X

A PLL-Free Robust Control Strategy With Application For Grid-Tied Fuel Cell DGs Under Asymmetrical Voltage Sags

Science Contributor
on
June 13, 2019
 Leave Comment! 🤔

MIke Angelo, research assistant, tests fuel cells at the Hawaii Fuel Cell Test Facility in Honolulu, Hawaii. The test facility was established with a grant from the Office of Naval Research to conduct research on fuel cells and methane hydrates. (U.S. Navy photo by John F. Williams/Released)

The power grid of the future will see a heavy penetration of clean energy-based distributed generation (DG), such as solar photovoltaic (PV) power plants, wind turbines, and fuel cells. Such generation is often interfaced to the grid through power electronic converters (PECs). The interface commonly employs the dc-ac voltage source converter (VSC) which offers high efficiency and flexible operation through rapid control of active and reactive power.

Productive integration of clean energy resources is, for the most part, reliant on effectively controlling the interfacing converters. Over the past few years, fuel cell (FC) DGs (FCDGs) have become increasingly common as they possess many useful traits. They have a higher efficiency than diesel generators and can be readily incorporated with other types of renewable energy sources (RES). They can be used as primary energy sources or to supplement the intermittent nature of RES power.

Enormous benefits can be reaped from their integration into the power system, alongside a communications infrastructure, toward a reliable and stable grid operation, and two-way power flow. They can serve as key building blocks toward the rapidly emerging smart grid [2–5].

Literature Overview and Research Motivation

Control of VSCs with an application for FCDGs and hybrid FC-based DG has been broadly researched [1, 6–15]. An increase in DGs has led to new and stringent grid-connection regulations and standards [16] essential for maintaining stability and reliability. One such requirement is the ability of a DG source to maintain grid-connection the event of a voltage dip [17], also known as the low-voltage ride-through (LVRT) requirement. If the sag is not uniform across all the three phases (asymmetrical), the VSC must be carefully controlled to maintain grid connection and stability. In addition, there may be regulatory requirements on the DG source, such as injecting a prescribed amount of power into the grid. Under these conditions, it is common to decompose the measured asymmetrical voltages and currents into a set of symmetrical ones and control them separately [18, 19]. Such an operation is carried out using specialized and carefully synthesized phase locked loops (PLLs) e.g., the second-order generalized integrator-frequency-locked loop (SOGI-FLL) [20]. The controller design and PLL tuning tasks become nontrivial and challenging and also increase the controller’s computational complexity.

Most of the existing VSC control techniques for the grid-tied FCDG address only normal operation; asymmetrical voltage dips are not addressed. And many of the current LVRT-capable strategies for grid-connected RES utilize special PLLs, leading to extra design efforts and computational overhead. The key motivation behind this research is to address some of these limitations.

Research Contributions

This research proposes a robust, LVRT-enabled control solution for grid-tied FCDG converters having lower computational complexity and design requirements than some existing techniques. The key contributions of this work are:

These findings are described in the article entitled A PLL-free robust control scheme with application to grid-connected fuel cell DGs under balanced and unbalanced conditions, recently published in the journal Sustainable Energy Technologies and Assessments.

References:

