Future Power Distribution Systems Research Articles

Reliability Assessment of Power Distribution Cyber–Physical Systems Considering the Impact of Wireless Access Networks

With the rapid increase in the number of various terminal devices in distribution systems, the important impact of communication networks on power supply reliability in cyber–physical distribution systems (CPDSs) is becoming increasingly prominent. The traditional wired communication method makes it difficult to meet the demand in some scenarios due to high cost and construction difficulty. For this reason, this study evaluated the reliability of power distribution cyber–physical systems, considering fifth-generation (5G) mobile communication technology wireless access conditions. First, a reliability model of a communication channel in a 5G communication network was established, and the indirect impact of information system failure on the power distribution system was analyzed. Secondly, a reliability assessment method based on the improved least path method was devised by combining switch action failure, self-healing processing, and load transfer. The simulation results show that 5G communication technology has significant advantages in improving system reliability, and the proposed method is closer to the development direction of future power distribution systems, which provides an effective reference basis for the optimized operation of power distribution cyber–physical systems.

Investigation of active voltage support control approach of DC distribution networks based on virtual inertia coordination

AbstractDC distribution networks (DCDNs) possess the advantages of high power efficiency, low operation loss, and favourable control flexibility, and are regarded as an essential form of future power distribution systems. In order to increase the voltage transient performance of DCDNs against disturbances, this paper proposes a methodology for realising the active voltage support control of DCDNs based on virtual inertia coordination. Firstly, the impact of the inertia of DCDNs towards the transient voltage change is analysed, and the active voltage support mechanism considering the variable droop inertia control and virtual DC motor inertia (VDCMI) control is explored. Then, a time sequence coordination strategy based on the voltage grading of DCDNs is developed, and an adaptive inertia coefficient is designed to achieve the inertia adjustment in terms of the voltage sag and recovery processes. Using MATLAB/Simulink, a detailed model of the double‐terminal DCDNs is created to check the efficacy of the proposed approach. Different voltage disturbance scenarios are imitated, and the comparative simulations demonstrate that the proposed approach can fully utilise the inertia potential of the DCDNs to suppress the voltage sag and smooth the voltage recovery procedure. The proposed method's validity and feasibility can be well validated.The cover image is based on the Original Article Investigation of active voltage support control approach of DC distribution networks based on virtual inertia coordination by Lei Chen et al., https://doi.org/10.1049/esi2.12123.

Robust Stability Control for Electric Vehicles Connected to DC Distribution Systems

DC power distribution systems will play an important role in the future urban power distribution system, while the charging and discharging requirements of electric vehicles have a great impact on the voltage stability of the DC power distribution systems. A robust control method based on H∞ loop shaping method is proposed to suppress the effect of uncertain integration on voltage stability of DC distribution system. The results of frequency domain analysis and time domain simulation show that the proposed robust controller can effectively suppress the DC bus voltage oscillation caused by the uncertain integration of electric vehicle, and the robustness is strong.

Investigation on GaN HEMTs Based Three-Phase STATCOM with Hybrid Control Scheme.

The modern trend of decarbonization has encouraged intensive research on renewable energy (RE)-based distributed power generation (DG) and smart grid, where advanced electronic power interfaces are necessary for connecting the generator with power grids and various electrical systems. On the other hand, modern technologies such as Industry 4.0 and electrical vehicles (EV) have higher requirements for power converters than that of conventional applications. Consequently, the enhancement of power interfaces will play an important role in the future power generation and distribution systems as well as various industrial applications. It has been discovered that wide-bandgap (WBG) switching devices such as gallium nitride (GaN) high electron mobility transistors (HEMTs) and silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) offer considerable potential for outperforming conventional silicon (Si) switching devices in terms of breakdown voltage, high temperature capability, switching speed, and conduction losses. This paper investigates the performance of a 2kVA three-phase static synchronous compensator (STATCOM) based on a GaN HEMTs-based voltage-source inverter (VSI) and a neural network-based hybrid control scheme. The proportional-integral (PI) controllers along with a radial basis function neural network (RBFNN) controller for fast reactive power control are designed in synchronous reference frame (SRF). Both simulation and hardware implementation are conducted. Results confirm that the proposed RBFNN assisted hybrid control scheme yields excellent dynamic performance in terms of various reactive power tracking control of the GaN HEMTs-based three-phase STATCOM system.

