Space Vector Taylor–Fourier Models for Synchrophasor, Frequency, and ROCOF Measurements in Three-Phase Systems

Taylor-Fourier (TF) filters represent a powerful tool to design phasor measurement unit (PMU) algorithms able to estimate synchrophasor, frequency, and rate of change of frequency (ROCOF). The resulting techniques are based on dynamic representations of the synchrophasor, and hence, they are particularly suitable to track the evolution of its parameters during time-varying conditions. Electrical quantities in power systems are typically three-phase and weakly unbalanced, but most PMU measurement techniques are developed by considering them as a set of three single-phase signals; on the contrary, this peculiarity can be favorably exploited to improve accuracy and reduce the computational cost. In this respect, this paper proposes to directly perform the TF expansion of the space vector (SV) samples obtained from three-phase measurements. A new paradigm allows to independently estimate positive and negative sequence synchrophasors along with system frequency and ROCOF, leveraging the three-phase characteristics. The performance of the proposed technique is assessed by using test signals inspired by the standard IEEE C37.118.1-2011, including noise as well as magnitude and phase unbalance. Achieved results highlight the flexibility of the enhanced SV-based approach, which is capable to combine excellent dynamic performance together with an accurate estimation of both positive and negative sequence components

Modeling of a stand-alone H2-based Energy Storage System for electricity production and H2 mobility

The application of renewable energy sources (RES) during the last decades is increasing, with the aim to reduce carbon dioxide emissions and develop more sustainable energy systems. Referring to isolated microgrids and off-grid remote applications, because of the non-continuous RES production, energy storage systems (ESSs) are necessary to make the energy supply reliable and reach the energy selfsufficiency. Among the possible EESs, hydrogen-based storage solutions integrating electrolysers to produce hydrogen from surplus renewable energy and fuel cells to generate power from the stored hydrogen (called Power-to-Power systems) can represent a promising solution. The present study has the aim to analyse, from a technical and an economical point of view, a hybrid Power-to-Power and Power-toHydrogen system for a mountain off-grid village. The hydrogen is utilized in fuel cells for power generation to provide the electrical load of the site and also for mobility for fuelling a FCEV minibus line. The aim of this work is to find the optimal system configuration, with the minimum Net Present Value (NPV) at the end of system lifetime. The Levelized Cost Of Energy (LCOE) and the Levelized Cost Of Hydrogen (LCOH) are also computed, to understand the economic viability for electricity and mobility loads, respectively. These values were derived using cost inputs from literature, and a comparative analysis is performed for different system configurations. Results from the energy simulations revealed that the need for an external source is significantly reduced thanks to RES together with the hydrogen-based storage system, with zero emission respect to diesel solution and a cost of electricity slightly higher. Moreover, considering also a biomass-based CHP system as energy source, the cost is reduced more than three times. The cost of hydrogen for mobility instead, is still highly influenced by the lower development status of hydrogen technologies in the mobility sector

An MILP approach for the optimal design of renewable battery-hydrogen energy systems for off-grid insular communities

Abstract The optimal sizing of stand-alone renewable H2-based microgrids requires the load demand to be reliably satisfied by means of local renewable energy supported by a hybrid battery/hydrogen storage unit, while minimizing the system costs. However, this task is challenging because of the high number of components that have to be installed and operated. In this work, an MILP optimization framework has been developed and applied to the off-grid village of Ginostra (on the Stromboli island, Italy), which is a good example of several other insular sites throughout the Mediterranean area. A year-long time horizon was considered to model the seasonal storage, which is necessary for off-grid areas that wish to achieve energy independence by relying on local renewable sources. The degradation costs of batteries and H2-based devices were included in the objective function of the optimization problem, i.e., the annual cost of the system. Efficiency and investment cost curves were considered for the electrolyzer and fuel cell components in order to obtain a more detailed and precise techno-economic estimation. The design optimization was also performed with the inclusion of a general demand response program (DRP) to assess its impact on the sizing results. Moreover, the effectiveness of the proposed MILP-based method was tested by comparing it with a more traditional approach, based on a metaheuristic algorithm for the optimal sizing complemented with ruled-based strategies for the system operation. Thanks to its longer-term storage capability, hydrogen is required for the optimal system configuration in order to reach energy self-sufficiency. Finally, considering the possibility of load deferral, the electricity generation cost can be reduced to an extent that depends on the amount of load that is allowed to participate in the DRP scheme. This cost reduction is mainly due to the decreased capacity of the battery storage system

Evaluation of 7q31 region improves the accuracy of EGFR FISH assay in non small cell lung cancer

