Energy Scavenging Technology Based On Spatial Electromagnetic Energy For Powering Wireless Sensors

Development of smart grid technologies has been the kernel and prevailing tasks of nowadays power industry, among which wireless sensor technology as an important part of smart measurement and monitoring turns to be a hot area of research preference. Energy scavenging technology provides an effective solution to the self-sustained power supply issues that obstructs application of the wireless sensors. Energy scavenging technology based on spatial electromagnetic coupling renders outstanding advantages compared with other available methods and sightsee a promising future in high voltage power systems.The dissertation aims to develop energy scavenging technology based on special electromagnetic coupling for powering wireless sensors. Theoretical exploration and technological innovation are intentionally achieved as to solve the power supplying problem which restricts engineering application of the smart transducers.A new topology with spherical cap for energy harvesting is proposed to overcome the unsatisfactory adaptability and low efficiency of the traditional converting topologies. Based on the method of separated variables within the toridal coordinate system, a corresponding analytical model for spherical cap converter is further established so as to obtain the analytic expressions of the topology capacitance and the output voltage. The concept of energy increment factor is specifically defined to denote the improvement of energy storage efficiency. In term of the radius ratio between a spherical cap and a sphere cap, numerical expression of the energy increment factor is presented, which can be used as the objective function for topological optimization. With regard to spherical cap converters of different dimensions, the measured values of energy increment factor coincide well with the theoretical equivalents, indicating an effective verification of the proposed analytical model for the spherical cap converter topology. The research results present theoretical basis for optimal design of the energy scavenging devices.Traditional conditioning unit for energy scarvenging devices show some unique disadvantages such as poor adaptability, low transmission efficiency and long starting time. Two novel types of conditioning units are presented for different environmental conditions of electric field. A large-signal model as well as a dynamic disturbance model is established so as to analyze the static and dynamic characteristics of the conditioning unit, and the computational formula for key parameters are deduced, which form the basis for optimal design of the feedback compensation network. The relationship between the duty ratio and the output power is expored and the driving circuit is designed with a closed-loop control scheme as to obtain the maximum output power. Simulation results verified the effectiveness of the proposed topology structure and the parameter selection methodologies. Based on optimization of the converter topologies and the conditioning units, different prototypes of energy scavenging devices are designed and an experimental rig is also set up for overall performance test of these prototypes. Experimental results demonstrated the effectiveness of the proposed methodology for modeling and optimization. The optimal range of electric field intensity in which conditioning units can operate steadily is indicated, which is of sensible significance for engineering application of the energy scavenging devices.Exploratory research on magnetic energy scavenging is also carried out. Two types of magnetic energy converters, namely armillary and standalone, are proposed respectively. For the armillary topology, a mathematical model is established and the optimal design principle is further given. A specific inductive factor is defined to represent energy scavenging capability of the armillary converter. For the standalone topology, the concept of effective permeability together with corresponding algorithms is put forward. The ratio of framework's length to topology diameter being the variable, a formula for the effective permeability is achieved, with which an estimating method for maximum output power of the standalone converters is further proposed. Experimental studies show feasibility and effectiveness of the control scheme.The innovative research of the dissertation further develops fundamental theories, modeling schemes and simulation methodologies for the energy scavenging technology based on spacial electromagnetic coupling.