access icon free Modelling and robust control of digitally controlled large-scale PV plants

© The Institution of Engineering and Technology
Received 26/07/2019, Accepted 17/01/2020, Revised 18/12/2019, Published 20/01/2020

Large-scale photovoltaic (PV) plants may be destabilised by the large grid impedance introduced by transformers and long transmission lines. When considering the digital control delay of grid-connected inverters, the problem will become more serious. In this study, the equivalent impedance model of digitally controlled large-scale PV plants is established, considering that the values of the parameters of the LCL filter follow Gaussian distributions. Then, the system stability can be analysed conveniently, and the stability analysis shows that the digital control delay will make the system robust to large grid impedance worse. To enhance the stability-robustness of the system, an H ∞ robust controller is proposed in this study. By properly selecting the weighting functions, the desired tracking error performance and robustness are achieved on the basis of the mixed-sensitivity optimisation control design. Compared with the traditional dual current loop control strategy, the H ∞ robust controller improves significantly the system stability-robustness against large grid impedance. Finally, simulation and experimental tests are carried out in this study, and the results demonstrate the effectiveness of the proposed H ∞ robust controller.

Inspec keywords: H∞ control; photovoltaic power systems; power grids; robust control; digital control; control system synthesis; invertors; power generation control; Gaussian distribution; closed loop systems; power system stability

Other keywords: large-scale photovoltaic plants; desired tracking error performance; system stability; system stability-robustness; LCL filter; equivalent impedance model; robust controller; grid-connected inverters; traditional dual current loop control strategy; grid impedance; digital control delay; mixed-sensitivity optimisation control design; robust control; digitally controlled large-scale PV plants; Gaussian distributions

Subjects: Control of electric power systems; Solar power stations and photovoltaic power systems; Optimal control; Control system analysis and synthesis methods; DC-AC power convertors (invertors); Stability in control theory; Power system control; Other topics in statistics; Other topics in statistics

