Problems with hybrid wind /Solar - Page 1
Forum section: electronics / general

author: stubbs
author_rank: Unknown
timestamp: March 29, 2016, 09:45:14 am
content: Hi,I am facing a problem with my Wind Turbine.It is a 3kW 3Ph 0-380VAC PMG VAWT.The thing works in the present configuration.But only when the Sun shines. lolI have Solar Panels powering the lines in on the Inverter max. 220VDC. + Blocking Diode.On the same Line the Rectified Voltage from VAWT.The Inverter is a Wind Inverter. So no issues.So when the Sun is up. I have a very low and efficient start-up.The VAWT spins up and relives or adds to the load from the Solar side.All good...My "Problem"When the Sun is gone. The VAWT has issues starting up, because of the initial Inverter start-up.I would like to have Isolate the Turbines PMG. As well, a conditional Voltage sensing Contactor set at (or variable) ~75VDC or equivalent AC.The Transformer idea would be the easiest. But the start and load Freq. is very low ~3-30Hz. So this kills the Tansformer idea?or does it?The DC idea is a dangerous. To step down 200+ VDC safely is beyond my budget. Especially due to the wild Voltages /Transients.I wish to control a 3Ph SSR Contactor with 24VDC at a cut-in voltage of (variable) ~75VDC or equivalent AC.Can you help me out. Or set me on the right track???ThanksRob Brooks

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 29, 2016, 09:56:18 am
content: Can you get the turbine to work by itself? ie. get rid of the solar and get the turbine to work by itself. From what you said I guess not.That would be my starting premise. The turbine should be able to run as an independent system.Then think about joining the two together.I know you have described your system but a schematic or a block diagram is always useful. You probably already have this?

author: stubbs
author_rank: Unknown
timestamp: March 29, 2016, 01:15:07 pm
content: Hi,General idea of the system attached.I have a total of 3 Solar systems. Tracker, House Roof and the hybrid.Also two different Wind Turbines. Everything works as I designed it.Except the Turbine in the Hybrid. It works fine. Only with the Solar as Complement.At night is where the Problem occurs. The Start-up of the Inverter is 50VDC ~5%.This is what kills the Turbine; at Night that is. If I can figure out a way to electrically disengage theTurbine until it reaches a suitable speed (~75VDC) then engage it. It would start the Inverter. No problem.I have tested this manually for measurements.If the Freq. was not so low on the PMG. A Transformer would be perfect.Or if the working DC Voltage was not so high as to complicate things.Rob

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 29, 2016, 02:39:14 pm
content: So if the Solar panels and diode are disconnected does the system work?It doesn't seem like it should impact the system in a bad way but on the other hand the inverter should work with the turbine.I guess it's an impedance mismatch at startup that stops the turbine from turning.

author: stubbs
author_rank: Unknown
timestamp: March 29, 2016, 02:57:50 pm
content: The system works fine. The problem is the start-up of the Inverter comes too soon.The Turbine must spin up before the Inverter grabs. The Load Curve (attached)works fine once running. As you can see in the curve, the Inverter does not dump to Grid before 160VDC.The Inverter's start-up is between 40-50VDC.

author: stubbs
author_rank: Unknown
timestamp: March 29, 2016, 03:15:54 pm
content: I was thinking about a 3 phase SSR from CRYDOM. The problem with that is how to control it from HVDC.

author: stubbs
author_rank: Unknown
timestamp: March 29, 2016, 03:59:02 pm
content: Quote from: stubbs on March 29, 2016, 03:15:54 pmOr will there be a low Freq. problem on the AC side with a SSR?The Datasheets make no mention of this.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 30, 2016, 12:41:15 am
content: FYI. I am an EE but have never worked on a wind turbine. I was sort of expecting somebody with actual turbine experience to chip in but it hasn't happened. So I will do my best.I think the SSR idea has merit as part of a soft start.The soft start being just resistance in series with the blocking diodes.Once started the SSR would short out those resistances.As to turning off at low frequencies, I think you will have to test and see, my gut feeling is that it will be ok because the current will eventually reverse. Else you could use a small dc controlled 3 phase contactor.SSRs are quite cheap so it will be worth a test.You probably should aim to put in a bit of hysteresis into the SSR control. ie. Turn on at 150V and off at 100V.

author: stubbs
author_rank: Unknown
timestamp: March 30, 2016, 07:41:52 am
content: Quote from: HackedFridgeMagnet on March 30, 2016, 12:41:15 amMy thoughts as well. But when I am unsure of something like this; I ask. DC make nasty Fireworks.I am somewhat knowledgeable in electronics. But do need some help here as well.I have attempted to switch a 24VDC contactor, with success. But it will not disconnect until ~3VDC.I like what you said in your last line. On state @150 off @100VDC. Here @ the off bit; I am stumped.?How would I go about doing this. Do you know how to do this? please advise.Better bit of hysteresis would be between 100VDC on an 75VDC off.Thank so much for your help.Rob

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 30, 2016, 12:04:03 pm
content: Truly the hard bit is the power side, making sure you don't wreck the expensive stuff, the control side is relatively easy.Do the control at a relatively low voltage. say 5V or 12V or 24V. Whatever voltage you need to drive your SSR. Say 12V.So you need a power supply to generate this from 150V or whatever max you have, with a margin for surges.But to start just use a battery as stage 1. (You can choose something suitable to power it later. Maybe a resistive dropper or a buck converter.Make your power circuit and check that you can the turbine 'On' and 'Off' using the battery say in series with a resistor to limit to a safe current just in case, (batteries are good at killing power circuits) and check that the system works as desired.Once your happy that your soft start or whatever is working then put in the control circuitry.Something likehttp://www.eleccircuit.com/best-12v-battery-charger-circuit-using-lm311/or attached image.Will take a bit of playing around or simulating or calculating to get the resistor values.The values and components are all meant to be generic.Also check I have the polarity correct ie. Hi is on and V low is off.the hysteresis r5 needs to feed back into the the positive terminal.Obviously fully test control circuitry before attaching to actual power circuitry.

author: stubbs
author_rank: Unknown
timestamp: April 01, 2016, 02:13:41 am
content: Figured it out... It was relatively quite simple.I have a Mean Well LED PSU that has been collecting Dust for some time now.I new it was an electronic Transformer. LPV-60-12 60W 12VDC out and variable 220AC in. Cost me €26 7 years ago.Well I hooked it up to my PSU and gave it 360VDC. It regulated nicely all of the way up the scale.Now I can play with a control circuit. lolLiked the OP Amp on the fly. I built a OP Amp Regulator some time ago using 741 Amps.I'll have to dig it out and give it a try. Thanks for your help,