Single Phase Inverters on 208 3 Phase

[ggunn]

I might be a bit out of my depths here, but the Growatt WIT 100K-HU-US (three phase inverter, configured as either 3P3W+PE or 3P4W+PE) can be connected with 100% imbalance (i.e. one live conductor and neutral). The default voltage is 277 V, but the EPS voltage can be reconfigured to 127 V with the default firmware. I am assuming it has reduced power output at the lower voltage.

I am not familiar with it.

 

[bellington]

I used a fixed 32-amp current source to possibly simulate the inverter action. In this circuit, 32 amps is injected into a 416/240 Y in a L-N circuit the right side, almost cutting the AC generator output on the left in half, at peak positive output, connected to 480/277 Y AC generators connected L-N:

https://tinyurl.com/2botr2xb

In this circuit the fixed 32-amp current source on a 208/120 Y in a L-L circuit seems to do very little to reduce the output of the same AC generators on the 480/277 circuit on the left, at peak positive output:

https://tinyurl.com/25uvxm79

Why?

 

[Carultch]

I used a fixed 32-amp current source to possibly simulate the inverter action. In this circuit, 32 amps is injected into a 416/240 Y in a L-N circuit the right side, almost cutting the AC generator output on the left in half, at peak positive output, connected to 480/277 Y AC generators connected L-N:

https://tinyurl.com/2botr2xb

In this circuit the fixed 32-amp current source on a 208/120 Y in a L-L circuit seems to do very little to reduce the output of the same AC generators on the 480/277 circuit on the left, at peak positive output:

https://tinyurl.com/25uvxm79

Why?

What you've implemented are DC current sources. Since a transformer cannot transmit DC power in the steady state, A DC current source on the secondary of the transformer cannot transfer power to the primary side of the transformer. This is the fundamental reason why AC won "the current wars" of the 19th century; transformers were the only known way to convert voltages at the time, and transformers would only work with AC.

I don't think Falstad has voltage-following current sources for AC. You'd need to construct an op-amp configuration that can behave as a voltage-following AC current source.

 

[bellington]

What you've implemented are DC current sources. Since a transformer cannot transmit DC power in the steady state, A DC current source on the secondary of the transformer cannot transfer power to the primary side of the transformer. This is the fundamental reason why AC won "the current wars" of the 19th century; transformers were the only known way to convert voltages at the time, and transformers would only work with AC.

I don't think Falstad has voltage-following current sources for AC. You'd need to construct an op-amp configuration that can behave as a voltage-following AC current source.

Agreed a transformer does not transmit DC power. But, the current source, riding on top of the AC source, reduced the output of the AC source at peak voltage, with 15.35 kW still consumed by the 10 ohm resistor on the left side.



Without the current source on the right side, the AC source on the left had to deliver the total 19.061 kW of power to the two resistors.


Why does it appear that the current source is reducing the power demand of the AC source on the left, unless the current source is following the AC?

 

[ggunn]

Agreed a transformer does not transmit DC power. But, the current source, riding on top of the AC source, reduced the output of the AC source at peak voltage, with 15.35 kW still consumed by the 10 ohm resistor on the left side.

View attachment 2570565

Without the current source on the right side, the AC source on the left had to deliver the total 19.061 kW of power to the two resistors.
View attachment 2570566

Why does it appear that the current source is reducing the power demand of the AC source on the left, unless the current source is following the AC?

I'm not doing a deep dive into any of that, but why would you (or do you) have any DC sources at all in your analysis? There is no DC component to a grid tied PV inverter's output, nor is there any in the grid source.

 

[ggunn]

I'm not doing a deep dive into any of that, but why would you (or do you) have any DC sources at all in your analysis? There is no DC component to a grid tied PV inverter's output, nor is there any in the grid source.

Is there a point to any of this? In the beginning you were trying to show that there would be a difference between the VA delivered by three single phase inverters of a particular kW output rating at the voltages at which they would be connected, connected phase to neutral to a transformer, than that of another set of inverters of the same output rating at the voltages at which they would be connected, connected phase to phase to the same transformer; are you still down that rabbit hole?

 

[tortuga]

You should check out mathworks power grid modeling, I think what your using is aimed at low voltage electronics.

Power Grids - MATLAB & Simulink

Power system networks and loadflow and harmonic analysis

www.mathworks.com