Hi,
I am trying to find out what adjustments does the grid-tied/on-grid solar inverter make to send excess solar power back on to the grid. Basically how the inverter change the direction of power flow. Does it adjust the phase shift between the incoming supply/inverter output or adjust the magnitude of the voltage of the inverter output? Will appreciate any information and possible waveform if available.
Thank you.
Regards.
It has to do with how the inverter operates in the consatnt current or the constant voltage mode. In order to control the power flow from the inverter to the grid it is operated in the output current constant mode. The controller of the inverter forces it to source out consatnt current in the grid which has a constant voltage. When connecting a load across the output of the inverter its voltage will be constant. So it flows also a consatnt current towards the combination of the load and the grid. So, you can assume that the loads takes its power from the grid and the inverter injects its power to the grid. If its current is greater than the load current, the spurious will effectively flow in the grid. When its current is smaller than the load current it means that the load will take this deficiency current from the grid.
Best wishes
Hi there,
I think it is mainly the adjustment of phase shift between the inverter and grid voltage that helps to control the active power from the photovoltaic inverter.
As you might be well aware, active power flow in a less stressed condition (when angular difference is less) and in high (X/R) ratio, depends primarily on the angular difference whereas reactive power flow depends on the voltage difference between the buses.
You can have a look at the following paper for more information:
Have a look at:
https://www.sma.de/fileadmin/Partner/Solaracademy/Downloads/EN/IntensiveInverter-EN120910_web.pdf
Thank you very much Samundra Gurung Arnulf Jäger-Waldau . Appreciate your time to provide answers and documents, will have a look. Regards.
Dear Ruan,
The inverter is normally output current controlled while its voltage is eqaul to the voltage of the grid. When you connect at its output a load RL it will consume power 3 Vph^2/ RL and the the phase current to the load = Vph/RL.
If the current of the inverter is greater than the load current it will feed the surplus
to the network. If the current of the inverter is smaller the load will be partly fed from the grid.
We studied the grid connected inverters with different loads and found theresults which i explaind above.
We sent the paper for publishing we will notify you once it is published.
Best wishes
Abdelhalim abdelnaby Zekry Thank you sir. Looking forward to read the publication. Regards
Some inverters are smart, feeding your loads first and then any excess back into the grid. The little MPP LV2424 does this. Im trying to wire one of these up now. Check out the DIY solar forum where they are talking about this topic.
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