A fully integrated 660 MHz low-swing energy-recycling DC-DC converter

A fully integrated 0.18 μm DC-DC buck converter using a low-swing "stacked driver" configuration is reported in this paper. A high switching frequency of 660 MHz reduces filter components to fit on chip, but this suffers from high switching losses. These losses are reduced using: 1) low-swing drivers; 2) supply stacking; and 3) introducing a charge transfer path to deliver excess charge from the positive metal-oxide semiconductor drive chain to the load, thereby recycling the charge. The working prototype circuit converts 2.2 to 0.75-1.0 V at 40-55 mA. Design and simulation of an improved circuit is also included that further improves the efficiency by enhancing the charge recycling path, providing automated zero voltage switching (ZVS) operation, and synchronizing the half-swing gating signals. © 2009 IEEE.

Wave energy emulator and AC/DC rectifiers for direct drive wave energy converters

This paper describes a solid state electrical emulator devised for laboratory testing of power conditioning electronics for direct drive linear wave energy converters (DDLWEC). Two rectification strategies are considered; a uni-directional boost topology, and an H-bridge which may be controlled in either uni- or bidirectional modes.

SoC energy savings = reduce+reuse+recycle: A case study using a 660MHz DC-DC converter with integrated output filter

This paper advocates 'reduce, reuse, recycle' as a complete energy savings strategy. While reduction has been common to date, there is growing need to emphasize reuse and recycling as well. We design a DC-DC buck converter to demonstrate the 3 techniques: reduce with low-swing and zero voltage switching (ZVS), reuse with supply stacking, and recycle with regulated delivery of excess energy to the output load. The efficiency gained from these 3 techniques helps offset the loss of operating drivers at very high switching frequencies which are needed to move the output filter completely on-chip. A prototype was fabricated in 0.18μm CMOS, operates at 660MHz, and converts 2.2V to 0.75-1.0V at ∼50mA.1 © 2008 IEEE.

A 660MHz ZVS DC-DC converter using gate-driver charge-recycling in 0.18μm CMOS with an integrated output filter

The design and manufacture of a prototype chip level power supply is described, with both simulated and experimental results. Of particular interest is the inclusion of a fully integrated on-chip LC filter. A high switching frequency of 660MHz and the design of a device drive circuit reduce losses by supply stacking, low-swing signaling and charge recycling. The paper demonstrates that a chip level converter operating at high frequency can be built and shows how this can be achieved, using zero voltage switching techniques similar to those commonly used in larger converters. Both simulations and experimental data from a fabricated circuit in 0.18μm CMOS are included. The circuit converts 2.2V to 0.75∼1.0V at ∼55mA. ©2008 IEEE.

Three-port DC-DC Converter for Stand-Alone Photovoltaic Systems

System efficiency and cost effectiveness are of critical importance for photovoltaic (PV) systems. This paper addresses the two issues by developing a novel three-port DC-DC converter for stand-alone PV systems, based on an improved Flyback-Forward topology. It provides a compact single-unit solution with a combined feature of optimized maximum power point tracking (MPPT), high step-up ratio, galvanic isolation and multiple operating modes for domestic and aerospace applications. A theoretical analysis is conducted to analyze the operating modes followed by simulation and experimental work. The paper is focused on a comprehensive modulation strategy utilizing both PWM and phase-shifted control that satisfies the requirement of PV power systems to achieve MPPT and output voltage regulation. A 250 W converter was designed and prototyped to provide experimental verification in term of system integration and high conversion efficiency.

New modular structure DC-DC converter without electrolytic capacitors for renewable energy applications

Toroid inductor development for a SIC DC-DC converter up to 150kW, based on finite element method

Dissertação para a obtenção do grau de Mestre em Engenharia Electrotécnica Ramo de Energia

A comparison between bond graphs switching modelling techniques implemented on a boost dc-dc converter

A Bond Graph is a graphical modelling technique that allows the representation of energy flow between the components of a system. When used to model power electronic systems, it is necessary to incorporate bond graph elements to represent a switch. In this paper, three different methods of modelling switching devices are compared and contrasted: the Modulated Transformer with a binary modulation ratio (MTF), the ideal switch element, and the Switched Power Junction (SPJ) method. These three methods are used to model a dc-dc Boost converter and then run simulations in MATLAB/SIMULINK. To provide a reference to compare results, the converter is also simulated using PSPICE. Both quantitative and qualitative comparisons are made to determine the suitability of each of the three Bond Graph switch models in specific power electronics applications

Development of a DC-DC converter for DC bus voltage control of series connected device

The purpose of this work is to study voltage control and energy balance of a split DC bus topology within a power electronics equipment connected to the AC mains, such as UPS systems, wind power generators, active filters and FACTS devices. A typical configuration in such equipment has two mains connected converters sharing a common DC bus, one series connected and the other parallel connected. The DC bus is usually composed by a battery or a capacitor bank. In the proposed topology, the DC bus is divided in two sides, interconnected with a buck-boost converter, which controls power flow and DC voltage on both sides. © 2009 IEEE.

