Hi Kanuri Venkata Mohana,

If you can model the Grid-controlled Converter in Simulink based on a set of differential equations, then you should be able to systematically design an appropriate PI controller using the info from the same set of differential equations.

From the differential equations, you will know in which loop to insert the PI controller block. Naturally, the control goal is to (manually or computationally) tune the P and I parameters such that the system is stable and produces the desired output.

the easy way to design it, you can Drag and Drop the PID Controller From The List in Simulink and Drop it to you work and then open PID controller and Choose PI Instead of PID Controller.

Some references might be helpful for you.

- For the Strong Power Grid:

[1] C. Bao, X. Ruan, X. Wang, W. Li, D. Pan and K. Weng, "Step-by-Step Controller Design for LCL-Type Grid-Connected Inverter with Capacitor–Current-Feedback Active-Damping," in IEEE Transactions on Power Electronics, vol. 29, no. 3, pp. 1239-1253, March 2014.

[2] L. Harnefors and H. -. Nee, "Model-based current control of AC machines using the internal model control method," in IEEE Transactions on Industry Applications, vol. 34, no. 1, pp. 133-141, Jan.-Feb. 1998.

[3] D. Zhou and F. Blaabjerg, "Bandwidth oriented proportional-integral controller design for back-to-back power converters in DFIG wind turbine system," in IET Renewable Power Generation, vol. 11, no. 7, pp. 941-951, 7 6 2017.

- For the Weak Power Grid (Considering the Grid Impedance):

[4] S. Zhou et al., "An Improved Design of Current Controller for LCL-Type Grid-Connected Converter to Reduce Negative Effect of PLL in Weak Grid," in IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 6, no. 2, pp. 648-663, June 2018.