Homebrewed Electricity > Wind

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

(1/4) > >>

jondecker76:
A friend of mine owns a business installing and maintaining Asynchronous induction wind turbines. They have been using the same control system since the 1980s. The problem is, some of the older analogue controls are getting hard to get, and they are becoming a reliability issue. Add to that, the local power company is getting very picky on their new installs in regards to failsafes and THD on the line when the alternator is connected to the line. Their old control system simply was not up to the task - and because of this they have been having a very hard time getting new units installed (they have over 70 installations currently).
They asked me to build them a PLC based control system that was robust, adaptable to many different situations and with lots of fail safes built in. They also wanted each unit to have the ability to control 2 wind turbines.  I had never done any PLC programming before, but have a lot of C++ programming experience, so I figured that I would give it a try.
After a couple of months of programming and testing, its finally done! The unit has been operating 2 40KW wind turbines for the last few weeks. The techs from the power company are very happy with the failsafes and the much lower THD that we were able to attain on cutin to the line (due to how much faster the PLC can poll parameters and respond to them - for example the old control system could count 2 pulses for each revolution from the blades to calculate RPM.. The new PLC program counts 500 pulses per revolution). It has also been noticed that the system overall is much more efficient (this design is freewheeling, the old design used the line to spool the wind turbine up to speed, using a lot of power in the process)
Everyone has been so impressed with the unit that I now make and sell these the new units to this company for all of their new installs. They also have sent a letter out to all of their customers (70+) to upgrade their controls if they so desire.
I am going to be building an induction generator from the PrairieTurbines plans, and use this PLC system to control it. I hope to have this done by summer of next year. Another thing to note is that the screen is a touchscreen and makes changing settings very easy!
Now to show it off a bit:

bigpic1

First customers!
bigpic2

The first unit
bigpic3

The old control system - how ugly!
bigpic4

Settings can even be password (PIN) protected
Now some of the interface screens:











(the unit tracks 12 trends (6 per turbine) including windspeed avg last 24 hours, windspeed avg last 24 days, rpm avg last 24 hours, rpm avg last 24 days, grid connected % last 24 hours, grid connected % last 24 days)


you were over the size limits for posting images here on the board both on file size and on pixel size so i had to change some of your pictures to links.
Kurt

bob g:
now isn't that just the coolest thing!
good job :)
i have no background in plc's at all, and only took up stamp micro's about

a year ago.
i decided to morph the two technologies, by taking the control modules and implanting bs2 microcontrollers to make them smart controllers.
the plc manufacture is less than enthusiastic about the project to say the least.
i hope to use it to control a residential trigenerator and manage not only the trigen, but manage the complete system, AC generation, DC battery charging, heat and cooling, and refrigeration.
so when i see someone doing what you have done, i get all excited!
very cool indeed
can you tell me more how your system is used to control the windgenerators?

i understand the monitoring, but don't see how and what you are controlling.
bob g

jondecker76:
The controls aren't really all that complicated. More or less broken down, what was needed was:
A way to "Turn On" or "Turn Off" a wind turbine. When a wind turbine is turned on, a brake is released. When it is turned off, a brake is set (the brake is normally closed)
Now, when turned on, the wind turbine will cycle between 2 modes: Standby and online. In standby mode, the wind turbine is just waiting to be spooled up by the wind. Once the wind gets the blades moving, you must monitor the alternator rpm, and connect it to the grid as it crosses the generators syncronous speed (which in our case was around 1800 rpm). Of course, the phase of the alternator will likely not match the phase of the grid at this time. Slamming it to the grid will cause a lot of distortion on the line and could cause a brownout as well. For this reason, we use PWM to slowly connect it to the line. Depending on how fast the rpm is approaching synchronous speed, calculations are performed to command the SCR firing board to cut the turbine to the line as slowly as possible, while not letting it overspeed (as you can see from one of the settings screens, we set our overspeed to 1900 RPM). For reference, the power compand wants the THD on the line to be less than 4% while syncing the turbine to the line. Given how fast the RPM can spool up and only having about 100 RPM leadway, you can see how catching this in time and keeping the distortion down in the process can be very hard. I was somehow lucky enough to get this right on the first try! (I think this was just good luck)
Once connected to the grid, you must determine when to disconnect from the grid (again softly with PWM). Once the RPM goes below syncronous for an adjustable amount of time, then you disconnect from the grid (otherwise the mill will motor and use electricity from the grid). This cycling between standby and online will happen indefinitely.
Then, while running, fault conditions are monitored. Faults such as over rpm of the alternator, excessive windspeed, line voltage/frequency deviation, etc. When this happens the turbine is disconnected from the grid (if it were connected), and the brake is set. Once the fault condition clears a timer commences, after which the turbine is put back into standby mode, free to spool back up and connect to the grid.
Lastly, there are Trip conditions. They are similar to faults, except they don't reset themselves, and require an operator to manually restart the turbine. Examples of trips are:

Sensed bad anemometer (if there is alternator RPM yet no windspeed reading, then it is likely that the anemometer is bad)

Sensed bad encoder (a sudden loss of reading while connected to the grid, or no reading when windspeed is beyond a certain threshhold)

Sensed bad brake (brake is set  yet there is still an alternator RPM reading)

Vibration (Possible ice on blades)
While it sounds simple, it is actually much more involved than one would think. What made it nice to tune in is that every setpoint was made to be adjustable from the touchscreen. That way I didn't have to reprogram something every time something needed tweaked. There are 5 settings screens per wind turbine, and over 30 other operational screens per turbine.
There is also an engineering screen which shows number of relay cycles, runtime hours, etc, as well as a test screen when various inputs and outputs can be overridden.
Also, after a power outage, the turbine will be returned to the last state it was in before the loss of power.
One more interesting statistic - each unit, even with my markup, is actually cheaper than their older analogue units!
I actually made a manual for the unit for them to distribute to their customers. I'll post it on here when i get home from work. It give a better idea of how everything works.

jondecker76:
one more thing to mention.. Between the blades and the alternator is a 30:1 transmission. Realize that when using PWM to connect the turbine to the grid without killing the THD must happen within a 3 RPM (at the prop) swing, because of the 30:1 ratio. In gusts, this can happen in well under a second very easily!

wdyasq:
"The new PLC program counts 500 pulses per revolution."
And you are worried about catching it in a 3 RPM slot?
I am guessing this '40kW machine' is a grid tied device of some kind and using a 4 pole generator/motor. I am also guessing you are 'cutting in' at 1800 rpm and applying brake and cutting out at that 1900 rpm. What sort of braking device is used?
This is also not a small mill. Guessing again, I think a 12-15m diameter mill will be required to get 40kW of power at a reasonable wind speed.
Ron

Navigation

[0] Message Index

[#] Next page