High Voltage Distribution Network Research Articles

Photovoltaic hosting capacity assessment of a distributed network based on an improved holomorphic embedding load flow method and stochastic scenario simulation

The increasing proportion of distributed energy in the distribution network poses a significant challenge to effectively absorbing distributed generation (DG). On this premise, the DG hosting capacity (HC) assessment in the future distribution network based on the secure operation boundary of the power grid is necessary. In this paper, an improved holomorphic embedding load flow method (HELM) is employed to construct the relationship between the photovoltaic HC (PVHC) and each constraint to determine the upper limit of the comprehensive PVHC. Furthermore, a screening method of PV locations in the distribution network is constructed to screen the alternative PV locations with strong voltage regulation ability and reduce the alternative multi-point schemes, paving the way for simplifying the PVHC assessment based on a stochastic scenario simulation. Finally, a PVHC assessment based on the stochastic scenario simulation is proposed to expand the applicability of the assessment based on improved HELM. The negative impact of PV uncertainty is quantified by generating stochastic load flow scenarios based on the upper limit of the PVHC from improved HELM. The PVHC assessment in the high-voltage distribution network IEEE30 is analyzed to prove the efficiency and comprehensiveness of PVHC assessment in the distribution network.

Look-Ahead Rolling Economic Dispatch Approach for Wind-Thermal-Bundled Power System Considering Dynamic Ramping and Flexible Load Transfer Strategy

With a wind-thermal-bundled power system (WTBPS) under high wind penetration levels, the sharp power fluctuations of tie-lines for interconnected grids trigger a significant challenge of security-constrained power system operation. Smoothing power fluctuations with economic dispatch is widely concerned against this challenge. In this paper, an appropriate look-ahead economic dispatch framework for WTBPS considering the variable ramp rate of retrofitted coal-fired units and the flexible load transfer strategy (LTS) in high voltage distribution networks (HVDNs) is proposed. To cope with this issue, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> ) we derive a new family of tightened ramping constraints of retrofitted coal-fired units in the linear and second-order conic (SOC) forms, respectively. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ii</i> ) Using graph characterization of typical HVDNs, the simplified voltage-constrained LTS via topological structures can be developed. This proposed look-ahead economic dispatch model is cast as a mixed-integer second-order cone programming (MISOCP) problem, which can be reformulated by Multi-cut Generalized Benders Decomposition (MGBD). This MGBD enables multiple sub-problems can be solved in parallel and accelerates the solving process. Finally, simulation results of a large-scale practical system validate the computational accuracy and efficiency of the proposed approach.

Retracted: Two-Stage Research on AC/DC Hybrid High-Voltage Distribution Network Based on Network Reconfiguration and SOP Coordinated Control

Retracted: Two-Stage Research on AC/DC Hybrid High-Voltage Distribution Network Based on Network Reconfiguration and SOP Coordinated Control

Preface

The purpose of the three-day 2023 2nd International Conference on Energy Internet and Power Systems (ICEIPS 2023), held via virtual form on August 4th to 6th, 2023 in Chengdu, China, was to create a timely forum for multi-disciplinary discussions related to the recent developments on energy Internet and power systems.As usual, the program of the meeting mainly consisted of keynote speeches, oral presentations and poster presentations, with the former including speeches delivered by three sophisticated professors from different areas. The speeches covered three main topics: i) Challenges and Opportunities of Large Scale Electric Vehicles in Smart Grids with Renewable Generation, by Professor Jahangir Hossain from University of Technology Sydney, Australia; ii) Power System Security and Load Shedding, by Professor Mohamed EL-Shimy from Ain Shams University, Egypt; iii) Load-transfer Strategy for Urban High-Voltage Distribution Network based on Link-Path Model, by Professor Hongwei Li from Southwest Petroleum University, China.In the framework of experimental and theoretical approaches, the Conference gathered about 150 delegates from all over the world and addressed a number of highly relevant aspects of energy Internet and power systems. Covering Green Energy Development Technologies, Energy Internet Technology, Electric Motors and Drives, Smart Grid Power Transmission and Distribution, Intelligent Systems and Methods, etc., the selected contributions of this special issue provide guidance for future interdisciplinary developments. In this way, the multi-scale aspects of energy Internet and power systems should be considered.We received various manuscripts of invited papers and contributions presented at the Conference. All of these have been peer reviewed and are collected in this volume. We would like to thank all the anonymous colleagues who have acted as referees to assess the suitability of the various articles for publication in Journal of Physics: Conference Series. We are confident that the high quality of both invited and contributed papers contained in this Proceedings will be appreciated by the energy and power community.We would like to express our thanks to all the authors for their time and genuine efforts, and to the reviewers for their fruitful comments during the preparation of this volume. We also acknowledge the support provided in various ways by Northeastern University.List of Committee Member is available in the pdf.

