Technical data

With
Relay
input, the reference source is received via four discrete signals (K1-K4). This allows
for 16 different combinations and each one can be configured for a specific value of Q or PF
and power reduction (PLA).
Note:
For more information, refer to the Web Server User Manual and the Grid Management Box
Manual.
10.4.5. Theory
The principle in generating reactive power is that the phases between the voltage and the cur-
rent are shifted in a controlled way.
Reactive power can, in contrast to real power, not transport any consumable energy but it gen-
erates losses in power lines and transformers and is normally unwanted.
Reactive loads can be either capacitive or inductive in nature, depending on the current leads or
lags in relation to the voltage.
Utility companies have an interest in controlling reactive power in their grids, for example in:
Compensation for inductive loading by insertion of capacitive reactive power
Voltage control
To compensate for this a generator supplying reactive power operates either at a lagging power
factor, also known as over-excited, or at a leading power factor, also known as under-excited.
The technical definition of reactive power:
- Real power (P) measured in Watts [W]
- Reactive power (Q) measured in volt-ampere reactive [VAr]
- Apparent power (S) is the vector-sum of P and Q and is measured in volt-ampere [VA]
- φ is the angle between P and S
Illustration 10.5: Reactive Power
In the inverter, the reactive power is defined either as:
- Q: The amount of reactive power as a percentage of the nominal apparent power of
the inverter.
- PF, Power Factor: The ratio between P and S (P/S), also referred to as: Cos(φ).
10.5. Fault Ride Through
The grid voltage usually has a smooth waveform, but occasionally the voltage drops or disap-
pears for several milliseconds. This is often due to short-circuit of overhead lines, or caused by
operation of switchgear or similar in the high-voltage transmission lines. In such cases the in-
verter continues to supply power to the grid using fault ride through (FRT) functionality. Contin-
uous power supply to the grid is essential:
10. Ancillary Services
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