Issue with HDVC AC computation when output terminal is disconnected

[vidaldid-rte]

Describe the current behavior

The Pull Request #957 contains a minimal test that reproduces the issue (ACHvdcTest)

Basically when a line is disconnected from the output terminal of an HVDC station, the HVDC still delivers atcive power to that dandling terminal (and consumes it from upward).

Expected result; No electricity flow to the dandling terminal (no current, no active power, no reactive power).

Describe the expected behavior

No response

Describe the steps

No response

Environment

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Relevant Log Output

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Extra Information

No response

[vidaldid-rte]

Fixed for VSC HVDC during security analysis and sensi analysis by #961

Proposal for HVDC in N_situation (disconnect in the IIDM network) in #965

[annetill]

Still missing: Lccs after contingency or remedial action management.

[vidaldid-rte]

Needed also; detect also disconnection when there is a fictive load on the station's bus.