Primary Power Distribution Research Articles

Distributed photovoltaic power fluctuation flattening strategy based on hybrid energy storage

Aiming at mitigating the fluctuation of distributed photovoltaic power generation, a segmented compensation strategy based on the improved seagull algorithm is proposed in this paper. In this regard, a hybrid energy storage system comprising a lithium battery and supercapacitor is utilized. The internal power distribution of the hybrid energy storage system is adjusted using wavelet packet decomposition, and the state of charge is employed to adapt the primary power distribution. The start and end times for charging and discharging are determined by combining the time of use, electricity price, state-of-charge information, and load size at night to realize the economic operation of the system. The opposing search operator strategy and mutation operation are used to improve the seagull algorithm, optimize the controller parameters of the DC/DC converter, and improve its response time. Combined with the historical measured data of a distributed photovoltaic in Hubei Province, simulation results show that the proposed strategy can effectively smoothen the fluctuation of distributed photovoltaic generated power while reducing the charging and discharging frequencies of the energy storage system, hence improving its stability and service life.

Scheme design of brushless DC excess power generation system

Brushless motors have the advantages of no brush, low interference, long life, and low maintenance costs, which are increasingly used in aviation power systems. According to the reliability requirements of the aircraft power generation system, this paper proposes a brushless DC excess power generation system scheme, which sends the alternating current generated by the main motor of the brushless DC generator to the AC/DC converter and primary power distribution, while retaining the main motor power generation converted into DC power through the internal rectifier circuit of the motor. The generator controller is designed with double surplus output to improve the reliability of the system power supply.

Intermittent series direct current arc fault detection in direct current more‐electric engine power systems based on wavelet energy spectra and artificial neural network

The move towards More-Electric Aircraft (MEA) and Engine (MEE) systems has resulted in system integrators exploring the use of Direct Current (DC) for primary power distribution to both reduce energy conversion stages and enable parallelling of non-synchronised engine off-take generation. A prevalent challenge of utilising DC systems is the safe management of arc faults. Arcing imposes a significant threat to aircraft and can result in critical system damage. Series intermittent arc faults in DC systems are particularly challenging to detect due to the lack of a zero current crossing coupled with the intermittency caused by in-flight vibrations. Additionally, several state-of-the-art arc fault detection methodologies fail to address the handling of aircraft system-specific conditions such as dynamic loading and stability requirements. This paper addresses these unique MEA/MEE issues through the proposal of a new generalised real-time arc fault detection methodology (WaSp) based on time–frequency domain-extracted features applied to a feed-forward Artificial Neural Network (ANN). The paper outlines the analysis of arc fault time–frequency domain features. Simulation-based case studies emulating a range of on-board EPS conditions are presented and show the proposed system has the potential for highly accurate and generalised detection performance with fast detection times.

Key technology and application of primary and secondary fusion power distribution switchgear test and detection

In recent years, primary and secondary integration of distribution switchgear has been widely used in the distribution network. In the future, primary and secondary integration will become the mainstream development trend of power distribution switchgear, especially in 2021, the State Grid Corporation of China will issue a new type of primary and secondary integration standardization. The typical design plan of power distribution switchgear have added two configuration methods: electronic transformer and digital transformer. So the traditional independent test method of power distribution automation terminal or power distribution switchgear are no longer applicable to the current new-type primary and secondary fusion standardized power distribution switchgear. At the same time, there is no standard basis for direct reference. This article mainly analyzes the key test items for performance verification of primary and secondary fusion power distribution switchgear, and propose corresponding test detection methods.

Sealed Solution for Primary Power Distribution

A NEW BOX COMPLEMENTS EXISTING POWER DISTRIBUTION PLATFORM FROM ONE OF THE INDUSTRY'S LEADING ELECTRONIC SOLUTION PROVIDERS

