Renewable energy sources like wind, sun, and hydro are seen as a reliable alternative to the traditional energy sources such as oil, natural gas, or coal. Distributed power generation systems (DPGSs) based on renewable energy sources experience a large development worldwide, with Germany, Denmark, Japan, and USA as leaders in the development in this field. Due to the increasing number of DPGSs connected to the utility network, new and stricter standards in respect to power quality, safe running, and islanding protection are issued. As a consequence, the control of distributed generation systems should be improved to meet the requirements for grid interconnection. This paper gives an overview of the structures for the DPGS based on fuel cell, photovoltaic, and wind turbines. In addition, control structures of the grid-side converter are presented, and the possibility of compensation for low-order harmonics is also discussed. Moreover, control strategies when running on grid faults are treated. This paper ends up with an overview of synchronization methods and a discussion about their importance in the control

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Overview of Control and Grid Synchronization for Distributed Power Generation Systems

The use of distributed energy resources is increasingly being pursued as a supplement and an alternative to large conventional central power stations. The specification of a power-electronic interface is subject to requirements related not only to the renewable energy source itself but also to its effects on the power-system operation, especially where the intermittent energy source constitutes a significant part of the total system capacity. In this paper, new trends in power electronics for the integration of wind and photovoltaic (PV) power generators are presented. A review of the appropriate storage-system technology used for the integration of intermittent renewable energy sources is also introduced. Discussions about common and future trends in renewable energy systems based on reliability and maturity of each technology are presented

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Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey

This review focuses on inverter technologies for connecting photovoltaic (PV) modules to a single-phase grid. The inverters are categorized into four classifications: 1) the number of power processing stages in cascade; 2) the type of power decoupling between the PV module(s) and the single-phase grid; 3) whether they utilizes a transformer (either line or high frequency) or not; and 4) the type of grid-connected power stage. Various inverter topologies are presented, compared, and evaluated against demands, lifetime, component ratings, and cost. Finally, some of the topologies are pointed out as the best candidates for either single PV module or multiple PV module applications.

A review of single-phase grid-connected inverters for photovoltaic modules

This book, written by two major figures in adaptive control, provides a wealth of material for researchers, practitioners, and students. While some researchers in adaptive control may note the absence of a particular topic, the book‘s scope represents a high-gain instrument. It can be used by designers of control systems to enhance their work through the information on many new theoretical developments, and can be used by mathematical control theory specialists to adapt their research to practical needs. The book is strongly recommended to anyone interested in adaptive control.

Adaptive Control

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.

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

As the demands of systems such as power-to-hydrogen (P2H) and extreme fast charging (XFC) increase, there is a need for highly customizable and scalable grid-tied power electronics. This paper presents a bidirectional converter architecture comprised of stackable three-phase ac/dc converter modules, scalable to high-power and high-current applications. Multiple converter modules containing a converter power stage and controls can be stacked to obtain a medium-voltage ac (MVAC) tied system without the need for a line frequency transformer. The modular system architecture is made possible by a quadruple active bridge (QAB) dc/dc converter that provides isolation between each of the three ac-side phases within each module and the dc load. The system also removes the need for bulk energy storage by taking advantage of constant balanced three-phase power flow. Decentralized module-level controllers are also implemented to allow for system modularity and scalability. The proposed architecture is validated by simulations of a P2H system consisting of 18 modules and a scaled proof-of-concept hardware prototype consisting of two modules.

Modular Series-Stacked Bidirectional AC/DC Architecture for 3-Phase Grid-Tied Applications

A bidirectional composite converter is provided. The bidirectional composite converter can be used with power electronics, such as but not limited to electric vehicles and other applications. In some implementations, for example, the composite converter may be used in a powertrain of an electric vehicle to couple batteries to a high voltage bus of the vehicle to provide power to the motors and to one or more integrated charging ports (e.g., ac grid wired connections or a wireless charging port) for extremely fast charging. In various implementations, the bidirectional converter architecture may comprise one or more dc transformer modules (DCX's) arranged with output port(s) coupled in series at an output port of the composite converter.

Composite DC-DC Converter

This article presents a new integrated step-down dc–dc hybrid converter that uses only nano-Henry scale inductors at 2–5-MHz switching frequency. Since it is derived from a Dickson-star switched capacitor (SC) converter, the proposed converter inherits the benefit of low voltage stress on switches while enjoying an efficient fine regulation by phase shift, similar to a dual active bridge (DAB) converter. The converter is optimized, designed, and fabricated in 1.7 $\times $ 1.9 mm area of a 130-nm bipolar-CMOS-DMOS (BCD) process. The active die is flip-chipped on a 6.5 $\times $ 6.5 mm package substrate together with power capacitors and two 10-nH integrated passive device (IPD) inductors for demonstration, illustrating the feasibility of passive components’ integration, resulting in a peak efficiency of 91.2% and a peak power density of 1.36 W/mm3 from 9.6–12-V input to 2.15–3.3-V output. Another demonstration is constructed on the same package substrate but with discrete air-core inductors. It achieves a peak efficiency of 92.4% and a peak power density of 0.62 W/mm3, while delivering a max power of 7.5 W. To achieve the performance, a detailed loss analysis and a unique optimization methodology for the converter, together with the design of key sub-blocks, including gate drivers (GDs), phase shift modulator (PSM), and ramp generator (RG), are provided in this article.

A Highly Integrated Hybrid DC–DC Converter With nH-Scale IPD Inductors

This paper introduces novel minimum-deviation control methods to improve step-load transient responses in non-inverting (four-switch) buck-boost dc-dc converters. The approach utilizes all possible switching states to achieve sub-stantial transient response improvements compared to buck-only or boost-only minimum-deviation or time-optimal control (TOC) methods. Using state-plane trajectory analysis, analytical solutions with necessary conditions are developed for step-up and step-down load transient scenarios in both buck and boost modes of operation. An experimental low-voltage prototype intended for mobile applications is used for experimental verification. High effectiveness of the proposed solution is verified by circuit simulations and experiments.

Minimum-Deviation Transient Response in Non-Inverting Buck-Boost DC-DC Converters

This paper presents a transformer-isolated high step-down dc-dc converter based on a stacked active bridge (SAB) configuration. The isolated SAB (iSAB) converter consists of series-stacked inverter modules and parallel-connected rectifier modules. To achieve galvanic isolation, transformers are inserted between the inverter and rectifier bridges. The nominal step-down conversion ratio is determined by the number of inverter modules and the turns ratio of the transformer. In order to reduce the footprint of the magnetic components, the transformers are coupled on a single core, and the series inductances are realized as controllable leakage inductances within the same magnetic structure using a novel custom core and planar winding arrangement, a solution unique to the iSAB configuration. The approach is verified by experimental results on a 400-to-48 V, 3kW, 400kHz iSAB prototype using low-voltage GaN devices and having 96.7% peak efficiency.

Dragan Maksimovic

Papers

Modular Series-Stacked Bidirectional AC/DC Architecture for 3-Phase Grid-Tied Applications

Composite DC-DC Converter

A Highly Integrated Hybrid DC–DC Converter With nH-Scale IPD Inductors

Minimum-Deviation Transient Response in Non-Inverting Buck-Boost DC-DC Converters

400V-to-48V Transformer-Isolated Stacked Active Bridge Converter with Integrated Magnetics