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hybrid photovoltaic and wind turbine off grid system

hybrid photovoltaic and wind turbine off grid system

hybrid photovoltaic and wind turbine off grid system

Hello, first post for me.
This is the first power generation project for me (I am studying electrotechnical engineering presently, started 1 month ago)

So here it is, the questions I have are at the end of the post.
They are attachments linked so you'll have a global vision of the project.

Hybrid photovoltaic and wind power turbine off grid generation :

The goal is to have a reliable system, with environmental parameters monitoring. thermal control of the battery enclosure, and use of a dump load resistor as an heat exchanger to pre-heat cold water and pipes and thus prevent pipe damage in case of icing (de-ice system).
Dump load are active when the battery are full, there is no demand for power and the wind turbine generates power.
The de-ice/pre-heater would need of course to be active when there is no wind, batteries full or near full, and solar output is available, and low or no standard electrical load. So it would need a secondary de-ice activation (dump load for the charge controller i chose seems to divert power only for the wind turbine, not the solar panels.

Control systems would be implemented using an arduino microcontroller for :
-activation of the secondary dump load resistor/heat exchanger for water supply
-temperature and hygrometry control in the battery cabinet / charge controller / inverter
-watt metering and watthours metering through current transformers.
-alarms if a low battery condition is detected

The project will not lock the phase of the inverter to the phase of the grid since I plan to use the off-grid power only for specific house circuits.
An ATS (automatic source transfer) would kick-in if the inverter fails or goes offline in a fault or low battery condition.
Then the off-grid circuits would go back to the mains (the switching time is 3 seconds, but it doesn't matter, no critical loads)

An emergency switch would isolate all the components in case of a big fault (something burns :))
It will power off all solid state relays for all cables, (2 pole isolation)

The problem : it seems that the electrical installation use a TN-C earthing scheme (neutral and earth are mixed on the bus bars) I am currently auditing the electrical system and something seems wrong with the RCD (see attachments)

So, I think that if it is correct that it uses TN-C, it would be better to upgrade to a TN-CS (adding a separate earth busbar linked to an electrode in the ground) and connect all earth cable to it so the RCD will be triggered in case of current leak.) before adding the off-grid system.
And replace all 1P breakers by 2P breakers.

Then, implement the 2 pole ATS before the circuit breakers, and tie the neutral of the inverter to the neutral of the mains in normal operation.
When it comes to earth, I am confused, most inverters have a grounding screw. I plan to tie it permanently to the earth through the busbar
I plan to tie the negative electrode of the battery bank to the ground too.

If you see any mistakes in this project i would be glad to read them !
See the attachements for more info (the off grid project design shows the mains as one phase, but it is triphase, I need to correct it)
I have two files (seems you can only a add one attachment here) so i added the links directly in the post.


RE: hybrid photovoltaic and wind turbine off grid system

ATS = Automatic Transfer Switch

Solar panels don't care if you don't draw power from them so they never need a load dump if you can just not-draw-power.

Wind generators maintain allowed reasonable rotational speed by having a load, hence they need a power dump.

You mention, "emergency switch would isolate all the components in case of a big fault".

That doesn't do it. You need that to be automatic protection. Unless you want to stand there for the rest of your life with your hand on it. Do a little research on how to protect solar panels and wind generators from overloads. It's not trivial because they don't have enough power to actually blow most fuses.

Keith Cress
kcress - http://www.flaminsystems.com

RE: hybrid photovoltaic and wind turbine off grid system

Use a neutral bus and connect all the circuit neutrals to the neutral bus.
Use a ground bus and connect all your equipment grounds and your grounding electrodes to the ground bus.
Use ONE and ONLY ONE jumper between the neutral bus and the ground bus.
Monitor this jumper for leakage current.
Call it whatever you wish.

"Why not the best?"
Jimmy Carter

RE: hybrid photovoltaic and wind turbine off grid system

There are off the shelf products that will do most of what you propose, and if you really want to look at a custom solution, there are things like this that have at least done some of the work for you, which would reduce the amount of troubleshooting dramatically.

If it were me, I'd be looking at one of the existing inverter systems that can handle grid connection and islanding conditions rather than attempt to do an ATS. This reduces the complexity of the dump resistor, as then its just another switched load to heat water as needed, rather than having to worry about what power source is being used.

I'd also worry about the overall sizing and capacity before worrying about the details of how to connect it, such as how many solar panels you'd need to charge the batteries proposed in a day.

I'm also assuming that this is something you intend to put together, rather than a coursework project.

EDMS Australia

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