Can you attach a micro inverter after a ups to stop feeding back into the grid ?

I have a couple off ups set up so that they use solar to charge a battery bank and use that power before switching onto the grid (basically in reverse to how they should work). now id like to take some off the load off the inverter and use micro inverters to add to my inverter however i am not allowed to feed into the grid so if i attach the the micro-inverter after the ups would it feed into the grid when the ups is in grid mode or would it only power devices attached to the ups ?

Question by Kieren-J 1 year ago  |  last reply 1 year ago


Grid Tie and Induction Motors

Yes, I know it's nearly 3am on the east coast... but and idea struck me. So the idea is to feed small amounts of mechanical power into the power grid. Not necessarily run the meter backwards, but supplement power consumption.I've researched grid tie inverters - which are very expensive. For those wondering, a grid tie inverter is feeds mains power back into the grid by syncing phase angle and phase (no dead shorts :) ) and applying slightly higher voltage. They are very efficient and really not within a college student experiment budget :pSo I was thinking... Rather than go from mechanical to DC to AC to grid - go from mechanical to AC to grid VIA an induction motor. As a proof of concept, use a DC motor + battery to turn an induction motor. Plugged into the grid, in theory, should apply current. Oh, but the phase you say? How do you prevent a dead short?"I've thought of this -- before applying mechanical power - have the grid bring the induction motor up to speed. Then try to turn faster (apply a torque) with the DC motor, for example. In theory, the amount of extra power put into the grid will be related to the slip angle of the motor - which will also control the speed of the input (so you can't go over speed by too much).Keep in mind that this whole battery business is just a proof of concept sort of thing - I'm not talking perpetual motion or any hohaa craziness. In the end, the final mechanical input will be around 200 watts. I expect this to be very low efficiency (likely 50%ish), 100W isn't an answer to the energy issues - but it's an experiment. It's also not going to come even close to driving the meter backwards, but it should run (as supplement) my laptop + two to three 13w CFL's :DI think the theory is feasible -- the inspiration comes from flywheel driven UPS systems. An induction motor is driven while mains power is on to keep a flywheel in motion. When the power goes out, the FW drives the motor and feeds to local grid.I'm thinking of using a "low" rpm induction motor.... If I recall, ceiling fans are 16 pole? So that's 60Hz2*2/16=450rpm... Add ceiling fan motor to the list of things to hunt for :) Looking at the one above my head, it looks like it even has a nice bolt pattern for some sort of pulley shenanigans :DCan someone either throw some ice water on me and slap me for being an idiot -- or let me know if I've found a boat to Valhalla.Oh, and my apologies for dancing around the "mechanical input" details.... There's a reason for this, I promise :) In any case, insight and information is appreciated :)

Topic by trebuchet03 11 years ago  |  last reply 7 years ago


How to limit A/C current draw from gird and draw power from secondary grid tied solar inverter ?

Micro grid tie inverters are an excellent power source and can be linked together to generate energy, however they do not function when grid is down, this is for the safety of line workers. In a real world scenario I want to ensure that all power is drawn from the energy produced by the micro solar inverters as the primary source while it can produce power and not from the grid which will act as a secondary power source, this will require some sort of current limiting solution from the grid without reducing the voltage to keep the inverter working.   For the safety of line workers I would like to have an automatic transfer switch which will have both the primary power source from grid and a tertiary inverter backed battery backup so that when the grid is off, the power is drawn from the Inverter and there is no power fed back into the line keeping lineworkers safe and since pure sine wave produced by the inverter can activate the grid-tie inverters and it should theoretically increase the VA of the UPS to the size of the installed Grid-tie micro inverter capacity, the automatic transfer switch should take care of switching between grid when power is on and to the backup inverter when power is off.  TIA for any advice in this regard !

Topic by Ruben GeradM 2 years ago  |  last reply 2 years ago


Grid tie solar inverter power from a fixed voltage source?

