Traditional Distribution Network Research Articles

Power flow calculation of AC / DC hybrid distribution network considering energy router

Energy router (ER) is the key equipment in the construction of AC / DC hybrid distribution network in the future. Based on the characteristics of AC and DC ports and topological structure of ER, a steady-state model of ER with multi ports access was established, and a power flow model of AC / DC hybrid distribution network considering ER was constructed. Newton Raphson method combined with alternating iteration method was used to solve the problem. IEEE-33 was selected to calculate and compare the circular distribution network considering ER and the traditional AC distribution network. The results show that ER can improve the voltage level of nodes and reduce network loss in hybrid distribution network.

Technology and application of operation control of DC distribution network

DC distribution network consists of distributed generation, energy storage, load and AC distribution network, With the rapid development of DC distribution network and the increasing proportion of DC load, the operation mode of DC distribution network is more flexible. Different from the traditional AC distribution network, the traditional AC distribution network has a single operation mode, while the DC distribution network can operate in both parallel mode and island mode. Therefore, a control method suitable for different operation modes of DC distribution network is urgently needed. In this paper, a control method about loop closing and loop opening of DC distribution network is proposed. When receiving the command of loop closing or loop opening from the master station or local monitoring system, the loop closing control is judged by the switch state, fault state and operation state of converter. It solves the problem that the traditional AC distribution network control strategy is not applicable in DC distribution network, it realizes the smooth switching of DC distribution network closed loop operation and opened loop operation. This method has been used in the DC coordinated control device and successfully applied in the national key research and development plan of Suzhou active distribution network.

Virtual power plant: state of the art providing energy flexibility to local distribution grids

Integrating decentralised energy sources into the traditional distribution networks can result in technical issues impacting the power quality. Innovative ideas are, therefore, needed to promote the transformation of systems to a smart grid. Distribution System operator (DSO) could make use of the flexibility of emerging technologies as a method to address these power quality issues. This study aims to present an overview of a local flexibility market (LFM) which will allow DSO requirements to be fulfilled through the (VPP) as an energy flexibility provider. The required optimization loads, generators and as well as storage units, are undertaken in the general algebraic modeling simulation (GAMS) environment. The aim of the optimization problem is to provide DSOs the opportunity to increase or curtail the local generations and loads in order to satisfy their requirement. The VPP will then be responsible for handling the relevant requests in real time to ensure the correct operating schedule of a resource is applied. The preliminary results of simulation studies presented in this paper have shown that the local market framework for flexibility could have potential for deferring investments in distribution network capacity, minimizing energy costs and improving the hosting capacity of distribution networks.

Advanced Grid Integration Test Platform for Increased Distributed Renewable Energy Penetration in Smart Grids

Renewable energy-based generators are constantly being deployed to future grids. It is expected that their share in overall generation will increase in the future. These novel devices have unknown characteristics and cause novel issues in power system operation. Traditional distribution networks have been operated as passive networks. These devices, such as smart inverters, change this paradigm completely. Due to these considerations, grid operators insist on enforcing strict grid-integration requirements. These rules are developed to ensure the impact of the connected devices is minimized and their behavior can be accounted for, at least to some extent. Testing different devices for different grid codes is a daunting task. Since such tests are undertaken in lab environment with manual control and data collection, they are prone to errors, time-consuming and inefficient. A solution is required to standardize and automate such tests. This will provide consistent testing ability and minimize testing times and errors due to human-intervention. This article presents the design and implementation of an integrated testing platform. Steps of lab equipment integration and associated challenges are presented along with their solutions. Several smart inverter behavior tests are executed, and results are presented. The test durations are compared with traditional test durations and the benefits are reported. It is discovered that use of such platform can increase the system testing efficiency by 85 % while minimizing human-errors, inconsistencies and man-hours required to run the tests.

Technology and application of high speed fault location,isolation and self-healing in DC distribution network

With the continuous increase of DC load, the research of DC distribution network has been developed rapidly. Compared with the traditional AC distribution network, DC distribution network has the advantages of less conversion times, high efficiency, low cost, simple control structure, no need to consider the frequency and phase and reactive power compensation equipment. Compared with AC distribution network, DC distribution network has more flexible operation mode and less power supply points However, the more flexible operation mode of DC distribution network also brings the problem of fault location and self-healing. The fault location, isolation and self-healing control strategy of AC distribution network can not be applied to DC distribution network. In this paper, a high-speed fault location, isolation and self-healing method for DC distribution network is proposed. Based on high-speed goose communication, a comprehensive evaluation is carried out according to the fault status of the power grid, and the millisecond level fault location, isolation and self-healing of DC distribution network are completed. The coordinated control equipment based on this method is successfully applied in Tongli integrated energy service center. When the fault occurs in this area, uninterrupted power supply is realized in the non fault area, which verifies the correctness and practicability of this method.

A Multi-port DC Solid-state Transformer for MVDC Integration Interface of Multiple Distributed Energy Sources and DC Loads in Distribution Network

In traditional DC distribution networks with both a low-voltage DC (LVDC) and a medium-voltage DC (MVDC) bus, DC units are connected to the LVDC bus through LVDC converters. In this approach no galvanic isolation is provided and two power conversion stages are needed between the DC units and the MVDC grid, hence leading to a high number of converters and higher costs. To address these shortcomings, this paper proposes a novel multi-port DC solid-state transformer (MDCSST) to interface DC units directly to the MVDC bus. Multiple modules are connected in series on the medium voltage side to the MVDC bus, whereas DC units are independently connected on the low-voltage side of the MDCSST. Compared to a traditional DC distribution network, the proposed scheme connects DC units to the MVDC bus without an extra converter or an LVDC bus, therefore saving cost and reducing the number of converters. In addition, DC units are galvanically isolated by high-frequency transformers. The main challenge of the MDCSST is to resolve the voltage-imbalance problem on the MVDC side which is caused by the DC units power differences. An LC-branch is used to balance the voltages among the modules and to transfer their differential powers.

Research on Key Technologies of Intelligent Operation Control of Super-large Urban Power Grid Based on Multi-center Structure

Under the background of higher and higher requirements of intelligent, reliable, green and efficient operation of power grid, the traditional operation control technology of urban power grid can no longer fully meet the new requirements of integrated operation and intelligent dispatching. The increasing environmental pollution and the gradual shortage of natural resources promote the rapid development of intelligent technology for distribution network dispatching. Traditional urban distribution network management ideas, especially the concept and mode of distribution network dispatching, can no longer adapt to the new situation, and need to be repositioned and studied deeply. In the construction of intelligent distribution network, intelligent control system is a very important part, which has a very positive significance for the overall operation of the power grid. This paper takes the construction of intelligent distribution network dispatching system as the long-term vision, extends the development and application trend of intelligent distribution network dispatching technology, and puts forward ideas on how to construct the concept and key technology of intelligent distribution network dispatching suitable for China's super large cities based on the city multi center structure.

Research on Monitoring and Diagnosis Technology of Data Anomaly in Distribution Network

Aiming at the problems of a large amount of abnormal data in the distribution network and the poor adaptability of traditional distribution network data, the paper proposes an intelligent distribution network status and abnormal data monitoring method, which has undergone data pre-processing and data fusion, Data analysis and visualization, and state identification and processing, a total of 4 links, turning multiple electrical feature quantities into a single comprehensive feature quantity, monitoring the operation status of the distribution network, and according to the relationship between each node and the size of the local anomaly factor to achieve intelligence Judgment and location of distribution network fault areas. The thesis realizes the detection and location of faults according to the size of each node's LOF value and the node's association relationship. After RTDS semi-physical closed-loop test, the accuracy and reliability of fault determination and location are high, which has certain reference value.

