10,913 research outputs found
Real time power management strategy for hybrid energy storage systems coupled with variable energy sources in power smoothing applications
Abstract As the renewable energy sources (RES) production is strongly influenced by multiple geographic factors and highly variable, the need for both energy storage integration and robust real-time power management strategies development is obvious. Wind power represents the largest generating capacity among RES, being at the same time the most fluctuant. The capability to overcome the great disadvantage of wind power variability supports rising its penetration while preserving current operation modes of power systems, so new fashions to achieve this target are of great interest. This paper aims to prove the robustness of a recently introduced power management strategy, able to operate in online conditions, based on simultaneous perturbation stochastic approximation (SPSA) algorithm. To this regard, two different real datasets for wind power profiles with different statistical features are employed. The power management strategy is implemented on a hybrid energy storage system comprising a battery and a flywheel, modeled in Simulink/Matlab. The objectives of the proposed strategy are to reduce the instantaneous power ramp of the profile injected to the grid while smoothening the power profile exchanged by the battery in order to preserve it. Simulations are performed in representative conditions selected on statistical basis. It is demonstrated that the SPSA based power management achieves similar performances in all simulation conditions, proving to be robust. As a performance indicator, the reduction of the power ramp in reference to the 90% CDF threshold is evaluated. It is remarked as an 80% power ramp reduction is obtained towards the grid in both sites. Moreover, the further target is achieved in terms of battery lifetime extension; specifically, the fluctuation of the power profile exchanged by the battery is smoothed by 63% in the first site and 48% in the second, with respect to the flywheel one
Energy Storage Technologies for Smoothing Power Fluctuations in Marine Current Turbines
With regard to marine renewable energies, significant electrical power can be extracted from marine tidal current. However, the power harnessed by a marine current turbine varies due to the periodicity of the tidal phenomenon and could be highly fluctuant caused by swell effect. To improve the power quality and make the marine current generation system more reliable, energy storage systems will play a crucial role. In this paper, the power fluctuation phenomenon is described and the state of art of energy storage technologies is presented. Characteristics of various energy storage technologies are analyzed and compared for marine application. The omparison shows that high-energy batteries like sodiumsulphur battery and flow battery are favorable for smoothing the long-period power fluctuation due to the tide phenomenon while supercapacitors and flywheels are suitable for eliminating short-period power disturbances due to swell or turbulence phenomena. It means that hybrid storage technologies are needed for achieving optimal performance in marine current energy systems
An Optimized Combination of a Large Grid Connected PV System along with Battery Cells and a Diesel Generator
Environmental, economical and technical benefits of photovoltaic (PV) systems
make them to be used in many countries. The main characteristic of PV systems
is the fluctuations of their output power. Hence, high penetration of PV
systems into electric network could be detrimental to overall system
performance. Furthermore, the fluctuations in the output power of PV systems
make it difficult to predict their output, and to consider them in generation
planning of the units. The main objective of this paper is to propose a hybrid
method which can be used to control and reduce the power fluctuations generated
from large grid- connected PV systems. The proposed method focuses on using a
suitable storage battery along with curtailment of the generated power by
operating the PV system below the maximum power point (MPP) and deployment of a
diesel generator. These methods are analyzed to investigate the impacts of
implementing them on the economical benefits that the PV system owner could
gain. To maximize the revenues, an optimization problem is solved
Storage Size Determination for Grid-Connected Photovoltaic Systems
In this paper, we study the problem of determining the size of battery
storage used in grid-connected photovoltaic (PV) systems. In our setting,
electricity is generated from PV and is used to supply the demand from loads.
