OPENSOURCE HW/SW Grid Solar Microinverter 450W - 97% Efficiency, 25yrs Lifespan

[Phoenix]

I was thinking this was a great personal project... You have a long long way to go to become compliant. And need some really deep pockets.

What compliance region/country are you aiming for?

(I do design grid connect inverters for a living and have put one through AS4777. 2).

[KoRba88]

I've played a bit with dead time and minimum pulse width.

When I reduced the dead time near very low and very large pulses (but not to large, ie 96-98% of Dmax), the distortions at zero cross were smaller. Also when I put the limit to min pulse value, the distortion were smaller. With outsynchronizing LF leg the glitch disappeared but oscillations were bigger.

The effect was similar to that in this app note from TI "How to Reduce Current Spikes at AC Zero-crossing for Totem-pole PFC" . The modulation for this PFC is the same.

Moreover they completely removed the spike around zero and oscillations! Looks like I was close to achieve that.

https://www.ti.com/lit/slyt650

I will adopt that algorithm to see the effects.

My LF MOSFETs have also fast recovery diodes and fairly small output capacitance so it should be easier to achieve that.

[KoRba88]

I was thinking this was a great personal project... You have a long long way to go to become compliant. And need some really deep pockets.

What compliance region/country are you aiming for?

(I do design grid connect inverters for a living and have put one through AS4777. 2).

Polish market but now it's just only a wish rather than serious idea.

For now the plan is that in the end the HW will be open source and end user will pay only licence for the software.

[KoRba88]

I've implemented current spike reduction algorithm. Currently its only for open loop. For closed loop it will be not so easy.

Firstly I;'ve tried with ST version ( https://www.st.com/resource/en/user_manual/um2792-getting-started-with-the-stevaldpstpfc1-36-kw-pfc-totem-pole-with-inrush-current-limiter-reference-design-stmicroelectronics.pdf) since it was easier, to implement but result was poor. Spike was reduced but there was still huge oscillations.

TI approach although complicated in MCU implementation  is superior and there is significant spike reduction. My version of algorithm (i.e soft start) is not perfect yet but it works. That additional tiny pulses around zero cross do the job, discharging MOSFET capacitance.

The waveform is not smoothed as previously because I've reduced the current sensor filter so now is 5 times faster (10 us) also its only 350 mA here, at full 2A current will look even better.

[lyxer]

where and how to buy the transformer?

[jonpaul]

transformers are DIY, beware all ferrite cores are very delayed delivery 38..80 weeks

No off the shelf transformers

j

[ManniW]

I'm wondering: How much can this design be tuned for efficiency? If GaN-FETs are used they have a very low RDSon aswell as a very low switching time and charge, so losses could be reduced significantly. Also the choice of diodes could probably be improved a little, increasing the total efficiency even further. Is the LLC Tank really more efficient than the original design? They calculated a pretty good efficiency and using other diodes/FETs it could be bumped up to over 97% using the formulas in the AppNote.

Using the HERIC inverter design on the output side could give another efficiency bump (but it will make the software more complicated, but only slightly).

[Ali Elsayed]

hello, can anyone kindly advise ? can i make the original inverter but only change the DCAC side MOSFETs by GaN FETs and change the gate drivers ? and would it work without problems ? i'm not experienced, any help would be much appreciated

[Siwastaja]

hello, can anyone kindly advise ? can i make the original inverter but only change the DCAC side MOSFETs by GaN FETs and change the gate drivers ? and would it work without problems ? i'm not experienced, any help would be much appreciated

Of course not. This is state-of-art which requires months and months of design work from top-1% power electronics engineer to even build a prototype, and years for a complete product. Buy a ready made inverter, they are easily available.