The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

This paper proposes a step-by-step procedure for designing the LCL filter of a front-end three-phase active rectifier. The primary goal is to reduce the switching frequency ripple at a reasonable cost, while at the same time achieving a high-performance front-end rectifier (as characterized by a rapid dynamic response and good stability margin). An example LCL filter design is reported and a filter has been built and tested using the values obtained from this design. The experimental results demonstrate the performance of the design procedure both for the LCL filter and for the rectifier controller. The system is stable and the grid current harmonic content is low both in the lowand high-frequency ranges. Moreover, the good agreement that was obtained between simulation and experimental results validates the proposed approach. Hence, the design procedure and the simulation model provide a powerful tool to design an LCL-filter-based active rectifier while avoiding trial-and-error procedures that can result in having to build several filter prototypes.

Design and control of an LCL-filter-based three-phase active rectifier

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

/pdf/a-review-of-single-phase-improved-power-quality-ac-dc-2pm6h4zjxq.pdf

A review of single-phase improved power quality AC-DC converters

This chapter gives a description and overview of power electronic technologies including a description of the fundamental systems that are the building blocks of power electronic systems. Technologies that are described include: power semiconductor switching devices, converter circuits that process energy from one DC level to another DC level, converters that produce variable frequency from DC sources, principles of rectifying AC input voltage in uncontrolled DC output voltage and their extension to controlled rectifiers, converters that convert to AC from DC (inverters) or from AC with fixed or variable output frequency (AC controllers, DC–DC–AC converters, matrix converters, or cycloconverters). The chapter also covers control of power converters with focus on pulse width modulation (PWM) control techniques.

https://www.springer.com/cda/content/document/cda_downloaddocument/9781447151036-c2.pdf?SGWID=0-0-45-1404710-p175009438

Fundamentals of Power Electronics

This paper provides analytical and graphical methods for the study, performance evaluation and design of the modern carrier-based pulse width modulators (PWMs), which are widely employed in PWM voltage-source inverter (VSI) drives. Simple techniques for generating the modulation waves of the high-performance PWM methods are described. The two most important modulator characteristics-the current ripple and the switching losses-are analytically modeled. The graphical illustration of these often complex multivariable functions accelerate the learning process and help one understand the microscopic (per-carrier cycle) and macroscopic (per fundamental cycle) behavior of all the modern PWM methods. The analytical formulae and graphics are valuable educational tools. They also aid the design and implementation of the high-performance PWM methods.

/pdf/simple-analytical-and-graphical-methods-for-carrier-based-21p287uygo.pdf

Simple analytical and graphical methods for carrier-based PWM-VSI drives

In this paper, a generalized discontinuous pulsewidth modulation (GDPWM) method with superior high modulation operating range performance characteristics is developed. An algorithm which employs the conventional space-vector PWM method in the low modulation range, and the GDPWM method in the high modulation range, is established. As a result, the current waveform quality, switching losses, voltage linearity range, and the overmodulation region performance of a PWM voltage-source inverter (PWM-VSI) drive are optimized online, as opposed to conventional modulators with fixed characteristics. Due to its compactness, simplicity and superior performance, the algorithm is suitable for most high-performance PWM-VSI drive applications. This paper provides detailed performance analysis of the method and compares it to the other methods. The experimental results verify the superiority of this algorithm to the conventional PWM methods.

/pdf/a-high-performance-generalized-discontinuous-pwm-algorithm-3lrbvzvveu.pdf

A high-performance generalized discontinuous PWM algorithm

In this paper, the overmodulation region voltage-gain characteristics and waveform quality of carrier-based pulsewidth-modulated (PWM) methods are investigated. Through detailed analytical study, voltage-gain characteristics are extracted independent of carrier frequency. The influence of blanking time and minimum pulsewidth (MPW) control on the inverter gain characteristics are studied and shown to be significant. A comparative evaluation of the modulator characteristics reveals the advantageous high-modulation-range characteristics of discontinuous PWM methods and, in particular, the superior overmodulation performance of a discontinuous PWM method. The modulation methods under consideration are tested on a PWM voltage-source inverter (VSI)-fed induction motor drive in the laboratory, and the theoretical results are verified by experiments. Also, a gain linearization technique is presented and experimentally verified. The results of this study are useful in the design, performance prediction and development of high-performance overmodulation strategies for PWM-VSI drives.

/pdf/carrier-based-pwm-vsi-overmodulation-strategies-analysis-21hivzp1ac.pdf

Carrier-based PWM-VSI overmodulation strategies: analysis, comparison, and design

This paper surveys the reduced common-mode voltage pulsewidth modulation (RCMV-PWM) methods for three-phase voltage-source inverters, investigates their performance characteristics, and provides a comparison with the standard PWM methods. PWM methods are reviewed, and their pulse patterns and common-mode voltage (CMV) patterns are illustrated. The inverter input and output current ripple characteristics and output voltage linearity characteristics of each PWM method are thoroughly investigated by analytical methods, simulations, and experiments. The research results illustrate the advantages and disadvantages of the considered methods, and suggest the utilization of the near-state PWM and active zero state PWM1 methods as overall superior methods. The paper aids in the selection and application of appropriate PWM methods in inverter drives with low CMV requirements.

Performance Analysis of Reduced Common-Mode Voltage PWM Methods and Comparison With Standard PWM Methods for Three-Phase Voltage-Source Inverters

The near-state pulsewidth modulation (NSPWM) method, which reduces the common-mode voltage/current, is proposed for three-phase pulsewidth modulation (PWM) inverter drives. The method is described, its optimal voltage vectors are found, and the sequence that these vectors are applied is determined. Its voltage linearity and DC bus and AC output PWM current ripple characteristics are studied. Its output line-to-line voltage pattern is carefully studied with regard to switching transients that may cause overvoltages at the motor terminals, particularly for long-cable applications. The NSPWM method is thoroughly investigated, and its performance is compared to conventional PWM methods. Theory, simulations, and experiments show that NSPWM exhibits superior common-mode performance and satisfactory input/output PWM ripple performance characteristics. It is also illustrated that even though the method has bipolar line-to-line output voltage pulses, due to the sufficient zero-voltage time intervals for the switching transients to settle, these pulses do not cause additional overvoltages at the motor terminals compared to the conventional methods. The method is feasible for motor drives, particularly for operation in the high modulation index range, where its overall performance exceeds the performances of the state-of-the-art PWM methods.

Ahmet M. Hava

Papers

Simple analytical and graphical methods for carrier-based PWM-VSI drives

A high-performance generalized discontinuous PWM algorithm

Carrier-based PWM-VSI overmodulation strategies: analysis, comparison, and design

Performance Analysis of Reduced Common-Mode Voltage PWM Methods and Comparison With Standard PWM Methods for Three-Phase Voltage-Source Inverters

A Near-State PWM Method With Reduced Switching Losses and Reduced Common-Mode Voltage for Three-Phase Voltage Source Inverters