SLUAB06 January   2025 AMC131M02 , AMC3330 , ISO7731

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Topologies for Insulation Monitoring in ESS
    1. 2.1 Single Switch Topology
      1. 2.1.1 Test Steps
    2. 2.2 Dual Switch Floating Sampling Topology
      1. 2.2.1 Test Steps
    3. 2.3 Dual Switch Sampling in High Voltage Side Topology
    4. 2.4 AC Injection Topology
  6. 3Comparison of Designs
    1. 3.1 Injection Resistance Influence on Accuracy
  7. 4Capacitor Influence on Sampling Time
    1. 4.1 How to Choose Y Capacitor
    2. 4.2 Sampling Time
  8. 5Key Devices
    1. 5.1 BQ79731-Q1
    2. 5.2 UCC33421-Q1
    3. 5.3 AMC131M02
    4. 5.4 AMC3330
    5. 5.5 ISO773x
  9. 6Topos Simulation Result and Conclusion
  10. 7Summary
  11. 8References

2 Topologies for Insulation Monitoring in ESS

Currently, the methods used for insulation monitoring in the energy storage field are mainly external resistance method and AC injection method.

The AC current injection method generates a square wave signal which is then injected into the RC circuit between the HV line and the Protective Earth (PE) through an RC filter or transformer. The impedance is calculated based on the charge and discharge of the capacitor. The main drawbacks of AC injection are that the signal is susceptible to interference, difficult to achieve a reliable and accurate design, and that a large transformer is required to isolate the injection circuit from the HV circuit. The advantage of the AC current method is that it is not affected by the isolation capacitance.

The external resistance method connects a series of resistors between the positive and negative poles, using the set switch on and off in the circuit, the voltage value on the resistance in both states can be obtained by listing the circuit status equation. The two equations are combined to determine the positive and negative battery resistance values to ground and determine the positive and negative battery insulation.

The topology of the external resistance insulation monitoring method is mainly different in how many switches and whether or not to use isolating devices, according to the number of switches divided into single and double switches. Depending on whether the control is put on the high or low side