Search found 9 matches

by Yanda.Jiang
Sat Jul 27, 2019 10:11 am
Forum: WIND Toolkit
Topic: About the WIND Toolkit Forum
Replies: 1
Views: 15713

Re: About the WIND Toolkit Forum

Hi Jason,

Is it possible we can download solar irradiation data of wind toolkit? Since we need pair of solar/wind data from same model, NSRDB won't be a choice for us. Waiting for your reply.


Best,
Yanda
by Yanda.Jiang
Tue Apr 30, 2019 6:30 pm
Forum: General
Topic: Active stall control VS pitch control
Replies: 2
Views: 757

Re: Active stall control VS pitch control

Dear Yanda, Regarding (1), my guess is the difference in the two "active stall regulation" curves are just two different examples i.e. Figure 2-13b has better power regulation than Figure 4. Active stall regulation is not very common in practice. Regarding (2), while the power regulation ...
by Yanda.Jiang
Mon Apr 29, 2019 11:12 am
Forum: General
Topic: Active stall control VS pitch control
Replies: 2
Views: 757

Active stall control VS pitch control

Hi guys, I am reading papers and books about control method of WTG and confused by comparison between active stall control and pitch control. 1) What is power-wind speed curve with active stall and passive stall control? I attach two graphs I found from internet below. The first one is from "co...
by Yanda.Jiang
Tue Apr 16, 2019 2:04 pm
Forum: General
Topic: Question about Betz limit
Replies: 2
Views: 714

Re: Question about Betz limit

Dear Yanda, It is common practice to use the swept area of the rotor (A_t) as the reference in the Betz limit because if the rotor was absent, the flow would not slow down and would pass through that area unaffected. The area A_u is smaller than swept area because the wind slows down due to the pre...
by Yanda.Jiang
Tue Apr 16, 2019 11:20 am
Forum: General
Topic: Question about Betz limit
Replies: 2
Views: 714

Question about Betz limit

Hi guys, I just started to learn betz's law and wanna ask a question about it. Capture.PNG Capture2.PNG In betz's law, the "1/2*rho*At*Uu^3" is regarded as wind power input , but why don't we use "1/2*rho*Au*Uu^3" instead? I suppose this is the real wind power input at the very b...
by Yanda.Jiang
Mon Mar 11, 2019 11:35 am
Forum: General
Topic: FIXED and VARIABLE wind turbines, help pls!
Replies: 12
Views: 11162

Re: FIXED and VARIABLE wind turbines, help pls!

Dear Yanda, The power grid operates at a "fixed frequency", so, coupling a fixed-speed turbine to the grid is straightforward. Coupling a variable-speed turbine to the grid requires a fancy power electronics i.e. AC-to-DC-to-AC conversion. Best regards, Dear Jason, Thx very much for your ...
by Yanda.Jiang
Mon Mar 11, 2019 10:48 am
Forum: General
Topic: FIXED and VARIABLE wind turbines, help pls!
Replies: 12
Views: 11162

Re: FIXED and VARIABLE wind turbines, help pls!

Dear Yanda, The point is that the fixed-speed turbine actually has a small variation in generator speed, so that large variations in wind speed result in small variations in generator speed and large variations in torque / power i.e. the torque-speed curve is steep. Best regards, Dear Jason, Thx so...
by Yanda.Jiang
Mon Mar 11, 2019 10:19 am
Forum: General
Topic: FIXED and VARIABLE wind turbines, help pls!
Replies: 12
Views: 11162

Re: FIXED and VARIABLE wind turbines, help pls!

Dear Yanda, Yes, small changes in rotor speed together with a steep torque-speed curve will result in large variations in torque and power. The fixed rotor speed will be selected to maximize aerodynamic efficiency at a given wind speed together with structural design decisions of the wind turbine. ...
by Yanda.Jiang
Mon Mar 11, 2019 8:24 am
Forum: General
Topic: FIXED and VARIABLE wind turbines, help pls!
Replies: 12
Views: 11162

Re: FIXED and VARIABLE wind turbines, help pls!

Dear Lado, In an induction machine, the slope of the torque-speed is steep (the slip is small), so, the torque (and hence power) can vary considerably for small changes in speed. Best regards, Dear Jason, So do you mean the power output variation of fixed-speed wind turbine is caused by small chang...

Go to advanced search