Balance type PROPORTIONAL_TO_REMAINING_MARGIN checks active mismatch sign for participation factors

[vmouradian]

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines
• [x] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem?

What kind of change does this PR introduce?

feature

Does this PR introduce a new Powsybl Action implying to be implemented in simulators or pypowsybl?

• [ ] Yes, the corresponding issue is here
• [x] No

What is the current behavior?

When using PROPORTIONAL_TO_REMAINING_MARGIN balance type, participation factor of a generator is proportional to the difference maxP - tartgetP, even if the power distribution needs to reduce targetP.

What is the new behavior (if this is a feature change)? The factor depends on the sign of the mismatch that is distributed. If it is positive, behavior stays the same. If it is negative, participation factor is proportional to the difference targetP - minP.

Does this PR introduce a breaking change or deprecate an API?

• [ ] Yes
• [x] No

If yes, please check if the following requirements are fulfilled

• [ ] The Breaking Change or Deprecated label has been added
• [ ] The migration steps are described in the following section

What changes might users need to make in their application due to this PR? (migration steps)

Other information: