Aidan Tuohy

Electric Power Research Institute | EPRI · Grid Operations and Planning

As penetration of variable renewable power increases, the power system needs more flexibility to manage the variability and uncertainty in the operation process. Allowing solar generation to provide this flexibility can bring substantial benefits to the system. This article evaluates the impacts of flexible solar power generation in the Southern Co...

The demand for low carbon energy calls for close to 100% renewable power systems, with decarbonization of other energy sectors adding to the anticipated paradigm shift. Rising levels of variable inverter-based renewable energy sources (VIBRES) are prompting questions about how such systems will be planned and operated when variable renewable genera...

Close coordination between generation and transmission operations and planning is critical to cost effective and reliable energy production and delivery; such coordination, in the presence of ownership diversity, is indeed a primary and challenging goal of regional transmission organizations in the US and similar organizations worldwide. Optimizing...

Multicarrier energy systems (MCESs) are characterized by strong coordination in operation and planning across multiple energy vectors and/or sectors to deliver reliable, cost-effective energy services to end users/customers with minimal impact on the environment. They have efficiency and flexibility benefits and are deployed in large and small scal...

A multifaceted future for wind power Modern wind turbines already represent a tightly optimized confluence of materials science and aerodynamic engineering. Veers et al. review the challenges and opportunities for further expanding this technology, with an emphasis on the need for interdisciplinary collaboration. They highlight the need to better u...

On 18 Sept. 2019, the IEA Wind ExCo approved the release of the IEA Recommended Practice on Forecast Solution Selection. The ultimate objective of this set of documents is to (1) maximize the value of renewable energy forecast information in operational decision-making applications and (2) significantly reduce the costs of integrating large amounts...

Demand response (DR) can contribute to wind integration in different ways, using either price or incentive‐based programs; the extent to which they can be used to integrate wind depends on the nature of the program. This chapter describes the relevant technologies and possible wind integration issues that could be mitigated with DR or storage. The...

The IEA Wind Task 36 has therefore dedicated a work package (2.1) to generate a guideline for the power industry that is intended to provide a compendium of nformation for all those that are designing or renewing their forecasting system tools in the operation of the power system. The guideline will not only discuss how to setup a trial or benchmar...

With the increase in renewable generation in the power system, system planners have to account for the uncertainty introduced by these sources. However, in the time frame of a traditional transient stability simulation, the uncertainty can be assumed to be negligible. The importance of the uncertainty subsequently arises in the time period between...

This book outlines the challenges that increasing amounts of renewable and distributed energy represent when integrated into established electricity grid infrastructures, offering a range of potential solutions that will support engineers, grid operators, system planners, utilities, and policymakers alike in their efforts to realize the vision of m...

In this paper we consider the effects of the transmission grid on the operational system flexibility and evaluate the trade-offs between various options including committing flexible generation, curtailing Renewable Energy Sources (RES) generation, or allowing flexibility violations in the form of ramping up/down requirements in the presence of hig...

The deployment of solar-based electricity generation, especially in the form of photovoltaics (PVs), has increased markedly in recent years due to a wide range of factors including concerns over greenhouse gas emissions, supportive government policies, and lower equipment costs. Still, a number of challenges remain for reliable, efficient integrati...

Solar generation, both transmission and distribution-connected, can impact the reliability of a power system, especially once it reaches high levels of penetration. For example, the change in generation mix may reduce dynamic reactive power reserves in the system as synchronous generation is displaced to accommodate solar PV generation. This paper...

This paper assesses the implications of various fault ride-through settings of DER, particularly distributed Photovoltaic (PV), on voltage and frequency performance of the bulk system. Many DER interconnection standards were developed without consideration of bulk system reliability needs. These requirements allow, and in some cases require, DER to...

Many countries around the world have instituted policies with the aim of increasing the amount of installed variable generation (VG), such as wind and solar. A consequence of increased penetrations of VG is that changes in their output must be met by the remainder of a system’s resources so that the demand-generation balance is maintained. This pap...

This paper compares retail and wholesale electricity prices in SEM, the market of the island of Ireland, and BETTA in Great Britain. Estimated wholesale costs are much lower in BETTA. We show that this is mostly because the wholesale price in BETTA is set too low to cover generation costs, although it is compensated by large retail margins. The nee...

