Hasil untuk "Distribution or transmission of electric power"

Georgios Lampsidis Tompros, Vassiliki T. Kontargyri, Maria Fotopoulou et al.

The current energy transition has shifted the power system paradigm, including distributed resources (mostly renewables) and energy storage systems, the proper incorporation of which is beneficial for the power system but can also cause issues such as network instability, grid congestion or issues with power quality. Moreover, the exponential electrification of loads, especially ones with dynamic behavior, due to most sectors switching to electric mode, with prominent examples including mobility, heating, hydrogen production and marine applications, can pose challenges for the system operators. The purpose of this paper is to highlight the effects of this transition from the perspective of the distribution and transmission systems in Europe generally, but also in Greece specifically, by presenting key performance indicators (technical, economic, environmental, and social) related to expected EU targets, as well as selected real-life applications, future trends and challenges.

Koji Yamashita, Nanpeng Yu, Evangelos Farantatos et al.

As the power transmission system’s energy sources become increasingly diversified, the grid stability is experiencing increased fluctuations, thereby necessitating more frequent and near real-time monitoring by grid operators. The power system security has been monitored through real-time contingency analysis and dynamic security assessment framework, both of which are typically based on time-domain simulations or power flow calculations. Achieving higher accuracy in grid health level prediction often requires time-consuming simulation and analysis. To improve computational efficiency, this paper develops machine learning models with phasor measurement unit (PMU) data to monitor the power system health index, focusing on rotor angle stability and frequency stability. The proposed machine learning models accurately predict frequency and angle stability indicators, essential for evaluating grid health considering various contingencies, even when dealing with limited PMU deployment in transmission grids. The proposed framework leverages a physics-informed graph convolution network and graph attention network with ordinal encoders, which are benchmarked with multi-layer perceptron models. These models are trained on dataset derived from an augmented IEEE 118-bus system with different demand levels and fuel mix, including tailored dynamic generator models, generator controller models, and grid protection models. The numerical studies explored the performance of the proposed and baseline machine learning models under both full PMU coverage and various partial PMU coverage conditions, where different data imputation methods are used for substations without PMUs. The findings from this study offer valuable insights, such as machine learning model selection and critical PMU locations regarding power equipment, into the design of data-driven grid health index prediction models for power systems.

Xiaofei Wang, Jiazi Zhang, Leonardo Rese et al.

With the worldwide growth in deploying high-voltage direct current (HVDC) transmission systems, their ability to facilitate black-start (BS) restoration has been a research topic of interest. In this context, voltage source converter (VSC)-HVDC is regarded as a BS resource, and this paper proposes a VSC-HVDC-assisted parallel BS restoration strategy in bulk power systems. The proposed strategy consists of two stages: 1) determination of the VSC and generator startup sequence and 2) load restoration simulation. In the first stage, the entire blackout system is sectionalized into multiple subsystems. Each subsystem includes a VSC-HVDC station or traditional BS unit, it independently determines its generator startup timeline and the energization timelines for buses and lines. The second stage involves load restoration, conceptualized as a modified unit commitment problem, with the timelines established in the first stage work as critical inputs. The proposed BS restoration strategy is tested on the San Diego power system to simulate the 2011 Southwest blackout. The simulation results validate the effectiveness of using VSC-HVDC links as a BS resource which not only speeds up the restoration process but also reduces both energy and economic losses.

Mohammad Mehdi Amiri, Mohammad Ameli, Mohammad Reza Aghamohammadi

The integration of gas and electricity networks is pivotal for efficient energy management, particularly with the rising penetration of renewable energy sources. Compressor stations are critical for maintaining gas pressure and flow, and their optimal operation can significantly enhance system flexibility and reduce costs. While previous studies have explored coordinated operation of compressor units, this research introduces a novel price-responsive coordination strategy for compressor stations comprising both gas-driven compressors (GDCs) and electric-driven compressors (EDCs) within an integrated gas and electricity network. The proposed strategy operates GDCs when gas prices are lower and EDCs when electricity prices are lower, aiming to optimize linepack storage in gas pipelines. Using a mixed-integer linear programming (MILP) model, we optimize the scheduling of compressors based on hourly energy prices while ensuring network constraints are met. Simulations on a 24-bus electricity and 19-node gas network over a 24-hour period demonstrate that this coordinated approach leads to a substantial increase in linepack storage and a reduction in operational costs compared to uncoordinated operation. Simulation results show that in the proposed design, i.e., by integrating the optimized linepack model into the compressor station model, the amount of carbon dioxide produced has decreased by 33.3% and the total operation costs have decreased by 1.57%.