<p>Abstract</p> <p>Background</p> <p>Increase of <it>EGFR </it>gene copy number consequent to gene amplification and/or polysomy of chromosome 7 has been significantly associated with better clinical outcome in Non Small Cell Lung Cancer (NSCLC) patients treated with Tyrosin-Kinase Inhibitors (TKIs).</p> <p>The primary method to detect <it>EGFR </it>copy number is FISH (Fluorescence in Situ Hybridization), that in lung cancer requires a precise standardization due to the presence of intratumor heterogeneity and high frequency of chromosome 7 polysomy.</p> <p>Recommendations and interpretative guidelines to discriminate NSCLC patients into FISH positive (gene amplification and high chromosome 7 polysomy) and FISH negative have been proposed by the University of Colorado Cancer Center (UCCC). However, in a subset of cases the distinction between <it>EGFR </it>amplification and chromosome 7 polysomy can be controversial because of a complex pattern of multiple <it>EGFR </it>and centromere signals.</p> <p>Methods</p> <p>In order to distinguish more accurately these two genetic events, 20 NSCLC FISH positive patients, showing a controversial pattern of <it>EGFR </it>and centromere specific signals, were further evaluated for the status of 7q31 distal region.</p> <p>Results</p> <p>A discrepancy between FISH results obtained with UCCC scoring system and 7q31 control was evidenced in 2 patients (10%).</p> <p>Conclusion</p> <p>Our data strengthen the usefulness of 7q31 region evaluation to discriminate EGFR amplification from chromosome 7 polysomy in controversial <it>EGFR </it>FISH positive cases. Since it has been reported a possible different contribution of amplification and polysomy to TKIs susceptibility in NSCLC, the clear distinction between these two genetic events may be important to identify a subset of patients more responsive to the therapy.</p

H2-based energy storage systems in remote areas: the REMOTE project

The REMOTE project has the objective to demonstrate the techno-economic feasibility of hydrogen-based energy storage solutions in isolated micro-grids and off-grid remote areas. Four DEMOs will be installed in four different location across Europe: Ginostra (South of Italy), Agkistro (Greece), Ambornetti (North of Italy) and Froan Island (Norway). The four sites will be characterized by different types of renewable sources (i.e., solar, wind, biomass and water fall) and user loads (i.e., residential and/or industrial), which will affect differently the design and management of the hybrid storage solution. The variety of the DEMO cases can thus provide a robust demonstration of the benefits derived from these innovative storage systems paving way for their deployment at large. According to the ‘Power-to-Power (P2P)’ solution, renewable energy exceeding the electric demand, rather than being curtailed, is supplied to an electrolyzer for hydrogen production. In the four cases under consideration, the alkaline and PEM technology are considered for the electrolysis section. In case of renewable power shortages, PEM fuel cell stacks are then employed for hydrogen conversion into electricity. A battery bank is also coupled with the hydrogen section because of its short-term and quick response capability. Local Renewable Energy Sources (RES) can be therefore better used allowing to reduce or even eliminate the intervention of traditional diesel generators and avoid unstable connections to the grid, if present. The aim of the presented work is to demonstrate the effectiveness of the H2-based P2P solution in reducing the usage of external sources (e.g., diesel genset) by maximizing the exploitation of local RES. Operation strategy models have been developed in order to perform energy balance simulations on a yearly basis. Results showed the usefulness of the P2P operation: in Ginostra, for example, the intervention of diesel generators can be reduced to less than 5% of the total load. Hydrogen was found to be particularly effective as a longer term energy storage solution. Economic considerations are also provided to outline the economic viability of the suggested RES and H2-based scenario

Synchrophasor and frequency estimations: Combining space vector and Taylor-Fourier approaches

Taylor-Fourier (TF) filters represent a powerful tool to design PMU algorithms able to estimate synchrophasor, frequency and rate of change of frequency (ROCOF). The resulting techniques are based on dynamic representations of the synchrophasor, hence they are particularly suitable to track the evolution of its parameters during time-varying conditions. Electrical quantities in power systems are typically three-phase and weakly unbalanced, but most PMU measurement techniques are developed by considering them as a set of three single phase signals; on the contrary, this peculiarity can be favorably exploited. For the first time, in this paper, the TF approach is applied to the space vector obtained from three-phase measurements. The positive sequence synchrophasor can be easily extracted along with the system frequency and ROCOF leveraging the three-phase characteristics. Performance of the proposed technique is assessed by using test signals defined by the standard IEEE C37.118.1-2011. Results show that the positive sequence estimations are always more accurate when compared to the single-phase measurements provided by the conventional TF algorithms under the same conditions

Effect of Unbalance on Positive-Sequence Synchrophasor, Frequency and ROCOF Estimations

Phasor measurement units (PMUs) are the measurement devices fostering the transformation of electric power networks towards the smart grid paradigm. They should accurately measure synchrophasors, frequency, and rate of change of frequency (ROCOF), so that the management and control applications relying on PMU-based distributed monitoring systems can operate effectively. Commercial PMUs performance is typically guaranteed by the compliance with the IEEE standard C37.118.1, which is focused on PMUs for power transmission systems and defines testing conditions and error limits. However, actual operating conditions are much more variable than those covered by the standard, especially when PMUs are used in distribution networks. In particular, the standard does not consider unbalance, which may be negligible neither in transmission nor in distribution grids. For the first time, this paper analyzes the impact of unbalance on the accuracy of four of the most significant classes of signal processing algorithms for PMU measurements. Synchrophasor, frequency, and ROCOF estimation performances under different unbalance conditions are investigated in the test cases suggested by the IEEE C37.242-2013 guide. Novel analytic expressions to predict the errors are derived and validated, and they are proved to be useful for an effective implementation of PMU algorithms intended for both distribution and transmission systems