# Different Rectification Behavior of a Half-Bridge MMC in PLECS and RT Box

**URL:** <https://forum.plexim.com/t/different-rectification-behavior-of-a-half-bridge-mmc-in-plecs-and-rt-box/3366>\
**Category:** RT Box\
**Tags:** plecs, plecs-coder, rt-box\
**Created:** [October 29, 2026, 2:15am UTC](https://forum.plexim.com/t/different-rectification-behavior-of-a-half-bridge-mmc-in-plecs-and-rt-box/3366 "2026-10-29T02:15:41Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Wooyoung](https://avatars.discourse-cdn.com/v4/letter/w/59ef9b/32.png) [@Wooyoung](https://forum.plexim.com/u/Wooyoung)\
**Post date:** [October 29, 2026, 2:15am UTC](https://forum.plexim.com/t/different-rectification-behavior-of-a-half-bridge-mmc-in-plecs-and-rt-box/3366/1 "2026-10-29T02:15:41Z")

</div>

Hello,

I am currently testing the rectification behavior of a Half-Bridge MMC model in PLECS.

I am using the same circuit configuration and parameters in both PLECS Standalone and RT Box, but I am observing different results between the two environments.

The test is performed without any closed-loop control. A three-phase AC voltage is applied to the MMC, and the natural rectification behavior is evaluated by monitoring the DC-link voltage.

The test sequence is very simple. When `Grid_en` is changed from 0 to 1, the three-phase AC grid voltage is ramped from 0 V to `10 × sqrt(2) kV`.

 ![image](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/2X/e/e6d8209dbe09da621f2c31bd7ecc4edd2b4f5da6.png)

In PLECS Standalone, the MMC shows the expected rectification behavior, and the DC-link voltage settles at approximately `10 × sqrt(2) kV`.

 ![스크린샷 2026-10-29 101259](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/2X/c/cb8169cf5f6bd225b4d50e042d9021d1df29305c.png)

However, when the same model is executed on the RT Box, the DC-link voltage rises above `10 × sqrt(2) kV` and continues to increase instead of settling.

 ![스크린샷 2026-10-29 104123](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/2X/b/bd6311401ed0ff717d76c6f235c2733e7eaa99f5.png)

The purpose of this test is simply to verify the basic natural rectification behavior of the MMC. To isolate the issue as much as possible, I have removed the control functions and additional circuits that could potentially affect the result. Despite this, I have not been able to identify the reason for the difference between PLECS Standalone and RT Box.

Could you please advise on the following?

- What could cause the natural rectification behavior of the same Half-Bridge MMC model to differ between PLECS Standalone and RT Box?
- Are there any specific modeling considerations or settings required when performing this type of MMC rectification test on the RT Box?
- Is there a recommended way to resolve this issue?

I have attached the PLECS model used for the test for your reference.

Thank you.

[MMC\_Rectifying.plecs](https://forum.plexim.com/uploads/short-url/oh1rUX5w8BVL88DLYdi0429Xn5j.plecs) (163.2 KB)