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Most of the present electric vehicle (EV) on-board chargers utilize a conventional design, i.e., a boost-type Power Factor Correction (PFC) controller followed by an isolated DC/DC converter. Such design usually yields a ~94% wall-to-battery efficiency and 2~3kW/L power density at most, which makes a high-power charger, e.g., 20kW module difficult to fit in the vehicle. As described in this paper, first, an E-mode GaN HEMT based 7.2kW single-phase charger was built. Connecting three such modules to the three-phase grid allows a three-phase >20kW charger to be built, which compared to the conventional three-phase charger, saves the bulky DC-bus capacitor by using the indirect matrix converter topology. To push the efficiency and power density to the limit, comprehensive optimization is processed to optimize the single-phase module through incorporating the GaN HEMT switching performance and securing its zero-voltage switching.

Global CO2 reduction by 2021, according to some projections, will be comprised of multiple vehicle technologies with 7% represented by hybrid and electric vehicles (2% in 2014) [1]. Other low cost hybrid methods are necessary in order to achieve widespread CO2 reduction. One such method is engine-off coasting and regenerative braking (or recuperation) using a conventional internal combustion engine (ICE). This paper will show that a 48V power system, compared to a 12V system with energy storage module for vehicle segments B, D and E during WLTP and NEDC, is much more efficient at reducing CO2. Passive engine-off coasting using 12V energy storage shows a CO2 benefit for practical real world driving, but, during NEDC, multiple sources of friction slow the vehicle down to the extent that the maximum benefit is not achieved.

Most of the present EV on-board chargers utilize a three-stage design, e.g., AC/DC rectifier, DC to high-frequency AC inverter, and AC to DC rectifier, which limits the wall-to-battery efficiency to ∼94%. To further increase the efficiency and power density, a matrix converter is an excellent candidate directly converting grid AC to high-frequency AC thereby saves one stage. However, its control complexity and the high cost of building the back-to-back switches are barriers its acceptance. Instead, this paper adopts the 650V E-mode GaN HEMTs to build a level-2 on-board charger using the indirect matrix topology. The input voltage is 80∼260VAC, the battery voltage is 200∼500VDC and the rated power is 7.2kW. Variable switching frequency is combined with phase-shift control to realize the zero-voltage switching. To further increase the system efficiency, four GaN HEMTs are paralleled to form one switching module with a novel gate-drive technology.

Conventional charging systems for electric and plug-in hybrid vehicles currently use cables to connect to the grid. This methodology creates several disadvantages, including tampering, risk, depreciation and non-value added user efforts. Loose or faulty cables may also create a safety issue. Wireless charging for electric vehicles delivers both a simple, reliable and safe charging process. The system enhances consumer adoption and promotes the integration of electric vehicles into the automotive market. Increased access to the grid enables a higher level of flexibility for storage management, increasing battery longevity. The power class of 3.7kW or less is an optimal choice for global standardization and implementation, due to the readily available power installations for potential customers throughout the world. One of the key features for wireless battery chargers are the inexpensive system costs, reduced content and light weight, easing vehicle integration.

Current significant challenges in the automotive industry for increasing fuel economy and reducing CO₂ emissions remain with traditional combustion engines. Moderately small increases in fuel efficiency lead to major reductions in CO₂ emissions, primarily due to large production volumes utilizing incremental fuel saving technologies. Enhancements of today's vehicle powertrains, including micro-hybrids and mild-hybrids with stop-start systems, and coasting and energy recuperation have shown a positive cost benefit and shorter payback period. This is identified when the technology is compared to more complex and expensive HEVs (Hybrid Electric Vehicles) and BEVs (Battery Electric Vehicles).

Enhancements of today's Micro-Hybrids based on stop-start systems with and without coasting and energy recuperation show a positive cost-benefit and a much shorter payback period compared to more complex and expensive Full-Hybrid concepts. However, improved Micro-Hybrid functionalities have a higher demand on the vehicle's electrical power network, which cannot be covered with traditional topologies alone. To enable the advanced Micro-Hybrid features, additional energy storage elements like second lead acid batteries, double-layer capacitors or lithium-ion cell based storage systems will be integrated into the power network. This will stabilize the network and provide a reliable source of energy. To apply even further reaching measures like creeping (also called crawling), and high power recuperation, a dual voltage power network will be required. This can be achieved by adding a second voltage level to the traditional 12V power network.

A frequency-domain approach to balancing of air-fuel ratio (A/F) in a multi-cylinder engine is described. The technique utilizes information from a single Wide-Range Air-Fuel ratio (WRAF) or a single switching (production) O₂ sensor installed in the exhaust manifold of an internal combustion engine to eliminate the imbalances. At the core of the proposed approach is the development of a simple novel method for the characterization of A/F imbalances among the cylinders. The proposed approach provides a direct objective metric for the characterization of the degree of A/F imbalances for diagnostic purposes as well as a methodology for the control of A/F imbalances among various cylinders. The fundamental computational requirement is based on the calculation of a Discrete Fourier Transform (DFT) of the A/F signal as measured by a WRAF or a switching O₂ sensor.