Introducing a new wind speed complementarity model

The power system inertia is gradually decreasing with the growing share of variable renewable energy (VRE). This may jeopardize the frequency dynamics and challenges the secure operation of power systems. In this paper, the concept of frequency security margin is proposed to quantify the system frequency regulation ability under contingency. It is defined as the maximum power imbalance that the system can tolerate while keeping frequency within the tolerable frequency range. A frequency constrained unit commitment (FCUC) model considering frequency securitymargin is proposed. Firstly, the analytical formulation of system frequency nadir is derived while considering both the frequency regulation characteristics of the thermal generators and the frequency support from VRE plants. Then, the frequency security margin is analytically formulated and piecewise linearized. A novel FCUC model is proposed by incorporating linear frequency security constraints into the traditional unit commitment model. Case studies on a modified IEEE RTS-79 system and HRP-38 system are provided to verify the effectiveness of the proposed FCUC model. The impacts of VRE penetration on system frequency security are analyzed using frequency security margin.

The increasing share of variable renewable energy (VRE) generation poses challenges to power systems. Possible challenges include adequacy of reserves, planning and operation of power systems, and interconnection expansion studies in future power systems with very different generation patterns compared to today. To meet these challenges, there is a need to develop models and tools to analyze the variability and uncertainty in VRE generation. To address the varied needs, the tools should be versatile and applicable to different geographical and temporal scales. Time series simulation tools can be used to model both today and future scenarios with varying VRE installations. Correlations in Renewable Energy Sources (CorRES) is a simulation tool developed at Technical University of Denmark, Department of Wind Energy capable of simulating both wind and solar generation. It uses a unique combination of meteorological time series and stochastic simulations to provide consistent VRE generation and forecast error time series with temporal resolution in the minute scale. Such simulated VRE time series can be used in addressing the challenges posed by the increasing share of VRE generation. These capabilities will be demonstrated through three case studies: one about the use of large‐scale VRE generation simulations in energy system analysis, and two about the use of the simulations in power system operation, planning, and analysis.This article is categorized under: Wind Power > Systems and Infrastructure Energy Infrastructure > Systems and Infrastructure Energy Systems Economics > Systems and Infrastructure

As the share of variable renewable energy (VRE) such as wind and solar power continues to grow across Europe, understanding how climate change may affect their short-term variability and extreme events is critical for energy planning, system stability, and resilience. This study investigates projected changes in sub-daily variability and the frequency of extreme conditions in wind and solar energy resources using regional climate model simulations over Europe.We employ a suite of features to characterize the short-term dynamics of VRE resources, including ramp rates, lag-1 autocorrelation, and event-based metrics such as the duration and persistence of power drops (e.g., time below the P10 threshold). These features are computed from 3-hourly wind speed and surface solar radiation data, covering both historical and future periods from the Euro-CORDEX ensemble under the RCP8.5 scenario. To support the robustness of the analysis, model outputs are compared against long-term observations from tall towers and surface radiation stations at selected European sites.The results suggest that future climate conditions could lead to both beneficial and adverse changes in VRE variability: increased persistence may enhance predictability in some regions, while intensified ramp events and prolonged low-production periods may pose challenges for grid management and storage needs elsewhere. The spatially diverse impacts highlight the need for regional-scale assessments.These findings demonstrate the importance of integrating short-term variability and extremes into long-term energy system modeling and risk assessments, and they provide actionable insights for improving the resilience of future low-carbon energy systems.

India’s power system is facing growing challenges of ramping due to the increasing share of variable renewable energy (VRE) sources such as solar and wind. As net load profiles become steeper and more volatile, particularly during solar generation drops due to cloud cover and evening peaks, the ability to manage ramping, defined as the rate of change in generation output, has become critical in maintaining grid stability. A comprehensive analysis of state-wise ramping behaviour using hourly data for the year 2023 reveals that opposing ramp directions between states occurred in 30%-50% of time blocks, challenging the net national ramp and complicating system-level balancing. Despite these challenges, India possesses sufficient ramping capability, particularly from thermal generators, but lacks a mechanism to harmonize ramping efforts of generators across state as well as regions. The paper proposes a layered Security-Constrained Economic Dispatch (SCED) framework, which combines intrastate optimization with a national-level coupling layer to align state-level ramp vectors without disrupting existing contractual structures. The paper also includes the recommendations e.g. regulatory recognition of ramping, improved data transparency, and incentivization of flexible generation to support integration of renewables reliably in a cost-effective manner.

ABSTRACTLong‐term power system expansion planning aligned with current sustainable development policies plays a pivotal role in achieving global targets for energy transition, particularly in developing countries. This paper presents a comprehensive long‐term expansion planning model for Brazil, taking into account decarbonisation pathways using OSeMOSYS integrated with Flextool. Four scenarios explore the potential benefits of increasing the share of variable renewable energy (VRE), specifically photovoltaic (PV) and offshore wind, to 40% of the total energy produced, both with and without a storage system. Results indicate that policies better aligned with net‐zero strategies do not impose a significant cost burden.

