This paper presents a comparison between a proportional-integral controller, low pass filters, and the linear quadratic regulator in dealing with the task of eliminating harmonic currents in the grid-connected photovoltaic system. A brief review of the existing methods applied to mitigate harmonic currents is presented. The Perturb & Observe technique was employed for maximum power point tracking. The PI control, low pass filters, and the linear quadratic regulator are discussed in detail in terms of their control strategies. The grid current was analyzed in the system with all three of the controllers applied to control the voltage source inverter of the solar photovoltaic system connected to the grid through an L filter and LCL filter and simulated in MATLAB/SIMULINK. The simulation results obtained have proven the robustness of the linear quadratic regulator over other methods. The technique lowers the grid current total harmonic distortion from 7.85% to 2.13%.

• Arab, N., Vahedi, H., & Al-Haddad, K. (2020). LQR control of single-phase grid-tied PUC5 inverter with LCL filter. IEEE Transactions on Industrial Electronics, 67(1), 297-307. doi: 10.1109/TIE.2019.2897544

• Arora, R., & Arora, R. (2018). Experimental investigations and exergetic assessment of 1 kW solar PV plant. Pertanika Journal of Science and Technology, 26(4), 1881-1897.

• Azzam-Jai, A., & Ouassaid, M. (2018, November 21-23). A multifunctional PV-based shunt active power filter using neural network controller. In Proceedings of International Symposium on Advanced Electrical and Communication Technologies (ISAECT) (pp. 1-6). Rabat, Morocco. doi: 10.1109/ISAECT.2018.8618848

• Bag, A., Subudhi, B., & Ray, P. K. (2016, January 28-30). Grid integration of PV system with active power filtering. In Proceedings of 2016 2nd International Conference on Control, Instrumentation, Energy & Communication (CIEC) (pp. 372-376). Kolkata, India. doi: 10.1109/CIEC.2016.7513810

• Belaidi, R., Haddouche, A., Fathi, M., Larafi, M. M., & Kaci, G. M. (2016, November 14-17). Performance of grid-connected PV system based on SAPF for power quality improvement. In Proceedings of 2016 International Renewable and Sustainable Energy Conference (IRSEC) (pp. 542-545). Marrakech, Morocco. doi: 10.1109/IRSEC.2016.7984050

• Chtouki, I., Zazi, M., Feddi, M., & Rayyam, M. (2016, November 14-17). LCL filter with passive damping for PV system connected to the network. In Proceedings of 2016 International Renewable and Sustainable Energy Conference (IRSEC) (pp. 692-697). Marrakech, Morocco. doi: 10.1109/IRSEC.2016.7984020

• Colque, J. C., Ruppert, E., & Azcue, J. L. (2018, November 12-14). Performance analysis of a three-phase photovoltaic generation system with active filtering functions connected to the electrical grid. In Proceedings of 13th IEEE International Conference on Industry Applications (INDUSCON) (pp. 249-255). São Paulo, Brazil, Brazil. doi: 10.1109/INDUSCON.2018.8627249

• Darwish, A., Abdel-Khalik, A. S., Elserougi, A., Ahmed, S., & Massoud, A. (2013). Fault current contribution scenarios for grid-connected voltage source inverter-based distributed generation with an LCL filter. Electric Power Systems Research, 104(November 2013), 93-103. doi: https://doi.org/10.1016/j.epsr.2013.06.020

• Fekkak, B., Menaa, M., & Boussahoua, B. (2018). Control of transformerless grid-connected PV system using average models of power electronics converters with MATLAB/Simulink. Solar Energy, 173(October 2018), 804-813. doi: https://doi.org/10.1016/j.solener.2018.08.012

• Geddada, N., Mishra, M. K., & Kumar, M. V. M. (2015). LCL filter with passive damping for DSTATCOM using PI and HC regulators in dq0 current controller for load compensation. Sustainable Energy, Grids and Networks, 2(June 2015), 1-14. doi: https://doi.org/10.1016/j.segan.2015.02.001

• Jain, V., & Singh, B. (2019). A multiple improved notch filter-based control for a single-stage PV system tied to a weak grid. Proceedings of 2019 IEEE Transactions on Sustainable Energy, 10(1), 238-247. doi: 10.1109/TSTE.2018.2831704

• Jannesar, M. R., Sedighi, A., Savaghebi, M., Moghaddam, A. A., & Guerrero, J. M. (2018, September 17-21). Optimal passive filter planning in distribution networks with nonlinear loads and photovoltaic systems. In Proceedings of 20th European Conference on Power Electronics and Applications (EPE’18 ECCE Europe) (pp. 1-9). Riga, Latvia.

