Voltage droop control#

Revision 36 plant-level reactive droop control sets total plant reactive output from the regulated-bus voltage.

The characteristic#

A droop record names a regulated bus (REGBUS) and a piecewise-linear characteristic that sets the plant's total reactive output from the voltage at that bus. Writing \(V\) for the regulated-bus voltage in per unit, the plant reactive output in Mvar follows five segments:

Voltage at the regulated bus	Plant reactive output
\(V \le\) `VLOW`	`QMAX`
`VLOW` \(< V <\) `VDBLOW`	linear, `QMAX` down to `QDB`
`VDBLOW` \(\le V \le\) `VDBHIGH`	`QDB`
`VDBHIGH` \(< V <\) `VHIGH`	linear, `QDB` down to `QMIN`
\(V \ge\) `VHIGH`	`QMIN`

The characteristic is continuous and non-increasing, so a higher voltage calls VHIGH > VDBHIGH > VDBLOW > VLOW, each strictly. At the solution the plant output rests on this curve at the solved regulated-bus voltage, unless a member limit binds first.

Plant membership#

A machine joins a plant by naming the record in its DROOPNAME field. REGBUS names the regulated bus.

The regulated quantity#

The plant members supply the reactive output requested by the characteristic. Individual reactive limits remain active and can prevent the plant from reaching the requested output.