Development and Demonstration of New Technology for the use of Wind Turbines on Ships

Technology to substantially reduce commercial ship fuel consumption by harnessing sea winds for simultaneous generation of electricity and thrust, has been developed by the company PROPit AB. The basic idea is to apply conventional wind turbine technology for the marine environment, where the turbine will also take the function of sails. Primary target market is tankers or bulk ships with a large and open deck space. Chalmers, in a study co-sponsored by the Swedish Energy Agency and Chalmers Energy Centre, 2011, confirmed fuel saving estimates around 15-30 % for optimal routes, but with higher uncertainties

Inertia Support During Variable Wind Conditions

Wind variations are important to consider while designing inertia support strategies. A model has been evaluated but the findings should reflect issues with several control strategies utilizing a fixed inertia support pattern. Wind variability of 0.5 m/s from second to second is observed in real wind data. However, drastic changes in wind speed can occur within the duration of inertia support. An improved inertia control algorithm has been presented allowing a stable delivery of inertia support from variable speed wind turbines (VSWT) subjected to realistic wind conditions. The controller improves the previously presented inertia algorithm and smoothly transitions from a locked operation window to MPPT-operation. The impact of the utilized wind speed filter is described and its impact on the simulation found to be of great importance

The Effect of Wind Power Integration on the Frequency of Tap Changes of a Substation Transformer

As the capacity of wind power installed in a radial distribution system (DS) increases, there is a concern that it may introduce more frequent tap change operations in substation transformers. The increase in the frequency of tap changes (FTC) can accelerate the wear and tear of the tap changers. As a result, the introduction of wind power to DSs may be hindered. Hence the aim of this paper is to investigate the effect of wind power integration on the FTC in a radial DS. A case study shows that the changes on the FTC in DSs connected to relatively strong external grid is negligible up to significant level of penetration. But in DSs connected to a relatively weak external grid, a significant increase in the FTC has been observed as wind power penetration increases. Hence a further investigation is carried out to limit the FTC by using reactive power from local wind turbines. The results have shown that the methodology is very effective

An overview of proactive wind turbine control

Recent achievements in the proactive turbine control, based on the upwind speed measurements, are described in a unified framework (as an extension of the tutorial [1]), that in turn represents a systematic view of the control activity carried out within the Swedish Wind Power Technology Center (SWPTC). A new turbine control problem statement with constraints on blade loads is reviewed. This problem statement allows the design of a new class of simultaneous speed and pitch control strategies based on the preview measurements and look-ahead calculations. A generation of a piecewise constant desired pitch angle profile which is calculated using the turbine load prediction is reviewed in this article as one of the most promising approaches. This in turn allows the reduction of the pitch actuation and the design of the collective pitch control strategy with the maximum possible actuation rate. Two turbine speed control strategies based on one-mass and two-mass models of the drivetrain are also described in this article. The strategies are compared to the existing drivetrain controller. Moreover, postprocessing technique that can be used for estimation of the turbine parameters with improved performance is also discussed. Postprocessing-based estimation of the turbine inertia moment is given as an example. All the results are illustrated by simulations with a wind speed record from the H\uf6n\uf6 turbine, located outside of Gothenburg, Sweden. Recent achievements in the proactive turbine control, based on the upwind speed measurements are described in a unified framework that in turn represents a systematic view of the control activity carried out within the Swedish Wind Power Technology Center (SWPTC)

Optimal Maintenance Schedule for a Wind Power Turbine with Aging Components

Wind power is one of the most important sources of renewable energy available today. A large part of the cost of wind energy is due to the cost of maintaining wind power equipment. When a wind turbine component fails to function, it might need to be replaced under circumstances that are less than ideal. This is known as corrective maintenance. To minimize unnecessary costs, a more active maintenance policy based on the life expectancy of the key components is preferred. Optimal scheduling of preventive maintenance activities requires advanced mathematical modeling. In this paper, an optimal preventive maintenance algorithm is designed using the renewal-reward theorem. In the multi-component setting, our approach involves a new idea of virtual maintenance that allows us to treat each replacement event as a renewal event even if some components are not replaced by new ones. The proposed optimization algorithm is applied to a four-component model of a wind turbine, and the optimal maintenance plans are computed for various initial conditions. The modeling results clearly show the benefit of PM planning compared to a pure CM strategy (about 30% lower maintenance cost)

Optimizing Wind Power Hosting Capacity of Distribution Systems Using Cost Benefit Analysis

