question/discussion on solar inverter design

[hearter]

I want o start a new topic on solar inverter discussion. you have all kinds of inverters on the market. there is one inverter from ENphase, it is called microinverter, very interesting. they claim higher efficiency, I don't believe so. but what caught me is the question below:
How can they connect multiple inverters output in paralell? The output is AC, does that impact AC voltage if you add multiple inverters together?

also they claim Panel communication build-in module. anyone know how this was done?

The cost of innstalling such microinverters are way higher than centralized ones I believe.

shed any thoughts, idea? followups, welcome.
also if you have new ideas, found new inverter structures, please post here.

 

[hearter]

no body has followup?

my next question is:

what if you connect two solar inverters outputs together with same AC voltage(say 120VAC)? you get 120VAC? or depends on phase?

Added after 2 minutes:

one more question here to chew:

any one know what high voltage semiconductor process out there that we can use to design own inverter? does TSMC have high voltage process? I think at least 50V or even higher.

 

[keith1200rs]

Dalsa go over 300V I think.

Keith

 

[hearter]

Keith,
have you actually used Dalsa process?

Added after 1 hours:

inverter basics:

types of inverter topologies:

1.with transformer and
2.transformerless

transformerless is popular, but not in USA because of on-grid issue.

output stages usually in H-bridge or D-type

if anyone can point out what is the latest popular topology, that will help in this thread.

 

[keith1200rs]

Keith,
have you actually used Dalsa process?

Not yet. I have had discussions with them on a few occasions about high voltage applications and CCDs and they have been helpful. If you want a process without too much digital circuitry, there are other CMOS processes around which can handle 80V to 100V in 0.8um to 1um.

I have some experience with solar panel controllers but unfortunately cannot share them.

Keith

 

[hearter]

Keith,
why you need 300V to do inverter?
did you design transformerless inverter?

usually 24V or 48V is enough since most solar panels are 24V or 48V. I found HV CMOS from TSMC 32V, and IBM 0.18um which is 50V and also Austria microelectronics has 50V CMOS process.

Added after 1 minutes:

also Dalsa process is not high volume foundry, meaning high wafer cost for you, maybe TSMC is better choice interms of cost

 

[keith1200rs]

I used Xfab 0.35um. TSMC, SMIC, Tower have similar processes (some at 0.18um). The AMS process is probably similar.

The Dalsa was for another application. I was simply answering your question about processes above 50V.

Keith

 

[hearter]

Keith,
you don't need to put out details on your solar panel controller, but if you can shed some light on what is controller, that will be educational for the thread.

 

[retraeh]

what is more popular now for solar inverter design, transformer or transformerless?
anyone with experience can explain?

 

[prathamesh_d2001]

I have developed inverters with basically Full Bridge and Push-Pull Topology. In my inverter Transformer is used only to step up the input 12/24Vdc to 380Vdc. this high voltage is then passed through H-Bridge or Full bridge as we call it. at the output i get 230. these are very complicated pieces as we use TTL to drive each MOSFET. i have developed 12V/300VA inverter which is attached to solar panel thru a buck converter..working fine. Now i am alos new in industry, so please tell me - is the inverter i described above called transformerless ?

 

[hearter]

this is still called transformerless as the transformer is not used at output stage. true, your DC-DC has a transformer,but you use H-bridge.

question for you,prathamesh

did you design this as a integrated inverter? meaning integrate everything on chip except the transformer and cap?
what process do you use?
appreciate!

Added after 1 minutes:

one more question , did you implement MPPT in your inverter, how you do it?

 

[prathamesh_d2001]

Orry, but i did not get the part of the integration. it will be kind if u elaborate it. for MPPT it is developed separately. there r MPPT with Boost converters ( i.e. 18-24VDC to 250VDC) and Buck Converters (18 - 24VDC to 13.5VDC). i used buck MPPT as input for inverter. of course due to panel restrictions and buck' capacity, my 300VA inverter could work only till 150W, but its good enough.

 

[hearter]

"integrated inverter" means the inverter is a single chip design, what are integrated into one chip in your case?

if I understand correctly, you use buck converter for MPPT, I am trying to fugure out how to do it, what is the idea behind, and any circuit? appreciate!

Added after 1 minutes:

BTW, how do you isolate the inverter from grid if you don't use transformer at output?

 

[FvM]

this is still called transformerless as the transformer is not used at output stage.

A matter of convention, I think. All today's solar inverters are transformerless according to this definition. Or do you know recent products that are still using a mains frequency transformer?

how do you isolate the inverter from grid if you don't use transformer at output?

What do you exactly mean with "isolate"? To drive a sine current with tolerable low switching frequent interferences to the grid, the H-bridge needs an output inductor, respectively three for a three phase inverter, and possibly a filter. That's enough isolation in my opinion. If you intend galvanic isolation between solar panel and grid (I don't thinks it's required or usual), the DC/DC converter can provide it.

Regarding MPPT operation, besides possibly necessary voltage conversion, it requires to set the inverter output power for the intended operation point. In so far, it can't be completely separated from the inverter control. In some cases, a bus voltage control loop can provide the power control, without explicitely sending a delivered power setpoint from MPPT to the inverter.

 

[prathamesh_d2001]

actually buck converter is not used for MPPT, the buck converter itself contains Logic for MPPT. there is boost converter also available with such a logic. Unfortunately I worked only with inverter thus myself know less about those MPPT converters. for grid we have developed special type of UPS systems. this small inverter works on a single panel and will be useful in case of power failures. while buck converter will keep on charging battery of 12V in the daylight. Now about inverter, it is a complicated design and no microcontroller is used. we are using 4040 and 4060 ICs, with a sallen-Key Filter to generate reference sinewave, rest operation is assured as any transformerless inverter is.

 

[hearter]

It starts to become meaningful discussion here.
prathamesh,
so you said your inverter is for single PV panel, what you doing is basically purchase ICs from various vendors, and design your own PCB, to make a inverter, do you have your own IC? I mean do you design your own IC in this inverter?

does your inverter work on/off grid? are you saying you need one inverter for each PV panel?


I have included a conventional inverter block diagram here, do you think you can design your own IC to integrate DC-DC H-bridge, controller? I think many high voltage processes available out there now.

I still don't get your MPPT statement, do you have your MPPT designed in DC-DC converter?

 

[prathamesh_d2001]

I am working in a Power Electronics Company which develop many types of Converters and Inverters. This design of 300VA inverter (we r working on 200VA and 100VA versions also) is designed by reducing and editing some circuits of standard 1KVA inverter we develop. It fits behind the solar panel with a Buck MPPT converter. the standard 1KVA inverter works on/off grid but i have not tried it with 300VA one, and it is meant for 1 panel. so the design is pretty much like standard inverter and i didnt edit much. I saw the file u sent, we dont have that controller part, instad we r using normal opamp IC's for feedback and sinewave references. so there is no IC developed by me. for MPPT, yes its designed in DC-DC converter where micro controller will do MPPT's work, while other IC's will help in DC-DC conversion.

 

[karesz]

Hi all,
here is a similar & relative new Ref. Des. from On Semi too...
K.

 

[hearter]

prathamesh,
looks like you 300VA inverter is like the microinverter from ENphase. what switch transistors do you use? IGBT or JFET or others for the bridge, which micro controller do you use? 8051?

What is your application for 100VA inverter?

-H

 

[prathamesh_d2001]

I use N channel MOSFETs, as pert the rating we select them. as i said earlier, there is no controller and everything is analog based.

100VA inverter will be used most probably for small domestic applications as 300VA one, but its still under test.