[TRNSYS-users] Convergence error with Type 56 and Type 23

[Ethan Lust]

Hello,

 

I'm having a convergence error that seems to be rooted in the PID
controller.  I was wondering if anyone could shed some light on the subject.

 

I'm trying to model a long-haul truck sleeper cabin climate control system.
I'm using a Type 23 PID controller in conjunction with a "seasonal switch"
as the climate control unit.  The purpose of the seasonal switch is to  turn
the heater on and the air conditioner off when the temperature drops below
some low deadband temperature and vice versa when the temperature rises
above the high deadband temperature.  In other words, the purpose of this
switch is to keep the air conditioner from coming on during slight
over-heating and the heater from coming on during slight over-cooling.  The
deadband in the seasonal switch is set by default to 5 degrees Celsius.  

 

When just this group of components is run, the output signal from the PID
controller and seasonal switch match just as they should (climate
controller.tpf).  However, when a fuel-fired heater (Type 151, homegrown) is
added, the control signal starts doing some crazy stuff (Climate controller
with heater.tpf).  The control signals, which should align nicely, start
diverging considerably.  This (I assume) creates the convergence error that
stops the simulation after a little more than an hour with the current
settings.    

 

Is there something inherent in the way I am trying to string together these
components that is making the solver diverge?  Is there a better way to go
about it?  I'm not looking for a total solution- simply a pointer or two
towards why the program is behaving as it is and what I might do to get back
on track.  Please let me know if you need any other files.  

 

Thank you in advance for your time,

Ethan Lust

301.405.8672 (desk)

757.636.8727 (cell)

University of Maryland

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