Architectures and circuits for low-voltage energy conversion and applications in renewable energy and power management

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 337-343).In this thesis we seek to develop smaller, less expensive, and more efficient power electronics. We also investigate emerging applications where the proper implementation of these new types of power converters can have a significant impact on the overall system performance. We have developed a new two-stage dc-dc converter architecture suitable for low-voltage CMOS power delivery. The architecture, which combines the benefits of switched-capacitor and inductor-based converters, achieves both large voltage step-down and high switching frequency, while maintaining good efficiency. We explore the benefits of a new soft-charging technique that drastically reduces the major loss mechanism in switched-capacitor converters, and we show experimental results from a 5-to-1 V, 0.8 W integrated dc-dc converter developed in 180 nm CMOS technology. The use of power electronics to increase system performance in a portable thermophotovoltaic power generator is also investigated in this thesis. We show that mechanical non-idealities in a MEMS fabricated energy conversion device can be mitigated with the help of low-voltage distributed maximum power point tracking (MPPT) dc-dc converters. As part of this work, we explore low power control and sensing architectures, and present experimental results of a 300 mW integrated MPPT developed in 0.35 um CMOS with all power, sensing and control circuitry on chip. The final piece of this thesis investigates the implementation of distributed power electronics in solar photovoltaic applications. We explore the benefits of small, intelligent power converters integrated directly into the solar panel junction box to enhance overall energy capture in real-world scenarios. To this end, we developed a low-cost, high efficiency (>98%) power converter that enables intelligent control and energy conversion at the sub-panel level. Experimental field measurements show that the solution can provide up to a 35% increase in panel output power during partial shading conditions compared to current state-of-the-art solutions.by Robert C. N. Pilawa-Podgurski.Ph.D

Proceedings of the Flat-Plate Solar Array Project Research Forum on the Design of Flat-Plate Photovoltaic Arrays for Central Stations

The Flat Plate Solar Array Project, focuses on advancing technologies relevant to the design and construction of megawatt level central station systems. Photovoltaic modules and arrays for flat plate central station or other large scale electric power production facilities require the establishment of a technical base that resolves design issues and results in practical and cost effective configurations. Design, qualification and maintenance issues related to central station arrays derived from the engineering and operating experiences of early applications and parallel laboratory reserch activities are investigated. Technical issues are examined from the viewpoint of the utility engineer, architect/engineer and laboratory researcher. Topics on optimum source circuit designs, module insulation design for high system voltages, array safety, structural interface design, measurements, and array operation and maintenance are discussed

Performance evaluation of the photovoltaic system

The various renewable energy source technologies, Photovoltaics (PV) transforming sunlight directly into electricity, have become standard practice worldwide, especially in countries with high solar radiation levels. PV systems have been developed rapidly over recent years, and many new technologies have emerged from different producers. For each type of PV module, manufacturers provide specific information on rated performance parameters, including power at maximum power point (MPP), efficiency and temperature factors, all under standard solar test conditions (STC) 1000 W/m2. Air. In addition, the mass (AM) of 1.5 and the cell's temperature was 25 ̊C. Unfortunately, this grouping of environmental conditions is infrequently found in outdoor conditions. Also, the data provided by the manufacturers are not sufficient to accurately predict the performance of photovoltaic systems in various climatic conditions. Therefore, monitoring and evaluating the performance of the off-site systems is necessary. This thesis aims to overview various photovoltaic technologies, ranging from crystalline silicon (c-SI) to thin-film CdTe and GiCs. The following are the main parameters for evaluating the external units' performance to describe the PV systems' operation and implementation. In addition, a review of the impacts of various environmental and operational factors, such as solar radiation, temperature, spectrum, and degradation