A New Control Strategy of Hybrid Reactive Power Compensation System in Distribution Network

Reactive power compensation is an important measure to improve the power quality of distribution networks, especially with the increasing connection of distribution transformers, heavy industrial electrical equipment, and asynchronous motors, which generate a large amount of reactive power demand. Traditional reactive power compensation devices, such as fixed capacitors (FC) and thyristor switched capacitors (TSC), have some drawbacks, such as low response speed, harmonic generation, and switching shock. A static synchronous compensator (STATCOM) is a flexible AC transmission system (FACTS) device that can provide fast and continuous reactive power compensation, but it also has some limitations, such as high cost, large capacity requirement, and low utilization rate. Therefore, hybrid reactive power compensation systems that combine FC or TSC with STATCOM have attracted much attention in recent years. Many researchers have proposed and studied different topologies and control methods of hybrid systems to overcome the disadvantages of single devices and achieve better performance. However, most of the existing hybrid systems are designed for low or medium-voltage distribution networks, and their performance under high-voltage distribution networks is still unclear. Moreover, the coordination control strategy of the hybrid system and its subsystems is also a key issue that affects the effectiveness and efficiency of reactive power compensation. In view of this, this paper aims to propose a TSC+STATCOM hybrid reactive power compensation system for high-voltage distribution networks, which optimizes the shortcomings of traditional reactive power compensation devices. The system uses the synergistic effect of TSC and STATCOM to achieve large-scale static reactive power and small-scale dynamic reactive power compensation and adopts a switching strategy based on an expert decision system. This paper introduces the working principle of each subsystem of the hybrid reactive power compensation system in detail and builds a simulation model of the hybrid reactive power compensation system under a high voltage distribution network on Matlab/Simulink platform. The simulation results verify the feasibility and excellent performance of the system control method in reactive power compensation and improving power quality.

Probabilistic wind power expansion planning of bundled wind-thermal generation system with retrofitted coal-fired plants using load transfer optimization

The bundled wind-thermal generation system (BWTGS) is an attractive option to integrate wind energy to actively participate in power systems. With the greatly enhanced penetration of wind energy in BWTGS, wind curtailment against sharp wind power fluctuations is inevitable. Thus, our study is stimulated by whether and to what extent we can maximize wind power penetration with proper provision of dispatchable loads against wind curtailment, and this is exactly the problem we aim to solve in this paper. Here, we initially focus on the flexible characteristics of retrofitted coal-fired units in BWTGS and the load transfer optimization (LTO) for high voltage distribution networks (HVDNs). Then, an appropriate probabilistic wind power capacity expansion planning method for BWTGS with retrofitted coal-fired units using LTO can be reformulated as a mixed-integer second-order cone programming problem. Moreover, since load and wind power data have inherited uncertainty, we extend this proposed model to be a probabilistic expanding model. This contributes to better decision-making for the short-term wind capacity expansion under quantified uncertainty. Numerical results of the practical HVDNs demonstrate the effectiveness of the proposed method.

Hierarchical Distributed Optimal Power Flow of HV and MV Distribution Networks With Continuous and Discrete Devices

With large-scale distributed photovoltaics (PVs) being integrated into distribution networks (DNs), coordinated optimal power flow (OPF) of high voltage (HV) and medium voltage (MV) DNs should be investigated to optimally dispatch the distributed PVs and other network devices. This paper presents a hierarchical distributed OPF method for HV and MV DNs with on-load tap changers, reactive power compensators, feeder switches and distributed PVs. A hierarchical master-slave control architecture is applied to implement coordinated OPF of two-layer DNs. The HV master problem and MV subproblems are transformed into mixed-integer convex problems respectively with second order cone programming and LinDistFlow approximation. Since there is no efficient distributed algorithm to solve such OPF models with integer subproblems, a novel distributed algorithm is proposed in this paper to efficiently solve the hierarchical coordinated OPF model with integer subproblems in a distributed manner. In the proposed algorithm, the coordinated OPF model is solved in a branch-and-bound framework, where in each branch node generalized Benders decomposition (GBD) algorithm is applied to decompose the coordinated OPF model into a master problem and relaxed subproblems and solves them iteratively to get optimal solution. The GBD optimal and feasible cutting planes generated in a branch node are proved to be valid for its descendants. Moreover, three acceleration techniques are introduced into the proposed algorithm to improve computational efficiency. Finally, the effectiveness and accuracy of the proposed method are verified via simulation tests in Jinzhai DNs of China.