Fuzzy logic-based management of hybrid distribution transformer using LoRa technology

Hybrid distribution transformers (HDT) has a better performance than traditional distribution transformers on improving power quality, such as reducing harmonics, unbalance, voltage fluctuations and low power factor in the future smart power distribution system. In order to increase the service life and reliability of hybrid distribution transformers, this paper proposed a remote management system using LoRa technology based on fuzzy logic. HDT based on fuzzy logic judgment system (FLJS) replaces the Boolean logic with fuzzy logic and several power quality problems including power factor, load-side current harmonics and voltage unbalance are considered, as well as grid-side voltage deviation and unbalance. The management system can dynamically adjust the working states of HDT according to the output results of the FLJS to reduce the use time of power electronic devices. Due to the application of LoRa, the management system can remotely adjust the parameters of the FLJS in real time for different distribution network nodes to avoid frequent switching of HDT working states. Meanwhile, it is able to remotely monitor the real-time working states and fault states of HDT to reduce recovery time and maintenance costs in case of HDT failure. Finally, simulation and experimental results are provided to verify the effectiveness of the proposed management system for HDT.

Power Scalable Bi-Directional DC-DC Conversion Solutions for Future Aircraft Applications

With the introduction of the more electric aircraft, there is growing emphasis on improving overall efficiency and thus gravimetric and volumetric power density, as well as smart functionalities and safety of an aircraft. In future on-board power distribution networks, so-called high voltage DC (HVDC, typically +/−270VDC) supplies will be introduced to facilitate distribution and reduce the associated mass and volume, including harness. Future aircraft power distribution systems will also very likely include energy storage devices (probably, batteries) for emergency back up and engine starting. Correspondingly, novel DC-DC conversion solutions are required, which can interface the traditional low voltage (28 V) DC bus with the new 270 V one. Such solutions presently need to cater for a significant degree of flexibility in their power ratings, power transfer capability and number of inputs/outputs. Specifically, multi-port power-scalable bi-directional converters are required. This paper presents the design and testing of such a solution, addressing the use of leading edge wide-band-gap (WBG) solid state technology, especially silicon carbide (SiC), for use as high-frequency switches within the bi-directional converter on the high-voltage side.

Advanced FLISR With Intentional Islanding Operations in an ADMS Environment Using GridAPPS-D

An advanced distribution management system (ADMS) is a software platform that supports grid management and decision support applications to address the growing operational challenges faced by power distribution systems to ensure reliable, resilient, and economic operations. In this paper, a fault location, isolation, and restoration (FLISR) application is developed and integrated with an open-source standards-based platform for ADMS application development viz. GridAPPS-D, developed by Pacific Northwest National Laboratory (PNNL). Also, a new distribution system restoration (DSR) algorithm, an integral part of the FLISR application, is proposed that utilizes backup feeders and distributed generators (along with intentional islanding features) to restore critical loads. The proposed application is developed in python and is tested on a modified IEEE 8500-node test system using the GridAPPS-D platform. The successful deployment of the FLISR application on the GridAPPS-D platform provides a proof-of-concept for the adoption of new and advanced ADMS applications to support future power distribution systems.

Finite-Element Analysis Modeling of High-Frequency Single-Phase Transformers Enabled by Metal Amorphous Nanocomposites and Calculation of Leakage Inductance for Different Winding Topologies

The solid-state transformer (SST) is an emerging technology which is gaining increasing importance for future power distribution systems. Here, we present 2-D finite-element analysis (FEA) of single-phase SSTs for operating frequencies of 50 kHz. We consider designs to benchmark materials aimed at controlling high-frequency losses to achieve higher power densities. The FEA model is solved in the time domain for frequencies of 50 kHz, at a fixed 800 V input voltage and 10 kW output power for the first four cycles. This paper analyzes the influence of leakage inductance on the waveform with an increasing number of turns and discusses how to calculate the leakage inductance of the different winding topologies by FEA. In addition, transformer topologies are coupled to a power analysis using a Steinmetz parameterization of magnetic losses capturing induction and field scaling for transformer losses for FeNi-based metal amorphous nanocomposites (MANCs) for SST applications and their benchmarking with amorphous and other MANCs and ferrites. Recently, discovered FeNi-based MANCs allow smaller transformers at equivalent power as compared to Si steels, Metglas, and Co-based MANCs. These Fe-rich and non-Co containing MANCs also offer economies based on lower raw materials costs as compared with Co-based MANCs and significantly improved mechanical properties with respect to commercially available Fe-based MANCs.