The Overview of SDN Architecture and its Practical Application with Improving Methods

This paper presents a comprehensive analysis on Software Defined Network (SDN) based on these following main aspects: i) an overview of the SDN architecture, ii) the introduction of a practical SDN application, iii) characteristics and drawbacks of SDN, and iv) methods for improving the performance of SDN. By reviewing and researching the rise and development of SDN, it is proposed that SDN solves many issues of traditional distributed networks, including configuration and management difficulties due to network node diversity. However, it still has some limitations, such as decentralize tendency and code opacity caused by competition among vendors. The goal of SDN development is to put SDN in the details of real issues, to improve it from different aspects, and thus make it as a better network.

Research on Security Control Scheme of Power Distribution Internet of Things

With the rapid development of the Internet, the process of Power Distribution Internet of Things has been pushed continuously. At present, the number of IoT terminals has increased sharply, and the types are also diverse. Meanwhile, the requirements for the communication timeliness and transmission safety between distribution networks are increasing. The current traditional distribution network structure is unable to properly manage the new terminals. As an emerging technology for information security protection, trusted computing can guarantee a safe and reliable operating environment and management mechanism in the power distribution IoT. Through the optimization of the hierarchical structure of the distribution network and the use of binary trusted security control model, we can build the hierarchical control structure model of the power distribution IoT. It makes the security level of the system has been greatly improved.

Enhancing risk control ability of distribution network for improved renewable energy integration through flexible DC interconnection

The increased penetration of distributed renewable energy into modern distribution networks has resulted in a significant rise in the system operational risk. However, the risk control ability of traditional open-loop AC distribution networks is greatly limited due to the inherent restriction of the network structure, which hinders the integration of larger-scale renewable energy into the power grid. To address this issue, this paper developed an effective risk assessment model and risk averse method for fully utilizing flexible DC interconnections to enhance the risk control ability and to improve the penetration of renewable energy in distribution networks. Moreover, aiming at the complex coupling risk characteristics between the AC and DC system that are imposed by the DC interconnection and considering the inefficiency of traditional Monte Carlo sampling risk assessment methods, an effective point-estimation-based risk assessment method is proposed that conducts a limited number of sequential AC/DC power flow calculations with estimation points constructed from random input variables, thereby the operational risk of the system is effectively realized. On this basis, a risk-averse multi-objective optimization model is further established for minimizing both the operational risk and the expected network power loss, and an improved kriging-model-assisted multi-object gray wolf algorithm is proposed for quickly supporting the model solution. Finally, a fuzzy clustering method is presented for effectively identifying the optimal Pareto solution. A case study is conducted on an AC/DC hybrid system with three AC networks and one DC network. The results demonstrate that the proposed method can substantially improve the risk assessment efficiency compared with the traditional Monte Carlo method. In addition, the risk-averse optimization method can effectively reduce the system risk and improve the operational reliability as well as the penetration of renewable energy.

AN EX-ANTE ASSESSMENT OF CITY DISTRIBUTION ALTERNATIVES BASED ON MULTI ACTOR MULTI CRITERIA FRAMEWORK

Recently, urban areas face challenges that result from negative externalities of traditional distribution networks. Especially, city actors increasingly suffer from issues as inefficient load factors in operations, traffic volume on roads, and noise pollution. To overcome these problems, modern city distribution patterns integrated with the consolidation strategy have the potential to provide satisfying solutions. Align with city actors’ expectations, alternatives of consolidation-distribution schemes can offer improvements in both economic, social, and environmental issues. In particular, this study aims at an ex-ante evaluation of city distribution alternatives on the typology of consolidation-distribution schemes ensuring win-win solutions to each city actor. This paper adopts Multi Actor Multi-Criteria Analysis (MAMCA) as a novel approach to evaluating different city actors’ objectives and a set of city distribution alternatives comprehensively. The paper results highlight that micro consolidation centre facilities can be more suitable in response to city actors’ expectations among distribution alternatives to urban consolidation centre and mobile depot. Finally, future research in this topic can focus on evaluating distribution alternatives on a sector basis and marketing types such as B2B and B2C.