References

    1. 1)
      • 19. Tang, Y., Loh, P.C., Wang, P., et al: ‘Exploring inherent damping characteristic of LCL-filters for three-phase grid- connected voltage source inverters’, IEEE Trans. Power. Electron., 2012, 27, (3), pp. 1433–1443.
    2. 2)
      • 8. Zhang, S., Jiang, S., Lu, X., et al: ‘Resonance issues and damping techniques for grid-connected inverters with long transmission cable’, IEEE Trans. Power. Electron., 2013, 29, (1), pp. 110–120.
    3. 3)
      • 7. Reznik, A., Simões, M.G., Al-Durra, A., et al: ‘LCL filter design and performance analysis for grid-interconnected systems’, IEEE Trans. Ind. Appl., 2014, 50, (2), pp. 1225–1232.
    4. 4)
      • 9. Zheng, C., Zhou, L., Yu, X., et al: ‘Online phase margin compensation for a grid-tied inverter to improve its robustness to grid impedance variation’, IET Power. Electron., 2016, 9, (4), pp. 611–620.
    5. 5)
      • 36. Xie, B., Zhou, L., Mao, M.: ‘Analysis of resonance and harmonic amplification for grid-connected inverters’, IET Gener. Transm. Distrib., 2019, 13, (10), pp. 1821–1828.
    6. 6)
      • 31. Kahrobaeian, A., Mohamed, Y.A-R.I.: ‘Robust single-loop direct current control of LCL-filtered converter-based DG units in grid-connected and autonomous microgrid modes’, IEEE Trans. Power Electron., 2014, 29, (10), pp. 5605–5619.
    7. 7)
      • 26. Li, Y.W., Vilathgamuwa, D.M., Blaabjerg, F., et al: ‘A robust control scheme for medium-voltage-level DVR implementation’, IEEE Trans. Ind. Electron., 2007, 54, (4), pp. 2249–2261.
    8. 8)
      • 20. Parker, S.G., McGrath, B.P., Holmes, D.G.: ‘Regions of active damping control for LCL filters’, IEEE Trans. Ind. Appl., 2014, 50, (1), pp. 424–432.
    9. 9)
      • 25. Lee, T.-S., Chiang, S.-J., Chang, J.-M.: ‘H∞ loop-shaping controller designs for the single-phase UPS inverters’, IEEE Trans. Power Electron., 2001, 16, (4), pp. 473–481.
    10. 10)
      • 22. Xie, B., Zhou, L., Zheng, C., et al: ‘Stability and resonance analysis and improved design of N-paralleled grid-connected PV inverters coupled due to grid impedance’. Proc. IEEE 33th Applied Power Electronics Conf. Exposition, San Antonio, TX, USA, 2018, pp. 362–367.
    11. 11)
      • 6. Liserre, M., Blaabjerg, F., Hansen, S.: ‘Design and control of an LCL-filter-based three-phase active rectifier’, IEEE Trans. Ind. Appl., 2005, 41, (5), pp. 1281–1291.
    12. 12)
      • 21. Zou, C., Liu, B., Duan, S., et al: ‘Influence of delay on system stability and delay optimization of grid-connected inverters with LCL filter’, IEEE Trans. Ind. Inf., 2014, 10, (3), pp. 1775–1784.
    13. 13)
      • 14. Dannehl, J., Liserre, M., Fuchs, F.W.: ‘Filter-based active damping of voltage source converters with LCL filter’, IEEE Trans. Ind. Electron., 2011, 58, (8), pp. 3623–3633.
    14. 14)
      • 23. Li, Z., Zang, C., Zeng, P., et al: ‘Control of a grid-forming inverter based on sliding-mode and mixed H2/H∞ control’, IEEE Trans. Ind. Electron., 2017, 64, (5), pp. 3862–3872.
    15. 15)
      • 15. Säıd-Romdhane, M.B., Naouar, M.W., Slama-Belkhodja, I., et al: ‘Robust active damping methods for LCL filter- based grid-connected converters’, IEEE Trans. Power. Electron., 2017, 32, (9), pp. 6739–6750.
    16. 16)
      • 27. Li, Y.W., Blaabjerg, F., Vilathgamuwa, D.M., et al: ‘Design and comparison of high performance stationary-frame controllers for DVR implementation’, IEEE Trans. Power Electron., 2007, 22, (2), pp. 602–612.
    17. 17)
      • 5. Agorreta, J.L., Borrega, M., Lopez, J., et al: ‘Modeling and control of N-paralleled grid-connected inverters with LCL filter coupled due to grid impedance in PV plants’, IEEE Trans. Power. Electron., 2011, 26, (3), pp. 270–285.
    18. 18)
      • 29. Li, Y.W., Vilathgamuwa, D.M., Loh, P.C.: ‘Robust control scheme for a microgrid with PFC capacitor connected’, IEEE Trans. Ind. Appl., 2007, 43, (5), pp. 1172–1182.
    19. 19)
      • 30. Yang, S., Lei, Q., Peng, F.Z., et al: ‘A robust control scheme for grid-connected voltage-source inverters’, IEEE Trans. Ind. Electron., 2011, 58, (1), pp. 202–212.
