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The COVID-19 pandemic has caused fluctuations in electricity demand, altering people's lifestyles and electricity usage patterns, thereby affecting the accuracy of demand predictions. However, existing studies on electricity forecasting have not adequately considered the incorporation of COVID-19-related features and the analysis of electricity usage characteristics across different regions of the UK. Therefore, this paper, based on data of the UK's national electricity demand, conducts an analysis around the scenario of a large-scale health emergency in society. We explore the changing patterns and regional characteristics of electricity consumption during the COVID-19 pandemic, comparing the forecast results before and during the pandemic to illustrate its impact on the UK's electricity demand. By introducing COVID-19-related features into the models, we compare the forecast results before and after their inclusion. The results indicate that the COVID-19 pandemic has had a certain impact on the electricity prediction in the UK, leading to a 22.8% decrease in prediction accuracy. However, the models' correlation improved with the inclusion of COVID-19-related features, resulting in a 13.2% enhancement in prediction accuracy compared to the previous models. Additionally, the study summarizes other factors influencing electricity demand, such as power imports/exports and clean energy usage, as considerations for electricity distribution planning. This contributes to improving the accuracy of predicting the UK's electricity demand during COVID-19 pandemic, enabling the government to adjust power dispatching plans reasonably based on relevant factors, achieving rational distribution and efficient scheduling of power resources. [ABSTRACT FROM AUTHOR]

As the most promising alternative to internal combustion engines (ICEs), electric vehicles (EVs) have an excellent development outlook. The charging route scheduling of EVs can simultaneously affect traffic congestion in the transportation network (TN) and power flow distribution in the power distribution network (PDN). The research on TN and PDN coupling networks based on the static traffic flow model is relatively mature; however, it ignores that the traffic flow will spread across periods in a short scheduling period. In this paper, a semi‐dynamic traffic flow model is proposed to represent the dynamic propagation characteristics of EVs and ICEs flow. Furthermore, the cost of carbon emission and system operation are combined as the overall goal of system optimisation. Since the model has become a more complex non‐linear model, this paper proposes to combine the heuristic sequential boundary tightening and binary expansion method to linearise the model. The study compared four cases and found that a 20% penetration rate of EVs can reduce carbon emissions by 4.2% while reducing the system's total cost by 10%. Moreover, the impact of network congestion on the spatiotemporal distribution of traffic flow and power flow in the coupled network is alleviated. [ABSTRACT FROM AUTHOR]

Operation control of power systems has become challenging with an increase in the scale and complexity of power distribution systems and extensive access to renewable energy. Therefore, improvement of the ability of data-driven operation management, intelligent analysis, and mining is urgently required. To investigate and explore similar regularities of the historical operating section of the power distribution system and assist the power grid in obtaining high-value historical operation, maintenance experience, and knowledge by rule and line, a neural information retrieval model with an attention mechanism is proposed based on graph data computing technology. Based on the processing flow of the operating data of the power distribution system, a technical framework of neural information retrieval is established. Combined with the natural graph characteristics of the power distribution system, a unified graph data structure and a data fusion method of data access, data complement, and multi-source data are constructed. Further, a graph node feature-embedding representation learning algorithm and a neural information retrieval algorithm model are constructed. The neural information retrieval algorithm model is trained and tested using the generated graph node feature representation vector set. The model is verified on the operating section of the power distribution system of a provincial grid area. The results show that the proposed method demonstrates high accuracy in the similarity matching of historical operation characteristics and effectively supports intelligent fault diagnosis and elimination in power distribution systems. [ABSTRACT FROM AUTHOR]

Energy storage systems is expected to be utilized to cover the increased electrification of energy demands and to alleviate the electrical energy production from intermittent energy sources such as solar and wind. Aggregated and distributed battery energy storage systems may improve electricity grids operability and security by providing smart energy management options and efficient resources allocation. In this paper, battery storage at the secondary distribution level is explored. The investigation is based on the end-user energy demand behavior. As such, the electrical energy consumption patterns are measured and analyzed in a residential area. Measurements were collected and analyzed in order to record the customers' behaviors aiming to reveal their differences and similarities. Following this, aggregated and distributed battery energy storage systems are computed based on the features of the measured electrical power consumption patterns aiming to estimate the factors that could potentially incentivize the installation of a battery system either as aggregated at the low voltage transformer side or as distributed system at the load side. The parameters that affect the economic viability of the system are qualitatively evaluated with regard to the profitability of the system. [ABSTRACT FROM AUTHOR]

Power losses in distribution systems are among the most important performance indicators of electricity distribution companies’ economic operations. Therefore, the distribution system should be planned adequately to ensure working within permissible limits. Suppose that the actual losses are higher than the standard ones; the companies are economically penalized; otherwise, they obtain a profit. Continuous improvement for the grid is needed to keep the losses within reasonable limits. Companies invest in projects that are dedicated to reducing losses and keep them under control. Literature review states that load balancing is considered a critical issue in minimizing these losses. Feeder automation becomes much simple and more reliable due to the rapid penetration of artificial intelligence, smart grids, and telecommunication in the power system. This work shows that automated feeder reconfiguration is technically advantageous and economical for both customers and utilities. A case study from Irbid District Electricity Company (IDECO) is presented. The losses are reduced by around 253 JDs/year by balancing the loads over a specific three-phase feeder using smart meters’ installation. A mathematical model for three-phase balancing is formulated using many heuristic techniques and an optimized neural network (ONN). These model integrations are established using CYME load flow software, MATLAB/Simulink, and C programming language. [ABSTRACT FROM AUTHOR]

