Smart Distribution System Research Articles

Island Configuration for Service Restoration of the Smart Distribution System

sland operation is a special operation mode for service restoration for the smart distribution system with distributed generation. In this paper, a model of island reconfiguration of the smart distribution system is proposed. The objection of this model is maximizing the total power supply profit. Meanwhile, load priority, controllable and uncontrollable load, and the restrictions of power balance, voltage and equipment capability are all taken into account. The island configuration problem is first simplified as a special knapsack problem, and based on the solution of this knapsack problem an initial island scheme is gained. By feasibility checking and adjusting, a island configuration is finally proposed. The results of the samples demonstrate that the model and method presented in this paper is feasible and valid.

Integration of renewable energy sources, energy storage systems, and electrical vehicles with smart power distribution networks

In order to increase efficiency in the distribution of electrical energy, optimize energy consumption and increase the percentage of energy from renewable sources, thereby reducing emissions of greenhouse gases, the distribution networks and the equipment connected to them should be made more intelligent. The development of the future energy system will be based on planning and management of the distribution system in accordance with the philosophy of Smart grid (SG). This approach involves the extensive use of Information and Communication Technology (ICT) and innovative control systems in order to enable the realization of smart distribution systems, the active participation of demand, the availability of energy storage, as well as the integration of renewable energy sources (RES) and Distributed Generation (DG), as well as the growing number of electric vehicles. In the paper a review of the main current challenges and possible solutions to open problems in the development of smart distribution grids are presented.

A Linear State Estimation Formulation for Smart Distribution Systems

This paper presents a linearized, three-phase, distribution class state estimation algorithm for applications in smart distribution systems. Unbalanced three-phase cases and single-phase cases are accommodated. The estimator follows a complex variable formulation and is intended to incorporate synchronized phasor measurements into distribution state estimation. Potential applications in smart distribution system control and management are discussed.

Distribution System Modeling and Analysis [Book Reviews

This new edition is very timely given the international attention on smart grids, including increased demand for better modeling and analysis methods to support planning and operations of smart distribution systems. The book is an authoritative textbook on the subject of distribution system modeling and analysis. It develops models for each component in a distribution feeder using generalized matrices and develops the modified ladder technique to perform load flow analysis and a method in the phase domain to perform short circuit analysis.

Design of Smart Distribution Management System for Obtaining Real-Time Security Analysis and Predictive Operation in Korea

The Development of smart grids offers new opportunities to improve the efficiency of operating and controlling distribution systems. It allows network operators to optimize the use of dispersed generation resources and enables real-time communication between customers and utility service providers to allow optimization and balancing of energy usage. Such an improvement in the flexibility and control of the distribution network is only possible if the control center operator has more accurate knowledge of the real-time situation of the network. The Korean Smart Distribution Management System (KSDMS) project was started in 2009 to achieve advanced distribution operation for potential smart grid systems in Korea. In this paper, we summarize two KSDMS design strategies for situational awareness in real-time distribution operation. One is the preparation of standardized data acquisition networks. In the KSDMS, numerous data related to the voltage, current, faults, power quality and load profiles of the network are gathered using a standardized communication method based on IEC 61850. The other is a real-time security analysis tools for smart distribution systems, designed to provide the distribution operator with accurate real-time situational information and predictive operation. We present a database design which can be used commonly for all security analysis programs in KSDMS.

Discussion on “Imposing Radiality Constraints in Distribution System Optimization Problems”

We commend the authors of for bringing up a relevant issue: the mathematical formulation of radiality constraints in optimization problems at medium voltage levels. Certainly, smart power distribution systems demand of analytical optimization tools able to deal with radiality constraints in an efficient and compact way.

Closure to Discussion on “Imposing Radiality Constraints in Distribution System Optimization Problems”

We commend the authors of for bringing up a relevant issue: the mathematical formulation of radiality constraints in optimization problems at medium voltage levels. Certainly, smart power distribution systems demand of analytical optimization tools able to deal with radiality constraints in an efficient and compact way.

