DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

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Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

This paper reviews the relative merits of induction, switched reluctance, and permanent-magnet (PM) brushless machines and drives for application in electric, hybrid, and fuel cell vehicles, with particular emphasis on PM brushless machines. The basic operational characteristics and design requirements, viz. a high torque/power density, high efficiency over a wide operating range, and a high maximum speed capability, as well as the latest developments, are described. Permanent-magnet brushless dc and ac machines and drives are compared in terms of their constant torque and constant power capabilities, and various PM machine topologies and their performance are reviewed. Finally, methods for enhancing the PM excitation torque and reluctance torque components and, thereby, improving the torque and power capability, are described

Electrical Machines and Drives for Electric, Hybrid, and Fuel Cell Vehicles

This paper reviews the relative merits of induction, switched reluctance, and permanent-magnet (PM) brushless machines and drives for application in electric, hybrid, and fuel cellvehicles,withparticularemphasisonPMbrushlessmachines. The basic operational characteristics and design requirements, viz. a high torque/power density, high efficiency over a wide operatingrange,andahighmaximumspeedcapability,aswell as the latest developments, are described. Permanent-magnet brushless dc and ac machines and drives are compared in terms of their constant torque and constant power capabilities, and various PM machine topologies and their performance are reviewed. Finally, methods for enhancing the PM excitation torque and reluctance torque components and, thereby, improv- ing the torque and power capability, are described.

Electrical Machines and Drives for Electric, Hybrid, and Fuel Cell Vehicles Induction and switched-reluctance machines can provide the needed characteristics, but permanent magnet brushless machines offer a higher efficiency and torque density.

The torque pulsations in switched reluctance motors (SRMs) are relatively higher compared to sinusoidal machines due to the doubly salient structure of the motor. The magnetization pattern of the individual phases together with the T-i-/spl theta/ characteristics of the motor dictate the amount of torque ripple during operation. Both machine design and electronic control approaches have been used to minimize the torque ripple in SRMs. This paper presents an extensive review of the origin of torque ripple and the approaches adopted over the past decade to minimize the torque ripple. A hybrid torque-ripple-minimizing controller that incorporates the attractive features of some of the techniques developed in the past decade is presented along with simulation and experimental results.

Minimization of torque ripple in SRM drives

There is a great demand for efficient, quiet, reliable, and cost-effective motor drives for propulsion systems in hybrid and plug-in hybrid electric vehicles. Owing to a rigid structure and the absence of magnetic source on the rotor, a switched reluctance machine (SRM) is inherently robust and cost effective. In spite of these advantages, several challenges in the control of this machine remain an issue, including high levels of torque ripple, acoustic noise, and a relatively low torque density. This paper presents a new family of SRMs which have higher number of rotor poles than stator poles. Using a newly defined pole design formula, several novel combinations of the stator-rotor poles have been proposed. From the simulation and experimental analysis of a prototype 6/10 configuration, it has been observed that this machine produces higher torque per unit volume and comparable torque ripple when compared to a conventional 6/4 SRM with similar number of phases and constraints in volume. The results presented in this paper make this family of machines a strong contender for survivable high-performance applications for automotive propulsion systems. The simulation and experimental results for the prototype 6/10 configuration have been presented and compared to a conventional 6/4 design for verification.

Novel Switched Reluctance Machine Configuration With Higher Number of Rotor Poles Than Stator Poles: Concept to Implementation

This paper describes the results of an extensive study into the production and reduction of acoustic noise and vibration in the switched reluctance drive. Time domain analysis has been used to draw conclusions about the effects of changing the operating parameters of the power electronic controller on the vibration and acoustic noise. Experimental results have been taken from a four-phase switched reluctance drive with one-, two-, or four-phase excitation. The results of this time domain study reveal important information about the stator vibration which would not be apparent from frequency spectra. The results have been used to derive operational concepts for the power electronic controller to reduce the acoustic noise and vibration produced by the drive. A new control technique has been developed to cancel the stator vibration. Using this novel control method, experimental results show that the vibration and acoustic noise produced by a switched reluctance drive can be reduced dramatically without affecting the performance of the drive.

Analysis and reduction of vibration and acoustic noise in the switched reluctance drive

The levels of acoustic noise emitted by the switched reluctance drive are noted as being above those of competing variable speed drives. In other respects the switched reluctance drive offers distinct advantages. In a previous paper, the authors described a new technique for the cancellation of radial vibrations of the stator. This new technique was limited to power converters offering a zero voltage freewheel path. This paper describes further development of the technique which allows noise cancellation to be achieved with all types of power converter. The techniques disclosed in this paper include a smoothing method, a three stage commutation method for converters with one switch per phase and a noise cancellation technique suitable for switched reluctance drives incorporating an extended zero voltage freewheel period for improved efficiency. The techniques are all compared, with experimental and simulated results.

Acoustic noise cancellation techniques for switched reluctance drives

A new high efficiency light-emitting diode (LED) and an organic LED power supply are presented. An LED string is split into two sections. A first LED string is driven by a conventional dc-to-dc converter, while a second LED string is placed in series with the incoming dc supply current. Power is delivered to the second LED string without passing through the dc–dc converter, thus improving the system efficiency of the circuit. The equations presented show that the efficiency of the whole circuit will always be higher than the efficiency of the dc–dc converter alone. The performance of the new high efficiency circuit was tested and it was found that the new high efficiency circuit offered an improvement in efficiency of the LED driver of 3% at an automotive supply voltage of 14 V.

High Efficiency LED Power Supply

A method of driving an electric motor having at least one coil winding comprising using a switching operation when the current (10) in the winding is to be switched from a first state to a second state. The switching operation has at least first and second switching steps, the interval between which is approximately equal to half the period of a dominant frequency of vibration of the motor (or to an integral multiple of the period plus a half). This reduces vibrations causing acoustic noise, enabling the motor to be operated more quietly. One or more intermediate steps may be included in the switching operation.

Electric motor drive

An electrical machine having stator (30) and rotor (31) is disclosed. The motor has field windings (F) and armature windings (A) energized by a suitable power electronic controller (401). A controller (400) sends signals to the power electronic controller (401) to control the armature current to control operation of the machine. When the machine is operating as a motor, the armature windings (A) will be supplied with electrical current from the power electronic controller by the application of applied voltage in synchronism with the rotation of the rotor (31). A mutually induced first electrical signal dependent on rotational position of the rotor will be induced within the field windings (F). This will create a superimposed gradient in the field current delivered by the power electronic controller (401). The mutually induced first electrical signal can be extracted from the field current by block (402) which may be a differentiator circuit or may be a coil coupled to the magnetic field around the field current conductor. A signal conditioning circuit (403) is provided which may contain a filter circuit. Block (404) creates a reference voltage for the comparator (405). The reference voltage can be zero such that the comparator (405) determines the polarity of the mutually induced first electrical signal. The output from the comparator is a digital signal indicating if the mutually induced first electrical signal is less than or greater than the threshold applied by block (404). This comparator output, a second electrical signal, represents the rotational position of the rotor relative to the stator and is supplied to the controller (400) to maintain synchronism between the armature excitation and the rotor position.

Charles Pollock

Papers

Analysis and reduction of vibration and acoustic noise in the switched reluctance drive

Acoustic noise cancellation techniques for switched reluctance drives

High Efficiency LED Power Supply

Electric motor drive

Control of an electrical reluctance machine