Existing Power Distribution Systems Research Articles

Impact of Economic Growth on Carbon Emissions In Pakistan

Pakistan is a developing country that seeks economic growth. However, Pakistan needs to analyze the environmental cost associated with economic growth and adapt to sustainable growth accordingly. The data spanning 41 years was extracted from the World Bank and Our World In Data, which was then analyzed. This paper studied the relationship between economic growth and carbon emissions in Pakistan. It analyzed the impact of economic growth on carbon emissions by conducting a time-series data analysis and applying the Engle and Granger cointegration approach to examine the long-run relationship between the independent and dependent variables. Error Correction Model (ECM) was also applied to study the short-run impact of economic growth on carbon emissions. The results of this study reveal that (i) energy consumption per capita has a strong and positive relation with carbon emissions in the short-run and long-run, whereas (ii) GDP has a weak but positive relationship with carbon emissions in the short-run and long-run. The results also show that GDP and energy consumption per capita cause carbon emissions to increase faster in the long-run. The study concluded that long-run adjustment is possible since the ECM model predicts that 37.76% of the long and short-run discrepancy will be corrected within a year. The study recommends that increasing the share of hydel and renewable energy in Pakistan’s energy mix and revamping the existing power distribution system to minimize power losses will mitigate the carbon emissions caused by energy consumption. Moreover, the adoption of sustainable practices by manufacturers, installing catalytic converters in manufacturing plants, and incentivizing the use of renewable energy for manufacturers and households will mitigate the carbon emissions caused by GDP growth.

Деволюция в политико-правовой практике современных государств

The article analyzes he specifics of devolutionary processes in modern states. The author defines devolution as the transfer by the central power structures of part of the powers to autonomous territories. Criteria for differentiation of decentralization of power and devolution are singled out. A review of the existing scientific literature on the subject under consideration has shown that there is no consensus among researchers on the nature of the phenomenon of devolution. The author of the article comes to the conclusion that devolution is a product of globalization. Vectors of the implementation of devolution are presented: legislative powers, powers in the field of collecting and spending budget funds, language policy, ethnic policy, foreign policy powers. The systems of distribution of power between the center and regions in Germany, Italy, Spain, Great Britain are analyzed. The author notes the advantages and disadvantages of existing power distribution systems.

A High-Efficiency Low-Wearing Hybrid Voltage Regulator for Utility Applications

Step voltage regulator (SVR) has been utilized in power distribution systems for decades as the voltage regulation device. Due to the increasing integration of distributed energy resources, the conventional SVR is severely challenged by the modern power distribution pattern with high renewable energy penetration. The induced arc from the conventional SVR tap change and more frequent tap changes due to voltage instability from the renewable energy impose constraints on the conventional SVRs lifetime. Meanwhile, the conventional SVR device cannot regulate the voltage accurately since the SVR regulates the voltage step-by-step. This article proposed a hybrid voltage regulator with high-efficiency and low contact wearing, which can achieve arcless tap change and stepless voltage regulation by using a fractionally rated back-to-back power converter. The accurate load voltage regulation is guaranteed, while the tap changer mechanism remains in the system, which helps to promote the upgrade to the existing power distribution systems. The power converter capacity in the proposed topology is only 0.31% of the distribution transformer rating to achieve a stepless voltage regulation range of ±10%, significantly reducing the system cost compared with the full power electronics solutions and projects high total system efficiency. The proposed hybrid voltage regulator was simulated and experimentally validated. The experimental results demonstrate arcless tap change operation and stepless voltage regulation. Collaborative operation between the conventional mechanical tap change and the power converter operation is also demonstrated to acquire large voltage regulation with fast-acting voltage control.

Optimal Location and Sizing of Renewable Distributed Generators for Improving Voltage Stability and Security Considering Reactive Power Compensation

The integration of renewable resources into the existing power distribution system is expanding to reduce gas emissions, treat climate change and satisfy the current global need for clean energy. If the location and size of these renewable generators are determined without considering uncontrollable reactive power compensation caused by their intermittent nature, the resultant power system may suffer from system instability and decreased reliability. Therefore, the issue of optimal location and size of renewable resources attracts great attention. In this paper, a methodology is proposed to optimize the locations and capacities of distributed renewable generators installed in conventional power distribution systems. In particular, uncontrollable reactive power compensation of these renewable resources is considered in this paper and managed through the proposed methodology to ensure power system reliability and stability. As a result, the proposed methodology reminds us of the importance of reactive power compensation by performing better in power losses reduction and the robustness of voltage stability against variable reactive power compensation.

