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

2.3 Point C and D – AC/DC DC Link Current Sensing

This chapter provides the design considerations of current sensors used in the DC link for AC/DC converter.

Current sensors in the DC link are not mandatory for the basic functionality of the power conversion but sensors can be used for implementing features such as power measurement, protection and feedforwards for the voltage loop.

Sensing in the DC-link can be placed in point C or point D, before and after the DC-link capacitors used for PWM ripple frequency filtering and energy storage (Figure 2-1), respectively.

Offset, bandwidth, accuracy, and latency of current sensors are discussed at a system level base with the goal of determining the minimum requirements for each of the desired additional functions. Not all scenarios are discussed for both points C and D as many cases turned out to be a repetition, only the worst-case scenarios were analyzed to determine current sensor requirements. Details about each analysis follows:

  • Gain Error: impact of gain error is the same in both C and D points. Minimum gain error required by this sensor needs to be evaluated for power measurement and feedforwards.
  • Offset Error: impact of gain error is the same in both C and D points. Minimum offset error required by this sensor needs to be evaluated only for power measurement. Offset error is not critical for the feedforward since the error is compensated out from the integrative part of the DC bus voltage PI controller.
  • Minimum Bandwidth: impact of bandwidth is the same in both C and D points. Bandwidth is required for the feedforward application, and most effective when placed in point D.
  • Maximum Latency: Low latency is important for protecting the active switches of the power-stage, so it is evaluated for point C, the closest point to the active switches.