Increased penetration of low‐carbon technologies, such as residential photovoltaic systems, electric vehicles, and batteries, can potentially cause voltage quality issues in distribution networks. Active distribution networks adopt control schemes where these assets are actively managed to prevent potential issues, increasing the network utilization. Mathematical optimization is a key technology in enabling such applications, either directly as the underlying solution, or for benchmarking effectiveness. As networks are operated closer to their engineering limits, models representing distribution network physics become increasingly important. This article reviews how distribution networks are modeled with varying degrees of detail in the context of optimization problems. It goes on to catalog the applications that use such models, and ends with an overview of toolchains to implement them, to enable the transition from the passive to active management of the distribution system. This article is categorized under:Energy Systems Analysis > Systems and Infrastructure [ABSTRACT FROM AUTHOR]

The operation of more electric aircraft is dependent on the embedded power grid. Therefore, the on-board power-distribution system must be reliable, having a high level of survivability, and promptly respond to any change in aircraft's operation. Recent studies have presented a number of frequency-response-based tools with which to analyze both single- and multiconverter systems. The methods can be efficiently applied for on-board system analysis, stability assessment, and adaptive control design. Most often, wideband measurement techniques have been applied to obtain the frequency response from a specific converter or a subsystem required for the analysis. In the methods, a broadband excitation such as a pseudorandom binary sequence (PRBS) is used as an external injection, and Fourier techniques are applied to extract the spectral information. This paper presents implementation techniques of the wideband methods using power-hardware-in-the-loop measurements based on OPAL-RT real-time simulator. The presented methods make it possible to modify the system characteristics, such as impedance behavior, in real time, thereby providing means for various stability and control design tools for on-board power distribution systems. Experimental measurements are shown from a high-power energy distribution system recently developed at DNV GL, Arnhem, The Netherlands. [ABSTRACT FROM AUTHOR]

This paper presents an interface ac–dc converter to connect the 380 V bipolar dc microgrid with the 240 V split-phase single-phase ac utility. The design targets are high efficiency, leakage current attenuation, and symmetric bipolar dc bus generation. A transformerless two-stage topology is proposed to decouple the common-mode (CM) voltage between the connected ac and dc systems. The two-stage structure also reduces the required capacitance in single-phase power conversion by allowing a large voltage ripple on the intermediate dc link. Adaptive dc-link voltage control and interleaving of state-of-the-art silicon carbide (SiC) mosfets are adopted to achieve high efficiency. Interleaving angles are optimized to minimize the total volume of both differential-mode and CM magnetics. An active CM control method is incorporated to regulate the dc and low-frequency CM voltages on the dc buses with respect to the ground. The resultant dc bus voltages are rendered symmetric to the ground, and the leakage current is suppressed. The generated ±190 V dc bus is suitable for bipolar 380 V dc power distribution systems. Pluggable phase-leg modules with embedded driving and protection circuit are designed and tested, based on which a 10 kW all-SiC converter prototype is built achieving an efficiency >97%. [ABSTRACT FROM AUTHOR]

This paper presents a novel rectifier array for a wide dynamic range of RF-dc conversion. The rectifier array consists of multiple rectifier cells optimized for operation at different power levels and uses an adaptive power distribution method to divide the RF input power among these rectifier cells according to the RF power levels. The adaptive power distribution takes advantage of the power-dependent input impedances of the rectifier cells and is implemented with passive devices. This method both improves the rectification efficiency and minimizes the impedance mismatch as the input power level varies, and therefore, significantly enhances the dynamic range. The rectifier array can be designed using either the same type or different types of rectifying devices and can be expanded by including more cells in the network to further increase the dynamic range. In this paper, three different implementations of such rectifier array circuits are described, including a two-diode rectifier array designed with the same type of diodes, a two-diode rectifier array designed with different types of diodes, and a three-diode rectifier array with different types of diodes. The performances of these circuits are validated with measurement and compared with each other. Significant enhancement of dynamic range over conventional rectifiers is demonstrated. [ABSTRACT FROM AUTHOR]

A novel method is proposed to locate the source of events in power distribution systems by using distribution-level phasor measurement units, a.k.a., micro-PMUs. An event in this paper is defined rather broadly to include any major change in any component across the distribution feeder. The goal is to enhance situational awareness in distribution grid by keeping track of the operation (or misoperation) of various grid equipment, assets, distribution energy resources, loads, etc. The proposed method is built upon the compensation theorem in circuit theory to generate an equivalent circuit to represent the event by using voltage and current synchrophasors that are captured by micro-PMUs. Importantly, this method makes critical use of not only magnitude but also synchronized phase angle measurements, thus, it justifies the need to use micro-PMUs, as opposed to ordinary RMS-based voltage and current sensors. The proposed method can work with data from as a few as only two micro-PMUs. The effectiveness of the developed method is demonstrated through computer simulations on the IEEE 123-bus test system, and also on micro-PMUs measurements from a real-life 12.47 kV test feeder in Riverside, CA. The results verify that the proposed method is accurate and robust in locating the source of different types of events on power distribution systems. [ABSTRACT FROM AUTHOR]

Renewable distributed resources, energy storage systems, and improved load control options are introducing new challenges in electric power distribution. It is necessary to integrate such smart grid concepts into formal power engineering curricula. To help meet this need, solar microgrid experiments are being developed at Drexel University. This work presents: first, an overview of the laboratory-scale microgrid equipment at Drexel; second, upgrades to the distribution energy management system in the Reconfigurable Distribution Automation and Control Laboratory; third, a detailed educational microgrid experiment; and fourth, corresponding pre- and postlaboratory assignments. In the experiment, students analyze a microgrid network in grid-powered, grid-interactive, and island modes with a renewable source that is not electrically (or physically) co-located with the utility supply. Students will observe power flow characteristics in each mode. In island mode, students will make network or load control decisions in order to satisfy the operating constraints, and then connect the renewable source to the node of their choice. [ABSTRACT FROM AUTHOR]

