Skip to main content

Q(V) droop curve

Background​

Different parts of a grid operate at particular voltages. There are often 'standard' voltages in a grid for transmission and distribution levels. For example, in Victoria, Australia, the following voltages are commonly observed:

  • 500 [kV]: Transmission
  • 220 [kV]: Transmission
  • 66 [kV]: Sub-transmission
  • 22/11 [kV]: Distribution
  • 400 [V]: Low voltage

Grid operators must ensure that the grid voltage is maintained very close to the rated voltage. If the voltage deviates too far from the rated voltage, equipment connected to the grid can have serious issues or be damaged. Grid operators achieve this voltage control by implementing a collection of different systems. Common methods to achieve this are:

  • Transformers are equipped with On-Load Tap Changers (OLTCs) which adjust the transformer tap ratio based on locally observed voltage.
  • Static VAR Compensators (SVCs) are constructed at particular locations in a grid and adjust the amount of reactive power injected/absorbed based on locally observed voltage.
  • Generating systems locally adjust their reactive power output based on locally observed voltage.

This tool is designed to help you understand the latter method. In this method, it is very common for generating systems to have a Q(V) droop curve for local voltage control.

Tool​

Project settings
Q(V) droop settings
Slope outside deadband: 1737.500 [MVAr/p.u.](base = 69.5 MVAr)
Solve for
Reactive power at 0.970 p.u.
34.750 MVAr
ΔQ +34.750 MVAr
Reactive power increased for under-voltage (inject)
Sunny Solar Farm - Q(V) droop curve0.9000.9400.9801.0201.0601.100Voltage [p.u.]-70-40-10104070Reactive power [MVAr]Qnormal0.0 MVArVref1.000 p.u.ΔQ = +34.8 MVAr0.970 p.u.34.75 MVArDeadband ±: 0.0100 [p.u.]\Droop: 4.00 [%]Qbase: 69.5000 [MVAr]Qmin: -69.5000 [MVAr]Qnormal: 0.0000 [MVAr]Qmax: 69.5000 [MVAr]Base voltage: 345.00 [kV]Operating point:Vref: 1.0000 [p.u.]Voltage: 0.9700 [p.u.]Reactive power: 34.7500 [MVAr]
Diagram controls

Revision history​

Version 1 | 10 March 2026​

  • First release