Under high variable renewable energy (VRE) penetration, the occurrence of low VRE production, such as dark doldrums (Dunkelflaute) and wind-solar drought, can threaten a secure and continuous energy supply owing to an imbalance between electricity demand and supply. In this study, historically reconstructed long-term VRE generation and electricity demand were used to investigate the relationship between extremely high residual load (demand minus VRE output) with dark doldrums, and weather/climate in Japan. The impact of changes in the VRE's installed capacity on this relationship was also investigated using three simple future target scenarios. The results showed that the increase in installed VRE capacity causes greater daily and weekly residual load variabilities and affects the seasonality of its peaks. To study the weather patterns associated with high residual load events, self-organizing maps were applied to atmospheric circulation fields derived from atmospheric reanalysis data. The high residual load was associated with enhanced cold surge-type weather patterns during winter at the current low VRE installation level. However, under future increased VRE penetration, the weather patterns leading to high residual load will change to cloudy-windless types typically caused by a southern coastal extratropical cyclone. There is also considerable interannual  variability in the frequency of  dark doldrums and high residual load events, that is strongly connected to climate variations in the tropical Indo-Pacific. However, this linkages are changed significantly with increasing VRE capacity. It is crucial to incorporate the dependence of climatic conditions into designing power systems to maintain the stability of a power system under future conditions.

Effects of meteorological and climatological factors on extremely high residual load and possible future changes

Several countries continue to invest in variable renewable energy (VRE) sources to replace fossil fuels and achieve a nationally determined contribution. Consequently, as the share of VRE generation in each country's power grid increases, its curtailment also increases. Current studies on VRE curtailment are based on a comparative analysis of statistical data collected from different countries. However, only a few studies present detailed results based on historical curtailment data collected from individual wind farms. This study analyzes the curtailment data collected for three wind farms over four years. The duration, curtailed output, and cost per curtailment were determined to be 200 min, 38 MWh, and $3.02k, respectively. Finally, the curtailment loss to wind farms caused by the increasing share of VRE generation in the power grid was estimated. The curtailed output and curtailment cost are estimated to increase by 1.3 GWh and $107.6k, respectively, when the share of VRE in the power grid increases by 1%. These findings can aid in identifying the curtailment experienced by wind farm operators and subsequent potential economic losses. Moreover, they can form the basis for establishing an efficient curtailment cost compensation system.

Power system flexibility need induced by wind and solar power intermittency on time scales of 1–14 days

Gas switching reforming for flexible power and hydrogen production to balance variable renewables

This paper proposes a new method to assist in determining the suitability degree of site-matching between wind turbine generators and sites. For a given wind site, by considering power density and capacity factor, the optimum rated speed of a wind turbine generator is found to exhibit when the capacity factors at nonrated and rated operation region are mutually equal. A suitability function is meanwhile suggested as an aid to assess. Through the data acquired from utility, the proposed approach has been practically employed to inspect wind farms in Taiwan. Test results support the feasibility of the method for the application considered.

Assessment of curtailed wind energy potential for off-grid applications through mobile battery storage

The Impact of Wind Power Support Schemes on Technology Choices

The power generation mix of the Association of Southeast Asian Nations (ASEAN) is dominated by fossil fuels, which accounted for almost 80% in 2017 and are expected to account for 82% in 2050 if the region does not transition to cleaner energy systems. Solar and wind power are the most abundant energy resources but contribute negligibly to the power mix. Investors in solar or wind farms face high risks from electricity curtailment if surplus electricity is not used. Employing the policy scenario analysis of the energy outlook modelling results, this paper examines the potential scalability of renewable hydrogen production from curtailed electricity in scenarios of high share of variable renewable energy in the power generation mix. The study found that ASEAN has high potential in developing renewable hydrogen production from curtailed electricity. The study further found that the falling cost of renewable hydrogen production could be a game changer to upscaling the large-scale hydrogen production in ASEAN through policy support. The results implied a future role of renewable hydrogen in energy transition to decarbonize ASEAN’s emissions.

Energy systems with a high share of variable renewable energy are more vulnerable to sudden changes in the system operation. This is especially emphasized on small systems such as energy systems on geographical islands. Because of these reasons, there is a need for quantifying the risk of energy scenarios of such systems. This paper presents a novel robust risk assessment method under demand uncertainty for energy planning scenarios for the islands. The method uses graph theory for the representation of power system topology. The Poisson distribution is used for calculating the probability of power system element failure. The robust modelling approach is applied by the introduction of auxiliary variables and compared to the deterministic model results. Four energy planning scenarios for Unije island are modelled and subjugated to several power system outages resulting in a risk vector calculated as the product of probability vector and damage matrix. The study also presents a zero-import risk energy planning scenario for Unije island that is achieved for a system of 0.5 MW photovoltaic plant and 3.55 MWh battery storage system.