GE UR F35 Series Instruction Manual page 311

5 SETTINGS
A general form of a PID regulator in the s domain is shown below.
The following terms apply to the block diagram:
• y is the process signal
• r is the setpoint signal
• w is the tracking signal
• u is the regulator output
• K is the proportional gain
• b is the setpoint weighting
• T is the derivative time constant
d
• N is the derivative limit
• T is the integral time constant
i
• T is the anti-windup time constant
t
• s is the domain
In discrete form, the equations for the regulator are:
e k ( )
p k ( )
d k ( )
u k ( )
i k (
Where T is the sampling time and AW is a flag which enables anti-windup. The incremental form of the above equation is:
S
Where:
GE Multilin
Figure 5–91: PID BLOCK DIAGRAM
r k ( ) y k ( )
= –
K br k ( ) y k ( ) ( )
= –
T
  
d
----------------------- - × ( )
d k 1
= – –
  
T NT
+
d S
p k ( ) i k ( ) d k ( )
= + +
e k ( )
KT T

S S
------
1 ) i k ( ) ---------------------- - ×
+ = + +

T T
i t
Du k ( ) u k ( ) u k 1
= –
Dp k ( )
= +
F35 Multiple Feeder Protection System
kT N

d
----------------------- - × ( y k ( ) y k 1 ( ) )
– –

T NT
+
d S

( w k ( ) u k ( ) ) × AW
–

( )
–
Di k ( ) Dd k ( )
+
5.7 CONTROL ELEMENTS
(EQ 5.27)
(EQ 5.28)
5-187
5