The study of electrical distribution of primary networks design is oriented to reduce the construction costs and the energy losses by transmission. The topology for the implementation of distribution networks may vary according to the geographical characteristics of the final users and requires specialized optimization solutions with metaheuristics to improve the energy performance of the electrical power systems. A parallel genetic algorithm (PGA) is proposed to optimize a tree-based topology for large-scale electric power distribution networks. The proposed PGA uses the dandelion code, which allows obtaining tree-feasible solutions within each iteration of the PGA. This cannot be achieved with other metaheuristic approaches directly. Eight cores are used simultaneously. We achieve a 22.05% improvement when compared to the tree-feasible solutions obtained with its sequential version. Moreover, the computational time required by the PGA is on average 23 times lower than the sequential version. Finally, we find feasible solutions for instances of the problem with up to 50,000 nodes. [ABSTRACT FROM AUTHOR]

One of the most important aspects that characterizes smart grids is the widespread integration of loads and renewable-based generators connected to the distribution network. In general, sequence or phase based network models have included the effect of ground return on equivalent phase and neutral impedances using the Kron's reduction and Carson equations. Under unbalanced grid operation, these traditional models can produce inexact results being inadequate for advanced grid analysis and optimization. This paper presents a detailed and compact formulation for the analysis of multi-grounded distribution systems. The key contribution of the paper is to introduce a detailed representation of the ground loops in the distribution system model suitable to be applied under different analysis methods as power flow, optimal power flow, state estimation and network pricing in an integrated manner. This contribution is meaningful since it allows to analyze future electrical systems with severe unbalanced operation due to high penetration of single-phase renewable and load sources. The ground parameters can be adjusted in the context of a state estimator that integrates ground voltages and currents. The proposed model is tested using illustrative and real-world large-scale test cases. Results reveal significant differences when compared with system analyses using standard three phase network model approach. [ABSTRACT FROM AUTHOR]

This paper proposes a novel control method for an asymmetrical-cascaded-multilevel-converter-based hybrid energy storage system (HESS), which includes one battery and several electrical double-layer capacitors (EDLCs). Traditionally, it is challenging to control the power distribution between different cascaded H-bridges by using different energy storage components as dc sources. In this paper, a feedforward space-vector-modulation (FFSVM) technique is used to distribute the active power between the battery and EDLCs. With the proposed voltage feedforward mechanism, the HESS can flexibly operate in the normal operation mode, the high-power output mode, and the reverse power absorption mode. The principle and effectiveness of the improved FFSVM technique are analyzed. Meanwhile, the state-of-charge-balancing mechanisms are introduced. The simulation results obtained in MATLAB/Simulink as well as the experimental results of a hybrid energy storage test bed based on the proposed system are presented to verify its performance. [ABSTRACT FROM PUBLISHER]

This paper presents a novel power distribution system (PDS) algorithm to be employed in a hybrid energy storage system (HESS). PDS is responsible for sharing the demand power between energy storage modules, which are battery and ultracapacitor (UC) in this study. The challenge in designing PDS is in assigning the power-share between these modules. A state of available power technique is proposed based on the prediction of the power limitations for a predefined time frame in the future. Another PDS based on the UC state of charge is developed. Various design variables are defined that affect the performance of the PDS. The genetic algorithm optimization technique is employed to determine the design variables. The proposed PDS techniques along with an energy storage system (ESS) consisting of a single battery and a basic PDS system is studied on a 12-kW electric motorcycle during the standard FTP and the New York City Cycle (NYCC) driving cycles. Battery lifetime, vehicle range, and regenerative braking energy recovery functions for the proposed methods compared with the ESS are improved by 2.6 times, 25%, and 29%, respectively. The results suggest that employing the proposed novel PDSs improves the performance of the HESS significantly. [ABSTRACT FROM PUBLISHER]

The conservative power theory (CPT) is a time-domain theory applicable to any periodic signal single- or polyphase system with or without a neutral conductor. The principle operation is the orthogonal decomposition of electrical variables, resulting in electrical quantities with physical meaning. An important feature of the CPT is the current decomposition. It consists of decomposing any current into five parts. The label of these parts is active current, reactive current, scattered active current, scattered reactive current, and generated current. This paper proposes the application of the current decomposition of the CPT in distributed energy resources (DERs). A supervisory controller (SC) uses the current decomposition in a load power-sharing strategy. The combination of these two issues is the main contribution of this paper. Moreover, the proposal of this paper is more attractive than the conventional droop strategy since the DERs follow their current reference in a current-controlled mode, making the load sharing faster, more reliable, and more accurate. A clear understanding of how the CPT decomposes load currents into its parts is presented, as well as the drawback found in droop strategy when dealing with load power sharing. Later, the SC load power-sharing strategy is described, indicating that the proposal of this paper makes an SC to have a broad option when managing a smart grid with dispatchable DERs. A case study with experimental results shows the efficacy of applying current decomposition of the CPT in load power-sharing strategies. [ABSTRACT FROM AUTHOR]

