Publications

This article provides a methodology for deriving a family of output characteristics (dc-side I–V and P–V curves) for a passive magnetic energy harvester (MEH) clamped on a sinusoidal current-carrying conductor. It is demonstrated that MEH characteristics depend on primary current magnitude and frequency as well as on load voltage. First, expressions for power harvested by an MEH are derived employing a nonlinear B–H curve approximation of the core. Then, conversion losses are assessed to provide respective estimates for the power provided by the MEH to the load. Presented analytical findings are accurately supported by experimental results of MEH designed to harvest up to 240 W from a conductor carrying currents of up to 350 A.

Type-II and proportional-integrative (PI) compensators are often employed as DC-link voltage controllers in practical single-phase power factor correction rectifiers (PFCRs). Corresponding controller coefficients are typically designed in frequency domain according to a rule-of-thumb imposing crossover frequency around 10 Hz, yielding unnecessarily high (>45°) phase margin. Recently, analytical guidelines for deriving PI controller coefficients set, allowing the system to comply with grid current total harmonic distortion (THD) and DC link voltage loop phase margin (PM) constraints, were established. This paper demonstrates that an additional degree-of-freedom (DOF) present in type-II compensator (compared to PI) permits optimizing DC-link voltage response to load step in addition to the above-mentioned constraints fulfilment. Design guidelines for deriving optimal type-II compensator coefficients set by means of combined time and frequency domain analysis are provided. The revealed findings are accurately supported by simulations and experiments.

The paper concerns designing a passive (i.e. employing an uncontrolled rectifier) magnetic energy harvester (MEH) clamped on a high-AC-currents-carrying conductor, aimed to power rechargeable batteries under maximum allowed charging current constraint. Such a system may serve as e.g. a part of platform residing on a split phase of an overhead power line for uninhabited aerial electrical vehicle batteries charging. It has been recently shown that a passive MEH may be optimally matched (in terms of harvested power amount) to a given constant voltage load (CVL) by appropriate selection of core cross-sectional area and secondary conductor turns number. However, battery terminal voltage does not remain constant but undergoes significant increase during charging process. Hence, MEH power averaged over the range of voltage values expected during charging cycle should be maximized in such a case. Corresponding simplified design guidelines are derived and verified by both simulations and experiments. The guidelines are used to design a MEH capable of charging a 44.4 V, 10 Ah Li-Ion battery with nearly constant power of ∼115 W when clamped on a conductor carrying 200 A current while complying with 3 A maximum charging current constraint. It is revealed that due to relatively low sensitivity of output passive MEH power-voltage characteristic around corresponding maximum power point, average charging power remains within the range of 2% of the maximum device yield while battery terminal voltage undergoes 31.25% variation.

This article concerns passive magnetic energy harvesters (PMEHs) employed to supply low-voltage (typically dc) loads from high-ac-current-carrying conductors (e.g., a drone battery charging platform residing on a split phase of an overhead power line). It has recently been shown that a unique load voltage value maximizes harvested device power, regardless of primary current magnitude, assuming a sufficiently low magnetizing current in the PMEH transformer core. Corresponding simplified design guidelines were derived, allowing optimal matching of a PMEH to a constant-voltage-type load (CVL) by properly selecting the transformer core cross-sectional area and the number of secondary winding turns. However, disregarding core magnetizing current may not be accurate in practice even under high primary currents due to the utilization of a gapped core, required for the PMEH to clamp on/off an existing power line. This article aims to assess the actual performance of a clamped-on PMEH designed to drive a certain CVL using aforementioned simplified guidelines under a wide range of primary current magnitudes. It is revealed that the loci of harvested PMEH power deviates noticeably from the corresponding maximum power line (MPL). However, the harvested power difference is negligible due to the low sensitivity of power–voltage PMEH characteristics in the vicinity of the MPL. The presented findings are accurately supported by experimental results of a PMEH sized (using simplified design guidelines) to harvest 220 W from a conductor carrying 300 ARMS current while supplying a 45-V CVL.

The letter discusses the performance of clamped-type active magnetic energy harvester (MEH), supplying power to a constant-voltage-type load via transfer-window-alignment controlled rectifier. Presented analysis investigates practical harvesting potential of active MEH operating under high primary currents and compares it to that of a passive (uncontrolled rectifier equipped) MEH. It is revealed that harvested active MEH power may be increased for a given core by reducing the number of secondary conductor turns N, yet it is accompanied with escalated current ratings of secondary conductor and rectifier components. Theoretical harvesting potential of active MEH is shown to be ∼38% higher than that of an optimally designed passive MEH utilizing the same magnetic core under similar operating conditions (i.e. primary current magnitude and load voltage). However, somewhat lower figure of merit should be expected in practice since N cannot be reduced to zero. Experimental results of active MEH harvesting ∼285 W (which is ∼95% of the theoretical upper harvested power bound) from a conductor carrying 300ARMS at 50Hz validate the revealed findings.