Timing relay in Simulink

[Said1]

I am trying to model a plant control system i.e governor, AVR and PSS. The PSS should be disabled under some conditions like P<10 % for 10 sec.

I appreciate it if anybody help me develop such timing block in simulink?

 

[FeX32]

You can accomplish that in many different ways.
Try an embedded function block and then write your code (if PSS<(something), PSS=0; end) something like that.




Fe

 

[Said1]

But how to take care of the timing issue?

 

[FeX32]

Input to the embedded block a clock signal that outputs the simulation time in seconds.
So then you can say for example when 30<t<40 seconds PSS=0 like above.


Fe

 

[Said1]

Thanks Fex32

However the initial time for the relay timing is conditioned with P becoming less than some setting. The P signal is time varying and I need to know the instant of time where P goes below the setting. How do I find this time?

 

[FeX32]

If I understand you correctly.
You input P, this setting you talk about (say "k") and the time ("t") into this embedded block where you write you code. Then you can define another variable say "T". Then you have something like
if P<k
T=t;
PSS=0;
end


Fe