Excess electricity generated from the PV can be stored in a battery to be used
later on, and electricity must be purchased from the electric grid if the PV
generation and battery discharging cannot meet the demand. Due to the
time-of-use electricity pricing, electricity can also be purchased from the
grid when the price is low, and be sold back to the grid when the price is
high. The objective is to minimize the cost associated with purchasing from (or
selling back to) the electric grid and the battery capacity loss while at the
same time satisfying the load and reducing the peak electricity purchase from
the grid. Essentially, the objective function depends on the chosen battery
size. We want to find a unique critical value (denoted as ) of the
battery size such that the total cost remains the same if the battery size is
larger than or equal to , and the cost is strictly larger if the
battery size is smaller than . We obtain a criterion for evaluating
the economic value of batteries compared to purchasing electricity from the
grid, propose lower and upper bounds on , and introduce an efficient
algorithm for calculating its value; these results are validated via
simulations.Comment: Submitted to IEEE Transactions on Sustainable Energy, June 2011; Jan
2012 (revision
Grid integration of intermittent renewable energy sources using price-responsive plug-in electric vehicles
Plug-in electric vehicles (PEVs) are expected to balance the fluctuation of re-newable energy sources (RES). To investigate the contribution of PEVs, the availability of mobile battery storage and the control mechanism for load man-agement are crucial. This study therefore combined the following: a stochastic model to determine mobility behavior, an optimization model to minimize vehicle charging costs and an agent-based electricity market equilibrium model to esti-mate variable electricity prices. The variable electricity prices are calculated based on marginal generation costs. Hence, because of the merit order effect, the electricity prices provide incentives to consume electricity when the supply of renewable generation is high. Depending on the price signals and mobility behavior, PEVs calculate a cost minimizing charging schedule and therefore balance the fluctuation of RES. The analysis shows that it is possible to limit the peak load using the applied control mechanism. The contribution of PEVs to improving the integration of intermittent renewable power generation into the grid depends on the characteristic of the RES generation profile. For the Ger-man 2030 scenario used here, the negative residual load was reduced by 15 to 22 percent and the additional consumption of negative residual load was be-tween 34 and 52 percent. --Plug-in electric vehicles,demand-side management,variable prices,intermittent generation
Impact of different time series aggregation methods on optimal energy system design
Modelling renewable energy systems is a computationally-demanding task due to
the high fluctuation of supply and demand time series. To reduce the scale of
these, this paper discusses different methods for their aggregation into
typical periods. Each aggregation method is applied to a different type of
energy system model, making the methods fairly incomparable. To overcome this,
the different aggregation methods are first extended so that they can be
applied to all types of multidimensional time series and then compared by
applying them to different energy system configurations and analyzing their
impact on the cost optimal design. It was found that regardless of the method,
time series aggregation allows for significantly reduced computational
resources. Nevertheless, averaged values lead to underestimation of the real
system cost in comparison to the use of representative periods from the
original time series. The aggregation method itself, e.g. k means clustering,
plays a minor role. More significant is the system considered: Energy systems
utilizing centralized resources require fewer typical periods for a feasible
system design in comparison to systems with a higher share of renewable
feed-in. Furthermore, for energy systems based on seasonal storage, currently
existing models integration of typical periods is not suitable
Power Fluctuations Smoothing and Regulations in Wind Turbine Generator Systems
Wind is one of the most popular renewable energy sources and it has the potential to become the biggest energy source in future. Since the wind does not always blow constantly, the output wind power is not constant which may make some problem for the power grid. According to the grid code which is set by independent system operator, ISO, wind turbine generator systems need to follow some standards such as the predetermined acceptable power fluctuations.
In order to smooth the output powers, the energy storage system and some power electronics modules are employed. The utilized power electronics modules in the wind turbine system can pursue many different goals, such as maintaining the voltage stability, frequency stability, providing the available and predetermined output active and reactive power. On the other side, the energy storage system can help achieving some of these goals but its main job is to store the extra energy when not needed and release the stored energy when needed. The energy storage system can be designed in different sizes, material and also combination of different energy storage systems (hybrid designs). Combination of power electronics devises and also energy storage system helps the wind turbine systems to smooth the output power according to the provided standards. In addition prediction of wind speed may improve the performance of wind turbine generator systems.
In this research study all these three topics are studied and the obtained results are written in 10 papers which 7 of them are published and three of them are under process
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