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

This paper derives physical constraints for the output filter of a Point-of-Load (POL) converter. Time-optimal control theory is employed to translate the POL static and dynamic specifications into boundaries in the L-C design space, ultimately defining a set Σ of L and C values compatible with the application requirements. Outside the identified set Σ, no controller is capable of meeting the POL specifications; inside the identified set Σ, various degrees of approximation of the time-optimal response are possible, depending on the specific control approach in the field application. The identified set shows the minimum possible values of L and C such that the specifications can be met, which allows the designer to evaluate the impact of a practical controller implementation on the size of the output filter. The design space and boundaries for a digital PID controller are derived, leading to a combined L-C filter and controller design approach. Experimental results validating the design space boundaries are presented for a 12V-to-1 V, 20 A POL converter.

Specifications-driven design space boundaries for Point-of-Load converters

This paper presents the design and characterization of a 880-MHz class-E power amplifier (PA) designed to operate in a polar transmitter for EDGE signals. The amplifier is intended to be supplied from a 3.6 V battery using a linear amplifier as an envelope tracker, which limits the maximum drain voltage to 3.3 V. With a +7.6 dBm input signal the maximum output power (VDD = 3.3V) is +22.4 dBm with 14.9 dB of gain, a drain efficiency of 71.6% and PAE of 69%. An output power dynamic range of 15.4 dB is achieved when the voltage is varied from 0.5-3.3 V. Taking into account the statistics of an EDGE signal, the mean drain efficiency and PAE are 75.7% and 64.4%, with a mean output power of +18.26 dBm

Class-E Power Amplifier in a Polar EDGE Transmitter

Electric-drive vehicles require a battery management system (BMS) for normal, safe operation of the battery pack, and a DC/DC converter to supply auxiliary loads on the low-voltage (LV) DC bus. This paper presents a shared, central control approach for an integrated BMS/DC-DC system that uses modular DC/DC bypass converters to achieve battery management and supply auxiliary loads in electric vehicles. The motivation to integrate the BMS and DC/DC is to provide differential control of battery cells using the LV bus load and provide an opportunity for advanced battery management to achieve longer battery life and higher power limits. The proposed control approach, system modeling, loop gain analysis, and design of the feedback compensators are provided. Experimental results are presented for a prototype system consisting of eighteen series connected 25 Ah lithium-ion NMC battery cells and three isolated dual-active bridge bypass converters, with combined outputs rated to supply a 1.44 kW auxiliary LV load.

Design and control of an integrated BMS/DC-DC system for electric vehicles

Transformerless stacked active bridge (TSAB) converters are hybrid converters derived from switched capacitor converters by addition of small inductors. TSAB converters achieve the highest efficiency around a nominal conversion ratio because of "soft" charging/discharging of all flying capacitors, low rms currents and zero-voltage-switching of power switches. This paper introduces new configurations of TSAB converters with inductive filter as opposed to capacitive filter at the output port, which opens opportunities to merge a regulation stage at the output. The approach is applied to 48 V to 1 V point-of-load (PoL) conversion by merging a 6-to-1 Dickson TSAB with a multi-phase buck converter at the regulation stage, greatly reduced the need for a bulky intermediate bus capacitor. Experimental results are provided for a 48 V-to-1 V, 100 A prototype consisting of a 6-to-1 TSAB operating at 100-125 kHz using 120 nH inductors, and an off-the-shelf four-phase buck regulating stage operating at 500 kHz. The prototype has 91.5% peak efficiency at 25 A and greater than 85% efficiency up to 90 A.

48 V-to-1 V Transformerless Stacked Active Bridge Converters with Merged Regulation Stage

This paper introduces a digital multiphase modulator (MPM) using mismatch-error shaping techniques based on a digital-to-analog converter view of multiphase power converters. The proposed modulator has relatively simple implementation requiring no explicit pulsewidth modulation and generates control pulses for any number of phases using a single, low-frequency clock. Advantages and disadvantages of the mismatch-error shaping MPM are examined through analysis, simulations, and experimental results. The proposed MPM is particularly well suited for multilevel envelope-tracking amplifiers supplying power to linear RF power amplifiers. Results are shown for an experimental eight-phase buck converter in an envelope-tracking application.

Dragan Maksimovic

Papers

Specifications-driven design space boundaries for Point-of-Load converters

Class-E Power Amplifier in a Polar EDGE Transmitter

Design and control of an integrated BMS/DC-DC system for electric vehicles

48 V-to-1 V Transformerless Stacked Active Bridge Converters with Merged Regulation Stage

Mismatch-Error Shaping-Based Digital Multiphase Modulator