Xinliang Dai, Yi Guo, Yuning Jiang et al.

Sayed Mahdi Koloushani, Seyed Abbas Taher

Abstract This article introduces innovative protection strategies, including cooperative protection, for power transmission grids amidst a significant shift towards renewable energy sources (RES) such as wind and solar power, as well as inverter‐based resources (IBRs). The method employs a global consensus algorithm to achieve cooperative protection efficiently. This scheme leverages consensus protocols to dynamically oversee distance relay decisions, ensuring efficient fault detection and localization. The decentralized nature of the proposed method enhances robustness and security, while its high‐speed operation is ensured through non‐iterative global consensus algorithms, which provide rapid fault detection and localization crucial for real‐time protection. By incorporating virtual leaders and leveraging existing communication infrastructure, the method achieves superior selectivity in identifying faulty lines, enhancing the reliability and stability of power transmission grids with high‐RES penetration. Notably, the method does not require learning and training processes, making it adaptable to varying power system topologies without the need for extensive retraining or adaptation periods. The proposed methodology enables simultaneous participation in multiple protection zones by establishing interaction rules between agents. Virtual leaders simplify the selection of protection areas, enhancing scalability and fault localization. Simulation results conducted on the IEEE 39‐bus test system validate the effectiveness of the proposed method.

Ali Azizi, Frede Blaabjerg, Saeed Peyghami

Abstract Stability issues can significantly increase the risk of hybrid microgrids (HMGs), particularly during island mode operation. The dynamic performance of the system can induce constraints and stability margins that may elevate the loss of load probability. This paper presents a new stability‐oriented risk assessment model that bridges the conventional reliability models, stability, and system risk. The proposed model ensures the risk of the system by considering the redesign or reconfiguration of HMGs to address stability issues. First, the interlinking converters (ICs) DC‐link voltage stability is analysed to determine the acceptable power flow margins in rectifying and inversion mode. Next, the new general risk assessment model is introduced. The results show that the stability margin significantly increases the risk of the HMG, particularly when considering the aging of converters. The study also examines the impact of various load characteristics and ICs with different numbers but the same total size. In some cases, the risk is acceptable for the desired loads, or it can be reduced to an admissible level by reconfiguring the ICs. Finally, the paper demonstrates the effectiveness of the proposed model in the optimal design of HMGs, aiming to guarantee the system's risk.

Nima Nasiri, Saeed Zeynali, Sajad Najafi Ravadanegh

Abstract The depleting oil reserves, air pollution and increasing energy demand, have overturned the focus of the scientific community to renewable energy sources. Among which the photovoltaic (PV) systems occupy more than half of the market share and are generally installed at the distribution level. The volatile and uncertain nature of these PV productions necessitates flexible resources in energy systems. To this end, the district heating systems have an outstanding flexibility on account of their high thermal inertia. This study investigates the optimal unit commitment scheduling for gas‐fired and non‐gas‐fired distributed generation units (NGU) in an integrated energy distribution system (IEDS) within the physical constraints of the electrical, natural gas and thermal energy distribution networks. Moreover, a planning‐based optimization framework is proposed to investigate the investment of battery storage systems in the electric distribution network under the high penetration of PV systems with the aim of enhancing flexibility and reducing the operating costs of the IEDS. In this framework, the information gap decision theory is deployed under risk‐averse and risk‐seeker strategies to deal with uncertain PV energy production. Additionally, the environmental emissions are considered in a multi‐objective approach. The IEDS is embodied through IEEE 33‐bus EDS, 20‐node natural gas network and an 8‐node district heating systems. Eventually, The proposed approach makes a noteworthy contribution to the advancement of solar energy systems in IEDS.