Integrating dynamic Bayesian network and physics-based modeling for risk analysis of a time-dependent power distribution system during hurricanes

Hurricane is one of the major natural hazards that bring significant damages and failures to the power distribution system for many coastal regions. For better decision-making, pre-hazard maintenance and post-hazard restoration of the power distribution system can be improved through the risk analysis of the distribution system. However, as a natural material, wood deteriorates with time. Therefore, the performance of the power distribution system could vary significantly during their life cycles. To quantify the time-dependent nature of the existing power distribution system due to material deterioration, a dynamic Bayesian network (DBN) is implemented for the risk analysis of a power distribution system against hurricanes. To capture the failure probabilities of the poles in the power distribution system, fragility surfaces for the poles are generated through physics-based fragility analysis, incorporating physical properties of the pole-wire components and the pole-wire system topology. The failure rate of the distribution system is obtained through the Bayesian network (BN) at each time step. With the observed failure data of poles, the material properties and the fragility surfaces of the components in the power distribution system are updated through Bayesian inferring. More specifically, the particle filter (PF) algorithm is utilized. To efficiently save computational cost in BN reasoning, the Gaussian process (GP) algorithm is adopted to build surrogate models to predict poles’ behaviors. Predictors are selected from the feature space to further reduce computational time and to enhance the prediction performance of the surrogate models through the automatic relevance determination (ARD) method. The failure rate is underestimated by 11% when the system deterioration process is ignored given a ten-year interval of hurricane events.

Improving reliability of the power distribution system in Goma (DRC) using solar distributed generation

The existing power distribution system of the city of Goma in the Democratic Republic of the Congo has many problems, including the scarcity of electric energy, power unreliability, the low access rate of electrification, poor flexibility in the network topology, and lack of demand response, which lead to shedding of load, unbalancing and overloading the system. The reliability of the Goma power distribution system is very poor by international standards. The major cause of this is the lack of adequate energy supply to meet demand. To mitigate the power reliability problem, a solar-based distributed generation (DG) is modelled and evaluated in this study. Each feeder has been considered separately with an appropriately designed DG. The work has evaluated initial investment cost and life cycle cost of the investment to assess the feasibility of the proposed solution. Based on the unserved energy and electricity tariff, an economic analysis was conducted. The reliability indices are computed and the modelled solution is designed for each feeder in PV syst software and simulated using ETAP, whose simulation results show that the reliability can be improved by up to 76%.

Validation of optimal electric vehicle charging station allotment on IEEE 15-bus system

Introduction. The diminishing conventional energy resources and their adverse environmental impacts compelled the researchers and industries to move towards the nonconventional energy resources. Consequently, a drastic paradigm shift is observed in the power and transportation sectors from the traditional fossil fuel based to the renewable energy-based technologies. Considering the proliferation of electric vehicles, the energy companies have been working continuously to extend electric vehicle charging facilities. Problem. Down the line, the inclusion of electric vehicle charging stations to the electric grid upsurges the complication as charging demands are random in nature all over the grid, and in turn, an unplanned electric vehicle charging station installation may cause for the system profile degradation. Purpose. To mitigate the problem, optimum allocation of the charging stations in existing power distribution system in a strategic manner is a matter of pronounced importance in maintaining the system stability and power quality. In this paper, optimum allocation of electric vehicle charging stations in IEEE 15-bus system is studied in order to minimize the highest over and under voltage deviations. Methodology. Primarily, voltage stability analysis is carried out for identification of the suitable system nodes for the integration. Voltage sensitivity indices of all the system nodes are calculated by introducing an incremental change in reactive power injection and noting down the corresponding change in node voltage for all nodes. Henceforth, dynamic load-flow analysis is performed using a fast and efficient power flow analysis technique while using particle swarm optimization method in finding the optimal locations. Results. The results obtained by the application of the mentioned techniques on IEEE 15-bus system not only give the optimum feasible locations of the electric vehicle charging stations, but also provide the maximum number of such charging stations of stipulated sizes which can be incorporated while maintaining the voltage profile. Originality. The originality of the proposed work is the development of the objective function; voltage stability analysis; power flow analysis and optimization algorithms. Practical value. The proposed work demonstrates the detailed procedure of optimum electric vehicle charging station allotment. The experimental results can be used for the subsequent execution in real field.

