I have a photovoltaic inverter related question. Recently I have been looking into the possibility of building a grid-tie photovoltaic inverter. A number of semiconductor vendors e.g., Freescale, TI etc., sell controller kitss that have built-in pulse width modulation units etc., to process the DC input from the solar panel, using Maximum Power Point Tracking and all. What seems to be missing, is how to synchronize with the phase of the grid. One would imagine that the power grid would tapped and the isolated input fed into a phase locked loop to synchronize with the grid supply phase. One cannot inject power into the grid without phase match. Am I missing some subtle point ? Any hints, suggestions would be of immense help.
What you need to use are inverters which sync to the grid. You might want to take a look here:
formatting link
These inverters sync the generated AC to the grid AC, so that you can feed back to the grid. However, when the grid fails, these inverters usually shut down for 2 simple reasons: (1) there is no reference anymore to sync the phase (2) the inverters would immediately be overloaded
Yes, you'd have to sense the line voltage to sync to it, and probably the inverter-line current.
You could do what the PFC power supply chips do, namely sense the AC line voltage waveform in real time and make a boost converter's output current track that. A slow control loop wraps around all that to get the average, in this case optimum, power transfer. Maybe you could use one of the PFC controller chips; they're cheap.
The problem is basically to present a negative resistance to the AC power line.
Get anything wrong and it goes boom. Expect a shoe box full of exploded fets if you do this from scratch. Wear eye protection.
There seems to be several "grid tie" inverters for sale on ebay. Here's a 300 watt unit for $50. But only 37 minutes left on the auction, so it might be gone now.
formatting link
300W GRID TIE INVERTER, for solar/wind panel use
12V/110V
feature:
power jack grid tie inverter is designed for small solar panel & wind energy market, it's suitable for family enengy system.
this inverter can directly use solar panel, wind charger through inverter to home grid.
easy to installation, just need solar panel, grid tie inverter, then directly can put into home grid.
note: this inverter only has grid tie inverter function, do not have tranditional inverter function, pls do not connect the battery for 12v dc source, for further questions, pls leave message to ask, tks.
1.idea for power jack
The inverter can be connected to any outlet at home, when this line run by the conventional electric network. The inverter IC will monitors the volume, frequency and phase of the home grid, then produce a pure sine wave that the frequency and phase will be match the grid's, and the volume will be higher than the grid's, then according to our current controlled PWM, to control the output power to the grid. The inverter will puts out power when the home grid is on.
why use power jack grid tie inverter? when you use solar panel through grid tie inverter, your home power meter will reduce the speed(if you are using other electric appliances), or your home power meter will backward(if you are not use any appliances)
difference of power jack grid tie inverter traditional grid tie inverter is the solar panel are connect in series, so if one solar panel did not work or bad efficiency, then the whole system will be effects, but power jack grid tie inverter, you can use every inverter in parallel, in this moment, each inverter has it's own MPPT, can make every solar panel got the max power.
island protection
power jack grid tie inverter has 3greens light, when the charge fucntion is normal, then this 3lights will turn on, but if there are not dc sources(like in the night, no sun shine or raining day), the red led light will turn on, the inverter will stop to work, in this moment, the inverter will close the door, the home grid power will not back to inverter.
What was the case style of the very bottom left "exfet"?
I had a hard time recently locating a specific power transistor in a TO-218 case, with the metal tab and not the lump of plastic with a metal back like everything seems to be now.
I suspect people using TO-3s felt the same way when the TO-218s came out.
to not have to modify existing heatsink clamps. The setup in the product was a bit weird with a clamp holding the metal tab onto the heatsink. I'm not sure why the transistor wasn't just screwed down. There was a screw and nut for the clamp anyways.
the TO-218 is actually somewhat compatible with the TO-3.
If you have an old SK or EGC cross book you might find a section where they show you how to wire the only available replacements for some TO-3 transistors using the TO-218 package.
If the original setup didn't use sockets, it wasn't a big deal.
The HF carrier is any old oscillator. The modulation signal (which controls boost converter duty cycle in a PFC-type power supply) is created by analog-multiplying the line voltage waveform by a loop error signal. It would probably be easier, nowadays, to do all this digitally, in a little PIC or ARM or something.
Look up some PFC power supply control chip datasheets and appnotes. It's a similar, or sort of reverse, problem.
** A well designed clamp does a far better job with TO-3P and similar single hole packs than using a bolt does. Normally the clamp supplies high pressure along the CENTRE line of the plastic body of the device. The body spreads the pressure evenly over the tab and there is then no tendency for it to lift up at the lead end as there is with a bolt.
** The main advantage of the TO3 pak is that there is no plastic in contact with the chip which sits in a hermetically sealed environment - means chips have a much longer service life even when running near max temps.
Internal feed wires can be sized to fuse immediately if a device fails - a valuable feature not seen in plastic paks.
Two bolt mounting is easy to get right - long as you avoid those soft plastic ( Nylon ? ) insulating bushes that crush under heat and pressure.
I'm not arguing that a TO-3 is better all around- it's just that fewer and fewer semiconductors are packaged as nicely these days so that's what you have to work with most of the time. The hermetically sealed and welded metal can obviously costs more than some plastic resin molded around a sliver of metal.
Sanken uses to have the most exciting TO-3 cases. The base was surprisingly thick and they felt like they were made of gold.
But the plastic ones explode and burn.
I think they were a glass filled plastic. I may still have some mounting kits with the mica washer, nuts, washer and lug.
I've seen lots of power supplies now have the power semiconductors glued to the heatsinks, or the thermal pad is sort of like a really hard two sided tape. I can't figure out if there is any repair method for that type of stuff.
I've not seen or heard of it, but never worked with high power stuff and to-3 cans.
The fist sized plastic shrouded mosfets or IGBTs they use in large online UPS explode though, and splash what seems to be silicone gel all over the place. That's not counting the sooty fire that usually happens at the same time.
Yep. One failure mode the base lead came *though* the case like a bullet. In another the whole top of the case came off and ricocheted around the room. They ended up putting the power supplies in a bullet-proof test chamber for their christening. Secondary breakdown can be an impressive event.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.