10.1.2
Dynamics and accuracy
In all control methods the specified target value at the inverter’s connection terminals is adjusted using a stationary de-
viation of the reactive power of maximum 2% S
N
. This maximum deviation always relates to the specified value as reactive
power. If the shift factor cos ϕ is specified in the control method, then the deviation relates to the reactive power value
brought about by the current power level.
The transient response of the control methods is determined by a PT-1 filter. In this case, the settling time corresponds to
5 Tau, or in other words, achieving approx. 99% of the final value for a PT-1 filter. Subject to the control method selected,
there are also other parameters that determine dynamic behaviour.
10.1.3
Reactive power functions
The following functions for controlling the reactive power are implemented in the devices listed above:
cos φ constant
Q constant
cos φ /(p/pn)
Q(U) 10 nodes
Reactive power is prioritised in each method. The maximum possible active power that can be fed in is reduced in line
with the P-Q operating range when a specific reactive power level is specified.
cos ϕ constant
In cos-φ constant mode the specified displacement factor cos-φ is set permanently by the inverter. In doing so, the reacti-
ve power level is set according Q=P*tan φ dependent on power output which produces the specified displacement factor
cos-φ continuously. If the specification is changed, the new value is adopted attenuated by a filter. The transient time is 1
s with the transient response of a first-order filter (PT-1) with a time constant of Tau=200ms. The specified displacement
factor may be configured in the display or via communication, via KACO RS485 protocol and MODBUS/SunSpec.
If the applicable grid code requires the cos-φ response to set point by a defined gradient or settling time slower than the
configured Tau=200ms, this gradient or settling time must be implemented in the plant control system.
Q constant
In Q constant mode, the specified reactive power value is set permanently by the inverter. If the specification is changed,
the new value is adopted attenuated by a filter. The transient time is 1s with the transient response of a first-order filter
(PT-1) with a time constant of Tau=200ms. The specified reactive power may be configured in the display or via communi-
cation, via KACO RS485 protocol and MODBUS/SunSpec.
cos ϕ /(P/Pn)
In cos ϕ/(P/Pn), mode, the set value of cos-φ and, derived from this, the set value of the reactive power is calculated con-
tinuously as a function of the actual power level. This function ensures that grid support is provided by the reactive power
when a significant voltage increase is anticipated due to a high feed.in level. A characteristic curve is specified which can
be used to configure up to 10 nodes, value pairs for active power and cos ϕ. The active is entered as a % in relation to the
nominal power. Other parameters allow to limit functionality and to limit activation to certain voltage range.
Fig. 46:
cos φ / (P/Pn) standard characteristic curve with 3 nodes
Kaco blueplanet 29.0TL3
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