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Pradeep S. Shenoy

Bio: Pradeep S. Shenoy is an academic researcher from Texas Instruments. The author has contributed to research in topics: Buck converter & Capacitor. The author has an hindex of 18, co-authored 44 publications receiving 1317 citations. Previous affiliations of Pradeep S. Shenoy include University of Illinois at Urbana–Champaign.

Papers
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Journal ArticleDOI
TL;DR: In this paper, an energy conversion approach that enables each PV element to operate at its maximum power point (MPP) while processing only a small fraction of the total power produced is presented.
Abstract: Conventional energy conversion architectures in photovoltaic (PV) systems are often forced to tradeoff conversion efficiency and power production. This paper introduces an energy conversion approach that enables each PV element to operate at its maximum power point (MPP) while processing only a small fraction of the total power produced. This is accomplished by providing only the mismatch in the MPP current of a set of series-connected PV elements. Differential power processing increases overall conversion efficiency and overcomes the challenges associated with unmatched MPPs (due to partial shading, damage, manufacturing tolerances, etc.). Several differential power processing architectures are analyzed and compared with Monte Carlo simulations. Local control of the differential converters enables distributed protection and monitoring. Reliability analysis shows significantly increased overall system reliability. Simulation and experimental results are included to demonstrate the benefits of this approach at both the panel and subpanel level.

411 citations

Journal ArticleDOI
TL;DR: In this article, an analytical and experimental comparison of a two-phase buck converter and a series capacitor buck converter is presented for high-frequency point-of-load voltage regulators with large voltage conversion ratio (10-to-1) is highlighted.
Abstract: This paper presents an analytical and experimental comparison of a two-phase buck converter and a two-phase, series capacitor buck converter. The limitations of a conventional buck converter in high-current (10 A or more), and high-frequency (HF, 3–30 MHz) point-of-load voltage regulators with large voltage conversion ratios (10-to-1) are highlighted. The series capacitor buck converter exhibits desirable characteristics at HF, including lower switching loss, less inductor current ripple, automatic phase current balancing, duty ratio extension, and soft charging of the energy transfer capacitor. Analysis of the topologies indicates that switching loss and inductor core loss can dominate at HF. Results from side-by-side 12 V input, 1.2 V output hardware prototypes demonstrate that the series capacitor buck converter has up to 12 percentage points higher efficiency at 3 MHz and reduces power loss by up to 33% at full load (10 A). Some guidelines for inductor selection are provided, and a switch stress comparison reveals that the maximum converter switch stress is reduced by 30%.

157 citations

Journal ArticleDOI
TL;DR: In this article, the performance of differentially power processing (DPP) architectures with rating-limited converters has been evaluated over 25 years of operation, and the results show that DPP converters outperform dc optimizers in terms of lifetime performance.
Abstract: When photovoltaic (PV) cells are connected in series, they experience internal and external mismatch that reduces output power. Differential power processing (DPP) architectures achieve high system efficiency by processing a fraction of the total power while maintaining distributed local maximum power point operation. This paper details the computational methods and analysis used to determine the operation of PV-to-bus and PV-to-PV DPP architectures with rating-limited converters. Simulations for both DPP architectures are used to evaluate system performance over 25 years of operation. Based on data from field studies, a PV power coefficient of variation can be estimated as 0.086 after 25 years. An improvement figure of merit reflecting the ratio of energy produced to that delivered in a conventional system is introduced to evaluate comparative performance. Converter ratings of 15-17% for PV-to-bus and 23-33% for PV-to-PV architectures are identified as appropriate ratings for a 15-submodule system (five PV panels in series). Both DPP architectures with these ratings are shown to deliver up to 2.8% more power compared to a conventional series-string architecture based on the expected panel variation over 25 years of operation. DPP converters also outperform dc optimizers in terms of lifetime performance.

121 citations

Journal ArticleDOI
TL;DR: Differential power processing enables independent load regulation, while processing only a small portion of the total load power as discussed by the authors, where load voltage domains are connected in series, and differential converters act as controllable current sources to regulate intermediate nodes.
Abstract: This paper introduces an approach to dc power delivery that reduces power loss by minimizing redundant energy conversion. Existing power distribution techniques tend to increase the number of cascaded conversion stages, which limits overall efficiency. Differential power processing enables independent load regulation, while processing only a small portion of the total load power. Bulk power conversion occurs once. Load voltage domains are connected in series, and differential converters act as controllable current sources to regulate intermediate nodes. This enables independent, low supply voltages, which can reduce system energy consumption, especially in digital circuits and solid-state lighting. Since differential voltage regulators process a fraction of the load power, decreased size, cost, and conversion losses are attainable. Under balanced load conditions, secondary differential converters do not process any power. This paper analyzes several differential power delivery architectures that can be applied to homogenous and heterogeneous loads at various levels: chip, board, blade, etc. A variety of operating conditions for a test system with four series voltage domains are examined in simulation and verified with experimental hardware. Results in a reference application show a 7–8% decrease in input power and 6–7 percentage points increase in overall conversion efficiency as compared to a conventional cascaded approach.

