Danfoss VLT AQUA Drive FC 202 Programming Manual page 141

Parameter Description
20-23 Setpoint 3
Range:
3.17.3 20-7* PID Autotuning
The frequency converter PID Closed Loop controller
(parameter group 20-**, FC Drive Closed Loop) can be auto-
tuned, simplifying and saving time during commissioning,
whilst ensuring accurate PID control adjustment. To use
auto-tuning it is necessary for the frequency converter to
be configured for closed loop in parameter 1-00 Configu-
ration Mode.
A Graphical Local Control Panel (LCP) must be used in
order to react on messages during the auto-tuning
sequence.
Enabling parameter 20-79 PID Autotuning, puts the
frequency converter into auto-tuning mode. The LCP then
directs the user with on-screen instructions.
The fan/pump is started by pressing [Auto On] and
applying a start signal. The speed is adjusted manually by
▲ ▼
pressing [ ] or [ ] to a level where the feedback is around
the system set-point.
NOTICE
It is not possible to run the motor at maximum or
minimum speed, when manually adjusting the motor
speed due to the need of giving the motor a step in the
speed during auto-tuning.
PID auto-tuning functions by introducing step changes
whilst operating at a steady state and then monitoring the
feedback. From the feedback response, the required values
for parameter 20-93 PID Proportional Gain and
parameter 20-94 PID Integral Time are calculated.
Parameter 20-95 PID Differentiation Time is set to value 0
(zero). Parameter 20-81 PID Normal/ Inverse Control is
determined during tuning process.
These calculated values are presented in the LCP and the
user can decide whether to accept or reject them. Once
accepted, the values are written to the relevant parameters
and auto-tuning mode is disabled in parameter 20-79 PID
Autotuning. Depending on the system being controlled, the
MG20O702
Programming Guide
Function:
NOTICE
The setpoint reference
entered here is added to
any other references that
are enabled (see
parameter group 3-1*
References).
Danfoss A/S © Rev. 2014-01-21 All rights reserved.
time required to carry out auto-tuning could be several
minutes.
It is advised to set the ramp times in parameter 3-41 Ramp
1 Ramp Up Time, parameter 3-42 Ramp 1 Ramp Down Time
or parameter 3-51 Ramp 2 Ramp Up Time and
parameter 3-52 Ramp 2 Ramp Down Time according to the
load inertia before carrying out PID autotuning. If PID
autotuning is carried out with slow ramp times, the auto-
tuned parameters typically results in very slow control.
Excessive feedback sensor noise should be removed using
the input filter (parameter groups 6-** Analog In/Out, 5-5*
Pulse Input and 26-** Analog I/O Option MCB 109, Terminal
53/54 Filter Time Constant/Pulse Filter Time Constant
#29/33) before activating PID autotuning. To obtain the
most accurate controller parameters, it is advised to carry
out PID autotuning, when the application is running in
typical operation, i.e. with a typical load.
20-70 Closed Loop Type
Option: Function:
This parameter defines the application
response. The default mode should be
sufficient for most applications. If the
application response speed is known, it
can be selected here. This decreases the
time needed for carrying out PID
autotuning. The setting has no impact on
the value of the tuned parameters and is
used only for the autotuning sequence.
[0] Auto
[1] Fast Pressure
[2] Slow Pressure
[3] Fast Temperature
[4] Slow
Temperature
20-71 PID Performance
Option: Function:
[0] Normal Normal setting of this parameter is suitable for
pressure control in fan systems.
[1] Fast Fast setting would generally be used in pumping
systems, where a faster control response is desirable.
20-72 PID Output Change
Range: Function:
0.10 [0.01 - This parameter sets the magnitude of step
*
0.50 ] change during autotuning. The value is a
percentage of full speed. I.e. if maximum output
frequency in parameter 4-13 Motor Speed High
Limit [RPM]/parameter 4-14 Motor Speed High
Limit [Hz] is set to 50 Hz, 0.10 is 10% of 50 Hz,
which is 5 Hz. This parameter should be set to a
value resulting in feedback changes of between
10% and 20% for best tuning accuracy.
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