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Electricity, Volume 2, Issue 1 (March 2021) – 6 articles

Cover Story (view full-size image): Due to capacity fade, the cells in second life EV batteries have a much wider capacity spread than those in EVs. A Passive Equalizer (PEQ), such as those used in EVs, only provides a battery capacity equal to that of the worst cell, but a Bilevel Equalizer (BEQ) provides a capacity close to the cell average. As a result, experimental results show that the BEQ can increase the lifetime of a second life battery by about 50% above that for a PEQ. The BEQ is an active/passive hybrid where the series connected cells are divided into sections of about 4 to 12 cells each. Each section has a separate PEQ to balance its cell voltages, which corrects for self-discharge, and a simple Active Equalizer (AEQ) is used to balance the section voltages. Ultimately, dividing the battery into sections dramatically reduces the number of AEQ drivers to minimize cost. View this paper
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Article
Optimized Strategic Planning of Future Norwegian Low-Voltage Networks with a Genetic Algorithm Applying Empirical Electric Vehicle Charging Data
Electricity 2021, 2(1), 91-109; https://0-doi-org.brum.beds.ac.uk/10.3390/electricity2010006 - 16 Mar 2021
Cited by 1 | Viewed by 791
Abstract
This article outlines methods to facilitate the assessment of the impact of electric vehicle charging on distribution networks at planning stage and applies them to a case study. As network planning is becoming a more complex task, an approach to automated network planning [...] Read more.
This article outlines methods to facilitate the assessment of the impact of electric vehicle charging on distribution networks at planning stage and applies them to a case study. As network planning is becoming a more complex task, an approach to automated network planning that yields the optimal reinforcement strategy is outlined. Different reinforcement measures are weighted against each other in terms of technical feasibility and costs by applying a genetic algorithm. Traditional reinforcements as well as novel solutions including voltage regulation are considered. To account for electric vehicle charging, a method to determine the uptake in equivalent load is presented. For this, measured data of households and statistical data of electric vehicles are combined in a stochastic analysis to determine the simultaneity factors of household load including electric vehicle charging. The developed methods are applied to an exemplary case study with Norwegian low-voltage networks. Different penetration rates of electric vehicles on a development path until 2040 are considered. Full article
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Article
A Study of Load Imbalance Influence on Power Quality Assessment for Distribution Networks
Electricity 2021, 2(1), 77-90; https://0-doi-org.brum.beds.ac.uk/10.3390/electricity2010005 - 01 Mar 2021
Viewed by 889
Abstract
Power quality studies for distribution networks are very important for future network expansions realized by utility companies, so the accuracy of such studies is critical. Load data, including information on load imbalance, could have in many situations a significant influence on the correct [...] Read more.
Power quality studies for distribution networks are very important for future network expansions realized by utility companies, so the accuracy of such studies is critical. Load data, including information on load imbalance, could have in many situations a significant influence on the correct estimation of many power quality indicators. This paper investigates the impact of load imbalance on several phase imbalance indicators and voltage quality indicators by comparing the values of these indicators, as calculated in a power quality study using, sequentially, different sets of load data characterized by different load imbalances. The results of this study confirm the original hypothesis, showing that the use of inaccurate consumption profiles for loads leads to an inaccurate estimation of some power quality indicators. In addition, the results highlight the difficulty of approximating the actual consumption profiles of electrical loads so that this approximation does not affect the correctness of the estimation of phase imbalance and voltage quality indicators. Full article
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Article
Bilevel vs. Passive Equalizers for Second Life EV Batteries
Electricity 2021, 2(1), 63-76; https://0-doi-org.brum.beds.ac.uk/10.3390/electricity2010004 - 07 Feb 2021
Viewed by 1197
Abstract
Once lithium-ion batteries degrade to below about 80% of their original capacity, they are no longer considered satisfactory for electric vehicles (EVs), but they are still adequate for second-life energy storage applications. However, once this level is reached, capacity fade increases at a [...] Read more.
