I am currently simulating an RTDS inverter model and want to add a cable module in RT-LAB. However, during debugging, I found that the model becomes unstable after adding the cable capacitance. The cable parameters are kept consistent with those in RTDS, as shown below
@zhang I would first check whether this is really a parameter mismatch or simply a timestep issue.
Once you add the cable capacitance you introduce a much faster LC dynamic into the network. A model that was perfectly stable with just R and L can become numerically unstable if the RT LAB simulation step is too large for that resonance.
I would try reducing the timestep first and see if the instability moves or disappears. Also double check the units for R, L and C, especially whether RTDS and the Simulink block expect values per km, total values, phase values or sequence values.
It may also be worth testing the cable separately with a simple source and load before connecting it to the inverter. If the cable model is stable by itself but becomes unstable only after connection, then I would look at the inverter control bandwidth, source impedance and any filter resonance.
Another thing to check is whether a single PI section is enough for the cable length you are modelling. If the cable is long or you are interested in higher frequency behaviour, a distributed parameter model or several PI sections may behave more realistically.