Academic paper related to the ISOP-DAB c2000 example

1

Dear specialist:

I'm quite interested in the C2000 demo of ISOP-DAB, but I still failed to understand the control strategy of the demo. And the references in the demo, 'Control of a Modular DC-DC Converter Dedicated to Energy Storage' is also a little difficult to understand. So could you provide other academic papers or technical reports related to the demo, thank you so much!

The link to this demo is: https://www.plexim.com/sites/default/files/demo_models_categorized/tic2000/isop_dual_active_bridge.pdf

If you can’t provide related learning materials related to this demo, please pardon my interruption.

Thank you!

2

I am reposting this from your support ticket:

The control strategy is a simplified implementation of the control approach given in 'Control of a Modular DC-DC Converter Dedicated to Energy Storage‘. We used only this reference to develop the demo model. We omitted the magnetizing current control loop for this demo since we assume an ideal transformation.

Maybe you can find additional hints in the papers referenced by the paper: https://ieeexplore.ieee.org/document/7309134/references#references

Some additional information on the control approach:
The goal is to control the current flowing between the battery (low voltage side) and the DC-bus (high voltage side).
Ideally, we would like to have equal current sharing among the two DABs. However, in reality balancing the voltages on the two input capacitors is not trivial, e.g. due to small differences in the passive elements. Without an appropriate control strategy, the two voltages would drift away.
In the demo model, this is prevented in the following way: The current is distributed among the two DABs in such a way that the two voltages equalise. Since we only use a simple proportional controller, there will be a small (uncritical) steady-state error.

3

Dear Kris or PLECS Team,

I can’t find this demo "ISOP-DAB c2000 example" in my actual Plecs Blockset installation Version 4.8.4. anymore. Where can I find this demo model?

Thank you very much and with best regards,

Lars

4

Hello, you can find it listed under the TI C2000 Target Support Demos menu and then Power Supplies Category:

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3600×426 86.9 KB

5

He Kris, so, thank you very much for your answer :slight_smile:

I searched it under “RT Box Demo Models” and also in the search bar using the string “Input-Series” and couldn’t get results, so I thought it was not installed in my plecs version.

With best wishes,

Lars

6

Dear Kris or PLECS Team,

I have now started to take a closer look at the ISOP-DAB example and have a few questions about it:

  1. Why we are multiplying the sign of Iref here?
    Strategy
    Strategy786×346 6.45 KB

→ Neither your tutorial, nor the paper “Control of a Modular DC-DC Converter Dedicated to Energy Storage” defines this!

  1. You implement the distribution block differently, than the formula on page 3 of your tutorial defines!
    Distribution
    Distribution476×244 3.68 KB

→ I would now assume that your formula on page 3 of your tutorial is wrong. Formulas (2) and (3) from the paper “Control of a Modular DC-DC Converter Dedicated to Energy Storage” should be correct.

  1. Where does the saturation in the “Ireftophi” block come from?

    Ireftophi_Sat
    Ireftophi_Sat1236×216 6.74 KB

  2. What is the purpose of the extra zero here?

    Ireftophi_Zeroref
    Ireftophi_Zeroref1236×216 6.8 KB

  3. Where does this “adjust” block come from?

    Ireftophi_adjust
    Ireftophi_adjust1236×216 6.77 KB

Thank you very much for your clarifications and with best regards,
Lars

7
  1. Why we are multiplying the sign of Iref here?

For a positive Iref and Vhv1 > Vhv2 then the control strategy should set Iref1 > Iref2 to balance the capacitor voltages. However, for a negative Iref and Vhv1 > Vhv2 the control strategy should have Iref1 < Iref2 to balance the capacitor voltages.

  1. You implement the distribution block differently, than the formula on page 3 of your tutorial defines! Why?

The variable naming in the documentation might be a bit confusing and can be improved. It was probably expressed that way for compactness.

  1. Where does the saturation in the “Ireftophi” block come from?

The current references are limited to the nominal rating of the power converter. The block itself is a standard PLECS library block. A more “correct” approach would probably be to implement anti-windup with feed-forward in the PI block. See the “Anti-Windup with External Saturation” part of the PI block help.

  1. What is the purpose of the extra zero here?

For each DAB converter a 2x PWM sets are generated: one for the primary and one for the secondary. Each group of PWM generators has the first channel configured as the primary channel and the other channels configured as secondaries. The primary phase shift is defined as “0” and the phase angle of the secondary adjusts according to the current reference.

  1. Where does this “adjust” block come from?

This is a “Function” block from the PLECS Library. The PWM block only accepts an input between 0 and 1 at the ph’ port. If the phase angle is <0 then the adjustment block maps the signal to the corresponding value in the 0 to 1 interval.

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