I have sort of a basic understanding of how a wind turbine works, how the goal is to keep the thing in a sweet spot of TSR to make the maximum power. I have a vague understand how MPPT works and how raising the turbine voltage lets the thing run at higher TSR and lower amps. This can be good because it frees the turbine from being clamped to battery voltage, where the TSR can be less than ideal. It also lessens the chance of stator burnout in axial flux designs.
However, In the few hours I have watched my 10' axial flux run on this thing, I haven't quite figured out how the graph works and exactly what the controller is looking at, what it is trying to accomplish, and how it is trying to accomplish it.
Basically I'm not real happy with how fast this turbine runs. This is a 24V axial flux and I've seen sustained peaks of 100 volts, yet only about 600-700 watts (20-25 amps)) out. At these times it's running fast enough that it starts to make helicopter noises. When this was happening, the absorb voltage is set at 31.5, battery voltage is at 29.5 and batteries are withing 5 degrees of 70F. I have the 16 steps divided from 25 to 70 or so volts in mostly equal steps. The amps are divided between 0 and 90 amps in 16 equal steps.
So is this graph capable of emulating a battery-voltage clamped system? Maybe if I knew how to do that, I could tweak for improved performance and dial it in so it wouldn't run so gosh darn fast. Perhaps I have an incomplete understanding of the whole turbine-controller dance, and I need to get used to the thing running fast too.
Any help appreciated.
Hi Volvo.
Yes, this wind graph editor is a bit intimidating and I intend to make it easier in the future.
Have you checked out the little video I did on this editor ??
http://www.youtube.com/watch?v=IpslcfvrT6c
You will also be able to adjust it on your PC.
boB
Hi boB, thanks for the quick response.
Yes, I have watched that video. I actually find the user interface pretty easy to work with.
I guess what I want the Classic to do is to heavily load the turbine when the voltage (RPM) gets above a certain point. I'd like to have some of the characteristics of a battery voltage clamped turbine, in that I'd rather not see the thing running at 500RPM in 15-20 mph winds. However, I'd like to retain improved performance in low and mid RPM range.
Do I want to flatten the top part of the curve, or make it steeper to accomplish this?
Also... what happens if I only have voltages up to 70V programmed into the curve and the turbine takes off and starts running at 95V? Should I program a curve with the full range of voltages, all the way to the clamped point?
The curve will want to be flattened out at the point you have hit the max voltage"RPM" you are happy with. The Classic should hold the 10ft machine down to what you have it programmed for.
Volvo, you will need a clipper.
Think about what happens when your batteries are full or if there is so much wind that
the Classic is going into current limiting... There is no option for the Classic itself but
to let the turbine fly.
With a Clipper, the turbine will only run as fast as it needs to to keep the battery voltage
and/or current where it needs to be, and no higher (not much higher V or RPM anyway)...
You can flatten out the curve at the top of course, and that will keep it from spinning
so fast but only if the batteries are not full and Classic is not current limited.
boB
Shouldn't I be able to configure my dump load to act as a sort of clipper? Isn't that what Halfcrazy is doing? I think my dump load will dump over 1000 watts. I tried to get it pretty near the current limit of the C60 when I built it, but maybe I should go out and measure it again.
Maybe if I crank the classic's absorb and float way up to 33V and have the dump load come on with the C60 at 29 or 30V, might that not be a solution? I realize I will have to be able to dump more than the Classic can put in at any given time.
Alternatively, might I find a way to control the dump load through Aux2 so that the Classic is never doing current limiting and never lets the turbine fly?
Thanks for helping me to understand what's going on here. I realize a clipper would be the ultimate solution, but I'm not adverse to the idea of finding a workaround in the interim.
Quote from: Volvo Farmer on April 27, 2011, 05:14:44 PM
Shouldn't I be able to configure my dump load to act as a sort of clipper? Isn't that what Halfcrazy is doing? I think my dump load will dump over 1000 watts. I tried to get it pretty near the current limit of the C60 when I built it, but maybe I should go out and measure it again.
Maybe if I crank the classic's absorb and float way up to 33V and have the dump load come on with the C60 at 29 or 30V, might that not be a solution? I realize I will have to be able to dump more than the Classic can put in at any given time.
Alternatively, might I find a way to control the dump load through Aux2 so that the Classic is never doing current limiting and never lets the turbine fly?
Thanks for helping me to understand what's going on here. I realize a clipper would be the ultimate solution, but I'm not adverse to the idea of finding a workaround in the interim.
Are the dump loads you speak of on the turbine side ? Maybe I forgot from an earlier post that they were.
Yeah, if what I'm remembering is that your loads are on the AC side of the turbine rectifier, then
you are doing the right thing.
boB
Quote from: boB
Are the dump loads you speak of on the turbine side ? Maybe I forgot from an earlier post that they were.
Yeah, if what I'm remembering is that your loads are on the AC side of the turbine rectifier, then
you are doing the right thing.
boB
No, the dump load comes straight off the battery, through a Xantrex C60 in diversion mode.