Hello there! We have a 4Kw solar system installed at our home. We also happen to have 2 seperate circuits (ie 2 electricity meters). Annoyingly the solar panels are installed on the circuit that we don't use much electricity off so most of the generated electricity flows into the grid and (I know it's selfish) we don't benifit from it at all. There happens to be one lonely socket next to the solar inverter that is powered off the other electricity circuit and I'm fairly sure that the two circuits are on different phases. This is what I wanted to do and I was hoping someone might be able to validate this: I install a 240v AC to 24v DC converter (PAK650-24) and then an inverter to convert this back to 240v AC to supply that lonely socket where we need the power. Our solar inverter has a clever power detecter that switches a relay when production goes above 1Kw so I would connect this circuit to that relay. I also wanted to use a solar grid tie inverter from ebay because they seem most reasonably priced. They do however have a MPPT algorithm which is where I am not sure how it would react to a voltage source. Might anybody be able to tell me whether it would be fine to do this and most importantly about fixed voltage sources and solar grid tie inverters (which aren't really meant for fixed v sources). Many thanks, James 

Question by fotherby 7 years ago  |  last reply 6 years ago


Variable DC input to a clean AC out put

So here is what I am trying to accomplish. I am trying to take an old Jacobs wind turbine controller that was designed for a grid tie application and make it off grid. There is a 3 phase "wild" ac input from the turbine that is rectifyed but not clipped by the internal SCR's to variable DC (40-180 volts). The sensing was designed to tie to the grid and power sync'd to line power and freq then exported or imported depending on demand. What I would like to do is build a Variable Dc input inverter that will put out a pure sine wave 120/240 vac split phase. Thus imprinting a usable power out put and allowing the cap/choke inverter to do its part. The design need not handle much power as it is only used as an imprint to regulate the power through the controller. If anyone had any idea on a build for this or a manufacturer that is producing such an item I could really use some ideas. Thanks

Topic by nbrooks 8 years ago


Maintaining a stable voltage on a wind turbine?

Every couple weeks a new instructable comes up on some green energy thing or another, but one I am really interested in is wind.  The problem I see is that with wind ranges from 5 - 25 mph, the voltage change is extremely problematic.  When I see people putting permanent magnets on alternators for use with wind, it seems ridiculous.  Even if you are using an inefficient battery-storage off-grid system, you still need to maintain 12-15 volts to charge your battery, and an alternator is made to do that by varying the magnetic power.  Now I understand the extremes of a alternator's voltage regulator are likely fairly narrow, but still quite useful in generating wind energy.  What I am looking at is 3-5kw of grid-tied power.  This is great and all, and possible in for me, but I don't see how I could maintain a stable enough input for it to work.  Most inverters are for solar power and aren't grid tied. The next most common are grid tied solar which take 12v DC and scale it to 115 ac across three phases.  Finding a grid-tie 5kw 3 phase in and out ac grid tie inverter is extremely hard, but not impossible.  The only thing that is impossible is finding one that can handle highly unstable voltages.  So the options I am left with are using a variable transformer to bring the wind power down to 12v and then rectifying it, then pumping it through an inverter which leaves me with 70 - 80 % of the original power.  My other option is to, like a car alternator vary the rotor voltage to maintain the desired end voltage.  The one problem I see with this is that there is a large amount of potential energy not tapped.  For example lets use 1 as the relative output as well as the input to generate a magnetic field.  If the speed is 1 then both in and out are 1.  If the speed is 2 then the in will be .5 now the out should stay at 1.  But if the in had remained at 1, then the out would be 2 so essentially you are losing half of your potential energy.  This isn't a problem in cars because they aren't tapping the maximum power possible. All the time, they don't need it.  This is a problem with wind turbines, so is there a way around this?  What wold you recommend to do for grid-tied wind power.

Question by jj.inc 5 years ago  |  last reply 5 years ago


Wind turbine to charge batteries

I have a solar electric system with a battery back up for power outages.(it is also grid tie) I would like to add a wind turbine to charge the batteries in extended outages with no sun and hopefully wind ( we normally have low wind but storm outages have lots of wind). The batteries are 12 volt connected in series to produce 48 volt. Can I, should I, get a 48 volt turbine and connect direct to the batteries or some other voltage and go through the inverter like the solar panels do and if so how and what voltage turbine?.. Chris

Question by papabear911 6 years ago  |  last reply 3 years ago