SBOA624 March   2025 TMCS1123 , TMCS1126 , TMCS1127 , TMCS1133

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Solar Application Scenarios with Hall-effect Current Sensing
    1. 2.1 String Inverter
      1. 2.1.1 String Current Sampling
      2. 2.1.2 Arc Current Detection (Optional)
      3. 2.1.3 MPPT Boost Current Sampling
      4. 2.1.4 3-Phase Current Sampling
    2. 2.2 Single-Phase Residential Inverter
    3. 2.3 3-Phase Hybrid Inverter
      1. 2.3.1 BDC Current Sampling
      2. 2.3.2 Off-Grid EPS 3-Phase Current Sampling
      3. 2.3.3 Neutral Current Sampling for Midpoint Potential Balancing
    4. 2.4 Split-Phase Hybrid Inverter
    5. 2.5 Micro Inverter
    6. 2.6 Solar Power Optimizer
    7. 2.7 Smart Combiner Box of Central Inverter
    8. 2.8 Summary of Solar Inverter System and In-package Hall-effect Current Sensor
  6. 3Summary
  7. 4References

2.1.4 3-Phase Current Sampling

Inverter 3-phase current sampling includes inverter’s AC current (R phase, S phase, T phase) and corresponding DC components. The typical block diagram of 3-phase current sampling and signal conditioning is shown in Figure 2-3. The phase current is sampled by the DSP ADC to be used for the inverter power stage control and power generation statistics. The AC component of the phase current is filtered out and only DC component is left, amplified and then sampled by the DSP ADC to be used for DC component suppression control.

For grid-connected inverter, theoretically, only AC current is allowed to inject into the grid. But in fact, inverter output current inevitably contains some DC component which does harm to the grid, grid load and grid equipment. Therefore, this is unlikely to completely remove inverter’s DC component but need to control this in a certain low range. Standards such as IEEE 1547-2018 have defined the limit for dc component in the grid-side ac current, for example, below 0.5% of the rated output current.

The accuracy of 3-phase current sampling is very important for inverter power stage control, power generation statistics and DC component suppression. Especially for DC component excess issue, using hall-effect current sensor with high accuracy and low drift can help a lot to solve the issue at the beginning.

Another issue regarding to the accuracy of current sensor is reactive power generation. For active power generation, the reference of current loop is generated by the voltage loop. The error of current sensor can be greatly alleviated by the current controller, in this case, the accuracy of DC bus voltage sensing is important. But for reactive power generation, the reference of reactive current is generated directly by the MCU. So, if the current sensor is not accurate, the output current of the inverter can not be the set value. Using a high accurate TI hall-effect current sensor can also help a lot of this problem.

Typical Block Diagram of 3-phase Current Sampling and Signal Conditioning Figure 2-3 Typical Block Diagram of 3-phase Current Sampling and Signal Conditioning