Is a C60 off the batteries too slow to respond in diverting power to keep up with a big wind gust on the Classic? Is that why you say a 3 phase diversion before the turbine would be OK?
I don't know if I'm dense, or not communicating well or a combination of the two...
What do you think of this idea? I would use a Xantrex, or Morningstar or some other type of PWM diversion controller (Aux2?) to divert power directly from the batteries at a voltage less than the Classic's absorb and float setpoint. The dump load would be able to divert more power than I could ever expect to see from the Classic through this wind turbine.
My intermediate goal is to run the Classic wide open 24/7, so that it never goes into current limiting mode. My long term goal is to not have the wind turbine overspeed. The result would be lots of heat in some sort of wasteful diversion heater, and living with batteries somewhat above optimum absorb voltage for indeterminate periods of time when it is extremely windy here.
Could anyone take a few minutes to critique this idea? It seems like it would work in my mind. Maybe I should just build it and test it and stop asking questions.
I do appreciate the feedback though. I'm right on the edge of my knowledge and experience in this area, which is why I am perhaps moving with such caution.
OK, I see what you're saying.
Well, You will certainly get more power out of the Classic if you raise the battery voltage as well as loading it down fully at the higher voltage...
Quote
The dump load would be able to divert more power than I could ever expect to see from the Classic through this wind turbine.
You may be right but how do you know this for sure ? 10 foot turbine.... 24V battery... Then a 70 to 80 MPH gust comes along when you least expect it
and the Classic goes into current limit and then the turbine basically gets unloaded and overvoltages. I've heard this quite a few times now and every situation without some kind of clipper has gone overvoltage.
As you are suggesting, changing the graph can help some (to a point) but an unfortunate fact is that the power available in high winds will make the turbine spin faster and output higher voltage unless it is loaded down enough, somehow. That is, if it can be slowed down by loading. If the turbine's magnets aren't coupled close enough to the stator, the turbine could possibly keep accelerating even if loaded in high enough winds. This behavior depends on the turbine design or in your axial flux case, the gap between stator and rotors, mainly.
You might even think about taking it one step further when the wind is howling by switching the battery bank to 48 Volts and loading it down fully at, say, 58 Volts. Then you will be able to pull (almost) twice the power out of the Classic and turbine than you would at 24V settings.
You would of course have to disconnect your inverter at that time too though. Automatically doing this might be a bit of an exercise.
But what happens when you get 70 MPH gusts ? Maybe at those times you could just have the turbine disconnect ? Or maybe just have it disconnect when the Classic current limits, maybe by a new Aux output mode ? If that last disconnection method was used, there would have to be a way to have it re-connect again when the wind dies down.
I think a clipper will eventually be the best solution since one Classic can only put out so much current and power. Now THERE'S another way to do it ! Use more Classics to handle the higher power and use it for something useful maybe !
Keep thinking of ways to achieving a solution for these problems as this as this is kind of new territory. High winds can be real pain !
boB
I think I understand the nature of the problem more clearly now. Thank you for taking time to explain it to me.
When the Classic became available, I got one thinking that Halfcrazy had been using one in a similar 10-foot axial flux application and I could do the same. I built his home-made voltage clamp and hooked it all up. I guess I did not realize that there would be significant differences between my 24V system and his 48V system with regards to how hard it is to hold the turbine back in high winds.
I might play with the system some more and if I make progress, report back. I know that I can significantly reduce the air gap on my turbine, as I had to open it quite a bit to make it fly properly when clamped to battery voltage. Maybe I could even program the aux1 to close the contactor at some silly low voltage, like 60-70 volts to prevent overspeeding.
Then again, maybe I'll put the thing back in it's styrofoam box and wait for the Clipper to come out. It sure does work good when I need the power, seat of the pants guess was 50% increase in moderate winds. It's just a little too scary to leave it spinning and unattended as I now have it configured.
Thanks again for your patience and willingness to help me understand the problem. ;D
The air gap will help. We had to open the 17footer up a bit and it would run away from the Classic. The 2 real issues are that a 24 volt battery with a 2-3kw turbine will set the Classic into current limiting mode causing the input voltage to skyrocket. I am not sure if the 10ft machine could actually ever get over 175 volts dc though? Although you would not want to run it unloaded. It must sound pretty wild around 100vdc out? Mine run one night at 224vdc and it sounded very scary. Mine is wound for 50vdc so that was about 4.5 times its cut in speed.
You could use a Triac and 3 resistors and tie the triac into the Aux and use the Clipper mode this works very well and is the base of the new clipper but if you could find the triac and 3 resistors this is something you could build asap to keep you online. The Clipper will be very helpful it is powered from the turbine and has a potentiometer to adjust the max VOC it will allow to pass through as well as interface with the Classic to run the Clipper when the battery's are full or the Classic is current limiting.
Actually the 3 phase crydom relay Edward used would work very well for a clipper as well it switches on the zero crossing the part number on that was Crydom D53TP50D
Hello Guys,
As the season has changed, I have been distracted with other things around the small farm that I live on. I haven't been on here as much. The Spring winds have been good so far. In any case, I just wanted to mention that my system continues to perform well. I am happy with my Classic 150. It continues to do it's job well.