Renewable Energy Supported Bi-directional Electric-Vehicle Charging Station Allocation in Distribution Network using INBPSO Technique

With the sustained growth in the electric-vehicle (EV) industry, the installation of a large number of electric-vehicle charging stations (EVCSs) is the utmost important in recent energy policies of all countries. On the other side, due to the augmented awareness on renewable energy especially the photovoltaic (PV) and wind energies, the installation of renewable energy based EVCSs and their integration into the radial distribution networks have become a promising choice with the feasible bi-directional power flow facility catered by the EVCSs. Bi-directional EVCSs can enable power flow from renewable source/EV to grid and grid to EV to balance power demand for EV as well as distribution network. The optimum allotment of renewable energy powered EVCSs in existing power distribution system is a matter of great significance to maintain the power balance as well as the voltage profile and minimize the total active power loss of the network. This paper presents a strategy for optimum allocation of renewable energy powered EVCSs in a large distribution network with the focus on power balance, voltage profile improvement and active power loss minimization. An improved new binary particle swarm optimization (INBPSO) technique is applied in collaboration with a fast and efficient power flow analysis technique for performing dynamic power flow computation. Validation is conducted on IEEE 15-bus system considering different cases of power flow directions and power ratings. Additionally, voltage as well as loss sensitivity analysis are performed to ascertain the acceptability of the optimum locations obtained by the computation approach. https://dorl.net/dor/20.1001.1.13090127.2021.11.2.24.3

An integrated and reconfigurable hybrid AC/DC microgrid architecture with autonomous power flow control for nearly/net zero energy buildings

With the ever-increasing of population and economy worldwide, buildings have become major energy consumers and greenhouse gas (GHG) emitters. The hybrid AC/DC microgrid is a promising alternative for existing power distribution systems to achieve the goal of nearly/net zero energy buildings (nZEBs). However, the increasing demand for compact structure, seamless integration of distributed generators (DGs) and loads, as well as more control flexibility of hybrid microgrids cannot be adequately satisfied by conventional grid architectures. In view of this, an integrated and reconfigurable hybrid AC/DC microgrid architecture with its hierarchical control strategy is proposed in this paper. Firstly, a novel interlinking converter named smart interlinking unit (SIU) is presented, which can provide multiple AC/DC interfaces and diverse operation modes with various control functionalities. Secondly, the SIU-based hybrid microgrid architecture and its hierarchical control structure are established. The dedicated interfaces and cluster controllers for electric vehicles (EVs) facilitate the implementation of centralized vehicle-to-grid (V2G) service. Thirdly, a hierarchical control strategy of SIU, which involves local control in primary control level and power flow control in secondary control level, is introduced to realize coordinated operation of microgrid. The model of the proposed hybrid microgrid architecture is built, and the simulation results demonstrate that the microgrid architecture and hierarchical control strategy can achieve a reliable and coordinated system operation under various kinds of scenarios. Additionally, the mutual power support between AC and DC sub-grids is realized with increased utilization and local consumption of renewable energy resources (RESs).

Sustainable protection coordination in presence of distributed generation with distributed network

The distributed generation (DG) is getting extensively integrated in existing power distribution system because of the massive development in green energy technologies and their economical, technical, and environment benefits. However, apart from beneficial aspects, DGs also have various and complex technical limitations, major of which are loss of protection coordination among protection devices which can lead to malfunctioning of protection devices, blind protection, fuse blowing, and permanent outage of power supply due to temporary faults. In this paper, a novel curve fitting technique is designed to restore much influenced recloser-fuse coordination using the directional properties of midline recloser for upstream and downstream protection devices coordination. It also works on fuse-saving scheme. Using Electrical Transient Analysis Program (ETAP) Software, the proposed methodology is implemented on a real 11 kV Rajewala radial distribution feeder starting from 132 kV Eimnabad grid station, district Gujranwala, Pakistan. Present here are some key results. Different case studies are carried out and results validate the effectiveness of the proposed methodology, and the coordination among protection devices is sustained even after DGs integration in the system.

