K omega**2 control, definition of K

[dzalkind]

Discussed in #330

^{Originally posted by lejeunemax April 5, 2024}
I stumbled upon the vs_rgn2K value used by ROSCO for the K omega**2 regulation
In the tune_controller function, it is defined as follows:

self.vs_rgn2K = (pi*rho*R**5.0 * turbine.Cp.max * turbine.GBoxEff/100 * turbine.GenEff/100) / \
            (2.0 * turbine.Cp.TSR_opt**3 * Ng**3) * self.controller_params['rgn2k_factor']

For VS_ControlMode == 1, in Region 2, this value is then used to compute the generator torque and accordingly stored in avrSWAP[46] (in python) which, in turn, is used to compute the generated power eg. : gen_power[i] = gen_speed[i] * gen_torque[i] * self.turbine.GenEff / 100 in sim_ws_wd_series.

From my understanding, there is therefore an inconsistency between the definition of K and the way it used there. More precisely LocalVar%GenTq = CntrPar%VS_Rgn2K*LocalVar%GenSpeedF*LocalVar%GenSpeedF should actually by LocalVar%GenTq = CntrPar%VS_Rgn2K*LocalVar%GenSpeedF*LocalVar%GenSpeedF/(CntrPar%VS_GenEff/100.0)) as VS_GenEff is currently accounted twice in the gen_power[I]computation. Also, the definition of the generator torque (coming from the hss) should not depend on the generator efficiency.

Curious to know if I am missing something or if this definition is indeed incorrect?

[dzalkind]

Thanks for the suggestion @lejeunemax. We think there is an error here and plan to fix it in a new release.