Im triyng to instal a projec with solar panels, i need them to give me 26 KW per day. but i never tough it willbe so difficult to find an inverter and controller..there are so many on themarket.. idont knwo wich one is better for my needs 
you need to buy one that can handle what your panels can produce at max output plus a little.
say you want 26kw but your panels can produce 35kw on a good sunny day. If you buy a 30kw inverter, there is a good chance you will fry it.
My advice is read up on your panels and find out what the max they can produce is and then start looking. Even though you will have some loss in the transfer and conversion from ac to dc, it is still better to buy more than you need. That way you can upgrade at a future date if you decide you want more and dont run the risk of having power trip failures or even worse destroying your entire system.
There is alot of information available on this topic on the internet if you search for how to choose and inverter. Some will give you a formula, say 110% of desired output, others will say this is not needed. Read about how to choose one to fit your demand then go looking for one that has the price and features you need.
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you need to buy one that can handle what your panels can produce at max output plus a little.
say you want 26kw but your panels can produce 35kw on a good sunny day. If you buy a 30kw inverter, there is a good chance you will fry it.
My advice is read up on your panels and find out what the max they can produce is and then start looking. Even though you will have some loss in the transfer and conversion from ac to dc, it is still better to buy more than you need. That way you can upgrade at a future date if you decide you want more and dont run the risk of having power trip failures or even worse destroying your entire system.
There is alot of information available on this topic on the internet if you search for how to choose and inverter. Some will give you a formula, say 110% of desired output, others will say this is not needed. Read about how to choose one to fit your demand then go looking for one that has the price and features you need.
References :
I think you should get someone competent and aware of local situations to do this for you as it is expensive and potentially hazardous. There are regulations to comply with, depending on where you live. I am assuming you mean a grid connect (grid tied) system with no batteries.
The information you have given is not quite right. You say 26KW per day, but that should be a figure in KWh per day. If you have 26KW of actual panels, first wow if it is your residential house, second, that is a different approach, and probably why you are having difficulty finding an inverter. Lets say it is 26KWh you meant… (kilowatt hours)
Working backwards to the panel sizes:
First determine the number of hours of full sun equivalent in your region. You may find this figure on the internet. That may be 2 to 5 hours a day. The sun may be out for longer, but that is the equivalent after correcting as if the sun was directly at right angles to the panel. Ten hours of sunlight may give 5 hours of full sun equivalent or less.
Determine the number of panels (KW) required to get 26KWh from the full sun equivalent hours:
Lets say it was 5 full sun hours.
26KWh / 5h = 5.2KW
Lets now say the panels you chose were 200W at the maximum power point each.
That would mean 5200W/200W = 26 panels.
The specified output of each 200W panel may be 20V @ 10A for peak power, and 30V (maximum voltage) for no load.
Determine how many panels in a series group and how many series groups of panels:
This is matching the inverter voltage range to the actual number of panels required. You can chose an oversized inverter sometimes to allow for further panels in future. It just needs to be more than 5.2KW at the input.
Lets say a 6KW inverter was chosen, and its maximum voltage rating was 800V.
Number of panels per series string = 800V/30V = 26.666 panels. Clearly it has to be 26 as there is no fraction of a panel, and we don’t want to go too close to the rating anyway. That just happens to be the number we have, so there is one group.
Check the voltages:
In this case there would be one string of 26 panels x 30V in series generating a maximum voltage of 780V if the inverter is not loaded for some reason. The voltage at maximum power would be 20V x 26 panels = 520V. The current is about 10A at full sun if the inverter determines that it will draw that much current. That is the expected maximum power of 520V x 10A = 5200W. With other loads from the inverter and other sun brightness the voltage and current change, and the inverter adjusts accordingly to extract the maximum power from the panels for the conditions.
There needs to be a special DC switch and circuit breaker to isolate the inverter from the panels. This would be 1000V and > 10A rated for DC.
Otherwise the inverter probably has to be approved by the power authority that you will be connecting to. It has to be connected to comply with regulations. It should incorporate a maximum power point tracking controller (probably they all do). It should be able to automatically disconnect if the grid connection is dead (no back feeding). As a first step I would contact the local supply authority/company and ask for advice. Oh, the panels will be intended for this use in series strings with insulation voltage of up to 1000V. The wiring/connection itself can be a hazardous task, as the panels have hundreds of volts and many amps output, lethal. Well you could do it at night?? There may be other regulations about panels on roofs, wind loading etc.
Note the above calculations are oversimplified, as I haven’t taken temperature into account, but they are good ballpark figures. If it is 26KW of panels, you have a lot more series strings, and may need to have several inverters, which in turn need special provisions for grid connection to prevent back feeding. It definitely needs you to work with a consultant, at least an experienced installer who can show you similar systems so you can ask the owners. Not just one, it might be their mother!
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The internet being overwhelming? no way I thought that’s what yahoo was for!! Just kidding, let me help.
I don’t know the specifics of your project (off grid vs grid tie, etc etc) but in general Inverters can be expensive and you need to know what you are buying before you jump in head first. (An Inverter from Schnieder Elec vs one from Tigo or SolarEdge?) Your best bet is to hire a professional, there is a place in Miami that I’ve heard about called Sun Electronics who specialize in exactly this. I know it may sound like a shameless plug but my uncle had them to a retro fit on his house in the Florida Keys and among other things he said that he did not feel ripped off….which says a lot these days! Good luck to you.
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