wind turbine

[Mathan]

your diagrams and formulas are missing (not visible). could you please reattach

[ikarus]

Here are the formulas:

http://i410.photobucket.com/albums/pp181/ikarus999/Dibujo-3.jpg

[johnsold]

I think I have an idea of where the problem is.  Unfortunately, I need to do some of my own work, so I may not be able to work through a solution.

The formulas all use a single data point except for the integration which calculates the angular velocity Wm.  Your VI is working with arrays of wind speed.   Those arrays have many points initialized to values which do not represent the actual data, but are still used by the integration and other parts of the program.

I think if you can convert the Wm calculation to work with incremental data, then the model should work.  Integration simply looks at all the data since the start of recording.  In the physical world the angular speed is an indication of past forces applied to the turbine (Velocity = integral of acceleration over time).  But the velocity at time t can be calculated from the velocity at t-1 and the force (torque) at t.

I hope to be able to do something with this later today or tomorrow.

Lynn

Message Edited by johnsold on 10-30-2008 01:07 PM

[ikarus]

Thanks for your kidness,

I understand what you say, you are right. I'm trying to make a discrete representation of the model, for programming it into a Matlab Script block. maybe works.

Thank you 

Mensaje editado por ikarus

[RavensFan]

I had no problems seeing the formulas, but others such as Mathan might.

Don't put your images on a 3rd party server.  Attach them to your message then post it.  Then edit your message to add the image link that points to the location on the NI server.  Then everyone should be able to see it.

For security reasons, many users may have firewalls that block the images coming from 3rd party sources.

Message Edited by Ravens Fan on 10-30-2008 04:44 PM

[johnsold · Accepted solution]

OK.  I think I have something which is close to what you want.

All the calculations are done on the current value of the wind speed.  This what a real system has: the current wind and the angular velocity which was imparted by the previous wind.

Using [i]  to designate the values calculated from the element i of the array of wind speeds Vm, I have the following equations:

Lambda[i] = R*Wm[i-1]/V[i].  Note that this is not the Lambda(sub)i from the equations you posted.  Lambda[i] is the Tip Speed Ratio calculated for interval i.

Cp[i] = function of Lambda[i] as given in your post above.

Pm[i] = 0.5*A*rho*Cp[i]*(Vm[i])^3 

Tm[i] = Pm[i]/Wm{i-1].  If Wm[i-1] = 0 then a finite value is substituted.  See discussion below.

Wm[i] = Wm[i-1]  + Tm[i]/It.  This is the incremental change in the velocity.  The "integration" of the acceleration term (Tm/It) is based on di = 1.

When I implement this I get results which are very similar to your Matlab results except for lambda.

Comment of the Torque calculation: The given formula for torque is valid, however it does not represent the physics of the production of the torque.  The torque is not produced by the power generated, it is produced by the change of momentum of the air passing the turbine blades.  If the formula for the torque was based on the wind and some geometric factors, the infinities produced by dividing by zero could be avoided.  I did a brief search but could not find any straightforward formula.

Lynn 

[ikarus]

Amazing!!, Thank you very much,

I had not thought of that way of calculating the torque and angular speed, and the results are the same that the Matlab simulation.

The tip speed ratio is different, and i don't know why, but the important results are the torque and the speed. 

Thank you again...

Reggards from Chile.

Mensaje editado por ikarus

[ikarus]

I run my Matlab simulation again, and the result of lambda is the same, now there is no objection to your work.

thanks a lot. 

[johnsold]

Glad I could be of assistance.

Sometimes someone with a different way of looking at things can offer a suggestion which would not have occurred to the person who was originally involved with the problem.

Lynn 

[ikarus]

Yes, your solution is wonderful.

Now I have to keep working, the torque signal must be sent to a frequency inverter which controls an induction machine, so to have a tangible form of torque produced by the turbine.

I thought in the Modbus protocol for communication, so if I have any problem, you will see me again here 😄

Thanks.