Analysis of Smart Grid with 132⁄33 KV Sub-Transmission Line In Rural Power System of Bangladesh

“Smart Grid” is a modern concept which refers to the conversion of the mainstream or typical electric power grid to a modern power grid. This new conversion is a foreseeable solution to the power system problems of the modern century. Rejuvenation of the current electric power distribution system is an important step to implement the Smart Grid technology. So, distribution system engineers should be acquainted with the knowledge of Smart Distribution System. Also the customers should acknowledge the benefits that they will be enjoying from this modernized power system. There are power crisis everywhere in the world, besides there is system loss in the existing power system. It is happening in Bangladesh also. To reduce power crisis renewable source of energy like solar energy, wind energy, raw coal energy may be used. But the quantity of electricity produced by this renewable energy source is low and several kilowatts range. This electricity is utilized by smart grid which is hard for usual power grid system. For this reason we need hybrid ac/dc smart control grid system. In this report models using Wind-mil Software is proposed for reducing system loss and also incorporate smart metering so that the power flow can reach easily to the consumers. Smart grid also helps sole proprietor and individual business man to sell their little amount of electricity to the grid which they produce by their own entrepreneurship through smart meter. Line loss and regulated voltage, regulator and capacitor are also inserted here to reduce the loss and make the effective and efficient power supply to the consumer. This metering is also centrally controlled and works over a huge area. At present developing country should develop this system.

Risk Identification based on Hidden Semi-Markov Model in Smart Distribution Network

The smart distribution system is the critical part of the smart grid, which also plays an important role in the safe and reliable operation of the power grid. The self-healing function of smart distribution network will effectively improve the security, reliability and efficiency, reduce the system losses, and promote the development of sustainable energy of the power grid. The risk identification process is the most fundamental and crucial part of risk analysis in the smart distribution network. The risk control strategies will carry out on fully recognizing and understanding of the risk events and the causes. On condition that the risk incidents and their reason are identified, the corresponding qualitative / quantitative risk assessment will be performed based on the influences and ultimately to develop effective control measures. This paper presents the concept and methodology on the risk identification by means of Hidden Semi-Markov Model (HSMM) based on the research of the relationship between the operating characteristics/indexes and the risk state, which provides the theoretical and practical support for the risk assessment and risk control technology.

Protection Scheme for DC Microgrid Distribution System

The low voltage DC (LVDC) distribution system is a new concept and a promising technology to be used in the future smart distribution system having high level cost-efficiency and reliability. In this paper, a low-voltage (LV) DC microgrid protection system design is proposed. Usually, an LVDC microgrid must be connected to an ac grid through converters with bidirectional power flow and, therefore, a different protection scheme is needed. This paper describes practical protection solutions for the LVDC network and an LVDC system laboratory prototype is being experimentally tested by MATLAB/SIMULINK. The results show that it is possible to use available devices to protect such a system. But other problems may arise which needs further study.

Integrating renewable energy using a smart distribution system: Potential of self-regulating demand response

A self-regulating distribution system simulation platform is presented for a smart-grid with Distributed Energy Resource (DER) wind power injection in which load flow fluctuations are controlled via self-regulating air-source heat pump (HP) cycling. The grid power injection fluctuations are mitigated by bus-level HP control, while ensuring compliance to both consumer comfort constraints and distribution grid load flow requirements.The effects of applying a number of different bus-level HP control algorithms are evaluated. The results show that using building thermal mass in conjunction with simple control strategies can effectively accommodate large fluctuations associated with high penetration of wind energy. The number of HPs in each distribution phase significantly affects the load flow characteristics and the ability of the bus-level control to smooth the distribution grid regulator power.The bus-level control improves power and voltage ramping rates, reduces wind power injection fluctuations, and also reduces the energy reserve requirements.

A Cooperative Multiagent Framework for Self-Healing Mechanisms in Distribution Systems

Because of society's full dependence on electricity and high cost of system outages, one important goal is to increase the reliability of the power system, which means that a salient attractive feature of smart grid is its self-healing ability. Smart grids will develop and enhance the automation of distribution by operating in a distributed manner through new digital technologies such as monitoring, automatic control, two-way communication, and data management. In this work, the smart grid concept and technologies have been applied to construct a self-healing framework for use in smart distribution systems. The proposed multiagent system is designed to locate and isolate faults, then decide and implement the switching operations to restore the out-of-service loads. The proposed control structure has two layers: zone and feeder. The function of zone agents in the first layer is monitoring, making simple calculations, and implementing control actions. Feeder agents in the second layer are assigned to negotiation. The constraints include voltage limits, line current limits, and radial topology. Load variation has been taken into consideration to avoid the need for further reconfigurations during the restoration period. The results of the simulation conducted using the new framework demonstrate the effectiveness of the proposed control structure.

