Electric field energy harvesting from medium voltage power lines

The Smart Grid is the response of the Electrical Engineering discipline to challenges of the 21st century such as global warming. It is envisioned as an automatic entity in charge of managing electrical energy in the most efficient way and with as small an ecological impact as possible. This new model is currently being materialized with continuous research efforts all over the world to develop the technologies that will compose it. As renewable generation resources become more popular, their introduction to the grid is now changing the paradigm of how the tasks for achieving safe and efficient management of electricity should be carried out. Hence the deployment of technologies around different sections of the grid are becoming increasingly important, in particular in distribution power lines, which are the large conductors in charge of the last stages of electricity dispatch, usually at 11 kV or 22 kV in Australia and New Zealand. For the task of continuously monitoring vital line parameters, the most effective approach is the sensing and transmission of the data using wireless communication technologies. The development of the electronic devices for power line monitoring requires a cost-efficient deployment, as their number will be considerable given the large distances that distribution lines usually cover. Hence, self-powering of these electronics is essential in the design. The research field that deals with this problem is Energy Harvesting, which addresses the transfer of low amounts of energy taken from environmental sources to feed low-power-consumption loads. For the environment of distribution power lines, the discernible environmental source is within the strong electric fields produced by the high voltages in these lines. The topic that addresses this problem is called Electric Field Energy Harvesting (EFEH) and the literature around this subject is moderate and has not yet defined the basis that underlays its maximum energy transfer. This thesis addresses EFEH from medium voltage distribution power lines, focusing on an optimal solution both in terms of its adaption to the grid and of the most adequate energy conversion strategy for maximum power transfer. A non-contact EFEH technique using power line insulators is introduced, and the specific conditions under which the energy is maximised are determined. Under such conditions, the limitations that a solid-state switching converter has when transforming the EFEH supply to usable levels for low-power loads has, are identified and then addressed by the proposal of a pulsed transfer-mode flyback conversion strategy. The implementation of a self-powered, pulsed-mode energy converter is demonstrated theoretically and then practically through the development of physical prototypes. The results obtained from the investigations indicate that this conversion strategy can outperform previous works, being able to harvest higher levels of power with a reduced volume and a weaker coupling capacitance. The contribution of this research work to the scientific community is the proof of concept that a better solution for EFEH can be achieved that will enrich the set of technologies for the upcoming Smart Grid and hence contribute to achieving a more sustainable future for our society.