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

2.2.3.1 Power Disturbance in AC/DC Caused by Gain Error

The goal of the current control loops of the AC/DC stage is to keep the currents detected by the MCU under control without determining the real currents in the system. If the measurement does not match the reality, there is an unwanted power disturbance in the system caused by the gain error, which is expressed in Equation 8.

Equation 5. ΔPGAIN=0.5 VI[ε1+ε2+ε3+0.5ε2+ε3-ε1cos2ωt+0.87ε2-ε3sin2ωt]

where

  • ΔP is the power disturbance caused by the gain errors in function of time, where this power is drained from the grid toward the DC link
  • ε1, ε2 and ε3 are the relative gain errors of each current-sensing stage
  • V is the phase-to-neutral RMS voltage
  • I is the RMS current controlled by the converter
  • ω is the electrical pulsation derived from the grid frequency

The power disturbance is a function of the converter power between the AC and DC stage and reaches the maximum when the maximum power is requested by the AC/DC converter. Furthermore, Equation 8 can be divided in two parts as in Equation 6 and Equation 7.

Equation 6. PGAIN_DC=0.5 VI[ε1+ε2+ε3]
Equation 7. PGAIN_AC=0.5 VI[0.5ε2+ε3-ε1cos2ωt+0.87ε2-ε3sin2ωt]

where

  • PGAIN_DC represents the presence of a fixed power disturbance drained by the PFC during the operation
  • PGAIN_AC represents a power ripple at double the grid frequency exchanged with the grid

Impacts of these power disturbances in the DC and AC sides are investigated by observing the voltage control loops together with the imperfection that was detected.