the Otherpower.com Discussion Board || 15KW PWM Inverter

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Rants & Opinion - Diaries - Our Products

15KW PWM Inverter
By hilo90mhz, Section Homebrewed Electricity Posted on Tue Apr 13th, 2004 at 02:13:25 AM MST
high frequency DC-DC converter stage, 48v = +/- 175v.

Ive been building an inverter for about a year now, slowly progressing.
My design uses similar technology to the professional inverters you can buy.
First there is a high frequency DC-DC converter stage, 48v = +/- 175v.
Then three half bridges convert the DC into a sine wave using a 19khz carrier frequency modulated with the 60hz sine wave. The signal generation is all done in a PIC microcontroller, the language is JAL, a free langage just for PICs.
Heres a link to the webpage documenting what ive done so far.
http://www.hot-streamer.com/hilo90mhz/electronics/Inverter/inverter2.htm
The design is all open source so if you want any more info or the source code just ask..
Ive already run smallish loads like a 500W induction motor fan and a 600W halogen lightbulb on the 1kw test inverter. The MOSFETs aren't yet properly heatsinked so I can only run it for a few seconds.
Any seggestions? I still have yet to implement all the safety features and feedback mechanisms. Any help is appreciated.
Chester

15KW PWM Inverter | 33 comments (33 topical, 0 editorial)

Re: 15KW PWM Inverter (3.00 / 0) (#33)
by chan tinh on Fri Oct 22nd, 2004 at 10:48:49 PM MST
(User Info)

Hi everybody!
I am newer and I hope to learn from you.Now I have to make a project on DC/AC.
Could anyone of you give me the chematic and the source code?
Thanks alot!

Re: 15KW PWM Inverter (none / 0) (#1)
by RatOmeter on Tue Apr 13th, 2004 at 06:51:02 AM MST
(User Info) http://www.rato.us

Hi, Chester. Great work.

This is almost exactly what I was thinking of when I posted this comment
http://www.fieldlines.com/comments/2004/1/29/112147/499/1#1

And to think, you were already working on something similar! I'm interested in the design, especially smaller-scale versions. I've got experience in digital electronics and microcontrollers, but am weak in analog and power electronics. I'd like to make a small version and fiddle with mains synch and grid inter-tie features. Thanks for the inspiring work!

-RatOmeter

Re: 15KW PWM Inverter (none / 0) (#14)
by hilo90mhz (hilo90mhz@hotmail.com) on Tue Apr 13th, 2004 at 05:43:13 PM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

Id really like to work with you to develop some more complex code if thats possible... I have no feedback on the sine wave right now, meaning if you put a load with a bad power factor the sine will start to get really messed up... Real time feedback at 19.53K samples per second would be the key, to actively change the PWM value so the output stays a true sine even with bad loads like switching powersupplies.

I dont think the PIC16F628 can do that alone.. I was contemplating doing it in analog, but that would have its problems also..

Chester

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#18)
by RatOmeter on Wed Apr 14th, 2004 at 06:22:24 AM MST
(User Info) http://www.rato.us

The sample rate could be much lower, but it depends on where you'd measure and relies on integrating/filtering the signal. Then detect the peaks, use that measured amplitude to scale a complete measured cycle to the same amplitude as a your source sine table then compare the phase lag, amplitude ratio and "quality". Some folks might use a DSP to do a Fourier analysis but I think that's overkill. I've done similar sine output, feedback and analysis with a Z80 at 4 MHz in assembly language in 1987, I think a PIC can do it too.

Anyway, I've got some ideas. I'll see if Microchip will sample me the part(s) and look into it further.

-RatOmeter

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#22)
by hilo90mhz (hilo90mhz@hotmail.com) on Wed Apr 14th, 2004 at 05:42:11 PM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

Hmmm, very good points you bring up. I was thinking that the output voltage could isolated and read by a DA and then compared to the current PWM value read off the sine table, and adjust the new PWM value accordingly....

But after reading your post I realized that wouldnt work at all because of the phase lag in the output, after the lowpass LC filter.

So your way of comparing one whole cycle seems much more feasible.

What carrier frequency were you outputing with the Z80 ?

I have the source code on my webpage now, theres some text at the top of the file that explains how it works pretty well.
http://www.hot-streamer.com/hilo90mhz/electronics/Inverter/inverter2.htm

JalCC is a a free IDE I use to write JAL in, it comes with abunch of usefull libraries and things also.
http://oase.uci.kun.nl/~mientki/PIC/Pic_frame.htm

Let me know what you think of it... Im not really a very good programmer at all, I learned that langage from trial and error starting with some simple projects, I know some C and CPP also.

