Need hello on ploting grid tie power curve for My Mann Smart Drive

[Robert Mann]

Hello
I need some help on ploting a good power curve for my Mann Smart Drive using the Ginlong 2 Kwatt Grid Tie.
Seeing this is a new design motor some one will have to lay out the best bench testing system to use. Thank You
Bob Mann

[Rob Beckers]

Bob,

The MPPT curve has mostly to do with the wind turbine (ie. the rotor) that's hooked up to the alternator, and less with the alternator that is used. The idea is to load up the rotor for each wind speed, extracting the exact amount of power to have it run at the best lift-to-drag ratio for the blades (optimal efficiency).

What goes in to an MPPT table is voltage vs. power. Keep in mind that there will be a balance between the power available from the rotor, and the power extracted by the alternator/inverter. If the inverter extracts too little power for the wind speed that the rotor is running at, it will speed up, the voltage will go up, and your MPPT table will tell the inverter to extract more power, until an equilibrium is reached. Extracting too much power for the wind speed will cause the rotor to slow down, voltage goes down, and the MPPT curve will make the inverter extract less power.

While the turbine will always reach equilibrium between rotor RPM and the power output from the inverter, you want this equilibrium to fall at the best lift-to-drag ratio for the blades. You want to make the right MPPT curve for the rotor, to get the most power out of the rotor for each wind speed. Instead of lift-to-drag we use blade TSR (Tip Speed Ratio); each wind turbine rotor, regardless of type, has a design TSR where it runs best. Normally there is little variation in the desired TSR between low and high wind speeds.

With that, the process is as follows: multiple TSR by wind speed, and you have the optimal RPM for each wind speed. The equation for kinetic energy in the wind, and rotor efficiency will give you the amount of power available from the rotor at each wind speed. Now you have power vs. RPM. The alternator will have curves for the voltage coming out vs. RPM, at various load levels. Translate those RPMs to loaded voltage (for the inverter you'll need to convert to DC), and now you have voltage vs. power. That's your MPPT curve.

There are a number of refinements, such as different alternator efficiencies vs. power, rotor efficiency changes vs. power etc., but by-and-large this is the process. Since wind speed and power in the wind follow a cube relationship, and since wind speed and optimal RPM, and therefore alternator voltage are linear, the overall curve of voltage vs. power should be mostly a cube (ie. Y=X^3). Anything very different is suspect.

Hope this helps!

-RoB-

[Robert Mann]

Thank you Rob
I am going to build a 8 ft Lenx2 for a water tower test site Steve has worked up some power plots to size for my unit.
http://www.vawts.net/t45294520/mann-smart-drive-needs-help-on-wings/

The plan is to power up the pump for the town water filtration in the tank with my turbine. I will keep you up to date on this will be up this month.
Bob Mann