for the inner current loop. The compensator of the inner current loop (GI) compares the reference (Iref) and actual value of sensed current (IOUT) and uses this error to adjust the phase of a PWM waveform to the leading or lagging bridge depending on the direction of the current. For constant current charging, the voltage loop is optional or can be implemented for protections only. For constant power charging, both loops are needed. The theoretical limits for the phase shift are ±π, practical implementations are much smaller than this.

GUID-20220718-SS0I-XMQP-MWJQ-QGCWD4CRC2GD-low.pngFigure 3-1 Typical Control Loop of Dual Active Bridge (DAB) DC/DC Converter With Phase-Shift Control