High Step-Down Bridgeless Sepic/Cuk PFC Rectifiers With Improved Efficiency and Reduced Current Stress

In this article, two high step-down bridgeless power factor correction rectifiers based on the switched inductor network (SIN) are introduced. The proposed rectifiers employ the SIN to provide high step-down voltage gain with a higher duty cycle than the competitors. They also offer higher efficiency, lower current stress, and total peak switching device powers. A thorough and straightforward design algorithm in the discontinuous conduction mode is provided that ensures a unity power factor and a low total harmonic distortion with a simple control scheme. As a demonstration of the superior performance of the proposed rectifiers, a 300-W high-gain sepic rectifier setup with 48Vdc output voltage from a 230Vrms/50Hz source is built in the laboratory

Highly Efficient SiC Based Onboard Chargers for Plug-in Electric Vehicles

Grid-enabled plug-in electrified vehicles (PEVs) are deemed as one of the most sustainable solutions to profoundly reduce both oil consumption and greenhouse gas emissions. One of the most important realities, which will facilitate the adoption of PEVs is the method by which these vehicles will be charged. This dissertation focuses on the research of highly efficient onboard charging solutions for next generation PEVs. This dissertation designs a two-stage onboard battery charger to charge a 360 V lithium-ion battery pack. An interleaved boost topology is employed in the first stage for power factor correction (PFC) and to reduce total harmonic distortion (THD). In the second stage, a full bridge inductor-inductor-capacitor (LLC) multi-resonant converter is adopted for galvanic isolation and dc/dc conversion. Design considerations focusing on reducing the charger volume, and optimizing the conversion efficiency over the wide battery pack voltage range are investigated. The designed 1 kW Silicon based charger prototype is able to charge the battery with an output voltage range of 320 V to 420 V from 110 V, 60 Hz single-phase grid. Unity power factor, low THD, and high peak conversion efficiency have been demonstrated experimentally. This dissertation proposes a new technique to track the maximum efficiency point of LLC converter over a wide battery state-of-charge range. With the proposed variable dc link control approach, dc link voltage follows the battery pack voltage. The operating point of the LLC converter is always constrained to the proximity of the primary resonant frequency, so that the circulating losses and the turning off losses are minimized. The proposed variable dc link voltage methodology, demonstrates efficiency improvement across the wide state-of-charge range. An efficiency improvement of 2.1% at the heaviest load condition and 9.1% at the lightest load condition for LLC conversion stage are demonstrated experimentally. This dissertation proposes a novel PEV charger based on single-ended primary-inductor converter (SEPIC) and the maximum efficiency point tracking technique of an LLC converter. The proposed charger architecture demonstrates attracting features such as (1) compatible with universal grid inputs; (2) able to charge the fully depleted battery pack; (3) pulse width modulation and simplified control algorithm; and (4) the advantages of Silicon Carbide MOSFETs can be fully manifested. A 3.3 kW all Silicon Carbide based PEV charger prototype is designed to validate the proposed idea

INTEGRATED INDUCTIVE AND CONDUCTIVE CHARGING SYSTEM FOR ELECTRIC VEHICLES

The global electric vehicle (EV) market acceleration is facilitated by supporting policies deployed by governments and cities to reap multiple benefits in the fields of transport decarbonization, air pollution reduction, energy efficiency, and security. Currently, conductive chargers are a customary method of storing electric energy into the storage elements present onboard of an EV which is inadequate in supporting complete autonomy. The thriving inclination towards the design of autonomous vehicles has shaped wireless charging as an attractive solution in favor of complete autonomy. As long as the wireless charging infrastructure, as well as interoperability standards, are not completely developed, wired and wireless chargers have to co-exist onboard the vehicles for user convenience. Incorporation of an entire parallel wireless charging system on-board an EV, either during manufacturing or after-market increases size, weight, or cost while declining the electric range of the vehicle. The current requisite for multiple on-board charging options motivate the necessity for a solution for efficiently integrating wired and wireless charging systems. In this Ph.D. research, we propose multiple charging architectures capable of integrating inductive and conductive charging systems. The proposed architectures merge the output rectifying stage of an inductive charging system to the existing on-board charger eliminating the additional weight and volume associated with a wireless charger. Since the proposed system involves multiple power conversion stages, a system level study is carried out to select feasible topologies capable of maximizing the efficiency of an integrated system. Additionally, an extended harmonic approximation (EHA) technique is introduced to increase the accuracy of a resonant converter model facilitating the optimized design parameter selection of an inductive charging system. Furthermore, a novel analog synchronous rectification circuit is proposed and designed to enable active rectification maximizing power transfer efficiency. For proof of concept verification, a laboratory prototype of a 3.3kW Silicon Carbide (SiC) based integrated wireless charger is developed that can be interfaced to a variable input voltage (85-265 Vrms) 50/60Hz AC grid. According to the experimental measurements, the charger draws an input current with a total harmonic distortion of 1.3% while achieving an overall efficiency of 92.77% at rated output power

Digital Control Techniques for Efficiency Improvements in Single-Phase Boost Power Factor Correction Rectifiers

Input current shaping has been required in AC-DC rectifiers in order to comply with regulations that specify limits on input current harmonics. Boost power factor correction (PFC) rectifiers are widely used to achieve near-unity input power factor and low current harmonic distortion. This thesis addresses digital control techniques aimed at improving efficiency and reducing harmonic distortion in digitally controlled single-phase boost PFC rectifiers operating over wide range of loads. By taking advantage of the flexibility of digital controllers and using a discontinuous conduction mode (DCM) detection circuit, several proposed control techniques achieve low current harmonic distortion and improve system efficiency over wide load range in DCM and in continuous conduction mode (CCM). In heavy load operation, a simple passive power sharing technique is introduced for interleaved boost PFC rectifiers to increase system power modularity; in medium to light load operation, proposed adaptive approaches improve light load efficiency by extending switching period to achieve low voltage switching and by adjusting switching frequency to scale with processed power. Furthermore, a new current error estimation approach is applied to relieve current sensing limitations and to reduce current controller design effort. Digital control techniques are implemented and verified using field programmable gate array (FPGA) in several boost PFC rectifier prototypes