It is essential to improve the resiliency of power distribution systems (PDS) given the increase in extreme weather events, number of malicious threats, and consumers’ need for higher reliability. This paper provides a formal approach to evaluate the operational resiliency of PDS and quantify the resiliency of a system using a code-based metric. A combination of steady state and dynamic simulation tools is used to determine the resiliency metric. Dynamic simulation tools help analyzing the impact of short-term events, which might affect operational resiliency in the long term. A dynamic optimization algorithm for changing operating criteria to increase the sustainability of the most critical loads has been proposed. The proposed theoretical approach is validated using a simple PDS model and simulation results demonstrate the ability to quantify the resiliency using the proposed code-based metric. The time-dependent quantification of resiliency has been demonstrated on a test system of two connected Consortium of Electric Reliability Technology Solutions (CERTS) microgrids. [ABSTRACT FROM AUTHOR]

This study presents a power distribution control scheme for a three-phase interleaved parallel DC/DC converter in a battery energy storage system. To extend battery life and increase the power equalization rate, a control method based on the nth order of the state of charge (SoC) is proposed for the charging and discharging processes. In the discharging process, the battery sets with high SoC deliver more power, whereas those with low SoC deliver less power. Therefore, the SoC between each battery set gradually decreases. However, in the two-stage charging process, the battery sets with high SoC absorb less power, and thus, a power correction algorithm is proposed to prevent the power of each particular battery set from exceeding its rated power. In the simulation performed with MATLAB/Simulink, results show that the proposed scheme can rapidly and effectively control the power distribution of the battery sets in the charging and discharging processes. [ABSTRACT FROM AUTHOR]

Quasi-static time-series (QSTS) simulation is used to simulate the behavior of distribution systems over long periods of time (typically hours to years). The technique involves repeatedly solving the load-flow problem for a distribution system model and is useful for distributed energy resource planning. When a QSTS simulation has a small time step and a long duration, the computational burden of the simulation can be a barrier to integration into utility workflows. One way to relieve the computational burden is to simplify the system model. The segment substitution method of simplifying distribution system models introduced in this paper offers model bus reduction of up to 98% with a simplification error as low as 0.2% (0.002 p.u. voltage). In contrast to existing methods of distribution system model simplification, which rely on topological inspection and linearization, the segment substitution method uses black-box segment data and an assumed simplified topology. [ABSTRACT FROM PUBLISHER]

This paper examined the extent of the dependence of the interrupting capability on the shape of the contact system in a molded case circuit breaker (MCCB). Thus, a simple analysis method was suggested for estimating the interrupting capability and used to investigate the magnetic flux density distribution in a contact system caused by a short-circuit current. However, the MCCB produced by a joint-research company turned out to have the poor interrupting capability and a low magnetic flux density distribution for driving arc plasma between two contacts in the contact system. To build up additional interrupting capability without making many changes, a new arc runner was devised to prevent arc plasma from returning to its original position in the contact system. The arc voltage characteristics were tested with a simplified synthetic testing facility using an LC resonant circuit. The result showed that the new MCCB had a much higher arc voltage than the existing MCCB. This implies that investigating the arc voltage is fairly comparable to predicting the arc plasma extinction and the interrupting capability. [ABSTRACT FROM AUTHOR]

A new three-phase active rectifier topology is proposed for bipolar dc distribution, which can achieve the independent dc-pole control, with only one two-level voltage source converter and an ac-side grounding inductor. The averaged large-signal model and linearized small-signal model of the rectifier are derived in the stationary reference frame. Moreover, a control system is proposed with proper controller parameters. Besides, the rectifier is tested on an experiment platform. Comprehensive experiment results are given and analyzed to validate the function of the proposed rectifier under different operation conditions, including the rectifier start-up performance, rectifier dynamics with unbalanced dc loads for two poles, and rectifier dynamics with asymmetrical dc voltages for two poles. Finally, the proposed rectifier is compared with other two existing ac–dc conversion approaches, in terms of required number and rating of components as well as power losses with different load imbalance levels, which further highlight some potential benefits of the proposed topology. [ABSTRACT FROM AUTHOR]

Energy grids are facing a relatively new paradigm consisting in the formation of local distributed energy sources and loads that can operate in parallel independently from the main power grid (usually called microgrids). One of the main challenges in microgrid-like networks management is that of self-adapting to the production and demands in a decentralized coordinated way. Here, we propose a stylized model that allows to analytically predict the coordination of the elements in the network, depending on the network topology. Surprisingly, almost global coordination is attained when users interact locally, with a small neighborhood, instead of the obvious but more costly all-to-all coordination. We compute analytically the optimal value of coordinated users in random homogeneous networks. The methodology proposed opens a new way of confronting the analysis of energy demand-side management in networked systems. [ABSTRACT FROM AUTHOR]

This paper presents a new system for reactive power compensation and suppression of negative-sequence current for power quality improvement in electrical railways and the feeding three-phase utility grid, based on YNvd-connected balance transformer. Different from the conventional railway static power conditioner based compensation systems, this system integrates multiplex back-to-back converters (MBTBC) into phase-β side flexible taps through a cascade connection instead of into phase-β side feeder via a coupling transformer, thus the installation space and initial costs are reduced significantly. In addition, a new power distribution strategy with simple implementation is adopted in this paper, by which the compensation capacity of MBTBC can be decreased by 25%, compared with the commonly used full compensation scheme. As the first part of this topic, this paper focuses on the theoretical analysis, including the system topology, basic and partial compensation principles and its implementation method. While, the controller design on converter-level, stability analysis, and simulation and experimental verification are the main tasks of the second part of this topic. [ABSTRACT FROM PUBLISHER]

