three phase grid connected inverter

[FF003]

Hi everyone,

I am working on simulation of three phase grid connected inverter with two transformers. The inverter side transformer is delta connection, so I connected the ground of my inverter to run the simulation, but after connecting the ground of inverter, the ripple in phase voltages at the PCC increases. So, I am not sure whether this is normal or I need to design my filter again. I will attach the figure of phase voltages at the PCC. Thank you for your help.

 

[BradtheRad]

The 2-AC-source scheme to generate 3-phase supplies seems workable to some extent. At least in my own simulations the current flow operates in 3 equally staggered phases.

However I wonder about current flow through a mix of 1 transformer and 2 transformers, and whether and how their flux fields build and collapse at the proper times.

Notice that another way to derive the same scheme is to begin normally with 3 AC sources arranged as conventional 3-phase delta, and then remove 1 source (while keeping its load in place). This does not prevent proper functioning afterward. The loads correctly continue to receive power.

However, yes, this does introduce power factor error which could resemble the problem you describe. Even as I remove 1 raw generator out of 3, I observe power factor error in the two remaining generators. No reactive component is present. No inductors or capacitors.

And if 2 transformers are contributing then it must depend on the accuracy of the simulator, as to how 2 transformer create a pattern of flux fields building and collapsing (120 degrees out of phase) and power their own loads as well as a third load 120 degrees out of phase with each.

 

[FvM]

You may want to show a schematic for clarification.
Above waveform shows PWM carrier superimposed to 50 Hz grid voltage, may that's what you mean with increased ripple.

 

[FF003]

You may want to show a schematic for clarification.
Above waveform shows PWM carrier superimposed to 50 Hz grid voltage, may that's what you mean with increased ripple.

Thank you for your reply. Please see the attached schematic of the system. With grounding the inverter, the ground of grid and inverter are connected. I think this is the problem. But by removing that I cannot run the simulation. My capacitor filter is in delta mode connection.

 

[Easy peasy]

this question by the OP is set out very poorly, we can't see the sw freq or the supposed filter - no mention of L & C values - or of any damping - are we supposed to have a crystal ball here ?