Synchronising of 1 Phase Inverters with 3 Phase Grid System

This may come as a stupid question but why go from a DC bus to single phase and then 3 phase?

Or have I miss read something?

This might be considered OT, and it may be too late to reconsider, but I'm wondering why you bother with the conversion of mechanical motion to electric and then back to mechanical motion--why not drive the borehole pumps directly with wind power.

Oh, I guess you probably want the grid as backup power?

So, then I would think about the two things separately: have the wind turbines feed the grid (by appropriate means, single or 3 phase inverters), and drive the pumps from the grid.

AFAICT (As Far As I Can Tell), you are just making the situation more confusing by trying to consider a relationship between the wind turbines feeding electricity to the grid, and the borehole pumps drawing electricity from the grid.

And, I guess there is nothing wrong with feeding the 3 phase grid with single phase inverters--I'd arrange them so they are distributed across the 3 phases--feed 1 phase with 1 wind turbine, feed the other 2 phases each with 2 wind turbines.

Dear All,

Thank you for your feedback. I agree with you that this is a bit of confusing concept.

I am also new to this concept and new in wind turbine field. Let me explain this concept.

Wind is not a constant source of energy and it is always fluctuating. if we consider the concept of thermal, hydral or diesel type of power plants, the fuel is channelized through valve and forced like a jet on the turbines. But wind is very open and very unpredictable.when the wind forces the turbine blades to rotate, there are high fluctuations in the AC wave output which cannot be properly synchronised to the grid considering the magnitude and phase angle of AC voltage. So, this wild AC wave from the wind turbine generator is rectified into DC and then fed to the single phase inverter for producing a constant and smooth AC wave which will be able to match the grid AC wave. I hope this solves the confusion

Now regarding my doubt, whether the synchronisation of 3 Nos of 1 phase inverter with the 3 phase grid voltage is stable. I would request the forum members who have practical experience in this field to suggest any drawbacks or any other points to be considered while synchronising.

I Thank you for your attention and would be grateful for your suggestions.

Regards

1)Why you want to convert turbine generated 5 kW, 3 ph,50 Hz power to DC and feed to grid.

2) You may feed , generated power to grid through synchronisation panel.

Regards,

M.Ayyavaru

Synchronize AC power from turbines with Grid power with field current from Grid power. When you have excess power, you can supply back to grid.

Distribute the combined AC and where ever required connect inverter with battery back up. But for such small turbines ,it is difficult to synchronize all.

If synchronization is a problem , supply power AC generated to 5 inverter separately with Automatic change over switch with grid power, at input of each inverter with battery. One AC input only can be fed to inverter at a time.

When either of AC power is available , they will supply the consuming point and also charge the battery bank.When no power is available from either source , battery will invert DC to AC and supply power to the local consuming point.

Hope It is clear.

Thank you for your suggestion. here in this case we are not using single phase loads. the load is three phase motor pump and so we need atleast 1 set (3 Nos)of 1 phase inverters to be connected to the 3 phase grid.

i would be grateful for any further suggestions or any write up on this matter.

Regards

You can use DC input to a 3 phase output Inverter. Normally, all Inverters are built with the possibility to feed them with a DC supply. What is needed is the correct DC Voltage to achieve the desired AC voltage.

Therefore, All the Wind turbines can feed and charge the batteries then the DC is taken to the Inverter.

Synchronising the Inverter o/p to the grid: This is more tricky. The inverter must have a means to synchronise Frequency and phase voltage + sequence. This is to be checked with the manufacturer. I have not tried to synchronise Inverter O/P to the grid. But this is possible since there are some used on solar panels to feed the grid.

Thank you Sir for the information. I agree with you that it is easy to synchronise 3 phase output with 3 phase grid system. but my main worry is we are synchronising 3 individual single phase to the 3 phase grid and the output is given to 3 phase pump load. since the output wave of inverter has to correctly match the individual waves of 3 phase( since they are at 120 degree electrical apart), does this fact cause a problem.

Many manufacturers have told that the above is possible. Since i have never had a practical experience regarding this, i would wish to understand whether any practical problems have occured, whether any practical point need to be considered while synchronising the above type of system.

I thank you all the forum members for your good feedback.

Regards

Since you have a grid supply consisting of a 3phase system and since the individual pumps are 3 phase, each:

- You can have ONE Inverter getting a DC supply (only One DC Supply of the required Voltage and Power to satisfy the Load). The O/Put of this Inverter will be 3 phase, like the grid supply.

- The Problem is how to synchronise this o/put with the grid, If you really want to supply the grid even when there is power on the grid: This requires a specially built Inverter that has the capability to synchronise. You cannot just put any inverter directly on the grid and hope for the best! The O/put of such inverter is filtered at the same time.

- Check with suppliers AND follow their suggestion.

Once the grid is supplied from the wind generators, you can use the existing set up if that is what you want.

on top of the excellent answers you have received, I would add that output from your wind generators will be 0-5KW, not 5 KW.