Power Electronic Circuits for Magnetic Energy Harvesters

Abstract

Compared to many other energy harvesting schemes, harvesting energy from magnetic fields offers potential advantages for energy extraction and sensing. A magnetic energy harvester provides great flexibility for sensors and monitoring applications for condition-based monitoring of electromagnetic actuators, including vibration and thermal monitoring. A core must be managed or operated with carefully timed saturation to ensure maximum power extraction, a complex problem given the nonlinear saturation characteristics of a magnetic core [1]. This paper presents a simulator-friendly "circuit model" for a magnetic core, and uses this model to design and demonstrate several power electronic circuit solutions for harvesting energy. The circuit model has an excellent accuracy to represent the core regardless of the level of saturation. The design techniques to enhance power harvest are proposed, and verified through simulation and experiments, substantially boosting the amount of power harvest.

Optimization design of toroidal core for magnetic energy harvesting near power line by considering saturation effect

“…The magnetic permeability of the saturated magnetic core is close to zero; this can cause power performance degradation due to such factors as insufficient induced voltage and power density. There have been several attempts to enhance the power density of magnetic energy harvesters, [9][10][11][12][13][14][15][16][17][18] but most of these attempts have not taken into account the effect of permeability variation, which is dependent on the geometrical parameters of the magnetic core and the magnetic field intensity. Assuming that permeability has a constant value at all locations of the magnetic core, regardless of the distance from the center of the power line, aspects of power performance like induced voltage of the magnetic core will be highly inaccurate.…”

A nonintrusive magnetically self-powered vibration sensor for automated condition monitoring of electromechanical machines

“…The detailed analysis on magnetic saturation and its importance in the scope of electromagnetic energy harvesting can be referenced at [5] and [6]. The importance of magnetic saturation in energy harvesting can be briefly explained in two ways: first, if the magnetic core is not saturated, the load voltage can be always increased until the core saturates, directly increasing the energy extraction (since it is a currentdriven transformer, the harvested current does not change until saturation); second, if the magnetic core is not saturated, the number of turns on the secondary side can be lowered until the core saturates, directly increasing the harvested current (hence energy extraction).…”

“…The importance of magnetic saturation in energy harvesting can be briefly explained in two ways: first, if the magnetic core is not saturated, the load voltage can be always increased until the core saturates, directly increasing the energy extraction (since it is a currentdriven transformer, the harvested current does not change until saturation); second, if the magnetic core is not saturated, the number of turns on the secondary side can be lowered until the core saturates, directly increasing the harvested current (hence energy extraction). An ideal magnetic core for this type of energy harvesting requires three properties: low hysteresis loss, high saturation flux density, and extremely high magnetic permeability [6], [12]. Another important property is the physical size of the core as VAMPIRE is to be enclosed in a small terminal box of the motor.…”

“…VAMPIRE uses the transfer window alignment (TWA) method [6] along with active rectification [6], [12] for enhancing energy extraction. The flux-shaping capacitor (FSC) method [6] is not employed as VAMPIRE is designed for a wide range of the primary current levels.…”

“…This paper presents a nonintrusive and self-powered embedded system and an associated performance analysis method for condition monitoring of electromechanical machinery. This embedded system is designed for installation inside the terminal block of a typical motor or generator and harvests power from the magnetic field emanating from a currentcarrying wire of the electromechanical load under monitoring [5], [6]. The energy harvester powers the sensor package, consisted of low-power microcontrollers and sensors, e.g.…”