DESIGN AND ANALYSIS OF AN UNCONVENTIONAL PERMANENT MAGNET LINEAR MACHINE FOR ENERGY HARVESTING

The rise of global energy consumption and the growing trend to utilize clean energy stress the demand to harvest the untapped green energy existing in every day life of human kind. Among the commonly over-looked energy resources, the kinetic motions including the vibration generated by linear motion and the vibration existent in ambient environment prove to own strong energy potentials. Though so far a number of such kinetic energy harvesters have already been studied, these existent energy harvesting devices can be improved on multiple aspects from power density, usage efficiency of expensive permanent magnetic material, to optimization of interface power electronics. This Ph.D. dissertation proposes an unconventional high power density linear electromagnetic kinetic energy harvester, and a high-performance two-stage interface power electronics to maintain maximum power abstraction from the energy source and charge the Li-ion battery load with constant current of low ripple at the same time. The proposed machine architecture is composed of a double-sided flat type silicon steel stator with winding slots, a permanent magnet mover, coil windings, a linear motion guide and an adjustable spring bearing. The unconventional design of the machine is that NdFeB magnet bars in the mover are placed with magnetic fields in horizontal direction instead of vertical direction and the same magnetic poles are facing each other. The derived magnetic equivalent circuit model proves the average air-gap flux density of the novel topology is as high as 0.73 T with 17.7% improvement over that of the conventional topology at the given geometric dimensions of the proof-of-concept machine. Subsequently, the improved output voltage and power are achieved. The dynamic model of the linear generator is also developed, and the analytical equations of output maximum xv power are derived for the case of driving vibration with amplitude that is equal, smaller and larger than the relative displacement between the mover and the stator of the machine respectively. Furthermore, the finite element analysis (FEA) model has been built and simulated to prove the derived analytical results and the improved power generation capability. Also, an optimization framework is explored to extend the dynamic system modeling method of the proposed single-Degree-of-Freedom (1-DOF) linear generator to the multi-Degree-of-Freedom (n-DOF) vibration based linear energy harvesting devices with multi proof masses and springs. Moreover, a boost-buck cascaded switch mode converter with current controller is designed to extract the maximum power from the harvester and charge the Li-ion battery with trickle current. Meanwhile, a maximum power point tracking (MPPT) algorithm is proposed and optimized for low frequency driving vibrations. Finally, a proof-of-concept unconventional PM linear generator is prototyped and tested to verify the simulation results of the FEA model. For the coil windings of 33, 66 and 165 turns, the output power of the machine is tested to have the output power of 65.6 mW, 189.1 mW, and 497.7 mW respectively with the maximum power density of 2.486 mW/cm3.Ph.D. in Electrical Engineering, December 201