Emissions caused by regular vehicles with fossil fuels are problematic for the environment. The integration of electric vehicles in public transportation can potentially cause zero emissions. This paper will focus on the implementation of electric buses together with inductive chargers at bus stops. These chargers will charge the bus battery while passengers enter or leave the bus. This is also known as opportunity charging. Opportunity charging could result in the easier implementation of electric buses within public transportation since it solves the range problem that electric vehicles have. The first parts of this paper will provide a discussion about the powertrain model made in Mat- lab/Simulink. The powertrain model input is the driving cycles from the Arnhem Trolleybus data. The outputs are the energy consumption during the driving cycle and the state of charge of the bus battery. The opportunity charger will then be added to the model to analyze the effects of opportunity charging on the bus. The implementation of opportunity charging increases the operational range of the electric bus, while also lowering the energy consumption. The chargers will operate at a high power rating which spans from 100 kW to 200 kW. These power ratings could cause congestion of the grid. This is why the feasibility of PV systems at bus stops is analyzed using a PV model. A PV system is insufficient to power the chargers on its own. The PV system can still provide a significant percentage of the charger power demand. ... Read more

With the popularity of electrical vehicles (EVs), the demand for EVs charging is also increasing. Compared to traditional wired charging, wireless charging can avoid many safety issues. The efficiency of wireless power transfer (WPT) system is determined by many factors, the coupling factor is one of the most important factors. Therefore, estimating the coupling factor of WPT system is necessary. The research objectives of this work are to review and benchmark different methodologies of coupling factor estimation. Besides, a comprehensive method is selected and simulated. This work is focused on magnetic inductive WPT systems. Five different methodologies of coupling factor estimation for static WPT system and one methodology for dynamic WPT system is reviewed and analyzed. The methodology that uses alternative capacitors to estimate the coupling factor of a static WPT system is analyzed in detail. By using the zero crossing unit, the primary side and secondary side of WPT system are under full resonant. The WPT system will work in two different modes by changing the primary side capacitance. The two sets of circuit parameters will be recorded and calculated by a PLL unit. Based on theoretical analysis and the calculated parameter, the load and mutual inductance of WPT system can be identified. Therefore, the value of the coupling factor can be determined. The accuracy of coupling factor estimation of this methodology is higher than 97 %.
Compared to the literature that proposed this methodology, this work made a sensitivity study. The circuit parameters are made to fluctuate in a certain range. The accuracy of estimation of mutual inductance is still higher than 95% when the primary side resistance, secondary side resistance and load fluctuate. However, the system becomes unstable when the primary side capacitance, inductance and secondary side inductance fluctuate. The reason is that when the capacitance and inductance change, the operating frequency will deviate from the resonant frequency. However, the mutual inductance identification unit is not able to detect this deviation. If the deviation of circuit parameters is updated, the accuracy of coupling factor estimation will remain at about 97%. ... Read more

Wireless charging technology, in particular, Inductive Power Transfer (IPT), has been evolving during the last decades, and it’s starting to become attractive for electric mobility applications. The working principle of the IPT technology is based on two coils separated by an air gap and magnetically coupled together; since the medium to transfer the energy is the air between the coils, the magnetic circuit of this system becomes remarkably important, as the magnetic flux need to be constrained as much as possible for the sake of securing the magnetic linkage between the coils. In this thesis, the design process of the casing of the coils is presented, such casing will ensure that the coils are always kept fixed according to their design.

From this point, the first goal of this thesis arises: Design an accurate and modular casing for the coils of a 50 kW IPT system that will fix such elements in the correct position, and which will allow for easy
changes/upgrades in the coil if required. The design process of such casing was to first do the CAD model of the coils, and then do the CAD model of the casing, by considering the following criteria: accurate dimensions, easy and fast to manufacture and assemble, modular-designed, light, adequately cooled, and robust. The result of such design was a casing that was actually manufactured and assembled, and that is currently being used to test a 50 kW IPT prototype system.

Besides procuring an efficient coil design for the IPT systems, it’s important to understand the dynamic behavior of the IPT electric system. One of the elements that could potentially influence the electric behavior of such system is known as parasitic capacitance. From here, the second objective of this thesis arises: Derive the parasitic capacitance of the coils in order to perform a better circuit modeling and to predict a possible over-voltage across such capacitance.

The methodology to derive the parasitic capacitance of the coils was first to perform an electromagnetic fields FEM simulation on the coils in order to obtain a set of parameters such as the coils impedance, resonance frequency and inductance. With these parameters and a set of equations, it was possible then to derive the parasitic capacitance of each coil. Finally, with this information, it was possible to build a (virtual) equivalent circuit of the IPT system and evaluate the voltage across the parasitic capacitance. It was concluded from this thesis that the parasitic capacitance at the standard operating frequency (85 kHz) does not represent a risk of over-voltage, but as the frequency goes close to the resonance frequency (1.46 MHz), the electric field across the capacitor could reach values up to 14 kV/mm. ... Read more

To enable the portable use of electronic devices, (rechargeable) batteries need to be used. These batteries require a battery management system in order for them to operate safely and efficiently. This thesis describes such a system for the Wireless Powerlizer: a power bank with wireless charging capabilities and an integrated sterilizer using UV-C light.

The battery management system comprises of a charging circuit, a protection module, and cell balancing features. These features are designed to function with Li-ion batteries, which are chosen for their high volumetric energy density, in a 5S1P configuration. These batteries will be charged via a constant-current, constant-voltage (CC-CV) scheme in order to improve charging speed. This charging scheme will be facilitated by a DC-DC boost converter with current and voltage control.

The mechanism behind the protection module (overcharge, overdischarge, overcurrent, and temperature) and passive cell balancing features are elucidated via flowcharts and also verified by simulation in Simulink. A prototype encompassing the charging circuit is implemented on a PCB and tested. The realized boost converter successfully allows for CC-CV charging: it operates at 263kHz, has a charging current of 1A, a constant voltage boundary of 19.6V, and shows an efficiency of 92—93.6%.
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