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

/pdf/overview-of-control-and-grid-synchronization-for-distributed-2nx31ovpe9.pdf

Overview of Control and Grid Synchronization for Distributed Power Generation Systems

The enabling of ac microgrids in distribution networks allows delivering distributed power and providing grid support services during regular operation of the grid, as well as powering isolated islands in case of faults and contingencies, thus increasing the performance and reliability of the electrical system. The high penetration of distributed generators, linked to the grid through highly controllable power processors based on power electronics, together with the incorporation of electrical energy storage systems, communication technologies, and controllable loads, opens new horizons to the effective expansion of microgrid applications integrated into electrical power systems. This paper carries out an overview about microgrid structures and control techniques at different hierarchical levels. At the power converter level, a detailed analysis of the main operation modes and control structures for power converters belonging to microgrids is carried out, focusing mainly on grid-forming, grid-feeding, and grid-supporting configurations. This analysis is extended as well toward the hierarchical control scheme of microgrids, which, based on the primary, secondary, and tertiary control layer division, is devoted to minimize the operation cost, coordinating support services, meanwhile maximizing the reliability and the controllability of microgrids. Finally, the main grid services that microgrids can offer to the main network, as well as the future trends in the development of their operation and control for the next future, are presented and discussed.

Control of Power Converters in AC Microgrids

Preface Acknowledgements Introduction: Modern wind energy and its origins Modern wind turbines History of wind energy Wind characteristics and resources Introduction General characteristics of the wind resource Characteristics of the atmospheric boundary layer Wind data analysis and resource estimation Wind turbine energy production estimates using statistical techniques Overview of available resource assessment data Wind measurements and instrumentation Advanced topics Aerodynamics of wind turbines General overview One-dimensional momentum theory and the Betz limit Ideal horizontal axis wind turbing with wake rotation' Airfoils and general concepts of aerodynamics Momentum theory and blade element theory Blade shape for ideal rotor without wake rotation General rotor blade shape performance prediction Blade shape for optimum rotor with wake rotation Generalized rotor design procedure Simplified HAWT rotor performance calculation procedure Effect of drag and blade number on optimum performance Advanced aerodynamic topics Mechanics and dynamics Wind turbine rotor dynamics Detailed and specialized dynamic models Electrical aspects of wind turbines Basic concepts of electric power Power transformers Electrical machines Power converters Ancillary electrical equipment Wind turbine design Design procedure Wind turbine topologies Materials Machine elements Wind turbine loads Wind turbine subsystems and components Design evaluation Power curve prediction Wind turbine loads Wind turbine subsystems and components Design evaluation Power curve prediction Wind turbine control Overview of wind turbine control systems Typical grid-connected turbine operation Supervisory control overview and implementation Dynamic control theory and implementation Wind turbine siting, system design and integration Wind turbine siting Installation and operation issues Wind farms Wind turbines and wind farms in electric grids Offshore wind farms Operation in severe climates Hybrid electrical systems Wind energy system economics Overview of economic assessment of wind energy systems Capital costs of wind energy systems Operation and maintenance costs Value of wind energy Economic analysis methods Wind energy market considerations Wind energy systems: environmental aspects and impacts Avian interaction with wind trubines Visual impact of wind turbines Wind turbine noise Electromagnetic interference effects Land-use environmental impacts Other environmental considerations Nomenclature Problems Index

Wind energy explained : theory, design, and application

The ever increasing progress of high-voltage high-power fully controlled semiconductor technology continues to have a significant impact on the development of advanced power electronic apparatus used to support optimized operations and efficient management of electrical grids, which, in many cases, are fully or partially deregulated networks. Developments advance both the HVDC power transmission and the flexible ac transmission system technologies. In this paper, an overview of the recent advances in the area of voltage-source converter (VSC) HVdc technology is provided. Selected key multilevel converter topologies are presented. Control and modeling methods are discussed. A list of VSC-based HVdc installations worldwide is included. It is confirmed that the continuous development of power electronics presents cost-effective opportunities for the utilities to exploit, and HVdc remains a key technology. In particular, VSC-HVdc can address not only conventional network issues such as bulk power transmission, asynchronous network interconnections, back-to-back ac system linking, and voltage/stability support to mention a few, but also niche markets such as the integration of large-scale renewable energy sources with the grid and most recently large onshore/offshore wind farms.

VSC-Based HVDC Power Transmission Systems: An Overview

Distributed generation: definition, benefits and issues

This chapter provides a brief discussion and analysis of the current status of interconnection regulations for wind turbines and wind turbines in Europe. The chapter starts with a short overview of the relevant technical regulation issues, which includes a brief description of the relevant interconnection regulations considered in this chapter. This is followed by a detailed comparison of the different interconnection regulations. The discussion also includes the capabilities of wind turbines to comply with these requirements. Finally, issues related to international interconnection practice are briefly discussed.

Technical Regulations for the Interconnection of Wind Power Plants to the Power System

The Energy [R]evolution Scenario has became a well known and
well respected energy analysis since it was first published for Europe
in 2005. Global Energy [R]evolution editions were published in
2007, 2008, 2010 and 2012. This is the first Dutch edition.
The Energy [R]evolution provides a consistent fundamental
pathway for how to protect our climate: getting the world from
where we are now to where we need to be by phasing out fossil
fuels and cutting CO2 emissions while ensuring energy security.

Energy [R]evolution - a sustainable Netherlands energy outlook. Report 2013 Netherlands energy scenario

There is a trend all over Europe towards power generation in the distribution network using wind, photovoltaic, and combined heat and power plants. The Danish power system can be considered a leader: already today more than 50 % of the total production capacity consists of distributed generation, mainly wind and combined heat and power plants. As a consequence of this development, it has become more difficult to predict and to control the total electricity generation. This article describes the Danish cell project, a new development for optimal management of distribution grids (cells) with large amount of distributed generation.

The Danish cell project ― Status and perspective of a smart grid demonstration

It is justified to ask why something potentially offering such benefits as Smart Grids seem to do, is not yet in place. As will be discussed in this chapter, this is due to the fact that many conditions must be fulfilled in order to really reap benefits of Smart Grids; if this is indeed the case, benefits can indeed be substantial. In order to get grip on the broad concept of Smart Grids and its interaction with wind power and its system integration, first some definitions of the Smart Grid concept will be analyzed. Thereafter, the reasons for considering Smart Grids are discussed and the question why Smart Grids presently attract so much attention whereas throughout the last century the topic was hardly known, is debated. In the next section, three different Smart Grid concepts are treated and the analysis of each of the three concepts is focused towards their relation with wind power. Finally, practical examples are discussed.

Wind Power and the Smart Grid

The Seychelles aim to cover 5% of electricity with renewables by 2020 and 15% by 2030. The local power system operator commissioned a Grid Absorption Study to determine the technical limits for reaching these targets. The study focussed on how much photovoltaic (PV) generation the grid can absorb. As result, the primary bottleneck was found to be the maintenance of backup generation reserves to compensate for fast down-ramping of PV generation.

/pdf/solar-power-integration-on-the-seychelles-islands-4jyv232uf5.pdf

Thomas Ackermann

Papers

Technical Regulations for the Interconnection of Wind Power Plants to the Power System

Energy [R]evolution - a sustainable Netherlands energy outlook. Report 2013 Netherlands energy scenario

The Danish cell project ― Status and perspective of a smart grid demonstration

Wind Power and the Smart Grid

Solar Power Integration on the Seychelles Islands