An adaptive Distance Protection for Distribution Network With Inverter-Interfaced Distributed Generation

Inverter-Interfaced Distributed Generation (IIDG) accessed to the high-voltage distribution network may cause protective device tripping missing when using regular distance protection. In case of non-metallic faults, the generation of additional impedance may lead to faulty action of the distance protection, which threatens the safety and stability of the distribution network. Therefore, an adaptive distance protection plan is suggested, which corrects the measured impedance according to the diagram, thus the corrected measured impedance can track the fault impedance. The suggested plan is insensitive to the fault resistance, fault locations and IIDG’s output. The simulation results indicate that the suggested plan can reflect the fault impedance correctly, and accurately identify internal and external faults.

Open capacity calculation method of distribution network

At present, there are few methods for quantitative calculation of installed load or new energy for distribution network equipment. Based on this, this paper proposes a calculation method for the open capacity of the distribution network. Firstly, the calculation methods of the open capacity of a 10 kV distribution transformer, 10 kV lines, and high-voltage substation three-level distribution network based on the conventional situation and new power system are studied, respectively. Then the calculation methods of the open capacity of the distribution system based on the conventional case and the new power system are studied, respectively. Finally, the empirical region is selected, and the research results are used for case analysis to verify the effectiveness and operability of the research results.

Control of electric power quality indicators in distribution networks comprising a high share of solar photovoltaic and wind power stations

Mass-scale integration of renewable power stations into distribution power networks is a main trend of power industry development aimed at its decarbonation. All solar photovoltaic (SPVS) and wind power (WPS) stations are connected to the existing medium- and high-voltage distribution networks, excluding large capacity wind power and photoelectric fields. Modern SPVS and WPS are integrated into energy systems with the use of inverters/converters into which control algorithms for output power and protection have to be included. Critical deviations of electric power quality indicator (EPQI) from their normal operation values may occur, in networks, in these inverters/converters low-load conditions. Such deviation appears in low irradiance conditions in SPVS and low wind speed in WPS. It has to be noted that various electric loads of industrial consumers can be connected to the distribution networks for which such EPQI deviations are critical. This article deals with the newly developed method and device for EPQI sampling control enabling to automatically detect EPQI deviations including short-term ones. Results of preliminary simulation modeling, in various operation conditions, of distribution network including SPVS and WPS are used in the newly developed device. Besides, the device implements automatic Wald’s sequential analysis procedure on the basis of a multiple-choice indicator distributed in accordance with the binomial law. The effectiveness of EPQI sampling control based on the mathematical statistics methods has been demonstrated. It has been proposed to apply an integrated indicator, i.e. the absolute value of intercorrelation coefficient, for current and voltage signals, in order to take account of the complex effect of EPQI on the electric loads. Implementing the developed method and device for sample-based EPQI control makes it possible to prevent considerable and long-term EPQI deviations, in order to ensure reliable operation of consumers’ electric receivers, in distribution networks comprising a high share of SPVS and WPS.

Two-Stage Research on AC/DC Hybrid High-Voltage Distribution Network Based on Network Reconfiguration and SOP Coordinated Control

DC power grid has the advantages of large power supply capacity, easy access to clean energy, low loss, and easy power control. With the increasing penetration rate of distributed generation and DC load in low-voltage transmission network, the traditional radial AC distribution form develops into AC-DC hybrid form. Large-scale distributed energy access is an important feature of future distribution system. Aiming at the AC-DC hybrid distribution system with soft tie-in switch and voltage source converter, considering the network congestion caused by large-scale access of distributed energy, a two-stage congestion management mechanism is proposed. This strategy solves the congestion problem of AC/DC hybrid transmission network with the help of the power flow control ability of AC/DC transmission network’s own optimization control means and congestion management services provided by distributed energy sources. According to the experiment, the total distributed generation power of DC link is 15 MW, and the load power is 10 MW, that is, the remaining power of DC link is 5 MW, the total distributed generation power of AC link is 8 MW, and the load power is 15 MW, that is, the power shortage of AC link is 7 MW. In the first stage, the tie-in switch, SOP and VSC are coordinated and optimized, and in the second stage, the flexible adjustment ability provided by distributed energy makes up for the deficiency of the adjustment ability of direct control means in some periods of severe congestion and meets the requirements of congestion management of AC-DC hybrid transmission network under high-permeability distributed generation.

