NOVAR 2100/2200 Operating Manual
If a number of chokes are available to the controller, the most suitable one, depending on their values,
is connected, and another one is connected if the above described situation has lasted for another
overcompensation control time specified.
If a combination of chokes are connected and undercompensation occurs, such a number of chokes
are disconnected after the undercompensation control time has elapsed, which prevent
overcompensation.
4.3.3.7.2 Choke Control Limit Power Factor (for Mixed Choke Control)
In mixed choke control mode, this parameter specifies power factor value at which the controller starts
using, besides capacitive sections, inductive compensation sections for compensation as well –
chokes (if available). Its value can be set in the line 3.
If the power factor measured is more inductive (current more lagging) than the value specified in this
parameter, the controller uses only capacitive sections (capacitors) to control compensation.
If the power factor in the power system changes so that it is more capacitive (current more leading)
than the choke control limit value, the controller starts using combination of capacitive and inductive
compensation sections for compensation.
Exception: This rule does not apply when offset control (see below) is activated ! In this case,
the value of measured power factor is not decisive and the controller uses both capacitive
and inductive sections, regardless of its value. This is true even if the offset power value is
set to zero.
4.3.3.7.3 Non-Mixed Choke Control
There exist some applications (such as renewable resources power plants) where continuous power
factor control in some range, usually symmetric to both sides from neutral value of 1, is required. In
such cases the same or similar sets of both capacitors and chokes are installed.
The mixed choke compensation mode is often unsuitable for such installations. Therefore, so called
non-mixed mode
is implemented, that differs from the mixed one in following :
•
during one control step, the controller switches combination of chokes to reach optimal
power factor
•
the controller never combines capacitors with chokes (first, it switches all of capacitors off,
then switches chokes on and vice versa)
The choke control limit power factor parameter setting is irrelevant for this control mode, therefore it is
not displayed.
4.3.3.8 Offset Control, No. 13
In some cases it may be necessary to control "shifted" by a certain value of reactive power. A typical
example is an installation of a power transformer compensating capacitor permanently connected to
the transformer before the controller CT, or an installation of long power cable with not-negligible
parasitic capacity. In such cases, so called
offset control
can be used.
As default, the parameter is
off
. In this setting, the offset control is disabled and the controller
maintains the preset target power factor value.
If you set it to
on
, the offset control is activated with following consequences :
•
offset power for tariff 1
(No. 03 and , optionally, No. 08 for
tariff2
too) parameters appear and
can be set in the PFC control setup group of parameters
•
after the power factor control deviation (i.e. reactive power difference to achieve target power
factor) is evaluated, the controller adds to it appropriate preset offset power value.
Therefore, it controls to this “shifted” reactive power.
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