  1. M. E. Raoufat, A. Khayatian, and A. Mojallal, “Performance Recovery of Voltage Source Converters With Application to Grid-Connected Fuel Cell DGs,” IEEE Transactions on Smart Grid, vol. 9, no. 2, pp. 1197–1204, mar 2018.
  2. S. Rahman and K. Tam, “A feasibility study of photovoltaic-fuel cell hybrid energy system,” IEEE Transactions on Energy Conversion, vol. 3, no. 1, pp. 50–55, mar 1988.
  3. P. A. Bernstein, M. Heuer, and M. Wenske, “Fuel cell system as a part of the smart grid,” in2013 IEEE Grenoble Conference. IEEE, jun 2013, pp.1–4.
  4. P. Patel, F. Jahnke, L. Lipp, T. Abdallah, N. Josefik, M. Williams, and N. Garland, “Fuel Cells And Hydrogen For Smart Grid,” 2011, pp. 305–313.
  5. J. Blanchard, “Smart energy solutions using fuel cells,” in 2011 IEEE 33rd International Telecommunications Energy Conference (INTELEC). IEEE, oct 2011, pp. 1–8.
  6. S. K. Mazumder, R. K. Burra, R. Huang, M. Tahir, and K. Acharya, “A Universal Grid-Connected Fuel-Cell Inverter for Residential Application,” IEEE Transactions on Industrial Electronics, vol. 57, no. 10, pp. 3431–3447, oct 2010.
  7. M. Jang, M. Ciobotaru, and V. G. Agelidis, “A Single-Phase Grid-Connected Fuel Cell System Based on a Boost-Inverter,” IEEE Transactions on Power Electronics, vol. 28, no. 1, pp. 279–288, jan 2013.
  8. S. A. Taher and S. Mansouri, “Optimal PI controller design for active power in grid-connected SOFC DG system,” International Journal of ElectricalPower & Energy Systems, vol. 60, pp. 268–274, sep 2014.
  9. T. Erfanmanesh and M. Dehghani, “Performance improvement in grid-connected fuel cell power plant: An LPV robust control approach,” International Journal of Electrical Power & Energy Systems, vol. 67, pp. 306–314, may 2015.
  10. H. R. Baghaee, M. Mirsalim, G. B. Gharehpetian, and H. A. Talebi, “De-centralized Sliding Mode Control of WG/PV/FC Microgrids Under Unbalanced and Nonlinear Load Conditions for On- and Off-Grid Modes,” IEEE Systems Journal, pp. 1–12, 2017.
  11. ——, “A Decentralized Power Management and Sliding Mode Control Strategy for Hybrid AC/DC Microgrids including Renewable Energy Resources,” IEEE Transactions on Industrial Informatics, pp. 1–1, 2017.
  12. M. Mohammadi and M. Nafar, “Fuzzy sliding-mode based control (FSMC) approach of hybrid micro-grid in power distribution systems,” International Journal of Electrical Power & Energy Systems, vol. 51, pp. 232–242, oct 2013.
  13. A. Eid, “Utility integration of PV-wind-fuel cell hybrid distributed generation systems under variable load demands,” International Journal of Electrical Power & Energy Systems, vol. 62, pp. 689–699, nov 2014.
  14. S. Patra, M. Narayana, S. R. Mohanty, and N. Kishor, “Power Quality Improvement in Grid-connected Photovoltaic–Fuel Cell Based Hybrid SystemUsing Robust Maximum Power Point Tracking Controller,” Electric Power Components and Systems, vol. 43, no. 20, pp. 2235–2250, dec 2015.3
  15. I. Abadlia, M. Adjabi, and H. Bouzeria, “Sliding mode based power control of grid-connected photovoltaic-hydrogen hybrid system,” International Journal of Hydrogen Energy, vol. 42, no. 47, pp. 28 171–28 182, nov 2017.
  16. H. R. Baghaee, M. Mirsalim, G. B. Gharehpetian, and H. A. Talebi, “Anew current limiting strategy and fault model to improve fault ride-through capability of inverter interfaced DERs in autonomous microgrids,” Sustainable Energy Technologies and Assessments, vol. 24, pp. 71–81, dec 2017.
  17. E. Troester, “New German grid codes for connecting PV systems to the medium voltage power grid,” 2nd International workshop on concentrating photovoltaic power plants: optical design, production, grid connection, pp.1–4, 2009.
