Novel maximum power point tracking strategies for electronically tuned linear alternators

Linear alternators (LAs) are widely applied in many energy conversion systems based on pressure waves, to avoid linear to rotary conversion mechanisms. The control of the LA is the key element to maximise the system's electric power and efficiency. However, the LA resonant frequency cannot be accurately controlled by mechanical design due to parameter tolerance. Furthermore, the operating frequency is generally not strictly constant in real-time, making maximum power point tracking (MPPT) hard to achieve. Two MPPT strategies are proposed here to adjust the electronic stiffness amount in real time. They are hereafter referred to as symmetrical signal injection method and electronic stiffness perturbation method. The latter one is selected and validated via simulation studies.