Adoption barriers for electric vehicles: Experiences from early adopters in Sweden

Electric vehicles are considered as one of the most effective technologies for reducing current greenhouse gas emissions from the transport sector. Although in many countries, local and national governments have introduced incentives and subsidies to facilitate the electric vehicle market penetration, in Sweden, such benefits have been limited. Results from a survey carried out among private owners of electric vehicles are presented in this paper, including the analysis of the respondents socio-demographic characteristics, reasons for choosing an electric vehicle, charging locations and driving preferences, among others. The main results characterize current electric vehicle drivers as male, well-educated, with medium-high income; electric vehicles are used mainly for private purposes and charged at home during night time. Furthermore, the paper presents an analysis of the impact of large-scale penetration of electric vehicles on existing power distribution systems. The findings presented in this paper provide important insights for assuring a sustainable large-scale penetration of electric vehicles by learning from the experiences of early adopters of the technology and by analyzing the impact of different EV penetration scenarios on the power distribution grid.

Performance Comparison of Circuits for Pole‐Mounted STATCOM Using SiC Devices

SUMMARYThe recent years have seen an increasing trend in the cumulative installed capacity of distributed generators. As a result, voltage management may become difficult in existing power distribution systems in the future. A STATCOM (STAtic synchronous COMpensator) is a promising option for solving this problem because it can control reactive power rapidly and continuously. For a distribution system, STATCOM needs to be pole‐mounted to realize its low cost. However, a transformer for a STATCOM is large and heavy, and hence it is difficult to install a STATCOM on a distribution pole. We adopt a transformerless STATCOM to reduce STATCOM size and use SiC devices with low‐loss performance to obtain a more compact and efficient STATCOM. There are a large number of circuits available for a STATCOM, and there has been considerable research on performance comparisons among these circuits. However, these comparisons were drawn under different conditions, including switching frequency and level number for the circuits. In addition, these comparisons do not include the use of SiC devices. We made an equitable comparison for a 100 kVa pole‐mounted STATCOM using SiC devices. We discuss the performance and characteristics of each circuit in terms of efficiency and volume.

Probabilistic estimation of plug-in electric vehicles charging load profile

Plug-in electric vehicles (PEVs) are widely considered as a sustainable mode of transport by countries worldwide due to high efficiency and low or zero carbon emissions. However, PEVs will add significant additional load to the existing power distribution system and it will be a challenge to meet the new demand. In this study, probabilistic modelling has been presented to estimate the system-wide PEV charging load within domestic grids. U.S. national household travel survey data set has been utilized to quantitatively determine the mobility behaviour of PEVs.Uncertain nature of the problem in modelling and data preparation should be taken into account. Due to the existence of complex interdependencies between the system inputs, the problem definition leads to a multivariate uncertainty analysis problem. The modelling procedure is decomposed into two basic components: the modelling of the marginal distributions; and that of the stochastic dependence structure. In addition, Copula theory is presented for the multivariate modelling of dependent random variable. The results indicate that the PEVs can contribute to increase the load demand at certain hours, although the charging demand is very limited most of the time. Moreover, the probabilistic distribution of aggregated PEV charging demand is compared with that obtained by the Monte Carlo simulation. The numerical results have shown the effectiveness of the proposed methodology.

Risk-Constrained Microgrid Reconfiguration Using Group Sparsity

The system reconfiguration task is considered for existing power distribution systems and microgrids, in the presence of renewable-based generation and load foresting errors. The system topology is obtained by solving a chance-constrained optimization problem, where loss-of-load (LOL) constraints and ampacity limits of the distribution lines are enforced. Similar to various distribution system reconfiguration renditions, solving the resultant problem is computationally prohibitive due to the presence of binary line selection variables. Further, lack of closed-form expressions for the joint probability distribution of forecasting errors hinders tractability of LOL constraints. Nevertheless, a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">convex</i> problem reformulation is developed here by resorting to a scenario approximation technique, and by leveraging the underlying group-sparsity attribute of currents flowing on distribution lines equipped with tie and sectionalizing switches. The novel convex LOL-constrained reconfiguration scheme can also afford a distributed solution using the alternating direction method of multipliers, to address the case where multifacilities are managed autonomously from the rest of the system.

On the Reclose Operation of Superconducting Fault Current Controller for Smart Power Grid With Increasing DG

At present, the operation of protection coordination in a complex and uncertain power distribution system is satisfied through the use of a recloser and fuse. Due to the increased adoption of renewable energy resources, distributed energy resources as well as expanded electric transportation and dynamic demand response technologies in the power industry confront significant challenges during grid operations. As a result, protection coordination may be broken due to an increase in the current level in a power system. In general, once the protection is well coordinated by a fault current controller (FCC), the previously installed recloser on the existing power distribution system becomes useless because the FCC plays the role of the recloser. In this work, we propose an operating strategy of protection coordination for the FCC, which is capable of replacing the recloser in an environment where various types of distributed generation are introduced simultaneously due to the proliferating demand of renewable energy sources. Specifically, the suggested method based on PSCAD/EMTDC is investigated.

