Inductive power transfer system using multiple concatenated segmented parallel line feeders
BROU William-Fabrice ( 1551121 )
This work presents a an inductive power transfer system, suitable for wireless charging of moving receivers such as automatic guided vehicles and electric cars. With the help of a significanlty newly introduced configuration of inductive power transfer system using parallel line feeders which can cover an extended area while been low cost, the perspective that the charging area be extended easily and at low cost. However, with these promising features, this system could not stably charge moving receiver because the electro- magnetic strength varying dynamically along the transmitting apparatus. This is due to standing wave phenomenon which occurs when the feeder length is longer than about one-tenth of the signal wavelength. In practice, the feeder length is from a few tens of meters to hundreds of meters, which is far longer than the wavelength (about 22 meters) if a 13.56MHz power supply is used. One known method for to suppressing the standing is by adding an impedance matched to the intrinsic impedance at the termination of the line. But doing so, the amount of power delivered to the terminating load will be the same as the power dissi- pated in the source. Therefore, the maximum power available on the line could only be a small portion of the transmit power and could not be applicable to our implementation of the parallel line feeder.
Therefore, in this thesis, we evaluated two other different schemes for mitiga- tion of the standing wave. The first scheme adopted a multiple-input multiple- output configuration of the parallel line feeders to expose and combine the different magnetic fields of every single parallel lines in a uniform way for better stability and higher output power. But, the employment of multiple parallel lines feeders adds up to the cost of the system which seems contrary to the perspective of our proposal in term of cost-effectiveness. Moreover, the efficiency of that first scheme is quite low as it is subject to severe dielectric loss caused by the exposure of electric field to the surrounding materials.
Therefore, as an improvement, a second scheme of dividing a single parallel line feeders into several resonant segments concatenated together has been evalu- ated. In this scheme, the length of each segment is kept under about one-tenth of the signal wavelength to avoid the impact of standing wave, resulting in a near- uniform magnetic field strength. Furthermore, this scheme exposes only magnetic field, and therefore it is able to significantly reduce the dielectric loss. As a conse- quence, this new scheme is shown to be capable of mitigating the standing wave issue and improving the efficiency as well; confirming its practicality for dynamic charging applications.