Coordinated Voltage Regulation by On-Load Tap Changer Operation and Demand Response Based on Voltage Ranking Search Algorithm

The growing penetration of photovoltaic (PV) systems may cause an over-voltage problem in power distribution systems. Meanwhile, charging of massive electric vehicles may cause an under-voltage problem. The over- and under-voltage problems make the voltage regulation become more challenging in future power distribution systems. Due to the development of smart grid and demand response, flexible resources such as PV inverters and controllable loads can be utilized for voltage regulation in distribution systems. However, the voltage regulation needs to calculate the nonlinear power flow; as a result, utilizing flexible resources for voltage regulation is a nonlinear scheduling problem requiring heavy computational resources. This study proposes an intelligent search algorithm called voltage ranking search algorithm (VRSA) to solve the optimization of flexible resource scheduling for voltage regulation. The VRSA is built based on the features of radial power distribution systems. A numerical simulation test is carried out on typical power distribution systems. The VRSA is compared with the genetic algorithm and voltage sensitivity method. The results show that the VRSA has the best optimization effect among the three algorithms. By utilizing flexible resources through demand response, the tap operation times of on-load tap changers can be reduced.

Decentralised resilient autonomous control architecture for dynamic microgrids

Microgrids serve as an integral part of future power distribution systems. Typically, microgrids are managed by centralised controllers. There are two major concerns about using a single centralised controller. The controller can become a performance and reliability bottleneck for the entire system, where its failure can bring the entire system down. Excessive communication delays can also degrade the system performance. As a solution, a true decentralised control architecture for microgrids is proposed, designed, developed, and tested here. Distributing the controls to local agents decreases the possibility of network congestion to occur. Decentralisation will also enhance the reliability of the system since the single point of failure is replaced by a distributed architecture. The proof-of-concept of true decentralisation of microgrid control architecture is implemented using Hardware-in-the-Loop Platform. Device level and system level controller and interaction models are defined for a self-coordination. Also, microgrid energy management system (EMS) and control case scenarios are demonstrated. The experimental results show the robustness of the proposed architecture.

An Aggregated Model for Energy Management Considering Crowdsourcing Behaviors of Distributed Energy Resources

Increasing deployment of distributed energy resources (DERs) is re-sculpturing the modern power systems in recent years. Future smart power distribution systems should be competent at accommodating extensive integration of DERs and managing the associated uncertainties at the distribution level. The electricity market has been proved to be an efficient way to employ market signals to direct behaviors of users and DERs with large capacity and homogeneous pattern. However, existing market frameworks cannot effectively handle a large number of small-scale DERs due to their diverse characteristics and arbitrary behavior patterns. In this context, an aggregated model which can represent and manage a diverse collection of DER, load, and storage is proposed. An additional trading platform, namely the energy sharing market, is established to reinforce the coordination and collaboration among various aggregators as well as operators. Energy sharing scheme is applied and a corresponding dynamic dispatch platform is designed to solve the crowdsource problem. The efficiency of the proposed model is validated by the numerical studies, and the market performance and impacts of energy sharing on the power systems are illustrated.

Dynamic Modeling and Feasibility Analysis of a Solid-State Transformer-Based Power Distribution System

This paper presents a comprehensive state-space dynamic model of a future power distribution system for plug-and-play interface of distributed renewable energy resources and distributed energy storage devices. The system, called the future renewable electric energy delivery and management (FREEDM) system, comprises of multiple solid-state transformers (SSTs), and load, generation, and storage connected to each SST in a distributed network. The system allows for high penetration of renewable generation with energy storage at the distribution level. A physics-based 70th-order state-space average model is first developed considering the physical and controller properties of a single-SST FREEDM system along with its distribution components. This fundamental model is then extended to build a multi-SST FREEDM system for feasibility and dynamics behavior analysis of the entire system, which is essential to ensure system power balance. The full average model with multiple SSTs has been incorporated in an IEEE 34 bus distribution testbed for a scaled analysis of the system.

Guest Editorial Distributed Control and Efficient Optimization Methods for Smart Grid

Smart grid proactively uses the state-of-the-art technologies in communications, computing, and control to improve efficiency, reliability, sustainability, and stability of the electrical grid. In particular, distribution networks are expected to undergo dramatic changes by incorporating a large number of sensors and thousands of controllable devices such as distributed generators, batteries and flexible loads. To be able to efficiently operate such complex large-scale systems, new sets of control and optimization tools should be developed. On a slow time scale, optimization theory plays a major role in solving various large-scale decision-making problems for future power transmission and distribution systems. One major challenge is the design of computational methods for handling fairly detailed power system models that often include continuous and discrete nonlinearities. It is also important to develop distributed computation techniques to shift the computation from a centralized platform to many computing devices.

Monitoring of Overhead Transmission Lines: A Review from the Perspective of Contactless Technologies

This paper describes a comprehensive review of non-contact technologies for overhead power transmission lines. Due to ever increasing emphasis on reducing accidents and speeding up diagnosis for automatically controlled grids, real time remote sensing and actuation is the new horizon for smart grid implementation. The technology overview with emphasis on the practical implementation of advanced non-contact technologies is discussed in this paper while considering optimization of the high voltage transmission lines parameters. In case of fault, the voltage and the current exceed limits of operation and hence real time reporting for control and diagnosis is a critical requirement. This paper aims to form a strong foundation for control and diagnosis of future power distribution systems so that a practitioner or researcher can make choices for a workable solution in smart grid implementation based on non-contact sensing.