• Kandpal, B., Tomar, K. P., Hussain, I., & Singh. B. (2017, October 26-28). Adaptive control of a grid-connected SPV system with DSTATCOM capabilities. In Proceedings of 4th IEEE Uttar Pradesh Section International Conference on Electrical, Computer, and Electronics (UPCON) (pp. 452 - 456). Mathura, India. doi: 10.1109/UPCON.2017.8251090

• Khomsi, C., Bouzid, M., Jelassi, K., & Champenois, G. (2018, March 20-22). Harmonic current compensation in a single-phase grid-connected photovoltaic system sypplying nonlinear load. In Proceedings of The 9th International Renewable Energy Congress (IREC). Hammamet, Tunisie. doi: 10.1109/IREC.2018.8362520

• Krama, A. Zellouma, L., & Rabhi, B. (2016, November 15-17). Improved control of shunt active power filter connected to a photovoltaic system using the technique of direct power control. In Proceedings of 8th International Conference on Modelling, Identification, and Control (ICMIC) (pp. 880-885). Algiers, Algeria. doi: 10.1109/ICMIC.2016.7804239

• Kumar, D. (2015, March 5-7). Modeling, simulation, and performance analysis of a grid-tied voltage source inverter based photovoltaic system underbalanced and non-linear load conditions. In Proceedings of 2015 IEEE International Conference on Electrical, Computer, and Communication Technologies (ICECCT) (pp. 1-5). Coimbatore, India. doi: 10.1109/ICECCT.2015.7225965

• Mohamed, J. M., Rasul, A., Khang, H. V., & Kolhe, M. (2017, August 11-14). Harmonic mitigation of a grid-connected photovoltaic system using shunt active filter. In Proceedings of 20th International Conference on Electrical Machines and Systems (ICEMS) (pp. 1-5). Sydney, NSW, Australia. doi: 10.1109/ICEMS.2017.8056401

• Naderipoura, A., Zinb, A. A. M., Habibuddinc, M. H., Khokhar, S., & Kazemi, A. (2015, October 19-20). Improved control of shunt active power filter using harmony search algorithm. In Proceedings of 2015 IEEE Conference on Energy Conversion (CENCON) (pp. 90-95). Johor Bahru, Malaysia. doi: 10.1109/CENCON.2015.7409519

• Oonsivilai, A., Zongo, O. A., & Oonsivilai, R. (2019). Stability enhancement of doubly fed induction generator using a linear quadratic regulator. GMSARN International Journal, 13(4), 194-201.

• Ouchen, S., Abdeddaim, S., Betka, A., & Menadi, A. (2016). Experimental validation of sliding mode-predictive direct power control of a grid-connected photovoltaic system, feeding a nonlinear load. Solar Energy, 137(November 2016), 328-336. doi: https://doi.org/10.1016/j.solener.2016.08.031

• Pereira, H. A., da Mataa, G. L. E., Xavierc, L. S., & Cupertinob, A. F. (2019). Flexible harmonic current compensation strategy applied in single and three-phase photovoltaic inverters. Electrical Power and Energy Systems, 104(January 2019), 358-369. doi: https://doi.org/10.1016/j.ijepes.2018.07.017

• Peterson, B., Rens, J., Meyer, J., & Botha, G. (2017, September 20-22). Evaluation of harmonic distortion from multiple renewable sources at a distribution substation. In Proceedings of 2017 IEEE International Workshop on Applied Measurements for Power Systems (AMPS) (pp. 1-6). Liverpool, UK. doi: 10.1109/AMPS.2017.8078327

• Singh, A. K., Hussain, I., & Singh, B. (2018, January 31-February 2). An improved adaptive P&O technique for two-stage grid interfaced SPVECS. In Proceedings of 2018 IEEE International Conference on Industrial Electronics for Sustainable Energy Systems (IESES) (pp. 320-325). Hamilton, New Zealand. doi: 10.1109/IESES.2018.8349896

• Srinivas, V. L., Singh, B., & Mishra, S. (2019). Fault ride-through strategy for two-stage GPV system enabling load compensation capabilities using EKF algorithm. Proceedings of 2019 IEEE Transactions on Industrial Electronics, 66(11), 8913-8924. doi: 10.1109/TIE.2019.2899546

• Upaphai, W., Bunyawanichakul, P., & Janthong, M. (2019). Design of self-tuning fuzzy PID controllers for position tracking control of autonomous agricultural tractor. Pertanika Journal of Science and Technology, 27(1), 263-280.

• Xie, B., Mao, M., Zhou, L., Wan, Y., & Hao, G. (2020). Systematic design of linear quadratic regulator for digitally controlled grid-connected inverters. IET Power Electron, 13(3), 557-567.

• Yousef, M. Y., Ismail, M. M., & El-Masry, S. M. (2018, December 18-20). The effect of grid-connected photovoltaic location and penetration level

• on total harmonic distortion. In Proceedings of Twentieth International Middle East Power Systems Conference (MEPCON) (pp. 141-145). Cairo, Egypt. doi: 10.1109/MEPCON.2018.8635252