Optimal allocation of soft open points in active distribution network with high penetration of renewable energy generations

With the integration of more and more renewable energy generations (REGs), the structure of traditional distribution networks is hard to accommodate the volatile power injections of REGs. As a new power electronic device, soft open point (SOP) can be installed to control both active and reactive power flow among active distribution networks (ADNs). This paper presents a comprehensive optimization method for allocating SOPs within an ADN with high penetration of REGs. In order to find proper SOP candidate locations, a selection strategy based on two technical indices is proposed. To mitigate the risk of voltage violation caused by REG forecast errors and improve the adaptiveness of allocation results, a two-stage robust optimization model for SOP allocation is formulated to minimize the total cost of SOP investment and network operation. The proposed model is converted into a mixed-integer second-order cone programming (MISCOP) problem, which is then decoupled into a master problem of planning and a subproblem of operation and solved by column and constraint generation (CCG) algorithm. Simulation results show that the proposed method can effectively find the optimal SOP allocation schemes. Comparisons with different mathematical formulation and solution methods show the advantages of the proposed method.

MACHINE LEARNING AND IOT FOR SMART GRID

Abstract. The current electricity grid is no longer an efficient solution due to increasing user demand for electricity, old infrastructure and reliability issues requires a transformation to a better grid which is called Smart Grid (SG). Also, sensor networks and Internet of Things (IoT) have facilitated the evolution of traditional electric power distribution networks to new SG, these networks are a modern electricity grid infrastructure with increased efficiency and reliability with automated control, high power converters, modern communication infrastructure, sensing and measurement technologies and modern energy management techniques based on optimization of demand, energy and availability network. With all these elements, harnessing the science of Artificial Intelligence (AI) and Machine Learning (ML) methods become better used than before for prediction of energy consumption. In this work we present the SG with their architecture, the IoT with the component architecture and the Smart Meters (SM) which play a relevant role for the collection of information of electrical energy in real time, then we treat the most widely used ML methods for predicting electrical energy in buildings. Then we clarify the relationship and interaction between the different SG, IoT and ML elements through the design of a simple to understand model, composed of layers that are grouped into entities interacting with links. In this article we calculate a case of prediction of the electrical energy consumption of a real Dataset with the two methods Recurrent Neural Network (RNN) and Long Short-Term Memory (LSTM), given their precision performances.

Acceptable DG Capacity for Radial Distribution System Based on Traditional Protection Scheme (Dept.E)

Traditional electric distribution systems are radial in nature. These networks are protected by very simple protection devices such as over-current relays, fuses, and reclosers. Recent trends in distributed generation (DG) and its useful advantages perfectly can be achieved while the relevant concerns are deliberately taken into account. For example, penetration of DG disturbs the radial nature of traditional distribution networks. Therefore, protection coordination will be changed in some cases, and in some other cases it will be lost which is very costly in that two cases. In developed countries it could be cost effective if adding DGs network keeping the traditional protection system unchanged. To tackle that point of research, authors proposed technique to maintain the old protective devices coordination unchanged up to a specific DG penetration level. In this paper, a framework is presented for determining the maximum capacity of DG penetration level to keep traditional protection scheme for distribution network unchanged. Applying that framework in the developing countries could save money and time during the integration of DGs to the network on a large scale based on country regulation. The proposed framework is implemented on a simple distribution network using MATLAB SIMULINK and finally the numerical results are presented in order to validate the suggested framework.