An energy internet-based distribution system morphology

The future power distribution system will play an important role in the future energy system - energy Internet. With an eye to the diversification of energy and power fusion to the distribution system form, the prospect of the future integrated power distribution system for energy Internet is proposed, from the three aspects of structure, equipment form and industrial form: a multi-level AC-DC ring network as a framework, including the P2P interconnection and DC information satisfied power grid integrated network structure, is given; the concept of energy exchanger, the concept of energy server is put forward, and on this basis, the future distribution system of the equipment is prospected; the future distribution of the three types of industrial forms is analysed.

Markovian model for reliability assessment of microgrids considering load transfer restriction

Reliability is an indispensable factor in power system design and operation and has a significant impact on grid safety and economy. Future power distribution systems are expected to be more sophisticated, owing to the increasing penetration of renewable resources and adoption of advanced information and communication technologies. Extant studies in this field tend to focus on the modeling and assessment of the reliability of future microgrid distribution systems, including distributed generation, without considering networked configuration and limited transfer capacity. In the work presented in this paper, a Markov model is implemented to perform a practical and accurate reliability evaluation of networked electric microgrids under load transfer restriction conditions. The Markov model is used to model the microgrid based on the connectivity between the source and the loads and to compute load and system reliability indices. Moreover, the distribution load flow (DLF) method is adopted when reclassifying the Markov model states based on the system's transfer capability during interruptions. The obtained results confirm that the proposed model is efficient and that the DLF provides a more accurate reliability analysis due to the computing of the voltage profile during the system outage restoration process. This model can also be used to optimally integrate distributed generators into the power system at proper locations and with proper capacities to enhance the system's reliability.

Local storage meets local demand: a technical solution to future power distribution system

Future power systems are expected to integrate large-scale stochastic and intermittent generation and load due to reduced use of fossil fuel resources, including renewable energy sources and electric vehicles (EV). Inclusion of such resources poses challenges for the dynamic stability of synchronous transmission and distribution networks, not least in terms of generation where system inertia may not be wholly governed by large-scale generation but displaced by small-scale and localised generation. Energy storage systems (ESS) can limit the impact of dispersed and distributed generation by offering supporting reserve while accommodating large-scale EV connection; the latter (load) also participating in storage provision. In this study, a local energy storage system (LESS) is proposed. The structure, requirement and optimal sizing of the LESS are discussed. Three operating modes are detailed, including: (i) storage pack management; (ii) normal operation; and (iii) contingency operation. The proposed LESS scheme is evaluated using simulation studies based on data obtained from the Northern Ireland regional and residential network.

Experimental validation of smart distribution grids: Development of a microgrid and electric mobility laboratory

Abstract The development of the Smart Grid concept is the pathway for assuring high reliability, control and management requirements in future electric power distribution systems. The Smart Grid can be defined as an electricity network supported by an intelligent infrastructure, both hardware and software, capable of accommodating high shares of Distributed Energy Resources. Within this line, a Smart Grid laboratorial infrastructure was developed, being dedicated to advanced research and demonstration activities. The adopted laboratorial architecture was developed according to the Microgrid concept, where Electric Vehicles are regarded as active and flexible players. Following the laboratory implementation, this paper provides a detailed description of its infrastructure and experimental capabilities, presenting and discussing different experimental set-ups and associated results.

Guest editorial introduction to the special issue on “advanced signal processing techniques and telecommunications network infrastructures for smart grid analysis, monitoring, and management”

Electrical power systems are undergoing a radical change in structure, components, and operational paradigms, and are progressively approaching the new concept of smart grids (SGs). Future power distribution systems will be characterized by the simultaneous presence of various distributed resources, such as renewable energy systems (i.e., photovoltaic power plant and wind farms), storage systems, and controllable/non-controllable loads. Control and optimization architectures will enable network-wide coordination of these grid components in order to improve system efficiency and reliability and to limit greenhouse gas emissions. In this context, the energy flows will be bidirectional from large power plants to end users and vice versa; producers and consumers will continuously interact at different voltage levels to determine in advance the requests of loads and to adapt the production and demand for electricity flexibly and efficiently also taking into account the presence of storage systems.

Corrections to “A Novel Method for Evaluating Future Power Distribution System Reliability” [Oct 13 2264-2272

Corrections to “A Novel Method for Evaluating Future Power Distribution System Reliability” [Oct 13 2264-2272