Design and experiment of a direct-drive wave energy converter using outer-PM linear tubular generator

Design and experiment of a direct-drive wave energy converter using outer-PM linear tubular generator

For access to this article, please select a purchase option:

Buy article PDF
(plus tax if applicable)
Buy Knowledge Pack
10 articles for $120.00
(plus taxes if applicable)

IET members benefit from discounts to all IET publications and free access to E&T Magazine. If you are an IET member, log in to your account and the discounts will automatically be applied.

Learn more about IET membership 

Recommend Title Publication to library

You must fill out fields marked with: *

Librarian details
Your details
Why are you recommending this title?
Select reason:
IET Renewable Power Generation — Recommend this title to your library

Thank you

Your recommendation has been sent to your librarian.

Research on direct-drive wave energy converter linear generators has mostly focused on synchronous inner permanent magnet (PM) linear generators. In this study, an outer-PM tubular linear generator is designed to increase the power density and distance of relative movement. The motion equations of heaving buoys are derived on the basis of hydrodynamic theory. Two buoys are designed in accordance with the real wave condition in the Yellow Sea in China. The design process of the proposed generator is elucidated. Considering cogging force and voltage, the authors optimise the linear generator and determine the final parameters. The generator performance is evaluated using the finite element method. The integrated wave energy converter system consists of a linear generator, inner buoys, outer buoys, an electricity post-processor, and a communication component. The system is manufactured and placed in the Yellow Sea based on the design results. The measured voltage is highly consistent with the simulation data. All results show that the system is well suited for wave energy conversion.


    1. 1)
      • 1. Titah-Benbouzid, H., Benbouzid, M.: ‘Ocean wave energy extraction: up-to-date technologies review and evaluation’. 2014 Int. Electronics and Application Conf. and Exposition, PEAC 2014, pp. 338342.
    2. 2)
      • 2. Falcão, A.F.D.O.: ‘Wave energy utilization: a review of the technologies’, Renew. Sustain. Energy Rev., 2010, 14, (3), pp. 899918.
    3. 3)
      • 3. Waters, R., Stålberg, M., Danielsson, O., et al: ‘Experimental results from sea trials of an offshore wave energy system’, Appl. Phys. Lett., 2007, 90, (3), ID 034105.
    4. 4)
      • 4. ‘AWS, Archimedes Wave swing Ocean Power’. Available at
    5. 5)
      • 5. Marei, M.I., Mokhtar, M., El-Sattar, A.A.: ‘MPPT strategy based on speed control for AWS-based wave energy conversion system’, Renewable Energy, 2015, 83, pp. 305317.
    6. 6)
      • 6. ‘Ocean Power Technologies (OPT) Inc, Recent News’. Available at
    7. 7)
      • 7. Brekken, T.K.A., von Jouanne, A., Han, H.Y.: ‘Ocean wave energy overview and research at Oregon State University’. Proc. of IEEE Power Electronics and Machines in Wind Applications, PEMWA 2009.
    8. 8)
      • 8. Vining, J., Lipo, T.A., Venkataramanan, G.: ‘Experimental evaluation of a doubly-fed linear generator for ocean wave energy applications’. IEEE Energy Conversion Congress and Exposition: Energy Conversion Innovation for a Clean Energy Future, ECCE 2011, 2011, pp. 41154122.
    9. 9)
      • 9. Du, J., Liang, D., Xu, L., et al: ‘Modeling of a linear switched reluctance machine and drive for wave energy conversion using matrix and tensor approach’, IEEE Trans. Magn., 2010, 46, (6), pp. 13341337.
    10. 10)
      • 10. Calado, M.R.A., Godinho, P.M.C., Mariano, S.J.P.S.: ‘Design of a new linear generator for wave energy conversion based on analytical and numerical analyses’, J. Renew. Sustain. Energy, 2012, 4, (3), Article ID 033117.
    11. 11)
      • 11. Brooking, P.R.M., Mueller, M.A.: ‘Power conditioning of the output from a linear vernier hybrid permanent magnet generator for use in direct drive wave energy converters’, IEEE Proc. Gener. Transm. Distrib., 2005, 152, pp. 673681.
    12. 12)
      • 12. Yu, H., Liu, C., Yuan, B., et al: ‘A permanent magnet tubular linear generator for wave energy conversion’, J. Appl. Phys., 2012, 111, (7), Article ID 07A741.
    13. 13)
      • 13. Hodgins, N., Keysan, O., McDonald, A.S., et al: ‘Design and testing of a linear generator for wave-energy applications’, IEEE Trans. Ind. Electron., 2012, 59, (5), pp. 20942103.
    14. 14)
      • 14. Delli Colli, V., Cancelliere, P., Marignetti, F., et al: ‘A tubular-generator drive for wave energy conversion’, IEEE Trans. Ind. Electron., 2006, 53, (4), pp. 11521159.
    15. 15)
      • 15. Eid, A.M., Suh, K.-Y., Choi, K.-J., et al: ‘A unique starting scheme of linear-engine tubular PM linear generator system using position feedback controlled PWM inverter’. 37th IEEE Power Electronics Specialists Conf., 2006, 18–22 June 2006, pp. 15.
    16. 16)
      • 16. Polinder, H., Mecrow, B.C., Jack, A.G., et al: ‘Conventional and TFPM linear generators for direct-drive wave energy conversion’, IEEE Trans. Energy Convers., 2005, 20, (2), pp. 260267.
    17. 17)
      • 17. Liu, C.Y., Yu, H.T., Hu, M.Q., et al: ‘Research on a permanent magnet tubular linear generator for direct drive wave energy conversion’, IET Renew. Power Gener., 8, (3), pp. 281288.
    18. 18)
      • 18. Ko, K.-J., Jang, S.-M., Park, J.-H., et al: ‘Electromagnetic performance analysis of wind power generator with outer permanent magnet rotor based on turbine characteristics variation over nominal wind speed’, IEEE Trans. Magn., 2011, 47, (10), pp. 32923295.
    19. 19)
      • 19. Polikarpova, M., Ponomarev, P., Röyttä, P., et al: ‘Direct liquid cooling for an outer-rotor direct-drive permanent-magnet synchronous generator for wind farm applications’, IET Electr. Power Appl., 2015, 9, (8), pp. 523532.
    20. 20)
      • 20. Falnes, J.: ‘Ocean waves and oscillating systems’ (Cambridge University Press, Cambridge, 2002).
    21. 21)
      • 21. Dai, Y.S.: ‘Potential flow theory of ship motions in waves in frequency and time domain’ (National Defend Industry Press, Beijing, 1998).

Related content

This is a required field
Please enter a valid email address