Convert load to constant power

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When preparing a case for dynamic simulation, we must convert the generators and loads. The default settings for loads are:

Active power component --> 100% constant current Reactive power component --> 100% constant admittance

I am developing a model that aims to be constant power - that is, the load calculates the total power and is able to disconnect given certain conditions. At the moment, when I want the load to "disconnect", I set the load to 0, however, when plotting I can see that the current returns to its steady-state value, rather than remaining at zero. Also, my model is designed to have time-varying power consumption, however, the current is held more-or-less constant by PSSE (I want a square-wave-like varying power, but when the power decreases to its minimum, the current droops down slightly then returns to nominal, and when the power increases to its maximum the current droops slightly up and then returns to nominal).

My question is: is there a way to keep the load component constant power, which will allow the voltage and current to be determined by the power value?

I have played around with keeping the load 100% power when converting, however the simulation does not work correctly.