You may also determine the current direction by the polarity of the voltage drop.

 

You may also determine the current direction by the polarity of the voltage drop.

Here the AC average (whole sinusoidal waveform ) of the current and voltage is zero so you need instantaneous values or indicators for synchronization.

 

You are correct the Voltage does alternate but the current flows in one direction yet I am sure I am in for a debate.

Not a very big debate. A = alternating, C = current. I think you mean that *power* moves from a source to a destination.

If you sample the voltage across an inline current shunt or the output of a current transformer *only* when the instantaneous line voltage is greater than the neutral, this will tell you which way energy is moving.

ak

 

I think you have a basic misunderstanding of electrical energy and how it works in DC or AC circuits.



To parallel your AC power sources you need to synchronize the frequency, phase and voltages of the AC outputs to the power grid. This is hard to do with equipment not designed for it. Not happening with a H-bridge or a 'AC diode'. It's much easier to combine DC sources into a common inverter power feed.

https://en.wikipedia.org/wiki/Synchronization_(alternating_current)

The grid won't change so you must have your system in almost exact sync for it to work.

I am not dealing with the grid in what I am trying to do. You misunderstand my intent. When the power goes off and the transfer switch engages it connects the load to the backup generator. I have a micro hydro that outputs 4.25K that is normally grid tied. The GT inverter will do all the adjustments necessary to match the phase but (I have been told) it may back feed into the generator or vice-a-versa.

 

Not a very big debate. A = alternating, C = current. I think you mean that *power* moves from a source to a destination.

If you sample the voltage across an inline current shunt or the output of a current transformer *only* when the instantaneous line voltage is greater than the neutral, this will tell you which way energy is moving.

ak

The AC voltage can be detected in a wire without closing the loop, there is no current if there is no load.

Thanks for the other info.

 

I think you have a basic misunderstanding of electrical energy and how it works in DC or AC circuits.



To parallel your AC power sources you need to synchronize the frequency, phase and voltages of the AC outputs to the power grid. This is hard to do with equipment not designed for it. Not happening with a H-bridge or a 'AC diode'. It's much easier to combine DC sources into a common inverter power feed.

https://en.wikipedia.org/wiki/Synchronization_(alternating_current)

The grid won't change so you must have your system in almost exact sync for it to work.

I am not dealing with the grid in what I am trying to do. You misunderstand my intent. When the power goes off and the transfer switch engages it connects the load to the backup generator. I have a micro hydro that outputs 4.25K that is normally grid tied. The GT inverter will do all the adjustments necessary to match the phase but (I have been told) it may back feed into the generator or vice-a-versa.

 

I am not dealing with the grid in what I am trying to do. You misunderstand my intent. When the power goes off and the transfer switch engages it connects the load to the backup generator. I have a micro hydro that outputs 4.25K that is normally grid tied. The GT inverter will do all the adjustments necessary to match the phase but (I have been told) it may back feed the generator or vice-a-versa.

In that case it would be wise to shut down the hydro power system bieng portable gensets do not take back feeding power well at all.

Especially at higher power levels since, even if they do handle the feedback at all, all they have for frequency and voltage overshoot limiting is the engine doing what level of dynamic braking it can handle which is maybe 10 - 15% of its rated load capacity at best.

Either run off the genset or redesign the hydro plant to charge batteries and then run the backup power off them through a proper power inverter. If you have a hydro plan that puts out 4+ KWH 24/7 with the addition of a 10 - 20 KWH capable battery bank and a large power inverter you would in effect have the capability to run a pretty big load indefinitely off of it in a full off grid mode.

 

The grid tie inverter will handle the power feedback as it needs to, it's what they do by design. As for the generator there is no easy and practical way to direct connect a common genset to a utility line unless you have a very solid background in AC power system theory and actual device design and operation. It's not something you just plug in and go to back feed with.

I've been building Grid Tie Inverters for years and have never written a number of basic DIY tutorial thread on designing and building one. Even as thoroughly distilled as I have so far the DIY info on the subject it's still a fairly mid to upper level electronics project to build one.

My threads on GTI design and construction found here. https://www.electro-tech-online.com/forums/alternative-energy

It's way more complex than just monitoring impedance or inductance or anything else to do live line power feedback. On a very basic and limited power level (sub kilowatt power inputs) is not terribly difficult to do variable DC to AC power feedback with simple common components but it gets more complicated as the power level go up.

I am not dealing with the grid in what I am trying to do. You misunderstand my intent. When the power goes off and the transfer switch engages it connects the load to the backup generator. I have a micro hydro that outputs 4.25K that is normally grid tied. The GT inverter will do all the adjustments necessary to match the phase but (I have been told) it may back feed into the generator or vice-a-versa.

 

Draw a picture.

 

I am not dealing with the grid in what I am trying to do. You misunderstand my intent. When the power goes off and the transfer switch engages it connects the load to the backup generator. I have a micro hydro that outputs 4.25K that is normally grid tied. The GT inverter will do all the adjustments necessary to match the phase but (I have been told) it may back feed the generator or vice-a-versa.

The synchronization problem is still the same. It's unlikely the GT inverter will qualify the generator output and supply power if the generator voltage or frequency increases beyond the UL 1741 limits even for a very short time. Even if it qualifies in a idle condition any change in generator voltage, frequency and waveform while the GT ramps up to supply full power to the circuit will kick it off again. If you have a large high quality utility grade generator with a load larger than the capacity of the GT inverter it might work.

 

Are you sure about that?

Of course not , It's just my theory. You can detect the Voltage in a wire stimulated with an AC source, so there is voltage but there is no current unless it is connected to a load. Therefor the current flows to the load or through the load. They should have named it AV and DV.

 

Of course not , It's just my theory. You can detect the Voltage in a wire stimulated with an AC source, so there is voltage but there is no current unless it is connected to a load. Therefor the current flows to the load or through the load. They should have named it AV and DV.

What does what they chose to call it have to do with your claim that, "You are correct the Voltage does alternate but the current flows in one direction." ?

 

Of course not , It's just my theory. You can detect the Voltage in a wire stimulated with an AC source, so there is voltage but there is no current unless it is connected to a load. Therefor the current flows to the load or through the load. They should have named it AV and DV.

The drift velocity for a 20 A current in a 12 gauge copper wire is ~0.4 mm/s, that means the current alternates back and forth a few um during each 60hz cycle. The average movement is zero.

Sure the electrons (current) are moving in the wire, but the only things outside of the wire are the electric and magnetic fields associated with the travelling wave. The Electric field is mostly between the 2 or 3 conductors of the transmission line, and the magnetic fields are encircling each wire. It is this oscillating travelling EM wave that drives the power down the transmission line.

 

I am not dealing with the grid in what I am trying to do. You misunderstand my intent. When the power goes off and the transfer switch engages it connects the load to the backup generator. I have a micro hydro that outputs 4.25K that is normally grid tied. The GT inverter will do all the adjustments necessary to match the phase but (I have been told) it may back feed into the generator or vice-a-versa.

I get what you are saying just fine. It likely won't work for a number of reasons as both Nsaspook and I have mentioned.

Either the generator won't like it or the GTI unit won't or both unless your gen-set is substantially larger than your GTI unit.

The next question is how big is your actual load and the gen set you have? Unless you have a rather large base load of at least a few times over what the GTI system puts out there's no point in trying to make the to power systems work together.