A fast battery cycle counting method for grid-tied battery energy storage system subjected to microcycles

In this paper, a fast battery cycle counting method for grid-connected Battery Energy Storage System (BESS) operating in frequency regulation is presented. The methodology provides an approximation for the number of battery full charge-discharge cycles based on historical microcycling state-of-charge (SOC) data typical of BESS frequency regulation operation. An enhanced frequency response (EFR) algorithm, a new and fast frequency response service in the UK, that provides a charge/discharge response with respect to the deviations in the grid frequency, is used for analysis. The obtained historical SOC data from the EFR analysis is then considered as an input for evaluating the proposed battery cycle counting estimation method

Bi-directional power control of grid-tied battery energy storage system operating in frequency regulation

This paper presents a design of an average value PWM voltage source converter (VSC) along with bi-directional active and reactive power flow control in a grid-tied battery energy storage system. A vector control strategy with PI controllers is proposed. In this paper, a grid frequency regulation control design is also implemented in the BESS in order to meet the frequency response requirement by the National Grid Electricity Transmission, the primary distribution network operator in the UK. Simulation results on a 2MW/968kWh lithium-ion BESS are provided to verify the proposed control design based on the control of an experimentally validated battery model

Battery SOC management strategy for enhanced frequency response and day-ahead energy scheduling of BESS for energy arbitrage

The electricity system has to balance demand and supply every second, a task that is becoming evermore challenging due to the increased penetration of renewable energy sources and subsequent inertial levels. In the UK, a number of grid frequency support services are available, which are developed to provide a real-time response to changes in the grid frequency. The National Grid Electricity Transmission (NGET) - the primary electricity transmission network operator in the UK - has introduced a new faster frequency response service, called the Enhanced Frequency Response (EFR), which requires a response time of under one second. Battery energy storage systems (BESSs) are ideal choice for delivering such a service. In this paper a control algorithm is presented which supplies a charge/discharge power output with respect to deviations in the grid frequency and the ramp-rate limits imposed by NGET, whilst managing the state-of-charge (SOC) of the BESS to maximise the utilisation of the available energy capacity. Using the real UK market clearing prices, a forecasted battery state of charge (SOC) management strategy has been also developed to deliver EFR service whilst scheduling throughout the day for energy arbitrage. Simulation results demonstrate that the proposed algorithm delivers an EFR service within the specification whilst generating arbitrage revenue. A comparative study is also presented to compare the yearly arbitrage revenue obtained from the model of the Willenhall and an experimental Leighton Buzzard battery storage system. Simulation results on a 2MW/1MWh lithium-titanate BESS are provided to verify the proposed algorithm based on the control of an experimentally validated battery model

A Battery Energy Management Strategy for UK Enhanced Frequency Response

Balancing the grid at 50 Hz requires managing many distributed generation sources against a varying load, which is becoming an increasingly challenging task due to the increased penetration of renewable energy sources such as wind and solar and loss of traditional generation which provide inertia to the system. In the UK, various frequency support services are available, which are developed to provide a real-time response to changes in the grid frequency. The National Grid (NG) – the main distribution network operator in the UK – have introduced a new and fast service called the Enhanced Frequency Response (EFR), which requires a response time of under one second. A battery energy storage system (BESS) is a suitable candidate for delivering such service. Therefore, in this paper a control algorithm is developed to provide a charge/discharge power output with respect to deviations in the grid frequency and the ramp-rate limits imposed by the NG, whilst managing the state-of-charge (SOC) of the BESS for an optimised utilisation of the available stored energy. Simulation results on a 2 MW/1 MWh lithiumtitanate BESS are provided to verify the proposed algorithm based on the control of an experimentally validated battery model

Sparse representation of two- and three-dimensional images with fractional Fourier, Hartley, linear canonical, and Haar wavelet transforms