Once lithium-ion batteries degrade to below about 80% of their original capacity, they are no longer considered satisfactory for electric vehicles (EVs), but they are still adequate for second-life energy storage applications. However, once this level is reached, capacity fade increases at a much faster rate, and the spread between the cell capacities becomes much wider. If the passive equalizer (PEQ) from the EV is still used, battery capacity remains equal to that of the worst cell in the stack, just like it was in the EV. Unfortunately, the worst cell eventually becomes much weaker than the cell average, and the other cells are not fully utilized. If operated while the battery is in use, an active equalizer (AEQ) can increase the battery capacity to a much higher value close to the cell average, but AEQs are much more expensive and are not considered cost effective. However, it can be shown that the bilevel equalizer (BEQ), a PEQ/AEQ hybrid, also can provide a capacity very close to the cell average and at a much lower cost than an AEQ. Full article
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Article
Assessing the Impact on Grid Infrastructure of Electrification Pathways for the Italian Residential Sector
Electricity 2021, 2(1), 48-62; https://0-doi-org.brum.beds.ac.uk/10.3390/electricity2010003 - 03 Feb 2021
Viewed by 666
Abstract
To achieve the decarbonization objectives described in the Paris Agreement, thermal appliances’ electrification is considered an essential factor. Unfortunately, the substitution of thermal appliances with electric alternatives will inevitably increase the load on the national electric system; thus, it is crucial to perform [...] Read more.
To achieve the decarbonization objectives described in the Paris Agreement, thermal appliances’ electrification is considered an essential factor. Unfortunately, the substitution of thermal appliances with electric alternatives will inevitably increase the load on the national electric system; thus, it is crucial to perform analyses to assess these policies’ impact. This paper, using as a reference the electrification pathways studied by Besagni et al. employing the MOIRAE (bottom-up MOdel to compute the energy consumption of the Italian REsidential sector) model, calculates the energy and power increase in the residential sector in 2030 due to the substitution of different thermal appliances and discusses potential policies to take into account the effect of their implementation on the Italian electric system. Even if the current generation capacity can sustain the electrification process without problems, investments will be needed to limit the possibility of congestions on transmission lines connecting the country’s northern and southern parts. Full article
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Review
Review of Deterministic and Probabilistic Wind Power Forecasting: Models, Methods, and Future Research
Electricity 2021, 2(1), 13-47; https://0-doi-org.brum.beds.ac.uk/10.3390/electricity2010002 - 08 Jan 2021
Cited by 3 | Viewed by 1022
Abstract
The need to turn to more environmentally friendly sources of energy has led energy systems to focus on renewable sources of energy. Wind power has been a widely used source of green energy. However, the wind’s stochastic and unpredictable behavior has created several [...] Read more.
The need to turn to more environmentally friendly sources of energy has led energy systems to focus on renewable sources of energy. Wind power has been a widely used source of green energy. However, the wind’s stochastic and unpredictable behavior has created several challenges to the operation and stability of energy systems. Forecasting models have been developed and excessively used in recent decades in order to deal with these challenges. Deterministic forecasting models have been the main focus of researchers and are still being developed in order to improve their accuracy. Furthermore, in recent years, in order to observe and study the uncertainty of forecasts, probabilistic forecasting models have been developed in order to give a wider view of the possible prediction outcomes. Advanced probabilistic and deterministic forecasting models could be used in order to facilitate the energy systems operation and energy markets management. This paper introduces an overview of state-of-the-art wind power deterministic and probabilistic models, developing a comparative evaluation between the different models reviewed, identifying their advantages and disadvantages, classifying and analyzing current and future research directions in this area. Full article
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Article
Effect of the Conductor Positioning on Low-Power Current Transformers: Inputs for the Next IEC 61869-10
Electricity 2021, 2(1), 1-12; https://0-doi-org.brum.beds.ac.uk/10.3390/electricity2010001 - 05 Jan 2021
Viewed by 851
Abstract
Low-power instrument transformers (LPITs) are spreading among the distribution network thanks to their features (e.g., compactness, lightness, enhanced bandwidth, etc.). It is then a fundamental to guide users and manufacturers to a correct usage and manufacturing of the LPITs. Technical committees, which are [...] Read more.
Low-power instrument transformers (LPITs) are spreading among the distribution network thanks to their features (e.g., compactness, lightness, enhanced bandwidth, etc.). It is then a fundamental to guide users and manufacturers to a correct usage and manufacturing of the LPITs. Technical committees, which are in charge of writing dedicated standards, often tackle such a task. Focusing on the current type of LPITs, the low-power current transformers (LPCTs), the associated standard is the IEC 61869-10, which is going to be improved in 2021. To this purpose, the work aims at providing new inputs for the future version of such a standard. In particular, the focus is pointed towards the effects of the conductor positioning on the window-type LPCT accuracy. Literature and gained experience in the field are the two pillars that have been used to refine the outcomes of the work, which are provided in terms of suggestions for each technical aspect, as discussed in the standard, related to LPCTs. Full article
(This article belongs to the Special Issue Electromagnetic Compatibility in Power Systems and Smart Cities)
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