Supply-Adequacy-Based Optimal Construction of Microgrids in Smart Distribution Systems

Recently, the concept of microgrids (clusters of distributed generation, energy storage units, and reactive power sources serving a cluster of distributed loads in grid-connected and isolated grid modes) has gained a lot of interest under the smart grid vision. However, there is a strong need to develop systematic procedure for optimal construction of microgrids. This paper presents systematic and optimized approaches for clustering of the distribution system into a set of virtual microgrids with optimized self-adequacy. The probabilistic characteristics of distributed generation (DG) units are also considered by defining two new probabilistic indices representing real and reactive power of the lines. Next, the advantages of installing both distributed energy storage resources (DESRs) and distributed reactive sources (DRSs) are investigated to improve the self-adequacy of the constructed micro-grids. The new strategy facilitates robust infrastructure for smart distribution systems operational control functions, such as self-healing, by using virtual microgrids as building blocks in future distribution systems. The problem formulation and solution algorithms are presented in this paper. The well-known PG&E 69-bus distribution system is selected as a test case and through several sensitivity studies, the effect of the total DESRs or DRSs capacities on the design and the robustness of the algorithm are investigated.

The Evolution for Voltage and Reactive Power Control in Smart Distribution Systems

This paper has been arisen to show the necessity of the evolution for voltage and reactive power control in distribution systems from conventional to active control techniques. The paper addresses the drawbacks and conflicts that the conventional voltage and reactive power control schemes will face in future distribution systems, especially with high penetration of Distributed Generation (DG). Some of these drawbacks have been verified by carrying out various simulation studies for different IEEE unbalanced radial distribution test systems. The results show that applying the conventional utility voltage regulation control practices in smart grid configuration is intolerable. Therefore, the issue of voltage and reactive power control in smart distribution systems is significant and an evolution of the current control schemes from passive to active is necessary. Using the smart grid technologies, a distributed single layer cooperative control scheme between substation regulators, line regulators and DG units has been proposed. The proposed cooperative scheme is based on the concept of multi-agent systems. Simulation results have been carried out to show the effectiveness of the proposed control scheme.

Interactive Distributed Generation Interface for Flexible Micro-Grid Operation in Smart Distribution Systems

This paper presents an interactive distributed generation (DG) interface for flexible micro-grid operation in the smart distribution system environment. Under the smart grid environment, DG units should be included in the system operational control framework, where they can be used to enhance system reliability by providing backup generation in isolated mode, and to provide ancillary services (e.g. voltage support and reactive power control) in the grid-connected mode. To meet these requirements, the proposed flexible interface utilizes a fixed power-voltage-current cascaded control structure to minimize control function switching and is equipped with robust internal model control structure to maximize the disturbance rejection performance within the DG interface. The proposed control system facilitates flexible and robust DG operational characteristics such as 1) active/reactive power (PQ) or active power/voltage (PV) bus operation in the grid-connected mode, 2) regulated power control in autonomous micro-grid mode, 3) smooth transition between autonomous mode and PV or PQ grid connected modes and vice versa, 4) reduced voltage distortion under heavily nonlinear loading conditions, and 5) robust control performance under islanding detection delays. Evaluation results are presented to demonstrate the flexibility and effectiveness of the proposed controller.

A Parallel Approach for Real-Time Power Flow in Distribution Networks

The new reality of smart distribution systems with use of generation sources of small and medium sizes brings new challenges for the operation of these systems. The complexity and the large number of nodes requires use of methods which can reduce the processing time of algorithms such as power flow, allowing its use in real time. This paper presents a known methodology for calculating the power flow in three phases using backward/forward sweep method, and also considering others network elements such as voltage regulators, shunt capacitors and sources of dispersed generation PV and PQ. After that, new elements are introduced that allow the parallelization of this algorithm and an adequate distribution of work between the available processors. The algorithm was implemented using a multi-tiered architecture which allows its use even in environments with low processing power, such as smartphones and tablets, and the processing times were measured in many network configurations and compared with the same algorithm in the serial version.