Microchip has a really great sample program.. I just ordered 30 chips for free... and over the course of a year have probably recieved 100 free chips.

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#2)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Tue Apr 13th, 2004 at 08:07:40 AM MST
(User Info)

Chester:

I designed DC/AC converter for a living so my two cents;

Convert 48 DC to +- 200 and not +- 175 Volts DC and these outputs need to be balanced, so they should be fed by a dual common mode choke at the operating current to maintain both voltages equal to each other.
The input for this converter should be set for around 42 volts IN-DC and the output regulated.
For noise reduction, the DC/DC converter and the AC converter should be frequency synchronized.
One single source should produce the 3 sine waves, SO ONE SINGLE PIC, with three outputs, include, as well, the capability of producing 230 Volts AC with a 180 degrees opposite sinewave
It is easier to generate Star voltages instead of Delta voltages.

I can send to you a file of a complete 10 KW 48 Volts DC to 115/230 AC Design, but the size is about 7 Megabytes and HOTMAIL can not handle it.

Regards

Nando

Re: 15KW PWM Inverter (none / 0) (#4)
by Budgreen on Tue Apr 13th, 2004 at 10:15:35 AM MST
(User Info)

I would love to see this =) if you are willing at share
haviland (AT) gbronline.com

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#5)
by RatOmeter on Tue Apr 13th, 2004 at 10:47:55 AM MST
(User Info) http://www.rato.us

I'd like to see it too, if you don't mind.

email: reagan-AT-brightok-DOT-net

Thanks.

-RatOmeter

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#6)
by John II (jjones2(at)inetvisions.net) on Tue Apr 13th, 2004 at 11:34:17 AM MST
(User Info)

I would also love to see this Nando. Email is: jjones2@inter-linc.net

John II

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#7)
by Larsanderss (larsanderss@brevet.nu) on Tue Apr 13th, 2004 at 12:21:50 PM MST
(User Info)

If it is possible i would also want to take a look at it..... I do not think i will ever be brave (or stupid in my case) to build such a thing but i am very curious about it.

Good evening

Lars A - larsanderss@brevet.nu

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#8)
by bsab33 on Tue Apr 13th, 2004 at 02:18:50 PM MST
(User Info)

This sounds very interesting.Is it possible to have a copy?

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#10)
by hilo90mhz (hilo90mhz@hotmail.com) on Tue Apr 13th, 2004 at 03:50:20 PM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

Hi Nando,

You are right about the 200v... It took me some experimentation to find that out, now I need to rewind some of that 15KW transformer... It wont be that hard tho, at least its not encased in epoxy or something.

I think I already have a dual common mode choke, not sure if you looked at the schematic or not... Its just a iron powder core with two seperate windings on it. Its in series with the output from the full bridge rectifier and the high voltage filter caps.

Thanks for the tips on how to set the regulation point... Im using one of TI/UCs phase shift dc-dc controll chips, with just voltage feedback.

I dont think synchronization of the two frequencies will be possible...
My ferrite core can handle 15KW at 50khz, 50KW at 250khz.. im running 80khz
My output frequency is 19khz.... limited by the processing power of the PIC. And im using IGBTs on the output, even though they are the "Ultrafast" variety, still prefer the slower speeds. I see why it would be good though, so the output filter could help filter out the DC-DC converter noise also.

I have to use 3 PICs because of the processing power reqired, if i had the capability to use one of the PIC18 core chips then maybe i could do it all on one chip.. Im also considering using a DSP or FPGA for the final one... but that would require learning ALOT.

I am going to generate Star voltages (thats the one with a common ground right?) and then be able to use 208V in place of 240v... At least thats the plan for now, I hadnt considered using a 4th output 180deg out of phase with one of the other phases, thanks for the idea.

"I can send to you a file of a complete 10 KW 48 Volts DC to 115/230 AC Design, but the size is about 7 Megabytes and HOTMAIL can not handle it.

Id really like to see the file, can you send it to lowrey@interpac.net

Thanks for all the input,
Chester

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#11)
by ibedonc on Tue Apr 13th, 2004 at 04:14:15 PM MST
(User Info)

TAMU project ?

:)

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#12)
by hilo90mhz (hilo90mhz@hotmail.com) on Tue Apr 13th, 2004 at 04:58:53 PM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

"TAMU project ?" the university?

I dropped out of high school... not in college by a mile.