The penetration of wind power into the electricity grid is growing significantly. A significant portion of this wind power is being installed in distribution systems, of which most are passively operated. Under this operating practice, wind power can only be admitted based on minimum load and maximum generation consideration. This severely limits the wind power hosting capacity of the system. Hence, the use of active-management strategies (AMSs) has been proposed to increase the hosting capacity of distribution systems. This paper incorporates AMSs into two optimization models whose objectives are to maximize the net benefit of distribution system operator and wind farm owner, respectively. The AMSs considered are wind energy curtailment, coordinated on-load tap changer voltage control, and reactive power compensation. The models development is based on a typical medium-voltage distribution system in Sweden although it can easily be adapted to other cases. The application of the model to a distribution system in Sweden shows an increase in hosting capacity of the distribution system by 78% with mere 2.6% curtailed energy. That is, the hosting capacity of the distribution system has almost been doubled by using AMSs

Integration Aspects of Full Converter Wind Turbines and the Impact on Long-term Voltage Stability

This paper examines how various integration aspects of full converter wind turbines, such as grid code design, control aspects, and placement of turbines, impact the long-term voltage stability of a power system. The simulations are conducted on a modified version of the Nordic32 test system. Different cases have been analyzed and show, for example, that if over-dimensioning of converters is implemented, it is mainly the converters’ currentcapacity that should be increased since the voltage limitation of converters seldom is reached during voltage instability events. Furthermore, a restrictive reactive control scheme is tested, with the aim of minimizing the wear and maintenance of converter components. Although found to generally reduce the voltage stability, the proposed control scheme could be adopted during specific conditions where the local need of voltage support is low. The placement of larger wind farms was found to have the largest impact, both on long-term voltage stability of the system itself, and on the effect that the analyzed design and control aspects had on the system stability. Consequently, the placement of WFs is found be an important factor to consider when designing ancillary services and grid codes for wind power

A Congestion Forecast Framework for Distribution Systems with High Penetration of PV and PEVs

This paper presents a congestion forecast framework for electrical distribution systems with high penetration of solar photovoltaic and plug-in electric vehicles. The framework is based on probabilistic power flow to account for the uncertainties in photovoltaic production and load demand. The proposed framework has been implemented and tested using the data of the real distribution grid of Chalmers University of Technology campus. Cases studies have been carried out using the framework to analyse the impact of different local production levels and operating modes of solar photovoltaic inverter. The results have shown that cumulative probability for network congestion in branches and transformers would increase by 30% and 20% respectively, when the level of local PV generation, demand and PEVs demand to increase by 100%, 95% and 100% respectively. Also, results have shown that network congestion in branches and transformers is 4% and 8% respectively, more likely to occur in the constant-V mode as compared to constant-pf mode. These results can help distribution system operators to predict any upcoming congestion in their system and subsequently help them in taking suitable actions in order to mitigate congestion

Energy Scheduling Strategies for Grid-connected Microgrids: A Case Study on Chalmers Campus

This paper focuses on the optimal energy managementof grid-connected microgrids with battery energy storagesystems. The microgrid energy management and the optimalpower flow of the distribution network are formulated as mixed-integerlinear optimization problems to evaluate microgrid energyscheduling strategies including cost minimization, maximum useof own resources, and minimum energy exchange with theupstream network. The real distribution network of ChalmersUniversity of Technology campus is used as a case study. Thestudy results show that economic optimization yields an annualmicrogrid cost reduction of 4%. Alternatively, if the microgridminimizes the energy exchange, virtual islanding operation (zeroenergy exchange) for 3211 hours can be achieved within a year.The results also present the effects on the operation and costof the distribution system and highlight a trade-off betweenmicrogrid cost minimization and battery lifetime

Key Drivers and Future Scenarios of Local Energy and Flexibility Markets

This paper explores the key drivers of local energy and flexibility markets, develops a set of plausible future scenarios for these markets, and analyzes the scenarios\u27 impact. The results can provide insight to policymakers, researchers, system operators, and aggregators in a better design and more successful implementation of local markets. This study is based on the well-established scenario planning technique of "intuitive logics"and it is conducted by means of qualitative methods, surveys, and cross-impact analysis. Results explore and rank the impact and uncertainty of 20 key factors and trends which can affect the future of local energy and flexibility markets. The results show that factors related to the availability of active and smart end-users, and regulatory incentives are the most impactful and uncertain ones in the future of local markets. Four future scenarios are introduced based on these factors and their impacts are discussed