Power Distribution Systems Using Bit-Shift Operator Based MOSOA

Abstract This paper presents a new approach based on the application of a bit-shift operator based multi-objective seeker-optimization-algorithm (BS-MOSOA) for designing of combined primary and secondary power distribution system (CPDS) considering both system cost and reliability. In number of researches works the planning of secondary power distribution system (PDS) has not been considered for planning strategy. However, it is observed that the total investment and operational cost components of secondary PDS plays an important role in the overall system cost. Thus, in this proposed research a CPDS has been considered for comprehensive planning of complex PDS. Furthermore, a reliability index called Contingency-load-loss-index is used for the reliability assessment of the network. The algorithm uses a modified version of seeker-optimization-algorithm (SOA), which is based on the status of changing switches and shift operator to generate a group of non-dominated solutions. Also, fuzzy theory approach is used for selection of most suitable solution among the non-dominated solutions from the obtained Pareto-front. The proposed method is illustrated on a real test case consist of a residential primary and secondary network of 75 electrical nodes. Furthermore, a qualitative comparison is made with existing traditional and classical methodologies, to show the efficacy of the proposed planning approach.

Probabilistic System Availability Model and Prevailing Factors for 33kV Primary Power Distribution Feeders in Nigeria

Outage and complimentary load flow analyses of a selected 33kV primary distribution network in Ughelli Delta State, Nigeria, were carried out to depict feeder availability obtainable in the country. Outage and load flow analyses were carried out using parametric statistics and Newton-Raphson computation algorithm respectively. The results provide model distribution of monthly feeder availability, contributions of outage factors and normal load flow values. It was concluded that: monthly feeder availability represented using normal probability distribution function of; shows that overcurrent and earth faults contribute to outage duration, taking 5% to 12% of the month outage duration respectively; coupled with significant line losses and weak voltage profile. Recommendations proposed include: replacement of weak or failed elements and insulations in the systems with new and modern ones to mitigate especially earth faults in the short term; planning for immediate increase in system capacity to accommodate the power demand effectively for present and forecast periods to eliminate load shedding, overload events, and high technical losses; maintenance practice at the planning and execution stages to mitigate failure events and repair time. Keywords – fault, outage, probability, load flow, availability, distribution network.

Kruskal's Maximal Spanning Tree Algorithm for Optimizing Distribution Network Topology to Improve Voltage Stability

—Alteration of power network topology is often required to meet important objectives, such as restoring connectivity, minimizing power losses, maintaining stability, maximizing power transfer capability etc., and is achieved by switching of circuit breakers and other switching devices in the power network. Primary power distribution networks are often interconnected and meshed but should be transformed to radial topology to achieve various operational advantages. Distribution networks also need to be reconfigured after faults to restore power at all the load points. Reconfiguring a power network, however, is a complicated multi-constrained optimization problem, as there may exist many feasible switching combinations in a large power network. This article proposes a novel application of graph theory, supported by Kruskal's maximal spanning tree algorithm, to search for the optimal network topology and to optimally convert an interconnected meshed network into a radial system to achieve best operational characteristics, cost, and control. The proposed technique has been demonstrated on a 30-node primary distribution network originally having a mesh topology, and the results indicate significant performance improvement after transformation into optimal radial topology.

Knowledge Mapping Analysis of Finance Research

Based on 4158 articles from 9 financial journals during 2009-2013 from Web of Science, we use CiteSpace III to construct the knowledge mapping of finance studies. As a result, the primary research power distribution is shown. Further, finance research hotspots and major research fields are revealed via keywords co-occurrence analysis and references co-citation analysis. The findings show that the United States plays a leading role in the research of finance. There are four major research fields: asset pricing, corporate finance, financial intermediation and investor behavior. The findings will contribute to following the international research frontier and catching research trends.

Design of an advanced electric power distribution systems using seeker optimization algorithm

The power distribution network design problem has a growing impact on secure and economical operation of distribution power system. This issue is well known as a non-linear, multi-modal and multi-objective optimization problem where global optimization techniques are required in order to avoid local minima. In this study, a new approach using seeker optimization algorithm (SOA) is proposed for distribution system planning problem with simultaneous placement of automatic reclosers (RAs), considering total system economic cost, overall system reliability, system power losses and voltage deviations as an objective functions. Normally, conventional power distribution systems (CPDS) are radial in nature and momentary fault in the system causes large area of the grid to be blacked out, which leads to huge load interruptions. Reliable distribution system minimize this effect by allowing faults to clear themselves by protection device operations such as automatic reclosers (RAs) and quickly restores the power through system reconfiguration by minimizing the loads affected. Thus, in order to prevent the system from momentary faults, simultaneous placement of RAs has been also done which leads to a design of an advanced power distribution system (APDS). Thus, the reliability issues are of major importance for effective planning of an APDS. For evaluation of reliability measure, the contingency-load-loss index (CLLI) is assessed in this paper, which is independent of the failure rate and fault repair duration of the feeder branches. The performance of the proposed algorithm is extensively assessed and comparisons are made with Particle Swarm Optimization (PSOs), Genetic Algorithm (GA) and graph theoretical approach (GTA) applied on the 54 and 100-bus primary power distribution systems. The simulation results show that the proposed approach performed better than the other listed algorithms and can be efficiently used for the optimal design of an advanced power distribution system.

