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

2.3.1 Impact of Bandwidth on Feedforward Performance

To evaluate the minimum bandwidth required of a current sensor located in position D, when used for feedforward, system simulations were executed by applying the following conditions:

  • DC bus voltage working at the minimum rated voltage (650 V)
  • Step power applied on the DC-link of 11 kW
  • Grid operating at 400 VRMS

Simulations were performed to compare load transient performance with and without feedforward. Figure 2-17 shows the results. Without feedforward, the DC-link voltage drops significantly when the load is applied, leading to possible unstable converter operation. With feedforward, performance is drastically improved and the load transient response is reduced by a factor of 5. Conversely, the simulation results show how this additional sensor, in addition to the possibility to measure the power on the DC rail, is very useful when deployed with the load which connects and disconnects without giving a warning.

Figure 2-17 DC-Link Voltage Response to Step Power With DC-Link Bandwidth as Parameter, With and Without Feedforward

Figure 2-18 shows that the bandwidth of the current sensor only plays a minor role in the performance improvement since the overall bandwidth is limited by the dq current loop.

Figure 2-18 DC-Link Voltage Response to Step Power With DC-Link Bandwidth as Parameter, With Feedforward

In summary, when placing a current sensor in point D for feedforward purposes, a low bandwidth of < 10 kHz is sufficient. In general, the bandwidth of the current sensor needs to be at least two times higher than the bandwidth of the current loop.