Cascaded DC-DC converter connection of photovoltaic modules

New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single dc-ac inverter connected to a series string of pv panels, or many small dc-ac inverters which connect one or two panels directly to the ac grid. This paper proposes an alternative topology of nonisolated per-panel dc-dc converters connected in series to create a high voltage string connected to a simplified dc-ac inverter. This offers the advantages of a converter-per-panel approach without the cost or efficiency penalties of individual dc-ac grid connected inverters. Buck, boost, buck-boost, and Cuk converters are considered as possible dc-dc converters that can be cascaded. Matlab simulations are used to compare the efficiency of each topology as well as evaluating the benefits of increasing cost and complexity. The buck and then boost converters are shown to be the most efficient topologies for a given cost, with the buck best suited for long strings and the boost for short strings. While flexible in voltage ranges, buck-boost, and Cuk converters are always at an efficiency or alternatively cost disadvantage.

Cascaded DC-DC converter connection of photovoltaic modules

New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single DC-AC inverter connected to a series string of PV modules, or many small DC-AC inverters which connect one or two modules directly to the AC grid. This paper shows that a "converter-per-module" approach offers many advantages including individual module maximum power point tracking, which gives great flexibility in module layout, replacement, and insensitivity to shading; better protection of PV sources, and redundancy in the case of source or converter failure; easier and safer installation and maintenance; and better data gathering. Simple nonisolated per-module DC-DC converters can be series connected to create a high voltage string connected to a simplified DC-AC inverter. These advantages are available without the cost or efficiency penalties of individual DC-AC grid connected inverters. Buck, boost, buck-boost and Cuk converters are possible cascadable converters. The boost converter is best if a significant step up is required, such as with a short string of 12 PV modules. A string of buck converters requires many more modules, but can always deliver any combination of module power. The buck converter is the most efficient topology for a given cost. While flexible in voltage ranges, buck-boost and Cuk converters are always at an efficiency or alternatively cost disadvantage.

Control of cascaded DC-DC converter based hybrid battery energy storage systems - Part II:Lyapunov approach

A cascaded DC-DC boost converter is one of the ways to integrate hybrid battery types within a grid-tie inverter. Due to the presence of different battery parameters within the system such as, state-of-charge and/or capacity, a module based distributed power sharing strategy may be used. To implement this sharing strategy, the desired control reference for each module voltage/current control loop needs to be dynamically varied according to these battery parameters. This can cause stability problem within the cascaded converters due to relative battery parameter variations when using the conventional PI control approach. This paper proposes a new control method based on Lyapunov Functions to eliminate this issue. The proposed solution provides a global asymptotic stability at a module level avoiding any instability issue due to parameter variations. A detailed analysis and design of the nonlinear control structure are presented under the distributed sharing control. At last thorough experimental investigations are shown to prove the effectiveness of the proposed control under grid-tie conditions.

Control of cascaded DC-DC converter-based hybrid battery energy storage systems - Part I:stability Issue

There is an emerging application which uses a mixture of batteries within an energy storage system. These hybrid battery solutions may contain different battery types. A DC-side cascaded boost converters along with a module based distributed power sharing strategy has been proposed to cope with variations in battery parameters such as, state-of-charge and/or capacity. This power sharing strategy distributes the total power among the different battery modules according to these battery parameters. Each module controller consists of an outer voltage loop with an inner current loop where the desired control reference for each control loop needs to be dynamically varied according to battery parameters to undertake this sharing. As a result, the designed control bandwidth or stability margin of each module control loop may vary in a wide range which can cause a stability problem within the cascaded converter. This paper reports such a unique issue and thoroughly investigates the stability of the modular converter under the distributed sharing scheme. The paper shows that a cascaded PI control loop approach cannot guarantee the system stability throughout the operating conditions. A detailed analysis of the stability issue and the limitations of the conventional approach are highlighted. Finally in-depth experimental results are presented to prove the stability issue using a modular hybrid battery energy storage system prototype under various operating conditions.

Ultrahigh step-up dc-dc converter for distributed generation by three Degrees of Freedom (3DoF) approach

This paper proposes a novel dc-dc converter topology to achieve an ultrahigh step-up ratio while maintaining a high conversion efficiency. It adopts a three degree of freedom approach in the circuit design. It also demonstrates the flexibility of the proposed converter to combine with the features of modularity, electrical isolation, soft-switching, low voltage stress on switching devices, and is thus considered to be an improved topology over traditional dc-dc converters. New control strategies including the two-section output voltage control and cell idle control are also developed to improve the converter performance. With the cell idle control, the secondary winding inductance of the idle module is bypassed to decrease its power loss. A 400-W dc-dc converter is prototyped and tested to verify the proposed techniques, in addition to a simulation study. The step-up conversion ratio can reach 1:14 with a peak efficiency of 94% and the proposed techniques can be applied to a wide range of high voltage and high power distributed generation and dc power transmission.

Three-port DC-DC converter for stand-alone photovoltaic systems

System efficiency and cost effectiveness are of critical importance for photovoltaic (PV) systems. This paper addresses the two issues by developing a novel three-port dc-dc converter for stand-alone PV systems, based on an improved Flyback-Forward topology. It provides a compact single-unit solution with a combined feature of optimized maximum power point tracking (MPPT), high step-up ratio, galvanic isolation, and multiple operating modes for domestic and aerospace applications. A theoretical analysis is conducted to analyze the operating modes followed by simulation and experimental work. This paper is focused on a comprehensive modulation strategy utilizing both PWM and phase-shifted control that satisfies the requirement of PV power systems to achieve MPPT and output voltage regulation. A 250-W converter was designed and prototyped to provide experimental verification in term of system integration and high conversion efficiency.