Fw: New Topic MPPT and wind power [RE-wrenches]

[Kent Sheldon]

I must have missed something in this thread. An MPPT algorithm dithers
commanded current based on direction of resulting power output. You can't
max power track a generator. Different animal. On a simple wind turbine the
wind spins a generator (which is commonly converted to DC on the small
turbines <20kW). There may be some mechanical control at the generator
(overspeed trip and yaw for example). The generator has a speed/power curve.
Monitor generator speed, and command power with the inverter. The current
regulator and speed feedback must be quite fast relative to wind dynamics.
The power curve is mapped in the inverter controller. Pretty simple in
theory. Of course, there are a number of tricky protection controls to
consider, and the dynamics of the whole system can also be difficult to
optimize, but that is solved with lots of testing. And wind turbines can
become infinitely complicated (VSVF with MG and blade controls in the
inverter) depending on the design. Chris is right, if you change output
current at the inverter, the generator is still turning. The generator
stored energy will rapidly increase output voltage, which can destroy the
generator/inverter if not handled properly.

Kent Sheldon
Sales and Marketing Manager
Distributed Industrial & Utilities Markets
Xantrex Technology Inc.
Direct 925 245 5463 - Fax 925 245 1022
kent.sheldon at xantrex.com  www.xantrex.com


-----Original Message-----
From: hugh piggott [mailto:hugh.piggott at enterprise.net]
Sent: Thursday, September 13, 2001 5:31 AM
To: RE-wrenches at topica.com
Subject: Re: Fw: New Topic MPPT and wind power [RE-wrenches]


At 5:57 pm +1200 13/9/01, Carl Emerson wrote:
>  I
>wonder if we may end up with a separate model for wind with Hall 
>Effect sensing
>to eliminate the need to disconnect at sample time.

I would use frequency as the input variable.

At 6:50 am +0000 13/9/01, Christopher Freitas  -  OutBack Power wrote:
>
>A MPPT type controller for a wind turbine will have to be different than
>a PV MPPT controller.  They are just too different type of power
>sources.  One can be open circuited while the other should be shorted.
>
You could use an overvolt clamping arrangement of some sort.  Having 
said that, it sounds as if you are right and they are two different 
beasts.  You would have to defeat the usual functioning of the MPPT 
and put its input voltage setting directly under control of turbine 
speed (frequency).
-- 
Hugh

http://www.ScoraigWind.co.uk

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