Functional Software description
44
DCS 500 Software Description
PI- Regulation
The parameters of the PI controller can be set either with the
autotuning or manual tuning function.
ARM CURR PI KP (407)
determines the gain of the regulator and
ARM CURR PI KI (408)
determines the integral time constant of the regulator.
Scaling of the
gain KP
PI-controller input and output values are scaled so that gain value
100% produces in the output the same value as can be seen in the
input. This kind of scaling is used in the current controller of the
DCS500B.
output
ARM CURR PI KP error
=
*
256
So, default value 300 is equal to gain 300/256=1.17 (117%)
Scaling of the
Time Constant KI
Integral gain is calculated from the time constant:
ARM CURR PI KI
scantime
TC
=
16384 *
where scantime
= 3.33 ms in 50Hz network
= 2.77 ms in 60Hz network
TC
= time constant in ms.
Discontinuous
Current Point
Parameter
ARM CONT CUR LIM (409)
is the converter actual cur-
rent at the point where discontinuous current of the armature circuit
changes to continuous current. By using autotuning this point will
be defined automatically. In manual tuning the point must be
measured from the armature circuit by means of e.g. an oscillo-
scope. Actual converter current value
CONV CUR ACT (10501)
is
set in parameter
ARM CONT CUR LIM (409)
. There is also a
status bit B6 at
TC_STATUS (11204),
bit value 1 = armature cur-
rent is discontinuous.
t
I
t
I
continuous armature current
discontinuous armature current
Figure
22
Waveforms of the armature current
Summary of Contents for DCS 500B
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