Solar photovoltaic is increasingly seen as a key technology for low-carbon electricity generation. However, the deployment of growing shares of this technology is not without important challenges for their efficient integration in power systems. This paper aims to contribute to overcoming the barriers that hamper a large-scale integration of photovoltaics in the electricity distribution grids. The methodology followed is problem oriented. The paper firstly reviews the technical solutions available to integrate distributed photovoltaics, classifying them in three areas: Distribution System Operator (DSO) solutions, prosumer solutions and interactive solutions. Then, the set of barriers that hinder the implementation of the solutions in a European context are identified, assessing the relevance of each barrier in different countries. Four major barriers are discussed in detail: (1) DSO regulation does not promote smart grid investments, (2) rules limiting PV curtailment, (3) missing frameworks enabling DSOs to access advanced PV inverter capabilities, and (4) regulation hampering storage solutions. Finally, recommendations to overcome these barriers are presented, highlighting that DSO regulation should shift the focus from a short-term to a long-term cost assessment and revenue setting framework, equalizing the treatment of capital and operational expenditures, and implementing specific incentives for DSO innovation. Moreover, a fair debate on the definition of the boundary conditions for the use of renewable curtailment when the other technical solutions cannot be applied or are not economically optimal is required. Regarding the provision of services to DSOs by prosumers and the deployment of distributed storage, the roles, rights and limitations of the different stakeholders need to be clearly defined. [ABSTRACT FROM AUTHOR]

This article analyzes the relative technical efficiency of Brazilian electricity distribution companies. The search for efficiency has been steady in many sectors and the industry now represents a significant source of economic development for the country. The electricity distribution companies have undergone major transformations due to the transference of share control to private initiatives. The primary research technique used was a quantitative approach known as the descriptive and data envelopment analysis (DEA) based on data from 2012. It was identified that just 1 out of 17 Brazilian electricity distributors of the census is classified as efficient. It is worth noting that COSERN and RGE are the best benchmarks for inefficient firms and hold various awards for quality and industry management. Of all the variables evaluated, Power installed most affected efficiency scores. Among the variables that are necessary to improve were Global Performance Continuity and Average Response Time. [ABSTRACT FROM AUTHOR]

Widespread three-phase imbalance causes inefficient uses of low voltage (LV) network assets, leading to additional reinforcement costs (ARCs). Previous work that assumed balanced three phases underestimated the reinforcement cost throughout the whole utility by more than 50%. Previous work that quantified the ARCs was limited to individual network components, relying on full sensory data. This paper proposes a novel methodology that will scale the ARC estimation at a utility level, when the data concerning the imbalance of circuits or transformers are scarce. A novel statistical method is developed to estimate the volume of assets that need to be invested by identifying the relationship between the triangular distribution of circuit imbalance and that of circuit utilization. When there are more data available in future, accurate probability distributions can be constructed to reflect the network condition across the whole system. In light of this, two novel generalized ARC estimation formulas are developed that account for generic probability distributions. The developed methodology is applied to a real utility system in the UK, showing that: 1) three-phase imbalance leads to ARCs that are even greater than the reinforcement costs in the balanced case; 2) a 1% increase in the demand growth rate, the maximum degree of imbalance (DIB) and the maximum nominal utilization rate leads to over 10%, approximately 1% and 2% increases in the ARCs, respectively; and 3) the ARC is not sensitive to the minimum DIB values and the minimum nominal utilization rates. [ABSTRACT FROM PUBLISHER]

The cascaded H-bridge (CHB) multilevel converter is a promising topology for large-scale photovoltaic (PV) systems. The output voltage over-modulation derived by the inter-module active power imbalance is one of the key issues for CHB PV systems. This paper proposed a dynamic power distribution strategy to eliminate the over-modulation in a CHB PV system by suitably redistributing the reactive power among the inverter modules of the CHB PV system. The proposed strategy can effectively extend the operating region of the CHB PV system with a simple control algorithm and easy implementation. Simulation and experimental results carried out on a seven-level CHB grid-connected PV system are shown to validate the proposed strategy. [ABSTRACT FROM AUTHOR]

Proactive preparedness to cope with extreme weather events is significantly helpful in reducing the restoration cost and enhancing the resilience of distribution systems. This paper is focused on the resource allocation problem in distribution systems ahead of a coming hurricane. Generation resources such as diesel oil and batteries are considered for allocation, which can be used to serve outage critical load in the post-hurricane restoration. Electric buses are also considered as a kind of resource. Considering the uncertainties of system faults, the allocation problem is formulated into a mixed-integer stochastic nonlinear program. A heuristic method is then proposed, which obtains the allocation plan by solving a mixed-integer linear program. Numerical simulations are performed on the IEEE 123-node feeder system under several scenarios to demonstrate the effectiveness of the proposed method. The impacts of resources transportation cost, initial distribution of electric buses, and hurricane severity on the allocation plan are discussed. [ABSTRACT FROM AUTHOR]

Improving the operation of power grid and offering new smart applications, the deployment of a supervisory infrastructure is necessary. One solution to transmit data may be based on the power-line communication (PLC) technology. It consists of the superposition of high-frequency signals with the electrical signal of 50/60 Hz. However, the power grids have not been designed to operate in high frequencies. Therefore, they provide a transmission channel with difficult propagation conditions. This paper deals with the modeling of the medium-voltage/low-voltage (MV/LV) power transformers in PLC frequencies. The proposed models are based on the “lumped model” and “black box model.” They are performed in the frequency band from 1 kHz to 1 MHz on SPICE and MATLAB software, respectively. These models are based on impedance measurements and validated by experimental data. The advantages and drawbacks of each model are detailed from the presentation of the modeling method and simulation results. The comparison of the simulation results show that “black box model” offers good accuracy. The transmission results show that transformers are an important element in PLC studies because they provide significant losses. Moreover, these losses depend mainly on the values of the impedance terminals of the MV/LV transformer. [ABSTRACT FROM PUBLISHER]