A Self-healing Scheme of Single-phase-to-ground Fault in Smart Power Distribution System

The paper presents a self-healing scheme of single-phase-to-ground fault in smart power distribution system. The scheme consists of three parts: single-phase-to-ground fault detection, faulted feeder selection and faulted feeder isolation. Fault detection is based on power-frequency voltage measured by a voltage transducer. A single-phase-to-ground fault is detected when measured voltage is greater than threshold. A fault generated current traveling waves are used to identify faulted feeder. The feeder with different initial traveling wave's polarity to other feeders is selected as faulted feeder. When faulted feeder is identified, the interconnection switch between different bus-bar is switched on firstly, then the switch at the load side of faulted feeder is switched off to isolate the load from the fault, the switch at the power source side of faulted feeder is switched off to isolate the source from the fault lastly. Simulation studies show that the scheme can meet the requirements of isolating single-phase-to-ground fault without affecting power supply to the load.

Distribution system security region: definition, model and security assessment

The region-based method has been successfully applied in transmission systems. This study proposes the definition, model and applications of security region for distribution systems. With the ongoing smart grid initiatives, a large amount of real-time network information will be available. This is the motivation of an accurate calculation of the security boundary. First, this study presents the concepts of distribution system security region (DSSR); and discusses N -1 contingency scenarios for both substation transformers and feeders. Second, distribution system security boundary is modelled in the Euclidean space as several intersected hyperplanes. Furthermore, DSSR for substation transformer contingency is modelled as the space surrounded by the security boundaries and the set of all operating points that ensure the distribution system N -1 security. Third, distance from an operating point to a security boundary is formulated and a new index is also presented for security evaluation. The proposed DSSR-based security assessment method provides a new approach for future smart distribution system operation. Finally, the results from a real distribution system have demonstrated the effectiveness of the proposed concepts and methods; and the geometric characteristics of DSSR are also illustrated by means of two-dimensional visualisation of the test system.

Coordination between mid-term maintenance outage decisions and short-term security-constrained scheduling in smart distribution systems

Distribution systems are the first volunteers experiencing the benefits of smart grids. The smart grid concept impacts the internal legislation and standards in grid-connected and isolated distribution systems. Demand side management, the main feature of smart grids, acquires clear meaning in low voltage distribution systems. In these networks, various coordination procedures are required between domestic, commercial and industrial consumers, producers and the system operator. Obviously, the technical basis for bidirectional communication is the prerequisite of developing such a coordination procedure. The main coordination is required when the operator tries to dispatch the producers according to their own preferences without neglecting its inherent responsibility. Maintenance decisions are first determined by generating companies, and then the operator has to check and probably modify them for final approval. In this paper the generation scheduling from the viewpoint of a distribution system operator (DSO) is formulated. The traditional task of the DSO is securing network reliability and quality. The effectiveness of the proposed method is assessed by applying it to a 6-bus and 9-bus distribution system.

The internet of things [Guest Editorial

The Internet has experienced a tremendous growth in the past three decades, evolving from a network of a few hundred hosts to a platform linking billions of "things" globally, including individual people as well as enterprises of various sizes, through computers and computerized devices of any conceivable size and capability and the applications running on them. The growth of the Internet shows no signs of slowing down and it steadily becomes the cause of a new pervasive paradigm in computing and communications. This new paradigm enhances the traditional Internet into a smart Internet of Things (IoT) created around intelligent interconnections of diverse objects in the physical world, such as vehicles, cell phones, habitats, and habitat occupants. It utilizes low-cost information gathering and dissemination devices, such as sensors and RFID tags, that facilitate fast-paced interactions among the objects themselves as well as the objects and persons in any place and at any time. IoT will usher in a wide range of smart applications and services to cope with many of the challenges individuals and organizations face in their everyday lives. For example, remote healthcare monitoring systems could aid in managing costs and alleviating the shortage of healthcare personnel; intelligent transportation systems could aid in reducing traffic congestion and inevitably the ills caused by it such as air pollution; smart distribution systems from utility grids to supply chains could aid in improving the quality and reducing the cost of their respective goods and services; tagged objects could result in more systematic recycling and effective waste disposal, and so on.