Issue in OneLiner CIR simulation in three-phase fault

Thanks to some feedback from our users, we discovered a bug in OneLiner's CIR model shutdown logic.  This bug causes the CIR model to show questionable current contributions to some three-phase bus faults.

The intended functionality of the OneLiner CIR model is to simulate a CIR fault-ride-through in grid-following operation and to assume that the CIR is shut down when no longer connected to a network having one or more conventional generators.  However, in the case of a bolted three-phase fault that isolates a CIR model from the rest of the network, OneLiner does not always detect the island condition of the CIR.  Therefore, the short-circuit solution resumes as if the CIR were supposed to remain online.

The diagram below illustrates some scenarios where the CIR model may not shut down properly during a fault simulation. In this network, both faults at Flt1 and Flt2 result in the CIR model being isolated from all conventional generators. Fault at Flt3 may result in the CIR model being isolated if the impedance of the branch from Bus Vx to Bus Vr is sufficiently small. 

It is recommended to identify simulations within your studies where a three-phase fault may isolate a CIR model from the rest of the network and ensure that the CIR model is shut down for this condition.

ASPEN has updated OneLiner V15.7 in Build B34489 to display an "Iterative solution does not converge" message when the above condition is detected within the OneLiner simulation. This software update is now available on the ASPEN software distribution portal:

https://webapps.aspeninc.com/aspen-dist/login