Iftikhar A. Khan

Power electronics in automotive electrical systems

The role of power electronics as an enabling technology for various automotive applications is illustrated with examples. Automotive electrical power systems that address the demands of increased electrical power, improved fuel economy and reduced emissions are discussed. Considerations related to high-efficiency automotive electrical power systems such as the selection of the types of electrical machines and power converters, selection of system voltages, battery voltage equalization, load management, energy management, regenerative braking, centralized and distributed power system architectures, DC and AC power distribution systems and multiplexing are also discussed.

Design of the parallel resonant converter as a low harmonic rectifier

A 1.4 kW single-phase high-efficiency AC-DC converter which draws sinusoidal and in-phase current has been designed, constructed, and experimentally tested. The converter is based on the parallel resonant converter (PRC) with active control of the input line current. It operates in the frequency range from 44 kHz to 71 kHz below resonance, and features zero current switching (ZCS) of insulated gate bipolar transistors (IGBTs). The converter steady-state input characteristics and component stresses are derived in closed form and in a new manner, which allows easy determination of how applied voltages, currents, and stresses on components vary with instantaneous input line voltage and load. Relevant transfer functions and equivalent circuit models in the presence of an input filter are also derived. The input filter is damped and the input current feedback loop is closed to actively regulate the input current waveshape. The results are verified by computer simulation and laboratory experiment.<<ETX>>

Synthesis and analysis of harmonic-free three-phase inverters

A systematic and straightforward procedure is developed for the synthesis and analysis of DC-to-three-phase-AC switched-mode converters. The procedure is useful in the derivation and design of converters with desirable characteristics such as harmonic-free power processing and low component stresses. Application of this procedure to a basic class of DC-to-three-phase-AC converters, namely, the four-topology single-inductor three-capacitor class leads to twenty-six converters in this class. This derivation is based on the assumption of processing power without the generation of supply-frequency harmonics. Other characteristics of converters include their ability to provide variable amplitude of output voltages both below and above the DC input value, variable frequency, and low component stresses. >

Control of switched-mode converter harmonic-free terminal waveforms through internal energy storage

It is shown that internal low-frequency energy storage can be used to achieve harmonic-free operation and controllable power factors in converters whose desired operations require unequal instantaneous input and output powers, such as in single-phase rectifiers, inverters, cycloconverters, and reactive power generators. A systematic synthesis and analysis technique is developed for such converters. This technique can be used to find all converters which can be obtained from a given set of network elements. Since this technique includes converter dynamics, it leads to a systematic procedure for the design of these converters for given specifications with minimum component size.

Synthesis and analysis of transformer-isolated converters

A systematic and straightforward procedure is developed for the synthesis and analysis of transformer-isolated power converters. The procedure can be used to determine the ranges of duty-ratio over which the transformer-isolated power converters of a given class can be operated without transformer saturation. The procedure can also be used to study the dependence of the power converter switch stresses on duty-ratios. This information is useful in the selection of the transformer-isolated power converter most suitable for a given application and in the design of this power converter with minimum switch stresses, high power density, and low cost. >

Synthesis of switched-mode converters suitable for magnetic integration

The requirement that the voltages across the integrated-magnetic components of a converter are proportional during all switching intervals is used to develop a systematic and straightforward procedure for the synthesis and analysis of integrated-magnetic converters. The integration of magnetic components of a converter leads to low component count, low cost, high power density, high reliability, reduced component stresses, and zero-ripple-current operation. The procedure is useful not only in the derivation and study of complete classes of integrated-magnetic converters, but also in the selection of the integrated-magnetic converter most suitable for a given application and in the design of this converter with minimum component stresses, high power density, and low cost. >

Half-cycle control of the parallel resonant converter operated as a high power factor rectifier

A half-cycle control technique for the parallel resonant converter operated as a high power factor rectifier is introduced in this paper. Switching of the bridge power transistors is determined such that the bridge input current averaged over the half switching cycle exactly follows the reference proportional to the input voltage. Zero-current switching and below-resonance operation are guaranteed, while control of the input current is the fastest possible, regardless of the operating point. In contrast to conventional regulators, the performance is preserved under both small and large signal variations, and also for large variations of the power-stage parameter values. Fast response, stability and robustness are experimentally verified on a 1.4 kW prototype.<<ETX>>

Synthesis and analysis of inductor-isolated switched-mode converter

A procedure is developed for the synthesis and analysis of complete classes of inductor-isolated PWM (pulse width-modulated) converters. The procedure is useful in the identification of converters in which the isolation inductors can be integrated with the rest of the inductors on the same magnetic structures. The information obtained from the procedure is useful in the selection of the converter most suitable for a given application and in the design of this converter with minimum component stresses, high power density, and low cost.

Low-harmonic three-phase inverters with nonpulsating terminal currents

A basic class of three-phase inverters with nonpulsating terminal currents, namely, the four-topology four-inductor four-capacitor class is derived and studied. The expressions of duty-ratios required for low-harmonic dc-to-three-phase-ac conversion, ranges of output voltage variation, and component stresses for given specifications of inverters are derived. The characteristics of inverters include low-harmonic power conversion, low component stresses, variable-frequency variable-amplitude output voltages of values both below and above the dc input value, and the use of minimum number of inductors to achieve nonpulsating terminal currents. >