The first part of this two-paper series discusses the motivation of implementing a primary frequency response (PFR) market in restructured pool-based power markets, as well as the market design that would create the right incentives to provide the response reliably. PFR is the immediate, autonomous response of generation and demand to system freque...

The historical time series data or Monte Carlo simulation approaches that are often used to represent wind power in transmission planning models will lead to large-scale optimisation problems. The complexity of such problems will be further compounded if advanced techniques for wind variability and wind forecast uncertainty management are also endo...

With the increased levels of wind power being seen worldwide and the projected further increases over the coming decades, there has been significant attention paid to emerging flexible resources such as storage and demand-side options as a means to meet many of the challenges associated with wind integration. In particular, these resources could me...

The second part of this two-paper series analyzes the primary frequency response (PFR) market design developed in its companion paper with several case studies. The simulations will show how the scheduling and pricing change depending on whether requirements for PFR are included as well as how the requirements are defined. We first perform simulati...

Wind and solar generation may consequently be difficult to predict over some time scales. Large penetrations of variable generation (VG) lead to increases in the variability and uncertainty in the system's generation output, driving a need for greater flexibility. This flexibility will need to come either from flexible generation technologies or fr...

Increasing levels of wind energy are adding to the uncertainty and variability inherent in electricity grids and are consequently driving changes. Here, some of the possible evolutions in optimal short-term energy balancing to better deal with wind energy uncertainty are investigated. The focus is mainly on managing reserves through changes in sche...

This paper presents a dynamic reserve determination method that can be applied to operations in order to facilitate renewable integration. The method is applied to a realistic system model and incorporates a multiple settlement process that includes a day-ahead unit commitment cycle, an hour-ahead cycle, and a real-time 5-minute cycle. By inserting...

Risk Limiting Dispatch (RLD) is a new framework that integrates complex inputs and allows decision makers to balance tradeoffs and quantify benefits from increased flexibility and improved forecasting. This paper describes a process of forward-contracting for production capacity while considering the full range of operational uncertainties in gener...

This paper will describe work done at EPRI over the past several years in relation to energy storage and bulk power system integration of renewables. In particular, applications of energy storage and related functional requirements are described and technologies are summarized. Insights and lessons learned from various case studies are also examine...

Frequency responsive reserve is the autonomous response of generators and demand response to deviations of system frequency, usually as a result of the instantaneous outage of a large supplier. Frequency responsive reserve arrests the frequency decline resulting in the stabilization of system frequency, and avoids the triggering of under-frequency...

This chapter examines electrical energy storage in systems with high amounts of wind power. Applications for energy storage and wind and storage technologies which could be used are outlined. A literature review is given on using storage to integrate wind. Storage is an expensive resource, and therefore hard to justify; ensuring studies capture the...

This article highlights and demonstrates the new requirements variable and partly unpredictable wind power will bring to unit commitment and power system operations. Current practice is described and contrasted against the new requirements. Literature specifically addressing questions about wind power and unit commitment related power system operat...

The IEA GIVAR project developed the Flexibility Assessment Tool (FAST) to broadly assess flexibility in different areas (which could be one power system or many power systems in the case of large countries). This tool determines the flexibility in an area, the operational, infrastructural and institutional factors limiting the usage of that flexibi...

This paper outlines recent work on development of an optimal power flow (OPF) model for use in systems with large amounts of uncertainty, specifically from wind generation. By incorporating the stochastic nature of wind into the OPF, and thus producing a Stochastic OPF (STOPF), the results seen are more robust to wind power output forecast inaccura...

The utilisation of demand side resources is set to increase over the coming years with the advent of advanced metering infrastructure, home area networks and the promotion of increased energy efficiency. Demand side resources are proposed as an energy resource that, through aggregation, can form part of the power system plant mix and contribute to...

This paper examines the operation of the Irish power system with very high levels of wind energy, with and without pumped storage. A unit commitment model which accounts for the uncertainty in wind power is used. It is shown that as wind penetration increases, the optimal operation of storage depends on wind output as well as load. The main benefit...

