Process Pid Control; Process Pid Control Parameters - Danfoss VLT AutomationDrive FC 300 Design Manual

Product Introduction

3.4.6 Process PID Control

The process PID control can be used to control application
parameters that can be measured by different sensors
(pressure, temperature, and flow) and be affected by the
3 3 connected motor through a pump or fan.
Table 3.9 shows the control configurations where the
process control is possible. When a flux vector motor
control principle is used, the speed control PID parameters
should also be tuned. Refer to 3.2.2 Control Structure in
NOTICE
The process control PID works under the default parameter setting, but tuning the parameters is highly recommended
to optimise the application control performance. The 2 flux motor control principles are particularly dependent on
proper speed control PID tuning to yield their full potential. The speed control PID tuning occurs before tuning the
process control PID.
Ref.
Handling
Feedback
Handling
Illustration 3.22 Process PID Control Diagram

3.4.7 Process PID Control Parameters

The following parameters are relevant for the process control
Parameter
7-20 Process CL Feedback 1
Resource
7-22 Process CL Feedback 2
Resource
7-30 Process PID Normal/
Inverse Control
7-31 Process PID Anti Windup The anti-windup function ensures that when either a frequency limit or a torque limit is reached, the
7-32 Process PID Start Speed
7-33 Process PID Proportional
Gain
38
VLT
+
% [unit]
_
*(-1)
% [unit]
P 7-30
normal/inverse
Description of function
Selects from which input the Process PID should get its feedback.
Optional: Determines if and from where the process PID should get an additional feedback signal. If an
additional feedback source is selected, the 2 feedback signals are added together before being used in the
process PID control.
Under [0] normal operation, the process control responds with an increase of the motor speed if the
feedback lower than the reference. In the same situation, but under [1] inverse operation, the process
control responds with a decreasing motor speed.
integrator is set to a gain that corresponds to the actual frequency. This avoids integrating on an error
that cannot be compensated for by means of a speed change. Disable this function by selecting [0] Off.
In some applications, reaching the required speed/set point can take a long time. In such cases, it is
beneficial to set a fixed motor speed from the frequency converter before the process control is activated.
This is done by setting a process PID start value (speed) in 7-32 Process PID Start Speed.
The higher the value, the quicker the control. However, too large a value may lead to oscillations.
®
AutomationDrive FC 300 Design Guide 90-1200 kW
plus
VVC Advanced Vector Control to see where the speed
control is active.
1-00 Configuration
Mode
[3] Process
Table 3.9 Process Control Configurations
Process PID
P 7-38
100%
Feed forward
% %
[unit] [speed]
PID
-100%
100%
-100%
MG34S202 - Rev. 2013-08-19
1-01 Motor Control Principle
U/f plus Flux
VVC
Sensorless
N.A. Process Process &
Speed
0%
0%
Scale to
speed
P 4-10
Motor speed
direction
Flux w/enc.
feedb
Process &
Speed
To motor
control