Multistage Bilevel Planning Model of Energy Storage System in Urban Power Grid Considering Network Reconfiguration

The large-scale integration of renewable energy sources (RESs) and the rapid development of loads cause frequent transmission congestion in the urban power grid (UPG). Transmission system operators usually perform the high-voltage distribution network (HVDN) reconfiguration to mitigate the transmission congestion. However, as the loads and RESs change rapidly, the HVDN reconfiguration might be conducted frequently. This might cause severe security problem. An energy storage system (ESS) provides an effective way of alleviating the transmission congestion. If the ESS is installed and operated elaborately, the transmission congestion of UPG can be mitigated with a little HVDN reconfiguration. Hence, this study proposes a multistage bilevel planning model for the optimal allocation of ESS. The upper-level model aims at maximizing the annual comprehensive revenue of HVDN, and the lower-level model focuses on the minimization of the operational cost. Simulation results carried out on a real-world test system verify that the proposed method has the great potential of reducing the investment and operational cost while mitigating the transmission congestion.

Load Transfer Optimization Considering Hot-Spot and Top-Oil Temperature Limits of Transformers

This paper proposes a load transfer optimization (LTO) model involving hot-spot temperature (HST) and top-oil temperature (TOT) limits of transformers. This work aims to address the overload problem and transformer HST and TOT excursions via LTO. First, the equivalent thermal model for the HST and TOT of transformers under external cooling conditions are discussed, and then the corresponding linearized HST and TOT constraints with varied thermal resistances are derived using the discretization method. Moreover, the proposed LTO model is formulated on the reconfigurable topology of high voltage distribution networks (HVDNs) in China. This proposed LTO model can achieve the optimal network reconfiguration scheme subject to temperature limits and system operation constraints, with the least switching operation cost and the maximum margins of reactive power exchange between HVDNs and transmission systems. Finally, the effectiveness of the proposed LTO model is validated by the modified <i>IEEE</i>-14 node system and the practical HVDNs in China.

Prosumer‐centric energy storage system and high voltage distribution network topology Co‐optimisation for urban grid congestion management

The surge of electricity load and the growing number of renewable energy sources (RESs) in urban power grid result in severe and frequent congestion for transmission networks. This causes the transmission system operators (TSOs) perform the high voltage distribution network (HVDN) reconfiguration frequently. The frequent reconfiguration of the HVDN will cause the fast degradation of high voltage circuit breakers, high maintenance and operational cost, and stability problems. To reduce the frequency of HVDN reconfiguration, this paper proposes a prosumer-centric energy storage system (ESS) and HVDN topology co-optimisation for transmission congestion management. Numerical results show that with the assist of ESS operational strategy, the reconfiguration frequency of HVDN can be significantly reduced while mitigating the transmission congestion.

DG Locational Incremental Contribution to Grid Supply Level

Due to decarbonisation and decentralisation of energy sectors, the rise of distributed generation (DG) will modify generation and demand patterns at grid supply points (GSPs), where the interface between distribution and transmission systems takes place. With the increasing penetration of such devices, methodologies able to evaluate its contribution to both local distribution network and transmission system become crucial. This paper proposes an analytical method to evaluate the DG locational incremental contribution (LIC) to the interface with the transmission grid. Accordingly, the original model of the UK engineering recommendation P2 is enhanced by studying the impacts from high-voltage distribution networks (i.e. ≤ 132 kV) under normal and contingent conditions. This approach enables a more accurate network security assessment, especially when considering contingencies such as distribution system faults. To illustrate the proposed method, the original P2 model is compared against different enhanced approaches on three basic distribution networks, followed by a case study and a sensitivity analysis on a revised IEEE 14-bus GSP system. The proposed LIC method produces results that assess a wider range of conditions including DG penetration, concentration, and system reliability. Furthermore, it provides an increased DG visibility for transmission planning and operation.

