Sathans SUHAG, Rahul SHARMA

Supercapacitor utilization for power smoothening and stability improvement of a hybrid energy system in a weak grid environment

In this paper, a novel control scheme based on the application of a supercapacitor (SC) is proposed for power smoothening and stability improvement of a hybrid energy system (HES) in weak grid conditions. The basic property of fast charging/discharging of the SC is utilized to design the proposed control. In weak grid conditions, the control structure is proposed for power smoothening and DC link voltage regulation with the help of the SC. Moreover, the stability is increased, ripples in voltage are reduced, there is fast dynamic response, and oscillations are damped out under different conditions. In conventional control, voltage controller stability is the main concern under weak grid conditions. On the other hand, the proposed control scheme has independent voltage controller stability in weak grid conditions. Drawbacks of the conventional scheme due to coupling components and large grid impedance in a weak grid are illustrated mathematically. The design and the steady-state stability analysis of the proposed control scheme are explained and compared with the conventional scheme. The HES is modeled and simulated in MATLAB/Simulink to verify the enhanced performance of the proposed scheme. In comparison with the conventional control strategy, the proposed scheme has an improved DC link voltage pro le and smoothened power, resulting in the fast dynamic response of the HES connected to the weak grid.

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[1] Sharma R, Sathans. Survey on hybrid (wind/solar) renewable energy system and associated control issues. In: Proceedings of the IEEE 6th India International Conference on Power Electronics; 8{10 December 2014; India. New York, NY, USA: IEEE. pp. 1-6.
[2] Nehrir H, Wang C, Strunz K, Aki H, Ramakumar R, Bing J, Miao Z, Salameh Z. A review of hybrid renew- able/alternative energy systems for electric power generation: con gurations, control, and applications. IEEE T Sustain Energy 2011; 2: 392-403.
[3] Han H, Hou X, Yang J, Wu J, Su M, Guerrero JM. Review of power sharing control strategies for islanding operation of AC microgrids. IEEE T Smart Grid 2016; 7: 200-215.
[4] Davari M, Mohamed YARI. Robust vector control of a very weak-grid-connected voltage-source converter considering the phase-locked loop dynamics. IEEE T Power Electr 2017; 32: 977-994.
[5] Pena-Alzola R, Liserre M, Blaabjerg F, Ordonez M, Yang YH. LCL-Filter design for robust active damping in grid-connected converters. IEEE T Ind Informa 2014; 10: 2192-2203.
[6] Tran TV, Chun TW, Lee HH, Kim HG, Nho EC. PLL-based seamless transfer control between grid-connected and islanding modes in grid-connected inverters. IEEE T Power Electr 2014; 29: 5218-5228.
[7] Xu JM, Xie SJ, Tang T. Improved control strategy with grid-voltage feedforward for LCL- lter-based inverter connected to weak grid. IET Power Electron 2014; 7: 2660-2671.
[8] Song Y, Nian H. Sinusoidal output current implementation of DFIG using repetitive control under a generalized harmonic power grid with frequency deviation. IEEE T Power Electr 2015; 30: 6751-6762.
[9] Zhang S, Jiang S, Lu X, Ge BM, Peng FZ. Resonance issues and damping techniques for grid-connected inverters with long transmission cable. IEEE T Power Electr 2014; 29: 110-120.
[10] Suul JA, D'Arco S, Rodrguez P, Molinas M. Impedance-compensated grid synchronisation for extending the stability range of weak grids with voltage source converters. IET Gener Transm Dis 2016; 10: 1315-1326.
[11] Chen X, Wang Y, Zhang Y, Chen J, Gong C. Impedance-phased dynamic control method for grid-connected inverters in a weak grid. IEEE T Power Electr 2017; 32: 274-283.
[12] Abusara M, Sharkh S, Zanchetta P. Adaptive repetitive control with feedforward scheme for grid-connected invert- ers. IET Power Electron 2015; 8: 1403-1410.
[13] Sun J. Small-signal methods for AC distributed power systems|A review. IEEE T Power Electr 2009; 24: 2545- 2554.
[14] Egea-Alvarez A, Fekriasl S, Hassan F, Gomis-Bellmunt O. Advanced vector control for voltage source converters connected to weak grids. IEEE T Power Syst 2015; 30: 3072-3081.
[15] Huang Y, Yuan X, Hu J, Zhou P, Wang D. DC-bus voltage control stability affected by AC-bus voltage control in VSCs connected to weak AC grids. IEEE J Emerg Sel Top Power Electron 2016; 4: 445-458.
[16] Gee AM, Robinson FVP, Dunn RW. Analysis of battery lifetime extension in a small-scale wind-energy system using supercapacitors. IEEE T Energy Convers 2013; 28: 24-33.
[17] Reznik A, Sim~oes GM, Al-Durra A, Muyeen SM. LCL lter design and performance analysis for grid-interconnected systems. IEEE Trans Ind Appl 2014; 50: 1225-1232.
[18] Xu J, Xie S, Tang T. Evaluations of current control in weak grid case for grid-connected LCL- ltered inverter. IET Power Electron 2013; 6: 227-234.
[19] Chen X, Wang Y, Zhang Y, Chen J, Gong C. Hybrid damping adaptive control scheme for grid-connected inverters in a weak grid. IET Power Electron 2016; 9: 2760-2768.
[20] Kollimalla SK, Mishra MK, Narasamma NL. Design and analysis of novel control strategy for battery and super- capacitor storage system. IEEE T Sustain Energy 2014; 5: 1137-1144.
[21] Chetrai S, Azli N, Ayob S, Mortezaei A. Design of a current mode PI controller for a single-phase PWM inverter. In: Proceedings of the IEEE Applied Power Electronics Colloquium; 18{19 April 2011; Johor Bahru, Malaysia. New York, NY, USA: IEEE. pp. 180-184.
[22] Jin Y, Xu J, Zhou G, Mi C. Small-signal modeling and analysis of improved digital peak current control of boost converter. In: Proceedings of the IEEE 6th International Power Electronics Motion Control Conference; 17{20 May 2009; China. New York, NY, USA: IEEE. pp. 326-330.