24 Program features
In Grid support current curve - K factor mode, the reference voltage is shown as a dotted
vertical line. The actual voltage is compared against this reference line. The mapping of
voltage difference depends on the selected support mode.
• Grid support is active as long as the selected voltage stays outside the dead band, or
the voltage returns within the dead band for less than the time defined by parameter
125.36 Gs after dip time.
• Grid support is deactivated when the voltage returns within the dead band for the time
defined by parameter 125.36 Gs after dip time.
The total current during a grid fault can be limited with parameter 125.37 Frt Imax %.
There are also ramp times for active current and reactive current that are used during grid
fault. For example, the parameter 125.28 Frt Ireact ref ramp up defines how fast reactive
current is ramped up when voltage drops.
Note: Parameter 125.37 is visible only with Expert level access.
Support modes
Grid support mode is selected using parameter 125.01 Grid support. It defines how the
measured voltage value is converted into a reactive current reference. Four conversion
modes can be defined/selected.
Disabled – FRT grid support is not active. Instead, the inverter follows the reactive power
settings defined by parameter group124 Reactive power reference.
No support – I
delta
is set to zero and base current I
base
is defined by parameter 125.50 Gs
base current. In this case, the same base current value is used throughout the entire FRT
event.
K- factor – The amount of grid support is defined with the starting point P1 and the grid
support gains as described in Grid support current curve - K factor mode. There are
separate gains for low voltage and high voltage ride-through grid support. These are set in
125.05 Lv Gs K-factor and 125.19 Hv Gs K-factor. Point P1 is defined with voltage and
current settings using parameters 125.06 Lv Gs P1 volt %,125.07 Lv Gs P1 cur %,
125.20 Hv Gs P1 volt % and 125.21 Hv Gs P1 cur %. Note that point P1 can be different
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