  18. M. Mirhosseini, J. Pou, B. Karanayil, and V. G. Agelidis, “Resonant Ver-sus Conventional Controllers in Grid-Connected Photovoltaic Power PlantsUnder Unbalanced Grid Voltages,” IEEE Transactions on Sustainable Energy, vol. 7, no. 3, pp. 1124–1132, jul 2016.
  19. A. Merabet, L. Labib, A. M. Ghias, C. Ghenai, and T. Salameh, “Robust Feedback Linearizing Control with Sliding Mode Compensation for a Grid-Connected Photovoltaic Inverter System under Unbalanced Grid Voltages,” IEEE Journal of Photovoltaics, vol. 7, no. 3, pp. 828–838, 2017.
  20. P. Rodriguez, A. Luna, I. Candela, R. Mujal, R. Teodorescu, and F. Blaabjerg, “Multiresonant Frequency-Locked Loop for Grid Synchronization ofPower Converters Under Distorted Grid Conditions,” IEEE Transactions on Industrial Electronics, vol. 58, no. 1, pp. 127–138, jan 2011.
  21. A. Merabet, L. Labib, and A. M. Ghias, “Robust Model Predictive Control for Photovoltaic Inverter System with Grid Fault Ride-Through Capability.” IEEE Transactions on Smart Grid, vol. 9, no. 6, pp. 5699 – 5709,2017.
  22. V. Utkin and Hoon Lee, “Chattering Problem in Sliding Mode ControlSystems,” in International Workshop on Variable Structure Systems, 2006.VSS’06.IEEE, pp. 346–350.
  23. X. Wang, Z. Yang, B. Fan, and W. Xu, “Control Strategy of Three-PhasePhotovoltaic Inverter under Low-Voltage Ride-Through Condition,” Mathematical Problems in Engineering, vol. 2015, pp. 1–23, 2015.
  24. H. Tian, F. Gao, C. Ma, G. He, and G. Li, “Robust control of two-stage photovoltaic inverter for unbalanced low voltage ride-through operation,” Proceedings – 2014 International Power Electronics and Application Conference and Exposition, IEEE PEAC 2014, pp. 560–565, 2014.
  25. M. Eydi, J. Farhang, R. Emamalipour, and B. Asaei, “Low voltage ride-through of a two-stage photovoltaic inverter under different types of grid faults,” 4th Iranian Conference on Renewable Energy and Distributed Generation, ICREDG 2016, pp. 78–83, 2017.4
  26. N. Zhang, H. Tang, and C. Yao, “A Systematic Method for Designing a PR Controller and Active Damping of the LCL Filter for Single-Phase Grid-Connected PV Inverters,” Energies, vol. 7, no. 6, pp. 3934–3954, jun 2014.
  27. Chenlei Bao, Xinbo Ruan, Xuehua Wang, Weiwei Li, Donghua Pan, and Kailei Weng, “Step-by-Step Controller Design for LCL-Type Grid-Connected Inverter with Capacitor-Current-Feedback Active-Damping,” IEEE Transactions on Power Electronics, vol. 29, no. 3, pp. 1239–1253, mar 2014.
  28. G. Bonan, J. Flores, D. Coutinho, L. Pereira, and J. Gomes da Silva, “Repetitive controller design for uninterruptible power supplies: An LMI approach,” in IECON 2011 – 37th Annual Conference of the IEEE Industrial Electronics Society. IEEE, nov 2011, pp. 704–709.
  29. Q.-C. Zhong and D. Rees, “Control of Uncertain LTI Systems Based on an Uncertainty and Disturbance Estimator,” Journal of Dynamic Systems, Measurement, and Control, vol. 126, no. 4, p. 905, 2004. [Online]. Available: https://asmedigitalcollection.asme.org/dynamicsystems/article-abstract/126/4/905/471534/Control-of-Uncertain-LTI-Systems-Based-on-an?redirectedFrom=fulltext
  30. T. Inoue, M. Nakano, T. Kubo, S. Matsumoto, and H. Baba, “High Accuracy Control of a Proton Synchrotron Magnet Power Supply,” IFAC Proceedings Volumes, vol. 14, no. 2, pp. 3137–3142, aug 1981.
  31. B. A. Francis and W. M. Wonham, “The internal model principle for linear multivariable regulators,” Applied Mathematics & Optimization, vol. 2, no. 2, pp. 170-194, jun 1975.
Leave a Comment