Solar inverter design help - Page 1
Forum section: electronics / general

author: jpvolt
author_rank: Newbie
timestamp: October 22, 2016, 03:12:20 pm
content: Hello everyone recently I bought three 200w solar panels, and I want to build a 750w inverter, but i have little experience with ac circuits.My idea is a 750w(output) inverter , capable of dynamic loads, with reactive power provision.I need something like a guideline to design this inverter, articles, books, reference designs and tips would be very helpful as well.Thanks in advance.ps:Sorry if I wrote something wrong, I am still learning English.JpVolt

author: Simon
author_rank: Unknown
timestamp: October 23, 2016, 08:32:13 am
content: No offence but you sound like somebody who is at the beginning of their adventure with electronics and this is no beginner project although it does seem to be a popular beginner project. If a mass produced Chinese unit can blow up quite easily what chances do beginner hobbyists have producing something reliable and safe? If you don't have "much experience with AC circuits" thing going anywhere near the mains which is what this entails is a very bad idea. Your best bet is to buy one of those cheap city ones of eBay or get a good quality one but they do cost money.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: October 23, 2016, 08:48:51 am
content: http://www.ti.com/tool/tmdssolaruinvkitvery expensive but i think they may have open sourced it?Never the less if you follow the links there is plenty of learning to be had.

author: Simon
author_rank: Unknown
timestamp: October 23, 2016, 08:58:46 am
content: A very wise move on TI's part they have obviously noted all of the people out there trying to build their own grid tie inverter's. I suppose – I've not read the whole blurb – if somebody came up with a good enough controller with the flexibility you could add the required power station to suit the power you require.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: October 23, 2016, 09:27:03 am
content: Quote from: blueskull on October 23, 2016, 09:10:31 amYeah did not twig to that, it isn't the standard way to connect to the grid.They do seem to have fuses on the output though.Maybe FET overcurrent is controlled by the chip or a FET driver.

author: coppice
author_rank: Super Contributor
timestamp: October 23, 2016, 10:08:35 am
content: Quote from: blueskull on October 23, 2016, 09:10:31 amThat's certainly one of the benefits of using the C2000.

author: coppice
author_rank: Super Contributor
timestamp: October 23, 2016, 10:31:54 am
content: Quote from: blueskull on October 23, 2016, 10:12:10 amMaybe you need to look at the overcurrent features in the C2000s targeted at digital power applications.

author: jpvolt
author_rank: Newbie
timestamp: October 23, 2016, 11:05:09 am
content: Thanks Everyone for all the replies.QuoteVery good but very expensive indeed. Maybe I can use one of the Piccolo´s Microcontroller, but no way to buy this dev kit.Most of the schematics that i have found on internet use some PWM ic that use a capacitor and a resistor as oscillator, so frequency will change too much with temperature.I was thinking to use a pic16f628a to control the transistors on the output stage. It has a “precision internal 4 MHz oscillator”, should this be good enough?

author: Red Squirrel
author_rank: Super Contributor
timestamp: November 02, 2016, 07:33:40 am
content: Start with building a regular SMPS... maybe a MPPT charge controller for the panels. Read up on SMPS design. I've been interested in it myself and reading about it on and off, but my lack of math skill does make it hard to understand most of it. There is a lot of math involved in designing power supplies. Especially in the magnetics. How big of a core you need, how many turns, etc.From my understanding so far an inverter is going to be very similar to a SMPS, except you vary the voltage in a controlled way to create the sine wave. So instead of monitoring the voltage and trying to keep it at a constant number, you vary it at a specific time interval to get the 60hz you need. The design is also going to need to be capable of going negative, which is a bit more tricky. A buck-boost topology may work for this, or two separate PSU circuits working together.You could also start with a square wave inverter, like UPSes, just as a start.