A Technique to Mitigate Zero-Sequence Harmonics in Power Distribution Systems

This paper presents a technique to mitigate zero-sequence harmonics in power distribution systems. The method is based on the concept of passive zero-sequence harmonic filters. However, its basic configuration has been expanded to create a double-tuned filtering feature. This feature makes it possible to trap two harmonics with one filter and is especially attractive in solving harmonic-caused telephone interference problems. Furthermore, this paper has shown that common utility service transformers can be used to construct the filter. As a result, a practical and low-cost solution to mitigating zero-sequence harmonics has been found. A method for sizing and loading assessment of filters has also been developed. As an example application, the proposed filter package has been applied to mitigate a telephone interference problem. Issues, such as filter location, the number of filters required, and the effectiveness of filtering harmonics produced by distributed residential loads have been investigated. The results show that the proposed filter is a very promising technique to reduce zero-sequence harmonics in primary power distribution systems.

Evolutionary Optimization of Electric Power Distribution Using the Dandelion Code

Planning primary electric power distribution involves solving an optimization problem using nonlinear components, which makes it difficult to obtain the optimum solution when the problem has dimensions that are found in reality, in terms of both the installation cost and the power loss cost. To tackle this problem, heuristic methods have been used, but even when sacrificing quality, finding the optimum solution still represents a computational challenge. In this paper, we study this problem using genetic algorithms. With the help of a coding scheme based on the dandelion code, these genetic algorithms allow larger instances of the problem to be solved. With the stated approach, we have solved instances of up to 40,000 consumer nodes when considering 20 substations; the total cost deviates 3.1% with respect to a lower bound that considers only the construction costs of the network.

Primary power distribution systems planning taking into account reliability, operation and expansion costs

In this work, the planning problem of primary distribution networks is formulated as a multi-objective mixed-integer non-linear programming model (MINLP). The objective functions of this model are the expansion and operation investment costs of primary distribution networks as well as the system's reliability costs in the contingency events. The reliability costs are obtained by means of calculating the non-supplied energy because of the repairing and switching operations in the distribution network carried out to isolate and to redistribute loads in the affected sections by permanent faults. In order to solve the expansion problem of the primary network a Multi-objective Reactive Tabu Search algorithm (MO-RTS) is proposed. The concepts of dominance are used to obtain Pareto's optimal frontier in the MO-RTS. The problem of placement of sectionalising switches (automatic or manual) to restore the distribution network and to reduce non-supplied energy costs when permanent faults occur in the network is solved simultaneously with the network expansion planning problem by means of a dedicated genetic algorithm. For testing, the proposed methodology is used as a primary power distribution system, with 180 points of consumption, where 49 already exist and 131 can be added to the system during the planning process.

Determination of protection system requirements for DC unmanned aerial vehicle electrical power networks for enhanced capability and survivability

A growing number of designs of future unmanned aerial vehicle (UAV) applications utilise DC for the primary power distribution method. Such systems typically employ large numbers of power electronic converters as interfaces for novel loads and generators. The characteristic behaviour of these systems under electrical fault conditions, and in particular their natural response, can produce particularly demanding protection requirements. Although a number of protection methods for multi-terminal DC networks have been proposed in the literature, these are not universally applicable and will not meet the specific protection challenges associated with the aerospace domain. Through extensive analysis, this study seeks to determine the operating requirements of protection systems for compact DC networks proposed for future UAV applications, with particular emphasis on dealing with the issues of capacitive discharge in these compact networks. The capability of existing multi-terminal DC network protection methods and technologies are then assessed against these criteria in order to determine their suitability for UAV applications. Recommendations for best protection practice are proposed and key inhibiting research challenges are discussed.