Analyzing the Harmonic Distortion in a Distribution System Caused by the Non-Linear Residential Loads

Harmonic distortion has garnered a lot of interest in the recent past due to the high advent of the non-linear electronic loads. Moreover, newer technologies including distributed generation and electric vehicles are anticipated to be part of the distribution systems at a mass scale in the near future. This makes it of utmost importance to evaluate the existing power distribution systems and analyze the possible constraints. This research study makes an effort to evaluate the harmonic distortion in the distribution systems caused by the various non-linear residential loads. The experimentally developed harmonic spectrums, of several home appliances, are deployed for the simulation of a typical UK distribution system using Electrical Transient Analyzer Program (ETAP). The results show high level of harmonic distortion, at the Point of Common Coupling (PCC), in the distribution system which becomes even more aggravated when a higher loading level, of the distribution transformer, is considered.

Wind turbines as yet unsuitable as electricity providers

Wind turbines have been widely accepted as electricity producers thanks to claims that wind comes free of charge, and each kWh thus produced replaces a kWh provided by conventional techniques, i.e., it saves the fossil fuel otherwise needed. However, these assumptions have never been validated in existing power distribution systems even after the installation of as much as 86 GW of wind power in Europe alone.

배전계통의 보호협조측면에서 본 분산전원 연계용량 검토

정부의 신ㆍ재생 에너지 관련 정책으로 인해 앞으로 국내에서 신ㆍ재생에너지원은 보급은 증가할 것으로 예상된다. 신ㆍ재생에너지원은 전원의 특성상 전력계통에 연계되어 운전하는 것이 일반적이지만 이러한 연계 운전은 전력 계통 계획 및 운영상에 상당한 영향을 미치게 된다. 기존 배전계동의 전력조류는 변전소에서 수용가를 향한 단방향이며 이를 기반으로 계통운영이 이루어지고 있으나, 신ㆍ재생에너지원의 연계로 배전계통에 양방향의 전력조류가 형성되므로 기존의 보호시스템의 신뢰성 및 전력품질이 저하될 수 있다. 따라서 신ㆍ재생에너지원의 연계평가에 대한 기술적 평가절차가 필요하다. 본 논문에서는 국내 배전계통의 전형적인 보호기기인 자동 재폐로 차단기와 구분 개폐기의 특성을 살펴보고, 현재의 자동재폐로 차단기-구분개폐기 보호시스템에서 분산전원의 연계용량을 검토하는 방안을 제시하고자 한다.

분산전원이 연계된 배전계통의 온라인 보호협조 방안

최근 경제 발전으로 인한 전력 에너지 소비 증가로 발전설비의 확충이 요구되는 상황이다. 그러나 회석연료고갈 및 지구환경문제로 대형 화력 발전설비의 확충이 어려워지고 있다. 따라서 발전부지 확보가 용이하고 환경오염의 위험이 적은 분산전원에 대한 관심이 한층 더 고조되고 있다. 그러나 이러한 분산전원이 배전계통에 연계되면 전압 변동, 고조파, 보호협조, 고장전류 증가 등의 문제를 일으키므로 이에 대한 적절한 연구가 필요하다. 본 논문에서는 국내 22.9[㎸] 배전계통에 다수의 분산전원이 연계되었을 경우, 각 계전기가 감지하는 고장전류의 크기와 방향성을 고려하여 고장 감지 및 고장 지점을 확인하는 방법을 제안하였다. 이를 기반으로 하여 배전계통 보호기기인 자동재폐로 차단기-구분개폐기 보호시스템이 상호협조를 이루기 위한 온라인 보호 협조방안을 제시하였다.

Damage of a distribution transformer due to through-fault currents: an electrical forensics viewpoint

Insurance coverage for commercial premises includes direct loss and damage of the mechanical and electrical plant as well as consequential loss or damage. In recent years, many electrical failures have given rise to huge claims. It is, therefore, also in the interest of the electric power engineering community that the reliability of new systems being designed is acceptable and justified in the light of escalating claims for consequential loss or damage. For many existing power distribution systems in Singapore, it may require a reassessment of the need for additional features to improve the reliability. A case study is presented in this paper to illustrate this point. The case involved a failure investigation that was conducted on a distribution dry-type transformer.