Current-Modulation-based on-line Resonance Tuning Strategy for Linear Generator Drives

Min Zhang, Alexey Bodrov, Roger Shuttleworth, Matteo Iacchetti

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Linear Generators (LGs) are frequently used for energy harvesting with free-piston Stirling engines, thermoacoustic engines and wave energy converters.
This paper presents a control strategy to track and maintain LG resonance conditions in real time. The algorithm is based on the LG response to a low-frequency amplitude modulation of the current component in phase with the instantaneous position (d-axis). The averaged product of modulated airgap power and modulation signal is fed into a controller to adjust the d-axis current and restore resonance. The use of airgap power instead of dc power improves resonance tracking accuracy and eliminates steady-state low-frequency stroke oscillations. The paper presents a full theoretical analysis providing accurate steady-state and small-signal models for control synthesis. The broad experimental validation included in the paper proves that the control is able to restore resonance even when the force-source introduces significant additional mechanical impedance
Original languageEnglish
Article number9032374
Pages (from-to)2812-2822
Number of pages11
JournalIEEE Transactions on Industrial Electronics
Issue number4
Publication statusPublished - Apr 2021


  • Energy harvesting
  • linear alternator
  • permanent magnet (PM) linear generator
  • resonance tracking
  • thermoacoustic electric generator
  • wave energy converter


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