This work presents a study of the reduction in battery stresses by using supercapacitors (SC's) in a 500 kVA rated UPS. We aim at investigating the optimal supercapacitors-battery combination versus the SC's cost. This investigation is threefold; first, supercapacitors and battery models developed using Matlab/Simulink® are presented and validated. Second, the architecture and the simulation of the designed system that combines the SC's and the battery are shown. The supercapacitors are used as high power storage devices to smooth the peak power applied to the battery during backup-time and to deliver full power during short grid outages. By charging the SC's through the battery at a suitable rate, all impulse power demands would be satisfied by the supercapacitors. Third, extensive simulations are carried out to determine the gain in battery RMS current, the gain in energy losses, the energy efficiency and the elimination rate of surge load power. These four performance parameters are determined by simulation and then analyzed. The influence of the SC's recharge on the performance indicators is highlighted. A thorough analysis involving optimal study proposes to draw the optimal SC's number and filter constant from the variation of the aforementioned parameters versus the cost of the SC's.

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Purpose -This paper seeks to discuss the implementation of the rotor flux oriented control (RFOC) in a four-switch three-phase inverter (FSTPI)-fed induction motor drive. Design/methodology/approach -The implementation is achieved considering a current regulation of the FSTPI. Such a regulation is done thanks to bang-bang regulators. As far as the FSTPI is fed by a battery pack, the paper considers an electrical equivalent circuit of such a power supply. Findings -Simulation works, carried out considering the case of an ideal model of the battery pack and the case where the electrical equivalent circuit of the battery pack is taken into account, have shown that the drive dynamic performance are practically the same. Furthermore, and in order to highlight the performance of the induction motor fed by a FSTPI, these are compared with those obtained with the induction motor fed by a conventional six-switch three-phase inverter (SSTPI), considering both models of the battery pack. It has been found that the drive offers almost the same dynamic and steady-state performance.Research limitations/implications -The work should be extended by an experimental validation of the simulation results. Practical implications -The established results open up crucial benefits from the point of view of cost-effectiveness and volume-compactness improvements of induction motor drives especially in large-scale industries such as the automotive one where electric and hybrid propulsion systems are currently regarded as an interesting alternative to substitute or to assist the thermal propulsion systems. Originality/value -The implementation of the RFOC in FSTPI-fed induction motor drives is feasible and exhibits almost the same performance as those obtained by conventional SSTPI-fed induction motor drives under the same control strategies.

Purpose -The paper aims to discuss the comparison of the performance of four space-vector pulse-width modulation (SVPWM) strategies dedicated to four-switch three-phase inverters (FSTPI). Design/methodology/approach -The comparison is based on three comparison criteria: the total harmonic distortion, the switching loss factor, and the quality factor. The comparison is extended to the FFT of the phase currents and to the analysis of the ripples of the electromagnetic torque of the induction motor. Findings -It has been clearly shown that the basic SVPWM strategy of the conventional six-switch three-phase inverter (SSTPI) offers better performance than those of the four FSTPI-SVPWM strategies. This said, it has been found that the performance of two among the four FSTPI-SVPWM strategies tend to those of the SSTPI-SVPWM basic strategy, especially in high switching frequencies.Research limitations/implications -The work should be extended by an experimental validation of the simulation results. Practical implications -The established results open up crucial benefits from the point of view of cost-effectiveness and volume-compactness improvements of induction motor drives especially in large-scale industries such as the automotive one where electric and hybrid propulsion systems are currently regarded as an interesting alternative to substitute or to assist the thermal propulsion systems. Originality/value -The implementation in the FSTPI feeding an induction motor of SVPWM strategies exhibiting acceptable performance, which tend to those yielded by the SSTPI-SVPWM basic strategy especially in high switching frequencies, is extended here.

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