# power microgrid simulink - power grid injection

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Giulia on 13 May 2023
Answered: Shaik on 14 May 2023
Hello,
I'm currently working on a project on microgrid control and I have been using the Simulink "power_microgrid" model, however, I still have some doubts related to how the connection with the main grid works.
Is the three-phase generator that represents the electricity on the transmission line constant? Is the electricity injected into the migrogid constant? What does the current Iprim represent in the power system?
I'm struggling to infer the value of the power injection from the components in the model and I don't understand how it is related to the right side of the transformer.
Thank you for you help!

Shaik on 14 May 2023
Hi Giulia,
Hope you are doing good,
In the Simulink "power_microgrid" model, the three-phase generator represents the electricity supply from the main grid or utility. The power injected into the microgrid from the main grid is typically assumed to be constant unless there are variations or control mechanisms applied to it.
The value of the power injection from the main grid can be inferred from the parameters of the generator block in the model. The generator block should have properties such as rated power, voltage, and frequency. These properties determine the constant power injection from the main grid into the microgrid.
The current Iprim in the power system represents the primary side current of the transformer. In the microgrid context, it represents the current flowing from the main grid side to the microgrid side of the transformer. The transformer is responsible for stepping down the voltage from the main grid to the microgrid voltage level.
To understand the relationship between the power injection and the right side of the transformer, you need to analyze the transformer block in the model. The transformer block should have properties such as turns ratio, impedance, and losses. These properties determine the transformation of voltage and current from the primary side (main grid side) to the secondary side (microgrid side) of the transformer.
In summary, the three-phase generator in the "power_microgrid" model represents the constant power supply from the main grid to the microgrid. The power injection can be inferred from the generator block properties. The current Iprim represents the primary side current of the transformer, indicating the flow of current from the main grid to the microgrid. The transformer block determines the voltage and current transformation between the main grid and microgrid sides.
For a detailed understanding of the power flow and control mechanisms in the "power_microgrid" model, it's recommended to refer to the model documentation or the documentation of the specific blocks used in the model.