250 watt grid tie inverter build

[Nigel Goodwin]

What risk to others...i dont see the risk here...!!!..

The risk is pretty obvious - you're feeding mains voltage back up the infrastructure, which could kill some poor engineer working down the line when he';s disconnected all power (or so he thought!).

This is why it's an offence to connect an unapproved GTI to the grid - and why approved ones have to meet VERY strict safety regulations.

As a responsible engineer I consider it my duty to warn you of this, although I would have thought it was something you should be fully aware of?, but presumably don't care? - like tcmtech

 

[Barbe]

Will..i know that...that is why i have relay which will automatically off when ther is no power in the grid...! I thnk everyone who build this one is not stupid...as they know this is prohibited and most country...!!! So they will do ther best to hide it...you know...otherwise they will face the consequences of imprisonment and fines...! Im sure everyone knows that...They definitely crazy, but not stupid" that is why dey building dis...for the country which dis one is not allowed dis is cheating so u need to make sure...it safe...!!! Right...

 

[alec_t]

i have relay which will automatically off when ther is no power in the grid...!

Sounds difficult. How have you implemented that? If your inverter is pumping power into the grid, surely there won't be a 'no power in the grid' state?

 

[tcmtech]

Uuugh. This grid interconnect safety horse has been beat to death time and time again.

First off the utility crews put grounding jumpers and the like on any formerly live line before the ever physically touch them to do repair work.

Second without a stable 50 - 60 hz stable grid voltage to synchronized to the these small DIY units become quickly unstable and tend to crash dead off simply due to the overall utility grid that they are connected to being many magnitudes of order larger that they can support on their own.

I'm pretty confident that if Barbe turned off the main breaker to his house while his GTI was running at full capacity it would become unstable and stall out just from trying to supply the load of his own home at a non standard frequency and voltage.

 

[Barbe]

Will alec if someone need minimal parts...and lazy i think contactor will do the job...right...just no need to explain much...this is safe..i even have elcb in my house..!!

 

[Barbe]

 

[Barbe]

hi mate, as you suggest i increase the input of 18vdc/4ah lead battery output now is 250vac/90hz and connected to grid it become 228vac 49-51hz same with grid supply...i installed kilowatt meter. i used as a load the grid tie...so it should either reversing or it will not move...but instead its moving very slow moving forward in short is not feeding to grid right...but also become an actual load as its moving forward or it should not battery i need to used? You have any suggestion.I attached the imaged hope this will help. Thanks

 

[tcmtech]

Have you tried wiring the wattmeter in reverse to make sure it can read in both directions? Some have a mechanical stopper on the disk that prevents them from being spun backwards.

The next thought is that your zero cross dead band may be too wide due to insufficient gate drive voltage to turn them on and off early enough in each half of the cycle. If you added another 6 volts of battery and it starts to feeds back that would be it. If you do that I would recommend using some sort of large power resistor to limit the peak amps that the switching devices will see during the test.

Third thought is if you somehow got your drive transformer phasing 180 degrees off. If you are going to try reversing that make sure you have a a large current limiting resistor in series with your batteries so that you don't blow out your IGBT's.

 

[Barbe]

First, i did not try to wire backward the wattmeter.i will check that one.

Second, watt is the value of the resistor may be 100ohms 5owatts would be ok?

Third, i dont get phasing 180d. Sorry...could you plesse explain to me further..thank you so much

 

[Barbe]

Hi mate..its move backward when my input dc is 21 to 24dc...but after one round it just stop so i make move forward a little bit by touching my hand..and i switch on again the wattmeter..its start reversing again...i think there is some kind of stopper..do you have any idea maybe in how to hack this meter to make it move backward not just not moving...i did not put the 100ohms resistor in series as is not working the gti.

Thanks mate again....!!!

 

[Barbe]

 

[Barbe]

Hi mate, i found the problem the wattmeter should not be installed 45degree angle it should be 90degree..otherwise it will move forward very slow otherwise will not move...

After i made it right..i seen the wattmeter spin backward...my issue now is my power transformer after 20 to 30mins of using is getting hot..do i need just ventalation or fan. Or i forget something or i need to add something to make it normal warm not become hot...please advice

 

[tcmtech]

What is the transformers approximate VA rating and how many watts or VA are you running it at and how hot is hot?

Also how warm does it normally get if ran in typical power load application or idle opposed to GTI duty?

Most decent power transformers will easily handle running at 50 C over ambient without issue and some far higher than that.

 

[Barbe]

Hi mate, thank for your prompt replay...its 12 0 12, 10amps and i parallel to make it 0-12v. And my battery is 7ah24v now but is only 21v output. Later i will measure the exact temperature. And size of wire. Thnks mte

 

[Barbe]

Hi mate, the temperature of the transformer as per below, also i attached photo;

Core: 50 degree
Coil Primary: 121degree

Thanks...is this normal? Or should i put some fan on it? Thanks mate

 

[tcmtech]

Sounds like reasonable temperatures to me. As long as it does not give off overheated transformer smell its working just fine.

 

[Barbe]

Thanks mate for everything..your help...i put fan on it...

 

[tcmtech]

The next step will be to build the control circuit A and power driver circuit from the GTI 2.0 thread.

They will help you with fine tuning the zero cross deadband to get better power feedback numbers at lower input voltages plus pick up the overall efficiency a measurable amount.

 

[Barbe]

Hi, tcm thanks again in advance on which tread is that i dont get the control a and power driver circuit...you mean with the scr x1 and the ssr on output....i seen some diagram you post but i dont get opto coupler side...on scr the the only way i can connect is the gate to activate it...and for the ssr i understand...but not really sure how to connect there is 4 pin the two pins are negative and positive sign and the others is ac sign..please advice for me to be more...sorry for being stupid...i just compuse on that side...how do i need to connect the scr and the ssr part as per the diagram...im just thinking just contactor..when i plug automatic...both the grid and inverter activated at the same time no delay ,,, but still not really much sure.

Please advice me mate...till now i cant leave this running at home coz of the control part....i just dont get the end part symbol optocoupler how to connect...

 

[tcmtech]

What exactly are you wondering about? The solid state relays can be thought of as being just like nay normal relay with a DC input switching an AC output.

As far as the input goes if you are not using a two stage system the SCR setup can be ignored and the normal blocking diode with an optional mechanical relay for input isolation could be used instead. No need to over complicate things if you don't want.

Personally I generally set up my single stage systems to let the input power come in through the blocking diode and just switched the driver IC's (or transformers) on and off for input isolation or simply just let the input driver system run all the time and only switched the line side on and off as the input power went above or below the minimum power set point.