An alternative approach to fault location on power distribution feeders with embedded remote-end power generation using artificial neural networks

In this paper, the design and implementation of a feed-forward artificial neural network (ANN)-based fault locator to classify and locate shunt faults on primary overhead power distribution lines with load taps and embedded remote-end power generation is presented. In the ANN algorithm, the standard back-propagation technique with a sigmoid activation function is used. The fault locator utilizes fault voltage and current samples obtained at a single location of a typical radial distribution system. The ANNs are trained with data under a wide variety of fault conditions and used for the fault type classification and fault location on the distribution line. A 34.5 kV distribution system is simulated using electro-magnetic transients program and their results are used to train and test the ANNs. The ANN-based fault locator gives high accuracy for the vast majority of the practically encountered systems and fault conditions, including the presence of load taps and the remote-end in-feed source.

Fault Detection in Power Distribution Systems Using Automated Integration of Computational Intelligence Tools

The main purpose of this paper is to present architecture of automated system that allows monitoring and tracking in real time (online) the possible occurrence of faults and electromagnetic transients observed in primary power distribution networks. Through the interconnection of this automated system to the utility operation center, it will be possible to provide an efficient tool that will assist in decision-making by the Operation Center. In short, the desired purpose aims to have all tools necessary to identify, almost instantaneously, the occurrence of faults and transient disturbances in the primary power distribution system, as well as to determine its respective origin and probable location. The compilations of results from the application of this automated system show that the developed techniques provide accurate results, identifying and locating several occurrences of faults observed in the distribution system.

Location of faults in power distribution laterals using superimposed components and programmable logic controllers

In this study, a digital fault location and monitoring technique using programmable logic controller (PLC) for primary overhead power distribution networks is presented. This technique employs pre- and post-fault current and voltage information along with data from the laterals. By using lateral current data transferred through shielded coaxial cables to the substation, the possibility of multiple fault point locations are eliminated. The effectiveness of this method is verified through Electromagnetic Transients Program (EMTP) simulations.

Life Cycle Assessment of Overhead and Underground Primary Power Distribution

Electrical power can be distributed in overhead or underground systems, both of which generate a variety of environmental impacts at all stages of their life cycles. While there is considerable literature discussing the trade-offs between both systems in terms of aesthetics, safety, cost, and reliability, environmental assessments are relatively rare and limited to power cable production and end-of-life management. This paper assesses environmental impacts from overhead and underground medium voltage power distribution systems as they are currently built and managed by Southern California Edison (SCE). It uses process-based life cycle assessment (LCA) according to ISO 14044 (2006) and SCE-specific primary data to the extent possible. Potential environmental impacts have been calculated using a wide range of midpoint indicators, and robustness of the results has been investigated through sensitivity analysis of the most uncertain and potentially significant parameters. The studied underground system has higher environmental impacts in all indicators and for all parameter values, mostly due to its higher material intensity. For both systems and all indicators the majority of impact occurs during cable production. Promising strategies for impact reduction are thus cable failure rate reduction for overhead and cable lifetime extension for underground systems.

Optimum VAR control of radial primary power distribution networks by shunt capacitor installation

A complex method for the optimum var control of radial primary power distribution networks, dealing with the proper selection and installation of shunt capacitors, is developed in this article. The problem is examined both on an annual and a long-term basis. First objective functions and relative algorithms which determine the kind, the size, the minimum number, the locations and the adjustments of the possibly installed standard capacitors are developed. Then all these are embodied in a complex software package, which examines all the technically acceptable var control solutions, it compares them economically and finally proposes the more profitable. Results of the application of this package on a practical network are also given.

Long-term optimization of radial primary distribution networks by conductor replacements

A method dealing with the technoeconomical long-term optimization of currently operating radial primary power distribution networks is developed in this paper. This method, taking into account the realistic locations and growth of the load served by the examined network and specific technoeconomical constraints, results in the proposal of conductor replacements which must be realized in the network segments at specified years of the plan period. This is in order to optimize the network technically as much as possible, defraying the minimum cost.