The deepening penetration of distributed energy resources into distribution networks (DNs) is causing relevant issues to be addressed by distribution system operators (DSOs), such as quality of service, security and safety, both at medium-voltage and low-voltage distribution levels. This paper presents how Unareti SpA, an Italian DSO, has addressed those challenges launching a set of research activities in different areas of distribution automation. Results collected during field experiences have been used to design the reference model of the next generation of DN secondary substations. [ABSTRACT FROM PUBLISHER]

Increasing demands for power supplies have contributed to the population of high-frequency ac (HFAC) power distribution system (PDS), and in order to increase the power capacity, multilevel inverters (MLIs) frequently serving as the high-frequency (HF) source-stage have obtained a prominent development. Existing MLIs commonly use more than one voltage source or a great number of power devices to enlarge the level numbers, and HF modulation (HFM) methods are usually adopted to decrease the total harmonic distortion (THD). All of these have increased the complexity and decreased the efficiency for the conversion from dc to HF ac. In this paper, a nine-level inverter employing only one input source and fewer components is proposed for HFAC PDS. It makes full use of the conversion of series and parallel connections of one voltage source and two capacitors to realize nine output levels, thus lower THD can be obtained without HFM methods. The voltage stress on power devices is relatively relieved, which has broadened its range of applications as well. Moreover, the proposed nine-level inverter is equipped with the inherent self-voltage balancing ability, thus the modulation algorithm gets simplified. The circuit structure, modulation method, capacitor calculation, loss analysis, and performance comparisons are presented in this paper, and all the superior performances of the proposed nine-level inverter are verified by simulation and experimental prototypes with rated output power of 200 W. The accordance of theoretical analysis, simulation, and experimental results confirms the feasibility of proposed nine-level inverter. [ABSTRACT FROM AUTHOR]

The open winding permanent magnet generator system is suitable for applications such as renewable energy power generation systems with multiple power sources, due to its high power density, relatively few power switches, and high degree of integration. However, for this system, it is difficult to quantitatively control the power distribution between different energy sources. In this paper, an open winding hybrid excitation generator system is presented, and for this system, a controllable power distribution strategy is investigated. In the proposed strategy, the excitation current is regulated according to the error in the current loop of the auxiliary energy source, which can achieve the regulation of the output power of the generator and finally realize the power quantitative control of the auxiliary energy source. Then, the topologies of the hybrid excitation machine are analyzed and chosen with emphasize on the influence of the flux regulation capability on the control capability of system power distribution. The experiments are carried out on a parallel hybrid excitation flux-switching (PHEFS) generator system, and the results verify the correctness and effectiveness of the proposed controllable power distribution strategy and the power distribution capability of the PHEFS generator. [ABSTRACT FROM AUTHOR]

This paper proposes a necessary condition for power flow insolvability in power distribution systems with distributed generators (DGs). We show that the proposed necessary condition indicates the impending singularity of the Jacobian matrix and the onset of voltage instability. We consider different operation modes of DG inverters, e.g., constant-power and constant-current operations, in the proposed method. A new index based on the presented necessary condition is developed to indicate the distance between the current operating point and the power flow solvability boundary. Compared to existing methods, the operating condition-dependent critical loading factor provided by the proposed condition is less conservative and is closer to the actual power flow solution space boundary. The proposed method only requires the present snapshots of voltage phasors to monitor the power flow insolvability and voltage stability. Hence, it is computationally efficient and suitable to be applied to a power distribution system with volatile DG outputs. The accuracy of the proposed necessary condition and the index is validated by simulations on a distribution test system with different DG penetration levels. [ABSTRACT FROM AUTHOR]

This paper presents a novel modified Viterbi algorithm to identify the optimal distribution system restoration plan for improving the grid resiliency. In the proposed algorithm, the switching operations performed for system restoration are the states with the minimum bus voltage being seen as the cost metric for each state and the extent of load recovery as the observed event. When full load recovery is spotted, the dynamic programming algorithm stops, thereby giving the least number of switching pairs necessary for system restoration. Moreover, an improved flexible switching pair operation is employed to maintain the radial nature of distribution system. Several case studies are presented for verifying the performance of the proposed strategy. Multi-fault conditions are considered in testing the system restoration scheme on 33-bus and 69-bus distribution systems. Furthermore, the effects of integrating distributed energy resources and microgrid systems are analyzed. [ABSTRACT FROM AUTHOR]

This paper introduces an improved detection and classification technique of harmonic signals in power distribution using time-frequency distribution (TFD) analysis which is spectrogram. The spectrogram is an appropriate approach to signify signals in jointly time-frequency domain and known as time frequency representation (TFR). The spectral information of signals can be observed and estimated plainly from TFR due to identify the characteristics of the signals. Based on rule-based classifier and the threshold settings that referred to IEEE Standard 1159 2009, the detection and classification of harmonic signals for 100 unique signals consist of various characteristic of harmonics are carried out successfully. The accuracy of proposed method is examined by using MAPE and the result show that the technique provides high accuracy. In addition, spectrogram also gives 100 percent correct classification of harmonic signals. It is proven that the proposed method is accurate, fast and cost efficient for detecting and classifying harmonic signals in distribution system. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the impact of switching harmonics on the instantaneous power distribution in the cells of a cascaded H-bridge-based STATCOM when using phase-shifted pulse width modulation. The case of high- and low-switching frequency for the converter cells is investigated and the interaction between voltage and current harmonics is analyzed. It is shown that in both cases, this interaction results in an uneven power distribution among the cells in the same phase leg, leading to drifting of the dc-capacitor voltages and thereby the need for proper stabilization control loops. It is also shown that the selected frequency modulation ratio affects the active power distribution among the cells. In particular, the selection of a noninteger frequency modulation ratio helps in providing a more uniform power distribution among cells of the same phase leg, thus contributing to the capacitors balancing. A methodology for optimal selection of the frequency modulation ratio is given. Theoretical conclusions are validated through simulation and experimental results. [ABSTRACT FROM AUTHOR]

