Droop conversion to system MVA base

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No, it is the opposite.

Let us assume a 50 MVA generator with droop 4%:

• The governor will incease Pmech with 100 %, 50 MW, if frequence drops 4%.

A generator with Mbase equal to system base 100 MVA and droop 4%:

• The governor will increase Pmec with 100 %, 100 MW, if frequency drops 4%.

A generator with Mbase equal to system base 100 and droop 8%:

• The governor will increase Pmec with 100 %, 100 MW, if frequency drops 8%.
• The governor will increase Pmec with 50 %, 50 MW, if frequency drops 4%, i.e. the same response as the 50 MVA generator with droop 4%.

So,

R_system = R_machine * systemBaseMVA / machineBaseMVA
R_system = 4% * 100 / 50 = 8%

Droop is the inverse of gain (lower droop is higher gain), so the formula for conversion from Mbase to system base is also inversed!