Yi Zhou, Rui Zhang, Dinesh Kathriarachchi et al.

Abstract With the increasing penetration level of renewable generation, a shortage of system strength becomes a concern for the stable operation of the power system. Most commonly, Inverter Based Resources (IBR) plants are operated with grid following inverters (GFLI). However, a grid forming inverter (GFMI), which work as a voltage source and does not require direct reference and system strength from the grid, is now receiving increased attention. Here, Hardware‐in‐the‐loop (HIL) testing of a GFMI and its capability to actively damp sub‐synchronous oscillations and to provide synthetic inertia has been discussed. The improvement to system strength and transient stability have been presented using modelling of the transmission network in the Queensland (Australia). The study shows that with proper tuning and coordination with other generation in the area, the GFMI BESS will not only provide system strength to the grid, but also solve other stability issues.

Masume Khodsuz

Abstract This paper conducts the frequency‐dependent grounding system impact on externally gapped line arresters (EGLAs) operation and their placement effects on the lightning performance of a transmission line (TL). The study involves placing EGLAs at different phases of a 400‐kV double‐circuit TL with two downstream shield wires and selecting the optimal state with fewer back‐flashover incidents. The results show that using a non‐linear grounding system leads to a higher back return current from insulators or EGLAs, resulting in a higher flashover rate compared to the frequency grounding system (FGS). Installing four EGLAs in the middle and upper phases of the TL provides satisfactory lightning protection, and the flashover probability is zero and 4.2% for the FGS and the non‐linear grounding system, respectively. A sensitivity analysis including soil resistor variation, economic analysis, and grounding electrode configuration has been performed that confirms installing downstream shield wires and EGLAs is an effective and economical technique for lightning protection.

Fei Feng, Xin Du, Qiang Si et al.

Abstract Energy storage devices become an indispensable part of modern power systems with high renewable energy penetration level. To reduce the operating costs, it is a promising way to allow the sharing and leasing of energy storage devices. In this paper, a bi‐lever optimized dispatch scheme is proposed to improve the usage efficiency of cloud energy storage in multi microgrids (MMG) system. Minimizing the operating costs of shared cloud energy storage is the main task of the upper lever while maximizing the profits of MMG is the goal of the lower lever. Moreover, the transaction cost and benefit between the two levers play an important role in system level optimization. This leads to a hybrid optimization problem with both discrete decision variables and continuous decision variables. To solve the problem, a relaxation‐based bi‐lever reformulation and decomposition algorithm is developed. The effectiveness of the proposed bi‐lever dispatch optimization model is verified by carrying out numerical experiments in three scenarios. It is shown that the proposed cloud energy storage service can effectively reduce the operating cost of MMG.

Xiaolong Li, Mingde Wan, Wen Wang et al.

Abstract The temperature distribution of the tri‐post insulator in a ±500 kV direct current gas‐insulated transmission lines (DC‐GIL) is investigated. The influence of thermal gradient on the electric field characteristics is investigated as well. A horizontally installed GIL model is applied in the simulation. The thermal and electric parameters of the insulator are measured and employed. The temperature results indicate that the gas shows a layered distribution pattern while the insulator shows a radial distribution pattern. The temperature of the upper post is higher. With increasing ambient temperature, the surface temperature increases linearly following the variation of ambient temperature. With increasing load current, the temperature near the conductor shows an obvious increase. With increasing gas pressure, the temperature decreases due to the promotion of convection. Besides, the electric field strength of the insulator surface increases if the surface temperature increases during the variation of operating conditions. And the peak of field strength moves towards the enclosure. After 10 h, the temperature reaches a quasi‐stationary state. Since the thermal gradient affects the distribution of gas density and electric field strength of the insulator, the investigation of temperature characteristics is necessary when evaluating the insulating performance of DC‐GIL with insulators.