In some rural and sub-urban areas, the hosting capacity (HC) of low voltage networks is restricted by voltage limits. With local voltage control, photovoltaic generators can mitigate the voltage rise partly and, therefore, increase the HC. This paper investigates the effectiveness and general performance of different reactive and active power control concepts. It presents the findings of an extensive simulation-based investigation into the effectiveness of voltage rise mitigation, additional reactive power flows, network losses, and power curtailment. The two most common implementations of reactive power control have a similar effectiveness. The voltage rise can be compensated for by up to 25% and more than 60% for typical cable and overhead (OH) feeders, respectively. By additionally using active power curtailment of up to 3% of the annual yield, the HC can be increased by about 50% and 90% for the considered cable and OH feeder, respectively (purely rural feeders). [ABSTRACT FROM AUTHOR]

This paper presents the results of a power quality study carried out in an industrial distribution system. The main objective of this study was to quantify the negative impact caused by voltage sags in industrial processes and its relationship to generated interruptions. A series of measurements of power quality variations were taken at the substation that feeds the circuit and at the point-of-common coupling of each industrial user. The new standard IEEE Std 1564-2014 “Guide for Voltage Sag Indices” was used to determine the indicators to assess the severity of voltage sags and also the calculation method. Sag severity was selected as it allows the calculation of the probability of voltage sags to generate interruptions in industrial processes or electrical equipment. Thus, an analysis of the quality of the supply voltage can be done. Severity was initially calculated at the substation that feeds the industrial circuit and later, at the point-of-common coupling of each user. Subsequently, the relationship between user interruptions and severity values was determined. Finally, recommendations of good engineering practices in industrial processes were done. [ABSTRACT FROM AUTHOR]

With the advent of new electricity production modes, power electronics, LED lamps and underground cables, new types of disturbances will appear, including an increase in distortion between 2 kHz and 150 kHz that is referred to as ‘supraharmonics.’ A shift of resonances to lower frequencies may partly compensate for the increased emissions at higher frequencies, but the transfer of disturbances will become less predictable. Equipment immunity also is likely to become less predictable. [ABSTRACT FROM AUTHOR]

A power regulation algorithm was designed to address the load requirements of a power packet dispatching system of interest. The switch controller, to which the regulation algorithm is applied, was constructed and implemented in the prototype of the power packet dispatching system. This algorithm was designed by extending the optimal dynamic quantizer investigated in the context of control with a discrete-valued signal. In the controller, the prediction of the states for the controlled variable in one packet transmission time before is applied to support the term when the controlled load is insulated from the source. This predictive dynamic quantizer can realize the power regulation for multiple loads simultaneously through a common power line. The stability of the system with the predictive dynamic quantizer is verified analytically as a switched system. The performance of the controlled variable is verified with the series of results from both experiments and numerical simulations. From these results, it was possible to verify that simultaneous voltage demands from multiple loads in the power packet dispatching system are satisfied with the regulation method. [ABSTRACT FROM AUTHOR]

This paper deals with the attenuation and performance of dissipative device like hybrid silencer involving coupled wave scattering for two different mode incidents. In particular device comprises inlet/outlet duct sections and a membrane attached internally to the outlet duct which may vary to tune the device. The solution process using the hybrid mode matching technique insight the physical situation of the underlying problem. The power distribution between the fluid regions and the membrane(s) is discussed numerically. We also confirm the validation of power balance as a fundamental property of the truncated system. [ABSTRACT FROM AUTHOR]

Supply reliability can be effectively improved by a normally closed-loop operation of a distribution network with dual sources, in which there might be large circulating power flow. A unified power flow controller (UPFC) has the powerful capability to adjust the power flow, but it would face a technoeconomic bottleneck when applied to the distribution system. Based on the constant current load model, the power flow distribution of a normally closed-loop distribution network with dual sources is analyzed, and the relationship between the network loss, the voltage deviation of load nodes, and the compensated voltage is deduced. Then, the optimal power flow control model is presented considering such economic factors as the network loss, the voltage deviation of load nodes, and the cost of the apparatus used to produce the compensated voltage. In order to simplify the problem of multiobjective optimization into a single-objective optimization model, the fuzzy membership functions and their weight coefficients of the network loss, the voltage deviation, and the UPFC's cost are designed, and the weights are determined according to their contribution in economy. The optimal control model is solved with the global optimal algorithm. Simulation results based on PSCAD prove that this method can ensure overall economy of the system with balancing the power distribution, controlling the node voltage deviation, and decreasing the active power loss of the network effectively. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

An ultracapacitor–battery hybrid energy storage system (HESS) for an electric vehicle (EV) based on a bidirectional quasi-Z-source inverter (qZSI) is proposed in this paper. The buck/boost characteristic in the qZSI enables the HESS incorporated into the traction inverter system. The battery converter can be eliminated and the rated voltages for the battery package and UCs are reduced. The steady power distribution principle is explained under various operation modes. An enhanced frequency dividing coordinated control strategy is established to optimize the dynamic power regulation and the battery current stress in short timescale. Both the simulation and experimental results in time and frequency domain validate the performance of the proposed HESS. [ABSTRACT FROM PUBLISHER]

