This paper provides an overview of grid code technical requirements regarding the connection of large wind farms to the electric power systems. The grid codes examined are generally compiled by transmission system operators (TSOs) of countries or regions with high wind penetration and therefore incorporate the accumulated experience after several years of system operation at significant wind penetration levels. The paper focuses on the most important technical requirements for wind farms, included in most grid codes, such as active and reactive power regulation, voltage and frequency operating limits and wind farm behaviour during grid disturbances. The paper also includes a review of modern wind turbine technologies, regarding their capability of satisfying the requirements set by the codes, demonstrating that recent developments in wind turbine technology provide wind farms with stability and regulation capabilities directly comparable to those of conventional generating plants.

A review of grid code technical requirements for wind farms

The paper reviews different approaches, technologies, and strategies to manage large-scale schemes of variable renewable electricity such as solar and wind power. We consider both supply and demand side measures. In addition to presenting energy system flexibility measures, their importance to renewable electricity is discussed. The flexibility measures available range from traditional ones such as grid extension or pumped hydro storage to more advanced strategies such as demand side management and demand side linked approaches, e.g. the use of electric vehicles for storing excess electricity, but also providing grid support services. Advanced batteries may offer new solutions in the future, though the high costs associated with batteries may restrict their use to smaller scale applications. Different “P2Y”-type of strategies, where P stands for surplus renewable power and Y for the energy form or energy service to which this excess in converted to, e.g. thermal energy, hydrogen, gas or mobility are receiving much attention as potential flexibility solutions, making use of the energy system as a whole. To “functionalize” or to assess the value of the various energy system flexibility measures, these need often be put into an electricity/energy market or utility service context. Summarizing, the outlook for managing large amounts of RE power in terms of options available seems to be promising.

https://research.aalto.fi/files/6557604/lund_et_al_review.pdf

Review of energy system flexibility measures to enable high levels of variable renewable electricity

The Global Energy Assessment (GEA) brings together over 300 international researchers to provide an independent, scientifically based, integrated and policy-relevant analysis of current and emerging energy issues and options. It has been peer-reviewed anonymously by an additional 200 international experts. The GEA assesses the major global challenges for sustainable development and their linkages to energy; the technologies and resources available for providing energy services; future energy systems that address the major challenges; and the policies and other measures that are needed to realize transformational change toward sustainable energy futures. The GEA goes beyond existing studies on energy issues by presenting a comprehensive and integrated analysis of energy chalenges, opportunities and strategies, for developing, industrialized and emerging economies. This volume is a invaluable resource for energy specialists and technologists in all sectors (academia, industry and government) as well as policymakers, development economists and practitioners in international organizations and national governments.

Global Energy Assessment: Toward a Sustainable Future

The pumped hydro energy storage (PHES) is a well-established and commercially-acceptable technology for utility-scale electricity storage and has been used since as early as the 1890s. Hydro power is not only a renewable and sustainable energy source, but its flexibility and storage capacity also make it possible to improve grid stability and to support the deployment of other intermittent renewable energy sources such as wind and solar. As a result, a renewed interest in PHES and a demand for the rehabilitation of old small hydro power plants are emerging globally. With regard to PHES, advances in turbine design are required to enhance plant performance and flexibility and new strategies for optimizing storage capacity and for maximizing plant profitability in the deregulated energy market. In the early 2000s, this technology has again emerged as an economically and technologically acceptable option for peak load shaving and wind and solar energy storage for power quality assurance. Furthermore, renewable energy sources due to their fluctuating nature cannot maintain or regulate continuous supply of power and hence require bulk electricity storage. The present study aims at reviewing the existing global PHES capacities, technological development, and hybrid systems (wind-hydro, solar pv-hydro, and wind-pv-hydro) and recommending the best possible options. The review explores that PHES is the most suitable technology for small autonomous island grids and massive energy storage, where the energy efficiency of PHES varies in practice between 70% and 80% with some claiming up to 87%. Around the world, PHES size mostly nestles in the range of 1000–1500 MW, being as large as 2000–3000 MW. On the other hand, photovoltaic based pumped storage systems have been used for very small scale (load of few houses) only.

Pumped hydro energy storage system: A technological review

Virtual synchronous generators: A survey and new perspectives

Inertial response of variable speed wind turbines

There are already several power systems coping with large amounts of wind power. Hi h penetration of wind power has impacts that have to be manage through proper plant interconnection, integration, ...

Design and operation of power systems with large amounts of wind power

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Design and operation of power systems with large amounts of wind power: State of the art report

Europe is rapidly expanding its wind energy capacity, especially offshore. Hence, the construction of a multiterminal dc (MTdc) network could bring several advantages to accommodate the generated electrical energy, but will also bring many challenges. This paper focuses on one of these challenges, namely the operation and control of an MTdc network. Moreover, a study is carried on how to optimally operate and control an offshore MTdc network for integration of wind energy in the North Sea. An evolutionary strategy called covariance matrix adaptation (CMA) is employed to obtain optimal power flows inside the offshore network. The MTdc grid is composed of 19 nodes, interconnecting nine offshore wind farms to five European countries. The optimal power flow results obtained from the CMA algorithm are tested in a dynamic simulation model to check the control strategy performance in different case studies.

Jan Pierik

Papers

Inertial response of variable speed wind turbines

Design and operation of power systems with large amounts of wind power

Design and operation of power systems with large amounts of wind power: State of the art report

Optimal Power Flow Control of VSC-Based Multiterminal DC Network for Offshore Wind Integration in the North Sea

Design and operation of power systems with large amounts of wind power : Final report, Phase one 2006-08, IEA WIND Task 25