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#15)
by ibedonc on Tue Apr 13th, 2004 at 08:24:25 PM MST
(User Info)

I was refering to the 10k inverter mentioned above

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#17)
by hilo90mhz (hilo90mhz@hotmail.com) on Tue Apr 13th, 2004 at 08:54:56 PM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

sorry... i misunderstood

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#16)
by dozer on Tue Apr 13th, 2004 at 08:52:11 PM MST
(User Info)

Nando, how 'bout posting the file to your files-area on this forum ? Then we could get it when we're ready to download it; rather than having it suddenly come in the mail. For those of us on slow rural modems, it's a rude shock to get a 7mb email... <grin>

thanks!

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#3)
by John II (jjones2(at)inetvisions.net) on Tue Apr 13th, 2004 at 08:49:12 AM MST
(User Info)

I have a question for you both... but first a quickie explination abt myself.

I'm a little lacking on all fronts sorry to say.. No experience with PIC's and next to no experience with power electroics. Just a little experience in digital design, but can't bost there either ! I built a 2kw 120vdc PV array only to find out that a commercial inverter will probably forever be out of my affordability ! So I'm watching you guys as well as the work of ibedonc work and trying to learn.

I know you guys are taking the proper approach using a high frequency dc to dc converter to boost your voltage before pulse width modulating it into a sign wave is the proper and best route.

However just to satisfy my curiosity could you guys explain to me any postive as well as all the negative reasons for not just using pwm feed into a large step up transfomer ?

I'm aware that it would make an inverter weigh alot more (huge transformer), and it's effeciences might be down slightly from your higher quailty designs. What other negative reasons am I perhaps over looking ? Just had to ask : )

Also... I'm intrigued with the multiple transformer tap method to build a sinewave ( simular to traces approach ) but I suspect that it takes a larger quantity of power fets or igbts ? Whats the primairly down side and upside of this approach as you guys may see it ?

keep up the good work... and thanks for sharring your hard work with others..

John II

Re: 15KW PWM Inverter (none / 0) (#9)
by ibedonc on Tue Apr 13th, 2004 at 02:54:59 PM MST
(User Info)

However just to satisfy my curiosity could you guys explain to me any postive as well as all the negative reasons for not just using pwm feed into a large step up transfomer ?

you could do that but the losts would be greater , in fact one of my tests was to take
the output of my PWM and input it into a 24v transformer and I had 120vac out
now you still have to run the PWM though a choke/cap to filter out the 50khz switching
freq. , a 12 to 120v MSW inverter is a lot smaller and cheaper then same power 60hz transformer. I am still working on my inverter , but a few other non-related things have slowed me down

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#13)
by hilo90mhz (hilo90mhz@hotmail.com) on Tue Apr 13th, 2004 at 05:26:41 PM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

yeah I think it takes more MOSFETs also... And just the magnetizing current of a large steel transformer can be pretty high... i was contemplating using a HUGE 24KW steel core three phase transformer... But i think the magnetizing current at 240v was something like 5A.. or more, i cant remember really, but it was too high to be acceptable.

For smaller and cheaper inverters its the way to go.... only one switching stage in the whole thing... the power only passes through ONE set of semiconductors... unlike mine which has 3 sets.. first the MOSFETs of the dc-dc then the high speed rectifiers for the dc-dc, then the IGBTs of the output stage.

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#19)
by RobD on Wed Apr 14th, 2004 at 07:36:26 AM MST
(User Info) http://www.dsgnspec.com

Hilo,
A couple of questions on the design.
First you might want to look into the Allegro ACS750 series of current sensors as opposed to R1 (.0005 ohm). They are giving free samples.
I don't see any snubbers so I'm wondering if you're getting spikes that can destroy your mosfets.
As far as output distortion you should be able to clear that up with filtering and not need to adjust the PIC algorithm more than a few percent. A small amount of distortion won't do much harm.
Personally I've never been in favor of large ferrites so I'd go with several smaller ones. They are cheaper and easier to implement on pcbs. Also is there a reason you're using the 26 mix iron core over the ferrite 77 or 75 mix core? I would think you'd get much better results with the ferrite core material.
RobD

Re: 15KW PWM Inverter (none / 0) (#20)
by ibedonc on Wed Apr 14th, 2004 at 09:39:08 AM MST
(User Info)

I think he is using that core for his output filter , from what saw on his page

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#24)
by hilo90mhz (hilo90mhz@hotmail.com) on Wed Apr 14th, 2004 at 06:18:17 PM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

Hey,
Thanks for the tip on the allegro sensors, Ive already used them for a robotics project i did with a local high school... But didnt realize they were giving away free samples. That R1 must handle 400A continuous ;) I already have abunch of large .005 ohm resistors, planning to parallel up 10 of them.

ya, it was alot of work winding the huge ferrite, I dont have any small ones and only paid $50 for 3 of those cores which are rated for 15KW at 50khz, 50KW at 250khz -- im at 80khz.