This paper summarizes simulation based technical feasibility and cost benefit analyses of a range of off-the-shelf electrical losses reduction intervention solutions in the Isle of Wight (IoW) 11 kV distribution network in the United Kingdom (UK), assessed over a period of 45 years. Based on presented results, the paper provides a brief commentary on the merits, drawbacks, risks and recommendations associated with each considered network intervention. Among considered network interventions, the transformer auto stop-start scheme, where one of the transformers among a pair at a primary substation would be switched depending on the substation's varying load, was found to be the optimal solution, i.e., in reducing technical losses significantly and may also have a reasonable Net Present Value (NPV) with a good rate of Return on Investment (RoI) when fully implemented. [ABSTRACT FROM PUBLISHER]

Dynamic wireless power transfer (WPT) is a practical method to solve electric vehicle (EV) range anxiety and reduce the cost of on-board batteries. This paper presents a novel dynamic WPT system that combines the advantages of pads array and segmental long coils coupler. In the proposed circuit, several paralleled LCC reactive power compensation networks (RPCNs) in the primary side were excited by a sole inverter and the power distribution was realized automatically; an auxiliary LCC network was proposed to regulate current in the primary coil to minimize the electromagnetic interference (EMI) and reduce the system’s power loss. A scaled-down prototype of a dynamic wireless charging system was developed to prove the validity of the theoretical analysis. [ABSTRACT FROM PUBLISHER]

As a result of severe environmental pressure and stringent government regulations, refined energy management for vehicles has become inevitable. To improve vehicle fuel economy, this paper presents a bus-based energy management system for the electrical system of internal combustion engine vehicles. Both the model of an intelligent alternator and the model of a lead-acid battery are discussed. According to these models, the energy management for a vehicular electrical system is formulated as a global optimal control problem which aims to minimize fuel consumption. Pontryagin’s minimum principle is applied to solve the optimal control problem to realize a real-time control strategy for electrical energy management in vehicles. The control strategy can change the output of the intelligent alternator and the battery with the changes of electrical load and driving conditions in real-time. Experimental results demonstrate that, compared to the traditional open-loop control strategy, the proposed control strategy for vehicle energy management can effectively reduce fuel consumption and the fuel consumption per 100 km is decreased by approximately 1.7%. [ABSTRACT FROM AUTHOR]

Harmonic propagation between power-factor correction capacitors and system inductors seriously deteriorates power quality in a radial power distribution feeder. Installation of a resistive active power filter (RAPF) at the end bus only suppresses harmonic propagation, not attenuates harmonic voltages. This paper proposes a double-resistive active power filter (D-RAPF) system consisting of a terminal-RAPF and an attenuation-RAPF for each individual harmonic. The terminal-RAPF operating as the characteristic impedance of the feeder is installed at the end bus to suppress harmonic propagation at all harmonic frequencies. The attenuation-RAPF, whose control gain can be set according to the requirements of the harmonic voltage distortion limit, is installed at a specific position for each individual harmonic to attenuate the corresponding harmonic voltages. The D-RAPF system not only suppresses harmonic propagation and attenuates harmonic voltages more effectively, but also has the same rated power capacity as the RAPF. However, both the harmonic damping performance and the rated power capacity must be considered to choose the D-RAPF system or the RAPF when a harmonic current source exists at a position between the attenuation-RAPF and the terminal-RAPF. Simulation and experiment results verify the theoretical analysis and demonstrate the effectiveness of the D-RAPF system. [ABSTRACT FROM AUTHOR]

Running rails used as a return conductor and ungrounded scheme have been widely adopted in DC traction power systems. Due to the longitudinal resistance of running rails and insulation resistance of rail-to-ground, there will be a potential rise between running rails and the ground when return current flows through the running rails, which is known as rail potential. At present, abnormal rise of rail potential exists widely in DC traction power systems. The present rail potential model still cannot simulate and explain the abnormal rail potential in the system. Based on the analysis of power distribution with multiple trains running in multiple sections, a dynamic simulation model of rail potential in the whole line is proposed. The dynamic distribution of rail potential and stray current in DC traction power systems when multiple trains run in multiple sections is analyzed, and the impact of traction current distribution on rail potential is evaluated. Simulation results show that the abnormal rise of rail potential during the dynamic operation of the system can be evaluated effectively. [ABSTRACT FROM AUTHOR]

Supply noise is conventionally modeled as a fixed voltage noise specification. Modern integrated circuit design cannot meet a conventional fixed voltage noise specification due to large dynamic noise. These days, applications of multicore system-on-chip (SoC) and multichip system-in-package become very common. The impact of dynamic noise can be even more detrimental for multicore or SoC design as supply noise can be completely uncorrelated between two regions whose powers are different. Accurate modeling of noise impact requires a new approach that can account for any jitter tracking in clock forwarding systems. In this paper, a comprehensive dynamic noise modeling methodology is presented to analyze jitter impact in various clock forwarding interfaces for multicore and SoC designs. The proposed method uses the frequency-dependent jitter sensitivity function with a noise spectrum to model the desired jitter tracking. [ABSTRACT FROM AUTHOR]

An existing effective approach for the synthesis of linear arrays providing power patterns lying in arbitrary masks is extended to the case where an even distribution is required on element excitations. The approach consists of a linear programming optimization plus a polynomial factorization, and it allows one to deal with a considerably reduced computational burden with respect to the previous approaches. By so doing, it is now possible to solve problems that cannot be successfully tackled by the previous techniques. An extension of the overall strategy to the synthesis of fields guaranteeing optimal performances in terms of directivity or ripple in the main-beam region is also given. [ABSTRACT FROM AUTHOR]