Michael G. Egan

Power-Factor-Corrected Single-Stage Inductive Charger for Electric Vehicle Batteries

A novel power-factor-corrected single-stage alternating current/direct current converter for inductive charging of electric vehicle batteries is introduced. The resonant converter uses the current-source characteristic of the series-parallel topology to provide power-factor correction over a wide output power range from zero to full load. Some design guidelines for this converter are outlined. An approximate small-signal model of the converter is also presented. Experimental results verify the operation of the new converter

Wide-load-range resonant converter supplying the SAE J-1773 electric vehicle inductive charging interface

The recommended practice for electric vehicle battery charging using inductive coupling (SAE J-1773), published in January 1995 by the Society of Automotive Engineers, Inc., outlines values and tolerances for critical vehicle inlet parameters which must be considered when selecting a coupler driving topology. The inductive coupling vehicle inlet contains a significant discrete capacitive component in addition to low magnetizing and high leakage inductances. Driving the vehicle interface with a variable-frequency series-resonant power converter results in a four-element topology with many desirable features: unity transformer turns ratio; buck/boost voltage gain; current-source operation; monotonic power transfer characteristic over a wide load range; throttling capability down to no load; high-frequency operation; narrow modulation frequency range; use of zero-voltage-switched MOSFETs with slow integral diodes; high efficiency; inherent short-circuit protection; soft recovery of output rectifiers; and secondary d/spl nu//dt control and current waveshaping for the cable, coupler and vehicle inlet, resulting in enhanced electromagnetic compatibility. In this paper, characteristics of the topology are derived and analyzed using two methods. Firstly, the fundamental mode AC sine-wave approximation is extended to battery loads and provides a simple, yet insightful, analysis of the topology. A second method of analysis is based on the more accurate, but complex, time-based modal approach. Finally, typical experimental results verify the analysis of the topology presented in the paper.

Simplified electric vehicle power train models and range estimation

In this paper, simplified EV power train models are developed for new and existing production vehicles. The models are developed based on published vehicle parameters and range information for the Nissan Leaf and the Tesla Roadster. The models are compared with published manufacturer specifications for range under various route and driving conditions, and for various drive cycles. The models are additionally validated against test results for the Nissan Leaf and Tesla Roadster vehicles, where the test route topography is modeled using Google Earth and a GPS-based smart-phone application. Excellent correlations are demonstrated between the experimental results and manufacturer data and the vehicle models. Impacts of battery degradation with time and vehicle HVAC loads are considered in the study.

Torque ripple minimization in switched reluctance drives using self-learning techniques

The nonlinear torque-production mechanisms in the doubly salient, switched reluctance motor drive are both current and position dependent. It is shown that the shape of the static torque-angle-current characteristics of this drive can be fully determined by a series of measurements performed with the drive in a self-learning mode, without the need for an external loading device. These measurements consist of static tests, in which the torques produced by currents in different phases are balanced, and dynamic measurements, in which the relative currents required to produce the same torque at different positions are ascertained. The controller can then achieve very smooth low-speed performance by determining the current required to obtain the optimum torque contribution from each phase, at each rotor position.<<ETX>>

A BIFRED converter with a wide load range

In this paper, the boost integrated flyback rectifier energy DC-DC (BIFRED) power converter which incorporates power factor correction, output voltage hold-up and input-to-output isolation is examined. The particular problem of high bulk capacitor voltage at light loads is addressed and it is shown how this may be resolved if the boost and flyback sections of the power converter are allowed to operate discontinuously. The criteria for ensuring correct operation in the discontinuous mode are investigated. It is shown that operating in this mode places no restrictions on the minimum load and simplifies the control loop design.<<ETX>>

