Homebrewed Electricity > Wind

My home made Asynchronous Induction generator PLC controller (image heavy)

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StorminN:
Looks pretty cool, jondecker!
Do you have any plans to scale this down, or would it be relatively easy? I have a friend that just bought an Enertech 1800 (1.8kW, 13' prop) and will be setting it up soon. He's got the original analog control box that powers the prop up to speed, but a more efficient unit sounds better...
-N.

jondecker76:
Yes, this is grid tied via asynchronous induction - and yes, cutin in alternator is at 1800RPM (synchronous speed). Cutout happens at the cutout setpoint (1797 for us right now). The 1900 is an overspeed fault.

The braking is a custom made disc brake from a semi and released via air pressure.

I did not measure, but I was told the prop diameter was 45 ft.

jondecker76:


"The new PLC program counts 500 pulses per revolution."
And you are worried about catching it in a 3 RPM slot?


The 3 RPM slot is measured at the prop - at the alternator its about a 100 RPM slot.
When I say catching it in that slot, I'm not referring to just sensing the RPM - I'm talking about catching the RPM near asynchronous speed, and getting its phase synchronized with the grid within that 100 rpm (at the alternator) window before it overspeeds. It will be pulled back down to around 1800 RPM (and up to about 1830 RPM at the end of the generator's slip) when locked to the grid. Do this too fast and you'll be out of spec on THD. Do this too slow and you'll hit the 1900 RPM overspeed and the fault will happen, setting the brake and disconnecting from the grid.

jondecker76:
This unit scales nicely - all setpoints are adjustable. All induction generators are basically the same, so theoritically it will work with any asynchronous machine.
The problem with the original analogue controls are in how it operates. It must see >14MPH winds for 3 minutes, then it will use to line to spool its self to synchronous speed and continue to generate power from there on out. Once the windspeed drops below 9MPH, it would shunt the generator to a huge resistor box, then set a parking brake. This process would repeat indefinitely.

As you can imagine, in swinging winds, there are times where it will use more power to spool up than it will generate before the wind goes below 9 MPH again. This was a major problem to a lot of their customer base living in #2 wind zones.
This freewheeling design can engage its self to the grid if the wind gets up to about 12MPH for a minute or so, and will not kick out until it drops below the synchronous speed of the alternator. Add to that that in varying winds, we see the unit stay online generating power even when the windspeed drops down to 5 MPH for short periods, and 7 MPH indefinitely. It captures a lot more power from the wind, and uses none on startup.
Funny enough, these twin 40KW machines are Enertechs, and next week another unit is being put on 2 60KW Enertechs.
The modification inclues 1)Adding the 500PPR encoder to the back of the alternator shaft


Replacing the original NRG #40 anemometer with their #40H hall effect model
You re-use much of whats in the original cabinet, including the SCR firing board (which must be physically modified for soft-start capabilities and rewired at J1), 3 relay cubes and the voltage and frequency threshhold cubes. We also added a contactor in series with the SCR as an additional failsafe, which the electric company was thrilled to see.
We engineered a new braking system. The Enertech comes with a very small and cheap brake that is used for parking only. Actual braking was done with a resistive load, then the parking brake set. Our version uses a semi brake to both slow the unit to a stop, and hold it there. I would imagine that you may end up with premature brake failure on the stock unit if it is used for the actual braking. The large units pictured are using semi brakes (hoping for at least a 15 year service life) - but the cost just for parts is several thousand dollars. However, in a 13' machine, you can make a cheaper one from car disc brakes.


Though, if you were so inclined to use the resistive braking, you can probably use the brake relay to dump to the resistive load, and use a delay cube to power another relay after so long to set the original parking brake.

jondecker76:
I'm attaching my first draft at a user manual (in microsoft word format and Open Office (free and multiplatform) formats) for those interested in a better description of the unit's operations. I'd like to get the manual officially finished soon so any feedback would be appreciated.
I know this post isn't exactly on homebrew units, but I would like to see more asynchronous grid tie home brews in the future, and maybe having a control system already in place would help (as its the hardest part of these types of wind turbines). I plan on having a home brew asynchronous flying next year.... No batteries to maintain, and net metering to boot!

Manual

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