Increased interconnection has been highlighted as potentially facilitating the integration of wind generation in power systems by increasing the flexibility to balance the variable wind output. This paper utilizes a stochastic unit commitment model to simulate the impacts of increased interconnection for the island of Ireland with large penetration...

The article reviews the new requirements variable and partly unpredictable wind power could bring to unit commitment and power system operations. Current practice is shortly described and contrasted against the new requirements. Literature specifically addressing questions about wind power and unit commitment related power system operations is revi...

As integration of variable generation continues to grow rapidly in power systems globally, system planners are seeking new tools to understand the role of variable output generators and the challenges experienced with their integration. The North American Electric Reliability Corporation (NERC) has established a task force to examine the integratio...

This paper summarizes work that has been done to examine the impact of the uncertainty and variability of significant installed wind power on the Irish system. As more and more wind power is installed on the system, the operation of conventional plant on the system will be dramatically different. In this paper, three different aspects of the hour-t...

In this paper, the unit commitment and dispatch of a power system with and without a pumped storage unit is examined for increasing levels of installed wind power, from 17% of total energy to 80% of total energy generated by wind 3 (3GW to 15GW of installed wind on the Irish system in 2020). At high levels of installed wind, it is shown that storag...

This paper examines peat power production in Ireland under the three pillars of energy policy—security, competitiveness and environment. Peat contributes to energy security—as an indigenous fuel, it reduces dependency on imports. During a period of low capacity margins, the operation of the peat plants is useful from a system security perspective....

The stochastic nature of wind alters the unit commitment and dispatch problem. By accounting for this uncertainty when scheduling the system, more robust schedules are produced, which should, on average, reduce expected costs. In this paper, the effects of stochastic wind and load on the unit commitment and dispatch of power systems with high level...

This paper summarises some of the main impacts of large amounts of wind power installed in the island of Ireland. Using results from various studies performed on this system, it is shown that wind power will impact on all time frames, from seconds to daily planning of the system operation. Results from studies examining operation of the system with...

Wind energy on a power system alters the unit commitment and dispatch problem, as it adds a stochastic element due to the uncertainty of wind power forecasts. By explicitly taking into account the stochastic nature of wind power, it is expected that better schedules should be produced, thereby reducing costs on the system. This paper compares a sto...

An international forum for exchange of knowledge of power system impacts of wind power has been formed under the IEA Implementing Agreement on Wind Energy. The task “Design and Operation of Power Systems with Large Amounts of Wind Power” is analysing existing case studies from different power systems. There are a multitude of studies made and o...

High penetration of wind power has impacts that have to be managed through proper plant interconnection, integration, transmission planning, and system and market operations. This report is a summary of case studies addressing concerns about the impact of wind power’s variability and uncertainty on power system reliability and costs. The case studi...

As wind power penetration grows, the amount of reserve needed on the system also grows, due to the increases in the uncertainty of wind power, which grows larger as forecast horizon increases. By scheduling the system more often the amount of extra reserve to be carried to cater for wind uncertainty decreases, depending on the flexibility of plant...

An international forum for exchange of knowledge of power system impacts of wind power has been formed under the IEA Implementing Agreement on Wind Energy. The task "Design and Operation of Power Systems with Large Amounts of Wind Power" is analysing existing case studies from different power systems.There are a multitude of studies made and ongoin...

The amount of wind power in the world is increasing quickly. The background for this development is improved technology, decreased costs for the units, and increased concern regarding environmental problems of competing technologies such as fossil fuels. The amount of wind power is not spread equally over the world, so in some areas, there is compa...

In this paper we analyse the 2008 electricity price in the Irish All-Island Market. We test whether this price is 'efficient' by comparing it to the electricity price in Great Britain. This analysis suggests that around ?16 per MWh of the difference in wholesale prices between Ireland and Britain is due to differences in generating technology. The...

This paper outlines a study undertaken for the U.S. Eastern Interconnection in which different advanced unit commitment strategies were simulated for three different years to evaluate the benefits that may occur from using these strategies as an operational tool.

Wind power development in the United States is outpacing previous estimates for many regions, particularly those with good wind resources. The pace of wind power deployment may soon outstrip regional capabilities to provide transmission and integration services to achieve the most economic power system operation. Conversely, regions such as the Sou...