I am running a simulation of NREL 5MW baseline turbine with TurbSim FF binary wind inflow.
In the output, I got the electrical power output of generator, “GenPwr”, to be as low as -0.6 MW at some moment of time.
Is it considered as normal operation even if we have such large negative power output?
If it is normal operation, when we would expect negative power output, and what are the causes of the high power usage?
My guess is that when wind speed is lower than cut-in speed, the control system is consuming the power. If that is the case, I am really curious about how “GenPwr” is calculated in this case.
Thank you for your quick reply. In the .fst input file, I defined generator model and generator DOF to be
2 GenModel - Generator model {1: simple, 2: Thevenin, 3: user-defined from routine UserGen} (switch) [used only when VSContrl=0]
True GenDOF - Generator DOF (flag)
Some update about the negative values of GenPwr: the negative values are not synchronous with low wind speed. They occur even when the wind speed is 13 m/s.
What is VSContrl set to? (GenModel is only used when VSContrl = 0.) If VSContrl = 0, meaning that you using the Thevenin-Equivalent Circuit (TEC) generator model (GenModel = 2), then how did you derive the TEC model parameters for the NREL 5-MW turbine?
I see, I am setting VSContrl = 2 which means that FAST is using user defined variable speed control mode rather than the TEC model.
However, I do not think I have defined any UserVSCount ( I still do not know how to do this ), which means the generator is not driven correctly.
On the other hand, NREL 5MW baseline turbine uses conventional variable-speed configuration. So if I just use the simple variable speed control and define the following parameters, would we possibly solve the problem? Please let me know if any of the parameters are wrong, thanks again!
1 VSContrl - Variable-speed control mode {0: none, 1: simple VS, 2: user-defined from routine UserVSCont, 3: user-defined from Simulink} (switch)
1173.7 VS_RtGnSp - Rated generator speed for simple variable-speed generator control (HSS side) (rpm) [used only when VSContrl=1]
43093.55 VS_RtTq - Rated generator torque/constant generator torque in Region 3 for simple variable-speed generator control (HSS side) (N-m) [used only when VSContrl=1]
0.0255764 VS_Rgn2K - Generator torque constant in Region 2 for simple variable-speed generator control (HSS side) (N-m/rpm^2) [used only when VSContrl=1]
10 VS_SlPc - Rated generator slip percentage in Region 2 1/2 for simple variable-speed generator control (%) [used only when VSContrl=1]
I would like to share another update. After switched to simple variable-speed control mode, the power output looks reasonable now.
On the other hand, after a little bit research, I found that the problem that I had was caused by using user-defined variable-speed control routine without correctly compiling FAST according to the instruction given in page 6 of FAST User’s Guide.
Thanks again for pointing me to the right direction to go.
Yes, the baseline torque and pitch controller for the NREL 5-MW turbine is implemented as a GH Bladed DLL. You can find a version of FAST v7.02.00d-bjj compiled with the GH Bladed DLL interface here: wind.nrel.gov/public/jjonkman/FA … erface.exe.
When running OPenFAST for a wind speed of 26 m/s and a severe sea state defined by : Hs=9m, Tp=20s, i obtained negative generator power (Also in ElastoDyn, i set RotorSpeed equals zero and the blades are feathered (BldPitch=90 degrees)). I expect generator power equals zero due to the fact that this state contains wind speed greater than the cut-off wind speed.
My question is about the negative sign of the output channel GenPwr: Does it mean that the rotor rotates counterclockwise ?
When simulating a parked or idling rotor in high winds, I’d expect that you’d disable the generator or torque controller altogether, e.g., by setting GenTiStr = True with TimGenOn > TMax, in which case I’d expect GenPwr = 0.
Dear @Jason.Jonkman ,
I have read your discussion about idle condition above. And followed the guidance you provided in the above and other posts on how to build an idle condition. But there may still be issues with my simulation results .I am currently using the IEA-15MW wind turbine to simulate the structural response of the wind turbine blades under the condition of an average inflow wind speed of 47.5m/s. To achieve this, I need to set the wind turbine to idle operation. At present, the simulation results show that GenPwr=0, and the rotor will operate at a relatively low speed. Unfortunately, the rotor speed (RtSpeed) is a negative value (with an average of about -0.9, much lower than the rated speed of 7.56). I would like to ask if the above situation is reasonable. Will the rotor really rotate in the opposite direction at idle state?Below are my settings for certain modules:
AeroDyn:
The IEA Wind 15-MW RWT blades include some aerodynamic and structural pretwist, so, even if the blade pitch is 90 degrees, there can still be nonzero angle of attack and lift on the blades when the idling rotor is aligned with the wind, which could lead to a slow roll of the rotor. The magnitude (and sign) of the slow roll will depend on what angle you fix the blade pitch angles at. You haven’t stated if you have any yaw error or not, but that may may also have some influence.
Dear @Jason.Jonkman ,
Thank you for your detailed reply. I understand the issue now. Regarding the yaw error you mentioned above, in ElastoDyn, I have set the initial yaw angle to 0 (NacYaw=0), and I have not set any additional angles in the file related to inflow wind. Therefore, my setting should be an aligned case without yaw error.