Effect of Copper and Iron Particles on the Dielectric Strength of R410A Gas as an Alternative of SF 6 in GIS

The Gas Insulated Switchgears (GIS) used in high voltage transmission and distribution networks are reliable, compact, and maintenance-free. During the manufacturing process, some metal particles remain inside GIS which affects the breakdown strength of insulating gas and hence deteriorates the performance. The breakdown performance of R410A gas in the presence of free metal particles is presented in this paper. Iron and copper particles of various sizes and shapes are used in the research work. The impact of these free particles on the characteristic of R410A gas at various gas pressures and gap distances is elaborated. Power frequency breakdown voltage test in the presence of metal particles and self-recoverability test are performed in a high voltage lab. The effect of various dimensions of metal particles on the dielectric strength of R410A gas under the quasi-uniform field in alternating current is examined. The impact on the breakdown voltage of R410A is analyzed by increasing the pressure and gap distance. Experimental results are discussed in the paper. As metal particles in between them can disrupt the R410A reaction barrier. According to the results of the experiments conducted, the breakdown voltage was affected by 30% by the addition of iron particles and 46.89% by the addition of copper particles, and it is concluded that iron particles perform better at different gaps distances.

A Multilayer Path Planning Method for High Voltage Distribution Network Based on the Floyd-Warshall Algorithm

With the development of the city, a huge number of distribution networks are waiting for planning. A reasonable planning scheme can meet the power demand and reduce the investment cost. In this paper, a life cycle cost model including the investments of substation and wiring is established with the constraints about load flow calculation and maxi-mum load of wiring. Additionally, a multilayer planning method based on the Floyd-Warshall algorithm has been proposed to solve the model. The area of the city containing substations is divided based on the position of load through the hybrid clusters algorithm in the method. Then, using the divided result of power supply area, the cost matrix for the multilayer path planning method can be constructed through the principle of the method. Lastly, with the cost matrix, the planning scheme in each area will be provided by the Floyd-Warshall algorithm. The result on the actual planning area between the two algorithms shows the total cost of the investment is decreased through using the planning method in this paper.

Fuzzy Linear Active Disturbance Rejection Control of Injection Hybrid Active Power Filter for Medium and High Voltage Distribution Network

In order to reduce the capacity of the active power filter (APF), improve its dynamic tracking speed and anti-disturbance ability of harmonic currents, so as to better solve the problem of harmonic pollution in the medium and high voltage distribution network, this article is suitable for medium and high voltage distribution networks. The three-phase three-wire injection hybrid active power filter (IHAPF) of high voltage distribution network is the research object, and a fuzzy linear active disturbance rejection controller (Fuzzy-LADRC) suitable for IHAPF voltage outer loop control is proposed. The controller is composed of a fuzzy proportional controller, a linear extended state observer (LESO), and a total disturbance compensation link. The introduction of fuzzy logic control solves the difficult problem of controller parameter tuning, and uses Lyapunov stability definition to prove the stability of the system. Finally, the control performance of IHAPF under the control of Fuzzy-LADRC is simulated and verified by MATLAB&SIMULINK simulation platform, and compared with the traditional PI controller. The results show that the Fuzzy-LADRC controller is better than the traditional PI controller and has good tracking and anti-disturbance capabilities.

A Brief Discussion on the Overall Design of High Voltage Intelligent Reactive Power Compensation

Reactive power compensation can not only improve the voltage quality and the stability of the whole system, but also reduce the loss and improve the economic benefits. With the rapid development of social economy, people put forward higher requirements for the safety, stability and intelligence of power grid operation. At present, there are still some problems in the application of reactive power compensation devices in China’s high voltage distribution network. In this paper, the high voltage intelligent reactive power compensation device is designed from many aspects, and the feasibility analysis is carried out, which provides certain reference for reactive power compensation of high voltage system.

Improving the efficiency of technical means and methods for diagnostics of isolation of high-voltage distribution networks

This work is aimed at developing and improving diagnostic equipment used in high-voltage distribution networks by modeling electromagnetic transients and expanding the functional part of devices. Presented are models of a three - phase distribution network and a high-voltage part of a test installation forming a technological system “diagnostic device-distribution network”. Examples are shown of wave processes in the simulated system during insulation breakdowns, load characteristics of the test installation during operation of the device are shown, which makes it possible to optimize insulation control methods and technical diagnostic tools for electrical laboratories. Disclosed are examples of calculating the location of damage in case of insulation failures in different sections of the controlled network based on the analysis of wave processes in the line.