Modelling and optimisation of solar voltaic system using fuzzy logic

There is considerable increase in residential solar grid connected installations with many advantages offered by solar energy. As more solar panels are connected to grid, the Solar Inverter between solar panels and grid have to perform at optimum levels. Modern Inverters consist of DC-DC Converter and DC-AC Inverter. One problem associated with Inverter design is voltage fluctuation, this defect lies in the DC-DC converter Maximum power tracking (MPPT) algorithms responsible for extracting maximum power from the solar panels. The defect is due to large sampling number required for conventional MPPT algorithm. This thesis has proposed a new MPPT algorithm based on Mamdani Fuzzy logic. In research we use 5 parameter one diode model for solar cell modelling. The P-V/I-V characteristics curve is generated. The P-V characteristics curves sectioned and input membership and output membership functions is created. And unique fuzzy rules is used to optimize fuzzy controller output. Mamdani Fuzzy logic algorithm is compared to traditional PI controller hill climbing method. When small sampling number is used hill climbing method response is slow and good at tracking. When big sampling number is used hill climbing method response is fast and not good at tracking. The voltage also fluctuates when sampling number is big. Fuzzy logic provides a compromised solution with best response time and moderate tracking accuracy compared to hill climbing method. Fuzzy Logic based DC-DC converter together with PLL and Recursive Discrete Fourier Transform (RDFT) DC-AC inverter synchronization algorithm is employed and simulated in matlab. The MPPT simulation is conducted for a realistic 2.5KW solar panels in a 8 x 2 Matrix. In addition the MPPT algorithm is analyzed to see if it performs under power quality and voltage level tolerance of utility grid requirements. The Fuzzy Logic MPPT is excellent at tracking power. When temperature is fixed and irradiance is varied, the maximum tracking error is 5.2% in all scenarios with one exception. When irradiance is fixed and temperature varied, the maximum tracking error is 1.98%. Furthermore the Fuzzy Logic MPPT meets the power quality and voltage level tolerance requirements of utility grid for irradiance over 600 W/m2. Power quality and voltage level tolerance requirements for irradiance under 600 W/m2 is not critical as this is outside twilight conditions. Out of all the Synchronization algorithm identified in this Thesis, RDFT achieves synchronization very quickly and in addition it suppresses harmonics and noise. The possibility of future study to extend MPPT is also briefly discussed. The extension of future study is using Takagi-Sugeno fuzzy logic. Takagi-Sugeno uses more sophisticated inference and rule evaluation mathematics

Innovation in Energy Systems

It has been a little over a century since the inception of interconnected networks and little has changed in the way that they are operated. Demand-supply balance methods, protection schemes, business models for electric power companies, and future development considerations have remained the same until very recently. Distributed generators, storage devices, and electric vehicles have become widespread and disrupted century-old bulk generation - bulk transmission operation. Distribution networks are no longer passive networks and now contribute to power generation. Old billing and energy trading schemes cannot accommodate this change and need revision. Furthermore, bidirectional power flow is an unprecedented phenomenon in distribution networks and traditional protection schemes require a thorough fix for proper operation. This book aims to cover new technologies, methods, and approaches developed to meet the needs of this changing field

Innovation in Energy Systems

It has been a little over a century since the inception of interconnected networks and little has changed in the way that they are operated. Demand-supply balance methods, protection schemes, business models for electric power companies, and future development considerations have remained the same until very recently. Distributed generators, storage devices, and electric vehicles have become widespread and disrupted century-old bulk generation - bulk transmission operation. Distribution networks are no longer passive networks and now contribute to power generation. Old billing and energy trading schemes cannot accommodate this change and need revision. Furthermore, bidirectional power flow is an unprecedented phenomenon in distribution networks and traditional protection schemes require a thorough fix for proper operation. This book aims to cover new technologies, methods, and approaches developed to meet the needs of this changing field

Building integrated photovoltaics : a case study of the Northumberland Building

The aim of this work was to examine some of the main factors influencing the performance of a Building Integrated Photovoltaic (BIPV) system. BIPV systems are becoming increasingly common and it is anticipated that they will be installed in large numbers in the future, as a result of various political, environmental and economic factors. It is therefore important that their system performance is optimised during their demonstration phase. Three parallel BIPV projects have been coordinated for this research, with the primary objective of conducting comparative studies to assist in the analysis of the Northumberland Building BIPV system. The other projects include the installation and operation of a BIPV monitoring station, and the design, manufacture and testing of two alternative PV cladding prototypes. The performance of a BIPV system is dependent on a number of interrelated parameters. These include: system orientation, in-plane insolation and shading, temperature, array soiling, the type of PV installed, and the mismatch losses of the installation. This thesis presents an investigation of each of these parameters and assesses how they affect the performance of the Northumberland Building BIPV system as a whole. The approach used differs from that of other researchers, in that it assesses the performance of the whole system, rather than studying one or two issues in isolation. In addition, this work extrapolates the results to predict the performance of various alternative BIPV system designs. Finally an economic analysis of each alternative system is presented and a comparison of system performance and costs is made