Ive thought about using ferrite on the output filter... I would have to put an air gap or else the core starts saturating, other then that, the iron powder is wayyy cheaper then ferrite, a 5.2" toroid is only $13 where as a 3" ferrite toroid is $30.

Chester

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#25)
by RobD on Wed Apr 14th, 2004 at 08:45:06 PM MST
(User Info) http://www.dsgnspec.com

Chester,
I just took a quick look at the design and never figured the current on the sensor. I think the Allegro sensors only go to 100 amps. (400 x .0005 = .2 volts x 400=80 watts 15e3/80=.53% loss.) That's OK, What's the RDS(on) of the MOSFETS?

I didn't see a chip number on the feedback op amp. which one are you using?
RobD

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#29)
by hilo90mhz (hilo90mhz@hotmail.com) on Thu Apr 15th, 2004 at 01:46:11 AM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

RobD,
The MOSFETS are IRF1407 75v 130A .0078 RDS(on)

Im using the PMI OP177 op amp, the data sheet uses lots of phrases like "Ultra precision" "Ultra low Offset" hehehe... I have a scrap circuit board full of them... thats why I used it.

I requested some samples of the 50A sensors, they might be usefull to measure the output current at 120v.

Chester

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#30)
by RobD on Thu Apr 15th, 2004 at 05:50:22 AM MST
(User Info) http://www.dsgnspec.com

Nice mosfets!

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#21)
by bob golding (photoman290 at yahoo dot com) on Wed Apr 14th, 2004 at 02:30:52 PM MST
(User Info)

hi chesterm another refugee from the tesla list i see hehehe. talk to richie burnett or steve conner on the tcbouk site here in the UK they both did Phd's in invertor design and grid tie invertors. should find a link on the pupman list.

bob golding

Re: 15KW PWM Inverter (none / 0) (#23)
by hilo90mhz (hilo90mhz@hotmail.com) on Wed Apr 14th, 2004 at 06:07:42 PM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

Hey Bob, yup :) tesla = fun hehe. I already got Steve Conners Phd paper... Quite interesting and I learned alot from it, too bad he didnt build a standalone inverter ;) could have copied the design directly... Actually I just got it a week ago, met him on the 4hv.org forums.

Chester

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#27)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Wed Apr 14th, 2004 at 11:18:43 PM MST
(User Info)

CHESTER:
I would like to read the PHD inverter design, can you send it to me or direct me to download it.?.

Thanks in advance

Nando

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#28)
by hilo90mhz (hilo90mhz@hotmail.com) on Thu Apr 15th, 2004 at 01:37:11 AM MST
(User Info) http://www.hot-streamer.com/hilo90mhz/

Hey Nando,
heres a link directly to the file:
http://www.scopeboy.com/elec/RE/appendix-inverters3_3.zip

He says thats only a chapter of his thesis..

Heres a thread I started months ago on the 4hv.org forum that has some more info if anyones interested:
http://www.4hv.org/index.php?board=3;action=display;threadid=21819

Chester

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#26)
by Nando (nando37-at-tx-dot-rr-dot-com Correct theanti-spam) on Wed Apr 14th, 2004 at 10:08:49 PM MST
(User Info)

FOR ALL THOSE INTERESTED in the design of a 48 volts DC - 10 KW DC/AC inverter
go to the link below and down load at will, remember is long lllooooooonnnnnngggg.

I tried to send it to all that asked for it but my ISP allows not more than 3 MB per message -- Heck bad time to discover such limitation.

If the moderator wants in this site, he may load it there !!!

http://www.energychallenge.org/2001Reports/tamu.pdf

It is a good teaching tool for many

Regards

Nando

Re: 15KW PWM Inverter (none / 0) (#31)
by RatOmeter on Thu Apr 15th, 2004 at 07:07:26 AM MST
(User Info) http://www.rato.us

Hah! Now I understand the TAMU reference. Turns out I had already downloaded that (and other competing designs) last year in June when I first got interested in inverters. I really just skimmed through it at the time. Time to go back and look a little closer.

Thanks.

[ Parent ]

Re: 15KW PWM Inverter (none / 0) (#32)
by ibedonc on Thu Apr 15th, 2004 at 12:20:44 PM MST
(User Info)

this is the one I got some of my ideas from

[ Parent ]

15KW PWM Inverter | 33 comments (33 topical, 0 editorial)

Menu

� create account
� How to use the board
� FAQs
� search the board
� Google search the board
� Old Otherpower Board

Login

Make a new account

Username:

Password:

Total Views

��115 Scoop users have viewed this posting.

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest � 2003 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!