NREL 5MW turbine start up


I am trying to simulate turbine start up in Normal Wind Profile according to DLC 3.1 in the IEC 61400-3 standard for the NREL 5MW turbine. The conditions I am using for the simulation are -

ServoDyn -

PCMode = 0
GenTiStr = ‘False’
TPitManS = 70
PitManRat = -6
BlPitchF = pitch angle corresponding to the mean hub height wind speed (for example, 3.36 deg at 12 m/s)
SpdGenOn = gbRatio (which is 97) * 6.6 (minimum RPM for the 5 MW)

AeroDyn -
AFAeroMod = 2

ElastoDyn -
BlPitch = 90 (feathered blade)
RotSpeed = 0.9 (~1 rpm for idling)

I am simulating for 200 seconds, and I am giving 70 seconds for the transient conditions to die out, which is why I have given TPitManS a value of 70. My understanding is that at 70 seconds in the simulation the blades will start pitching from 90 deg to the final pitch angle at a rate of -6 deg per second. I simulated using these conditions, but at around 96 seconds the Mach number went over 1 and the simulation failed. So I turned off unsteady aerodynamics (AFAeroMod = 1) and simulated, and the simulation finished without errors.

However, the rotor speed kept rising above the rated RPM value, when the blades started pitching in from 90 degrees at 70 seconds. The rotor speed started increasing as the pitch angle started decreasing from 90 degrees after 70 seconds, but continued increasing even after the final pitch angle was reached. The generator turned on when the high speed shaft speed reached 660 RPM, but for a long time in the simulation, the electrical power was in the range of -300E3 kW (does not make any sense physically). The electrical power however reached a value of 5000 kW at some point in the simulation and it was maintained until the end but the rotor speed problem is quite serious. Have I missed some other parameters that I need to set to simulate turbine start up?

I would be very grateful if I can get some assistance in this matter.

Thanks in advance,
Best regards,

Dear Vishal,

What have you set VSContrl and GenModel to?

One problem I can see is that 12 m/s is above the rated speed for the NREL 5-MW turbine, where active pitch control should be enabled to regulate rotor speed. But the override pitch maneuver you are applying will override the active pitch controller, even if you enabled it, anyway. Does this same approach you are using work at a lower wind speed where pitch control is not active?

The override pitch maneuvers are most useful to instigating faults in the controller. Normally a pitch-angle based start-up event would require the implementation of a user-customized wind turbine controller.

Best regards,

Dear Jason,

I have set VSContrl to 5 and GenModel to 2.

I ran the same setup but at 4 m/s, and the rotor speed still had very high values of around 66 rpm.

I have read that pitch angle based start up is one of the most common methods of turbine startup procedures. Another option I can think of is turning on the generator at a certain time, but I feel it would not be a good representation of a startup because the rotor would still be spinning from time 0 (if the blades are not starting at a feathered angle and pitching in towards operational pitch angles). How would you suggest a turbine startup be simulated?

Best regards,

Dear Vishal,

I don’t really have experience with wind turbine start-up control logic. Perhaps someone else on this forum can comment.

Best regards,