Neural network based torque ripple minimisation in a switched reluctance motor

This paper presents an artificial neural network (ANN) solution to torque ripple reduction in a switched reluctance motor. Magnetic saturation together with salient stator and rotor poles give rise to a highly nonlinear torque/current/angle characteristic. The approach in this paper allows the neural network to be used to its full potential, that is, learning the nonlinear flux linkage characteristic while also incorporating a priori analytical knowledge of the torque production mechanism of the machine. This combination of neuro-learning and analytical insight results in a greatly simplified controller. Simulation results are presented to illustrate the performance of the proposed technique. Experimental results based on a floating point DSP processor are included.<<ETX>>

CCTT-Core Split-Winding Integrated Magnetic for High-Power DC–DC Converters

A novel CCTT-core split-winding integrated magnetic (IM) structure is presented in this paper. The IM device is optimized for use in high-power dc–dc converters. The IM structure uses a split-winding configuration which allows for the reduction of external leakage inductance, which is a problem for many IM designs. Magnetic poles are incorporated to help shape and contain the leakage flux within the core window. Low-cost and low-power loss ferrite is used which results in a very efficient design. An IM reluctance model is developed which uses fringing equations to develop a more accurate design. An IM design algorithm is developed and implemented in Mathematica for design and optimization. FEA and experimental results from a 72 kW, (155-V dc, 465-A dc input, and 420-V dc output) prototype validate the new IM concept. The 72 kW CCTT- core IM was shown to be 99.7% efficient at full load.

A Family of Single-Stage Resonant AC/DC Converters With PFC

A family of novel, single-stage, isolated, resonant-based AC/DC power supply circuits with inherently high power factor is presented in this paper. The three topologies in the family are transformer isolated; they contain a bulk energy storage capacitor to enable output voltage holdup, and they also contain a resonant circuit in which a resonant capacitor is connected directly across the mains input rectifier. The presence of this resonant circuit results in AC line current being drawn over much of the line cycle, as well as in soft switching of the power devices. The rectifier-compensated fundamental-mode approximation (RCFMA) method is used to provide an accurate yet simple analysis of the circuit. Experimental results for closed-loop operation of two of the topologies are also presented. This family of single-stage, high-power-factor converters provides for simple control and high-frequency operation, due to the resonant configuration of the power circuit, without the excessive conduction loss of fully resonant techniques.

Sensorless Current Estimation and Sharing in Multiphase Buck Converters

Virtually, all of the current-sensing methods for power converters presented to date rely on a priori knowledge of circuit parameters to ensure accurate current measurement. Also, the advent of digital control in low-cost high-volume applications-such as voltage regulator modules (VRMs) for computer microprocessors-has added the challenge and cost of analog-to-digital conversion to this task. This paper introduces a parameter-independent, sensorless current-sharing algorithm for multiphase power converters based on gradient estimation via low-frequency perturbation of the per-phase duty cycles, thus eliminating the need for current sensing. Measures of only the input and output voltages are required, so the analog-to-digital converter (ADC) and communication/interfacing overhead is low. The algorithm is demonstrated through both simulation and experimental implementation using a digitally controlled three-phase buck converter.

Magnetic Material Selection for High Power High Frequency Inductors in DC-DC Converters

Dc-dc converter size and efficiency are driving factors in industrial, aerospace and automotive applications. Thus, optimal component selection is essential for a compact design. The inductor often appears as the converters largest component. This paper presents analytical and experimental comparisons of the magnetic materials used in a practical design. The investigation is concerned with magnetic material selection for a dc-dc power inductor in the medium (20 kHz) to high (150 kHz) frequency range and the low (1%) to high (220%) current ripple range. The materials under investigation are iron-based amorphous metal, silicon steel, nanocrystalline, ferrite, powdered iron and gap-less powder materials. A newly developed silicon steel material from JFE-Steel Co. is presented. A novel material comparison which includes thermal conductivity and saturation capability is proposed. The area product analysis for material comparison is presented for 10 kW dc-dc inductor design examples. The variation of core power loss with dc-bias is experimentally investigated for different materials. A 1.25 kW half-bridge dc-dc converter is used in experimental validation.