    20. 20)
      • 17. Li, X., Wu, X., Geng, Y., et al: ‘Wide damping region for LCL-type grid-connected inverter with an improved capacitor-current-feedback methods’, IEEE Trans. Power. Electron., 2015, 30, (9), pp. 5247–5259.
    21. 21)
      • 32. Wang, Y., Wang, J., Zeng, W., et al: ‘H∞ robust control of an LCL-type grid-connected inverter with large-scale grid impedance perturbation’, Energies, 2018, 11, p. 57, doi: 10.3390/en11010057.
    22. 22)
      • 18. Liu, J., Zhou, L., Molinas, M.: ‘Damping region extension for digitally controlled LCL-type grid-connected inverter with capacitor-current feedback’, IET Power. Electron., 2018, 11, (12), pp. 1974–1982.
    23. 23)
      • 2. Zhang, Q., Zhou, L., Mao, M., et al: ‘Power quality and stability analysis of large-scale grid-connected photovoltaic system considering non-linear effects’, IET Power. Electron., 2018, 11, (11), pp. 4000–4014.
    24. 24)
      • 3. Liu, J., Zhou, L., Li, B., et al: ‘Modeling and analysis of a digitally controlled grid-connected large-scale centralized PV system’, IEEE Trans. Power. Electron., 2018, 33, (5), pp. 5795–5805.
    25. 25)
      • 28. Rahim, A.H.M.A., Kandlawala, M.F.: ‘Robust STATCOM voltage controller design using loop-shaping technique’, Electr. Power Syst. Res., 2004, 68, (1), pp. 61–74.
    26. 26)
      • 33. Maccari, L.A.M.Jr., Massing, J.R., Schuch, L., et al: ‘Robust H∞ control for grid connected PWM inverters with LCL filters’. Proc. 10th IEEE/IAS Int. Conf. Industry Applications, Fortaleza, Brazil, 2012, pp. 1–6.
    27. 27)
      • 12. Peña-Alzola, R., Liserre, M., Blaabjerg, F., et al: ‘Analysis of the passive damping losses in lcl-filter-based grid converters’, IEEE Trans. Power. Electron., 2013, 28, (6), pp. 2642–2646.
    28. 28)
      • 34. Wang, X.F., Blaabjerg, F., Liserre, M., et al: ‘An active damper for stabilizing power-electronics-based AC systems’, IEEE Trans. Power Electron., 2014, 29, (7), pp. 3318–3329.
    29. 29)
      • 10. Yang, D., Ruan, X., Wu, H.: ‘Impedance shaping of the grid-connected inverter with LCL filter to improve its adaptability to the weak grid condition’, IEEE Trans. Power. Electron., 2014, 29, (11), pp. 5795–5805.
    30. 30)
      • 4. Liserre, M., Teodorescu, R., Blaabjerg, F.: ‘Stability of photovoltaic and wind turbine grid-connected inverters for a large set of grid impedance values’, IEEE Trans. Power. Electron., 2006, 21, (1), pp. 263–272.
    31. 31)
      • 35. Aldershof, B., Marron, J.S., Park, B.U., et al: ‘Facts about the Gaussian probability density function’, Appl. Anal., 1995, 59, (1-4), pp. 289–306.
    32. 32)
      • 16. Wang, X., Blaabjerg, F., Loh, P.C.: ‘Virtual RC damping of LCL filtered voltage source converters with extended selective harmonic compensation’, IEEE Trans. Power. Electron., 2015, 30, (9), pp. 4726–4737.
    33. 33)
      • 24. Aten, M., Werner, H.: ‘Robust multivariable control design for HVDC back to back schemes’, IEE Proc.-Gener. Transm. Distrib., 2003, 150, (6), pp. 761–767.
    34. 34)
      • 1. Zhou, L., Zhou, X., Chen, Y., et al: ‘Inverter-current- feedback resonance-suppression method for LCL-type DG system to reduce resonance-frequency offset and grid- inductance effect’, IEEE Trans. Ind. Electron., 2018, 65, (9), pp. 7036–7048.
    35. 35)
      • 11. Pan, D., Ruan, X., Bao, C., et al: ‘Capacitor-current- feedback active damping with reduced computation delay for improving robustness of LCL-type grid-connected inverter’, IEEE Trans. Power. Electron., 2014, 29, (7), pp. 3414–3427.
    36. 36)
      • 13. Li, X., Fang, J., Tang, Y., et al: ‘Robust design of lcl filters for single-current-loop controlled grid-connected power converters with unit pcc voltage feedforward’, IEEE J. Emerg. Sel. Top. Power Electron., 2018, 6, (1), pp. 54–72.
http://iet.metastore.ingenta.com/content/journals/10.1049/iet-pel.2019.0888
Loading

Related content

content/journals/10.1049/iet-pel.2019.0888
pub_keyword,iet_inspecKeyword,pub_concept
6
6
Loading