The Paradigm Revolution in the Distribution Grid: The Cutting-Edge and Enabling Technologies

AbstractBi-directional information and energy flow, renewable energy sources, battery energy storage, electric vehicle, self-healing capability, and demand response programs, etc., revolutionized the traditional distribution network into the smart distribution network. Adoption of modern technologies like intelligent meters such as advanced metering infrastructure & Micro-phasor measurement units, data storage, and analysis techniques and incentive-based electricity trading mechanisms can bring this paradigm shift. This study presents an overview of popular technologies that facilitate this transformation, giving focus on some prime technologies such as real-time monitoring based on Micro-phasor measurement units, data storage and analytics, blockchain technology, multi-agent systems, and incentive-based energy trading mechanisms

The effect of subscription-based direct-to-consumer channel additions on firm value

Technological advancements have made it easier for firms to bypass traditional distribution networks and establish subscription-based direct-to-consumer (SBDTC) channels. Despite their growing popularity, little is known about the effectiveness of these channels. However, pursuing these new channels may not be the best decision for firms even though technology allows it and, in some instances, consumers demand it. Results from an event study of SBDTC channel additions in the cable television industry show that they complicate channel relationships and can lead to conflict, which reduce firm value. Further analysis reveals that firm-specific characteristics and strategic execution factors operate to mitigate the loss in firm value. Specifically, the study results show that channel power diminishes the negative impact of channel conflict, suggesting that firms with greater channel power benefit from adding SBDTC channels. The study also finds that firms marketing high-quality, differentiated offerings are rewarded with more favorable firm valuations.

A Research on the Priority of Power Distribution Based on Graph Computing

With the construction and gradual development of microgrids, multiple interest themes have emerged in traditional distribution networks, such as distributed power sources, flexible loads, etc. Microgrids can be integrated into large power grids or operated as independent power grids. Effectively improve the power grid’s ability to resist disasters and ensure the safety of power supply within the grid. It can also effectively achieve high-quality matching of power supply and consumption and optimize the distribution of power resources within the network. The ability to fully and effectively solve the problems of grid connection of distributed energy sources such as wind and solar is of great significance to the reasonable planning of the power system and the safe operation of the power system. This paper proposes a planning evaluation system that takes into account the microgrid connection, constructs a graph calculation-based distribution priority division and a node model under the microgrid central control system, and uses the Mean-shift clustering algorithm to obtain node attributes. Use the optimal sequence graph method to calculate the index weight of the distribution network planning scheme, and finally calculate the distribution plan between nodes through the graph path finding algorithm.

Research on Construction and Application of Power Distribution Internet of Things

As an important part of power grid aggregation and distribution, the distribution network is becoming more and more important and intelligent with the development of the Internet of Things technology. As a high-priority system for power supply services, the distribution network faces customers directly, so it also faces greater challenges. On this basis, based on the traditional distribution network, this paper studies and comparatively analyzes the advantages of the new distribution Internet of Things model, proposes a four-tier architecture system for the construction of distribution Internet of Things. Furthermore, the application and development process of the Internet of Things technology in the distribution network is explained from the three key technologies of comprehensive perception technology, diverse communications, and edge computing. Finally, from the perspective of operation and maintenance management and fault diagnosis and early warning, the application prospects of the Internet of things for power distribution are discussed.

Reliability evaluation of active distribution network considering various active adjustment means

With the large-scale configuration of distribution automation and the widespread implementation of distributed generation (DG) and flexible load (FL), the distribution network can achieve active regulation, which makes the traditional fault restoration strategy and distribution network reliability evaluation more complicated. Given this background, a method of reliability evaluation for the active distribution network considering ‘supply-grid-load’ is proposed. On the supply side, a distribution network islanding model considering DG is established, with the objective of supplying power to the maximised amount of equivalent power load. On the grid side, the influence of distribution network automation on the distribution network reliability is elaborately analysed and the time-varying failure rate model of equipment which considers the life cycle characteristics is presented. On the load side, an incentive-based FL model is proposed based on the elastic coefficient matrix. Finally, simulation results of RBTS-BUS6 system demonstrate the effectiveness of the proposed model and method.