In this paper, particle swarm optimization (PSO) optimized PI controlled five level UPFC is proposed for a double circuit transmission line. To enhance UPFC performance, a different approach is considered here. It uses simplified power system models to derive the decoupled power controllers, but detailed modeling of the UPFC power converters improves their ride-through capability. This paper introduces decoupled linear UPFC power controllers to obtain the reference ac voltages and currents for the two back-to-back-connected three-phase five-level NPC converters that enforce active and reactive power control in the transmission line. This paper proposes three main contributions to increase the dc-link voltage steadiness of multilevel UPFCs under line faults: 1) decoupled active and reactive linear power controllers; 2) real-time PWM generation; and 3) balancing of dc capacitor voltages. The MATLAB/SIMULINK model for the proposed circuit with PSO-optimized PI controlled five level UPFC is shown here with the results.
This paper proposes PSO optimization for tuning of PI controller of UPFC which controls active and reactive power flow in double circuit transmission line. Two five level NPC multilevel converters are adopted as shunt and series converters which are connected in back-to-back. The proposed UPFC control strategy includes: 1) decoupled active and reactive linear power control; 2) real-time PWM generation in both UPFC multilevel converters, dc-link voltage control gains with low sensitivity to dc link current, and 3) the balancing of the dc-link capacitor voltages using both multilevel converters. The dc-link capacitor voltages, which are usually balanced using only one of the multilevel converters, are balanced using both series and shunt multilevel converters, the results shows that the proposed technique with PSO gives better results. Optimization by PSO for PI controller gains improves tracking capacity of active and reactive power flow.
 J. Steffy Amirtham & V. Uma M.E, “Optimal Location of Unified Power Flow Controller Enhancing System Security,” IEEE Second International Conference On Science Technology Engineering and Management (ICONSTEM) , 2016, pp. 326-331.
 Y. Zhang, G. Lu, W. A. Khan, Y. Zhang and Q. Zhu, \"Direct Power Flow Controller—A New Concept in Power Transmission,\" in IEEE Transactions on Power Electronics, vol. 35, no. 2, pp. 2067-2076, Feb.2020.
 Y. Zhang, S. Guan and Y. Zhang, \"Single-Stage AC–AC Converter With Controllable Phase and Amplitude,\" in IEEE Transactions on Power Electronics, vol. 34, no. 7, pp. 6991-7000, July 2019, doi: 10.1109/TPEL.2018.2875093
 Ghadimi N, Afkousi-Paqaleh A and Emamhosseini A (2013) A PSObased fuzzy long-term multi-objective optimization approach for placement and parameter setting of UPFC. Arabian Journal for Science and Engineering 39(4): 2953–2963
 Shaheen H, Rashed G and Cheng S (2010) Application and comparison of computational intelligence techniques for optimal location and parameter setting of UPFC. Engineering Applications of Artificial Intelligence 23(2): 203–216.
 Hung GK, Chang CC and Chen CL (2003) Automatic phase-shift method for islanding detection of grid-connected photovoltaic inverters. IEEE Transactions on Energy Conversion 18(1): 169–173.
 Hunter L, Booth C, Finney S, et al. MVDC network balancing for increased penetration of low carbon technologies. Paper presented at: 8th IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe); October 2018; Sarajevo, Bosnia-Herzegovina. https://doi.org/10.1109/ISGTEurope.2018.8571838.
 . Chiandone M, Sulliogi G, Milano F, et al. Back-to-Back MVDC link for distribution system active connection. A network study. Paper presented at: 3rd International Conference on Renewable Energy Research and Applications (ICRERA); January 2015; Milwaukee, WI. https://doi.org/10.1109/ICRERA.2014.7016536.
 H. E. Tooraji and N. Abdolamir, “Improving Power Quality Parameters in AC Transmission Systems Using Unified Power Flow Controller,” Research Journal of Recent Sciences, Vol.2, No.4, pp.84-90, Apr. 2013.
 N. G. Higorani and L. Gyugyi, Understanding FACTS: Concepts and Technology of Flexible AC Transmission Systems, WileyIEEE Press, 2019.
 ] J. Liu, Z. Xu, W. Fei, et al., “Comprehensive power flow analyses and novel feedforward coordination control strategy for MMCbased UPFC,” Energies, vol. 12, no. 5, 2019