Pid Control; Process Controller Pid1; External/Trim Controller Pid2; Block Diagrams - ABB ACS350 User Manual

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PID control

There are two built-in PID controllers in the drive:
• Process PID (PID1) and
• External/Trim PID (PID2).
The PID controller can be used when the motor speed needs to be controlled based
on process variables such as pressure, flow or temperature.
When the PID control is activated, a process reference (setpoint) is connected to the
drive instead of a speed reference. An actual value (process feedback) is also
brought back to the drive. The drive compares the reference and the actual values,
and automatically adjusts the drive speed in order to keep the measured process
quantity (actual value) at the desired level (reference).
The control operates on a 2 ms time level.

Process controller PID1

PID1 has two separate sets of parameters
PID SET
In most cases when there is only one transducer signal wired to the drive
parameter set 1 is needed. Two different parameter sets (1 and 2) are used e.g.
when the load of the motor changes considerably in time.

External/Trim controller PID2

PID2
• External controller: Instead of using additional PID controller hardware, the user
can connect PID2 output via drive analog output or fieldbus controller to control
a field instrument like a damper or a valve.
• Trim controller: PID2 can be used to trim or fine tune the reference of the drive.
See section

Block diagrams

The figure below shows an application example: The controller adjusts the speed of
a pressure boost pump according to the measured pressure and the set pressure
reference.
Example:
Pressure boost pump
A C S 6 0 0
ACS350
A C T P A R . U N C D R I V E
E N T E R
L O C R E S E T R E .
R E M
3
0 . . . 1 0 b a r
2
4 . . . 2 0 m A
3
Program features
2). Selection between parameter sets 1 and 2 is defined by a parameter.
(42 EXT / TRIM PID) can be used in two different ways:
Reference trimming
PID control block diagram
%ref
Actual values
4014
.
. .
4021
AI1
AI2
IMOT
(40 PROCESS PID SET
on page 101.
PID
ref
4001
k
4002
ti
4003
td
i
4004
dFiltT
4005
errVInv
PIDmax
oh1
PIDmin
ol1
...
%ref = 4010
1, 41 PROCESS
only
,
Switch
Frequency
reference
Speed
reference
9904 = 0