91 citations

Journal ArticleDOI
TL;DR: The proposed series-stacked power delivery architecture is validated with real servers performing two different real-world operations: web traffic management and computation and up to a 20x reduction in power conversion losses compared to state-of-the-art hardware.
Abstract: In this paper, an alternative method to achieve more efficient dc power distribution and voltage regulation for future data centers is presented. This paper describes a series-stacked power delivery architecture, where servers are connected electrically in series, thereby, providing inherent step down of voltage. Server voltage regulation is performed by differential power converters, which only process the mismatch power between servers. The bulk power flows with no power processing, yielding greatly increased system efficiency compared to conventional architectures. We demonstrate the series-connected architecture with an experimental proof of concept and compare the proposed architecture with a conventional dc power delivery architecture employing a best-in-class power supply unit for servers. The proposed power delivery architecture is validated with a series-stacked server rack consisting of four 12 V servers, powered from a 48 V dc bus, performing two different real-world operations: web traffic management and computation. Through experimental measurements, we demonstrate up to a 40x reduction in power conversion losses compared to state-of-the-art hardware, and an overall best-case system conversion efficiency of 99.89%.

77 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors comprehensively review and classify various step-up dc-dc converters based on their characteristics and voltage-boosting techniques, and discuss the advantages and disadvantages of these voltage boosting techniques and associated converters.
Abstract: 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.

1,230 citations

01 Jan 1992
TL;DR: In this paper, a multilevel commutation cell is introduced for high-voltage power conversion, which can be applied to either choppers or voltage-source inverters and generalized to any number of switches.
Abstract: The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<>

1,202 citations

Journal ArticleDOI
TL;DR: The state-of-the-art dc microgrid technology that covers ac interfaces, architectures, possible grounding schemes, power quality issues, and communication systems is presented.
Abstract: To meet the fast-growing energy demand and, at the same time, tackle environmental concerns resulting from conventional energy sources, renewable energy sources are getting integrated in power networks to ensure reliable and affordable energy for the public and industrial sectors However, the integration of renewable energy in the ageing electrical grids can result in new risks/challenges, such as security of supply, base load energy capacity, seasonal effects, and so on Recent research and development in microgrids have proved that microgrids, which are fueled by renewable energy sources and managed by smart grids (use of smart sensors and smart energy management system), can offer higher reliability and more efficient energy systems in a cost-effective manner Further improvement in the reliability and efficiency of electrical grids can be achieved by utilizing dc distribution in microgrid systems DC microgrid is an attractive technology in the modern electrical grid system because of its natural interface with renewable energy sources, electric loads, and energy storage systems In the recent past, an increase in research work has been observed in the area of dc microgrid, which brings this technology closer to practical implementation This paper presents the state-of-the-art dc microgrid technology that covers ac interfaces, architectures, possible grounding schemes, power quality issues, and communication systems The advantages of dc grids can be harvested in many applications to improve their reliability and efficiency This paper also discusses benefits and challenges of using dc grid systems in several applications This paper highlights the urgent need of standardizations for dc microgrid technology and presents recent updates in this area

505 citations

Journal ArticleDOI
TL;DR: The results show that the proposed modified incremental conductance algorithm is able to track the GMPP accurately under different types of partial shading conditions, and the response during variation of load and solar irradiation are faster than the conventional Inc Cond algorithm.
Abstract: Under partial shading conditions, multiple peaks are observed in the power-voltage (P- V) characteristic curve of a photovoltaic (PV) array, and the conventional maximum power point tracking (MPPT) algorithms may fail to track the global maximum power point (GMPP). Therefore, this paper proposes a modified incremental conductance (Inc Cond) algorithm that is able to track the GMPP under partial shading conditions and load variation. A novel algorithm is introduced to modulate the duty cycle of the dc-dc converter in order to ensure fast MPPT process. Simulation and hardware implementation are carried out to evaluate the effectiveness of the proposed algorithm under partial shading and load variation. The results show that the proposed algorithm is able to track the GMPP accurately under different types of partial shading conditions, and the response during variation of load and solar irradiation are faster than the conventional Inc Cond algorithm. Hence, the effectiveness of the proposed algorithm under partial shading condition and load variation is validated in this paper.

415 citations

Journal ArticleDOI
TL;DR: In this paper, an energy conversion approach that enables each PV element to operate at its maximum power point (MPP) while processing only a small fraction of the total power produced is presented.
Abstract: Conventional energy conversion architectures in photovoltaic (PV) systems are often forced to tradeoff conversion efficiency and power production. This paper introduces an energy conversion approach that enables each PV element to operate at its maximum power point (MPP) while processing only a small fraction of the total power produced. This is accomplished by providing only the mismatch in the MPP current of a set of series-connected PV elements. Differential power processing increases overall conversion efficiency and overcomes the challenges associated with unmatched MPPs (due to partial shading, damage, manufacturing tolerances, etc.). Several differential power processing architectures are analyzed and compared with Monte Carlo simulations. Local control of the differential converters enables distributed protection and monitoring. Reliability analysis shows significantly increased overall system reliability. Simulation and experimental results are included to demonstrate the benefits of this approach at both the panel and subpanel level.

411 citations