The only thing I can see that would be better is when wind learning becomes a reality. Right now, I have my wind curve set to what I consider an acceptable curve, but I know that things could be better. I just stopped tweaking my curves so much, because I felt like I was getting to the point that I was running in circles. There is more power to be had with an optimized wind curve. I have seen 4400+W peak out of my turbine in the past, but since then I have not seen that much again. I made so many changes to my wind curves experimenting that I don't even remember what curve I had back then. I've experimented too much to be able to store them all in memory. For now, I'm just leaving good enough alone. In the future, I do look forward to tweaking my wind curve (or having the Classic do it for me with wind learning) and optimize my power output further.
Volvofarmer, It sounds like you've got a AUX1 Clipper in place. I am assuming that you are using to 3 phase contactor to short out the 3 phases, correct? You don't have any resistor loads? Have you experimented with setting your AUX1 PV input voltage to a low voltage in higher winds and watch to see if your Clipper is able to slow the turbine and keep the voltage clamped at your setpoint?
If you did do this and wrote about it, then sorry I missed it. I skimmed through the posts in this thread and might have missed something. As boB has said, if your turbine is hard to brake (large air gap or other factors), then it might be hard to use that "short out" type Clipper to slow your turbine. You might need to change the gap on your axial turbine or experiment with using some big resistors to load down each phase (rather than just shorting them out).
I am still glad that I made the switch to the Classic 150 on my wind turbine. My system is much safer now and more efficient. The Classic has been proving itself to me over time that it is a good controller.
Edward
Edward ! Good to see you on here today.... I was wondering where you'd been !
I see you understand how the learning can dramatically help the curve cuz just like you say, it's like running around in circles trying to chase the curves by hand.
It's one of those things where being automated will make it way easier. Getting to that fairly soon now but never soon enough !
boB
Quote from: keyturbocars on May 01, 2011, 01:16:11 AM
Volvofarmer, It sounds like you've got a AUX1 Clipper in place. I am assuming that you are using to 3 phase contactor to short out the 3 phases, correct? You don't have any resistor loads? Have you experimented with setting your AUX1 PV input voltage to a low voltage in higher winds and watch to see if your Clipper is able to slow the turbine and keep the voltage clamped at your setpoint?
Yes, that is what I built, the 3 phase contactor to short the phases, controlled off Aux1. I also have a Xantrex C60 hooked up in DC diversion mode with approximately 1KW worth of fan-cooled resistors.
I'm pretty sure that shorting will stop this turbine dead in it's tracks with anything under 40mph winds. I guess I need to test that on a really windy day, but we don't get too many of those here.
I don't know what was happening the first time I saw the turbine running unloaded. I think I may have had the Absorb configured too low. The controller was nowhere near it's 90 amp limit, yet it was letting the voltage rise and it wasn't putting much current into the batteries. I have since raised absorb and float to something ridiculous like 32V. I then configured the C60 to come on at about 30V. I did a little testing last week in 30mph winds and everything seemed to work well, just the batteries got a little bubbly for a couple hours.
I have lowered the Aux1 PV+ setpoint to about 90V. I have flattened the wind curve in the last 4 or 5 steps, and I have been happy so far with the RPMs that the turbine is running.
My setup is a little tenuous and I don't feel very safe letting it run unattended yet. If my batteries are full, and the classic is putting 1500W into batteries and I'm only dumping 1000W, I imagine that contactor might get quite a workout. However I have about 1100 Ahr of batteries here and it gets pretty tough to push them up to 32V, I don't think it's possible to get them that high with 2KW continuous input for several hours, though they might get a little warm
As long as I don't get any massive wind gusts, I think I might be OK, And even if I do get a few massive wind gusts, I would think that the shorting contactor would protect the Classic. I would still feel better being able to watch the whole system through a real howler and see how it reacts though.
VF, setting the Classic to 32 Volts and your C40 or C60 or whatever PWM controller to dump into your "Use It Or Lose It" loads as
we call it, is a great way to get the most use out of available energy. This is done in other systems that I have seen.
Just make sure you keep that turbine side clipper available for when you do get those big gusts. Soon as you do get some
good wind and you can verify things are dumping good, you'll feel better about leaving it running while going away.
I understand fully !
Thanks,
boB
Volvofarmer, It does sound like your turbine might have been running fast because your Classic was in absorb mode and allowing the voltage to climb as the amps were lowered. The way I do it is to keep my Classic in bulk mode at all times with the way I programmed the Classic charge voltages and by diverting power to heat water. This keeps the turbine loaded down at all times and maximizes the power output. Sounds like your set up is very similar, although it sounds like your 1kW diversion load might be undersized for your 10' axial turbine. If you are in a big windstorm, perhaps you could also use an inverter to power some loads and keep your Classic in bulk charge mode (and keep your turbine loaded down at all times).
Edward