I am trying to simulate a LCL filter based Grid Connected inverter in PSIM simulation software. My circuit is attached for reference.
As can be seen, a single DC source is used to simulate DC link. Also the negative of the DC source is grounded which is also the only ground in system. The grid and inverter filter are not grounded. Any clarification regarding whether this is correct or not will be helpful. A single resistor is used to simulate the load connected to the grid as well as inverter output.
My query is regarding the currents in the inverter side and grid side inductors. The waveforms are attached. The waveform of load resistance current is also attached.
As can be seen both the waveforms of inverter side and grid side inductors currents have DC offsets. The waveform of load resistance current is pure sinusoidal without any offset.
I would like to ask whether the simulation is correct and how can i remove these DC offsets from inverter side and grid side inductors currents? I have tried splitting DC source into two sources and grounding the middle point with no change in inductor currents. Also the difference in magnitude of inductors currents and load resistance current is significant. Any comments on this difference will also be helpful.
I would highly appreciate any help.
Mohamed Azab Thanks for your help. I ran simulation for 10 periods of grid voltage, however the results remains the same.
Mohamed Azab The circuit is currently running in open loop. Can you please elaborate about what you mean?
You need to design a current controller in order to control the current being injecting into the grid through L1 and L2. Following papers will help you in designing LCL filter and PR control.
Conference Paper Step-by-step design and control of LCL filter based three ph...
Article Control of Single-Stage Single-Phase PV Inverter
Article Proportional-resonant controllers and filters for grid-conne...
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