Sparse recovery aims to reconstruct signals that are sparse in a linear transform domain from a heavily underdetermined set of measurements. The success of sparse recovery relies critically on the knowledge of transform domains that give compressible representations of the signal of interest. Here we consider two- and three-dimensional images, and investigate various multi-dimensional transforms in terms of the compressibility of the resultant coefficients. Specifically, we compare the fractional Fourier (FRT) and linear canonical transforms (LCT), which are generalized versions of the Fourier transform (FT), as well as Hartley and simplified fractional Hartley transforms, which differ from corresponding Fourier transforms in that they produce real outputs for real inputs. We also examine a cascade approach to improve transform-domain sparsity, where the Haar wavelet transform is applied following an initial Hartley transform. To compare the various methods, images are recovered from a subset of coefficients in the respective transform domains. The number of coefficients that are retained in the subset are varied systematically to examine the level of signal sparsity in each transform domain. Recovery performance is assessed via the structural similarity index (SSIM) and mean squared error (MSE) in reference to original images. Our analyses show that FRT and LCT transform yield the most sparse representations among the tested transforms as dictated by the improved quality of the recovered images. Furthermore, the cascade approach improves transform-domain sparsity among techniques applied on small image patches. © 2017 Elsevier Lt

Scheduling of grid tied battery energy storage system participating in frequency response services and energy arbitrage

Battery energy storage systems (BESS) are widely used to smooth power fluctuations and maintain the voltage and frequency of the power feeder at a desired level. T he National Grid Electricity Transmission (NGET), the primary electricity transmission network operator in the UK, has introduced various frequency response servic es that are designed to provide a real - time response to deviations in the grid frequency. In this study , a control algorithm is developed which generates a charge/discharge power output with respect to deviations in the grid frequency and the requisite service specifications. Using historical UK electricity prices, a new balancing service scheduling approach has also been developed to maximize energy arbitrage revenue by layering different types of balancing services throughout the day . Simulation result s show that the proposed algorithm delivers both dynamic and non - dynamic firm frequency response (FFR) and also enhanced frequency response (EFR) to NGET specifications while generating arbitrage revenue as well as service availability payment s in the balancing market. A comparative study is also presented to compare the yearly arbitrage revenue obtained from the work presented in this paper and a previous reference study . Finall y, exper imental results of a grid - tied 2MW /1MWh BESS have been used for verification purposes

A Battery Energy Management Strategy for UK Enhanced Frequency Response and Triad Avoidance

This paper describes a control algorithm for a battery energy storage system (BESS) to deliver a charge/discharge power output in response to changes in the grid frequency constrained by the National Grid Electricity Transmission (NGET) - the primary electricity transmission network operator in the UK - whilst managing the state-of-charge (SOC) of the BESS to optimise the availability of the system. Furthermore, this paper investigates using the BESS in order to maximise Triad avoidance benefit revenues whilst layering other services. Simulation using a 2 MW/1 MWh lithium-titanate BESS validated model are carried out to explore possible scenarios using the proposed algorithms. Finally, experimental results of the 2MW/1MWh Willenhall Energy Storage System (WESS) verify the performance of the proposed algorithms

Design of a Gd-DOTA-Phthalocyanine Conjugate Combining MRI Contrast Imaging and Photosensitization Properties as a Potential Molecular Theranostic

Cataloged from PDF version of article.The design and synthesis of a phthalocyanine - Gd-DOTA conjugate is presented to open the way to novel molecular theranostics, combining the properties of MRI contrast imaging with photodynamic therapy. The rational design of the conjugate integrates isomeric purity of the phthalocyanine core substitution, suitable biocompatibility with the use of polyoxo water-solubilizing substituents, and a convergent synthetic strategy ended by the use of click chemistry to graft the Gd-DOTA moiety to the phthalocyanine. Photophysical and photochemical properties, contrast imaging experiments and preliminary in vitro investigations proved that such a combination is relevant and lead to a new type of potential theranostic agent