Ehsan Karami, Ehsan Hajipour, Mehdi Vakilian

The protection of transmission and sub-transmission lines is conducted by overcurrent, line differential and distance protections among which the use of distance protection is very common.Mal-operation of protection equipment, including distance protection, can occur due to improper choose of the setting. This paper presents the proper method for calculation of the phase-to-phase loop resistance reach of distance protection with Quad characteristic and the impedance starter at the sub-transmission level to prevent mal-operation of the distance relay when processing its algorithm. In this work, based on the practical experiences on several industrial distance relays, it is shown that there is a possibility of improper detection of the fault loop by distance protection and then improper relay operation for out of zone faults. After review of the subject, and expressing the mathematical relations governing the problem, the appropriate phase-to-phase loop resistance reach determination method is put forward. Finally, using the information obtained from a practical incident, the efficiency of the proposed method is verified.

Blazhe Gjorgiev, Alexander E. David, Giovanni Sansavini

Seyed Sina Taheri Otaghsara, Masoud Asghari Gharakheili

Abstract On the topic of power systems, the most critical assignment would be providing facilities to make electricity available at the lowest price with a fulfilled level of reliability for all consumers. Today, power transmission reliability has received more concentration due to the increasing essence of providing high‐quality energy to customers and operating competitive conditions in electricity markets. In this regard, this paper scrutinizes the reliability‐centred maintenance (RCM) issue in terms of considering two optimal maintenance strategies for transmission assets to decrease their forced outage rate (FOR). This techno‐economic budget‐based maintenance is a probabilistic approach to help asset managers and experts in the decision‐making process: to determine between maintenance strategies with associated costs and provide the most economical resource allocation for these elements, which leads to an improvement in the reliability of the whole network. Decreasing the average probability of Energy Not‐Supplied (ENS), the simulation determined the proper maintenance strategy for transmission components. After that, the repercussions of the fallen ENS will be analyzed in total maintenance cost (MC), operation cost (OC), and the system's total cost (TC). Also, the IEEE 24‐bus reliability test system is considered as a case study demonstrating the proposed technique's practicality.

Taehyung Kim, Nicholas G. Barry, Woosung Kim et al.

The objective of this paper is to analyze and identify the range of voltage balancing capability of grid-forming inverters serving three-phase unbalanced loads. These inverters are designed to compensate for voltage imbalance by controlling the negative-sequence components of voltage and current. However, the magnitude of the negative-sequence current an inverter can supply is limited by its relatively low rated current. Moreover, it becomes more challenging to estimate the amount of current needed for an unbalanced load when the inverter is interfaced using a delta-wye grounded interconnection transformer. Therefore, we investigate the range of negative-sequence current the inverter can supply and derive formulas to determine the minimum inverter’s capacity required to compensate for voltage imbalance while supplying unbalanced loads connected through a delta-wye grounded transformer. The proposed formulas can be used to estimate the capacity of an inverter in lieu of detailed analyses and electromagnetic transient simulations. The proposed equation is implemented in small and large scale microgrid systems and validated using a detailed model developed in PSCAD/EMTDC.

Zhenyu Zhang, Wei Cui, Shuanbao Niu et al.

Abstract Successive failure propagating through a power system, typically caused by extreme weather such as storm and lightning, can cause blackouts by means of a variety of processes. To address this issue, this paper proposes preventive control for successive failures of power system to mitigate the consequences of successive failures in extreme weather. First, based on the Poisson process theory, the authors model the successive failure propagation, and present the confidence interval estimation for the time interval between successive failures. Then, a failure pre‐control methodology that quantifies the grid regulating ability and actions is developed to make decisions for system operators on mitigating overloads of transmission lines. Furthermore, a systematic pre‐control framework for successive failures is first proposed to detect latent risks, eliminate predictable consequential outages, and secure power system stability. Results from IEEE‐9 bus and IEEE‐39 bus standard systems as well as a real‐world system show the feasibility and effectiveness of the proposed method. The proposed preventive control framework can provide a systematic pre‐control action scheme for system operators, and realize enhancement of stability and resilience to power system failures.

Stefano Massucco, Paola Pongiglione, Federico Silvestro et al.

S. Mazumder, Abhijit Kulkarni, Subham S. Sahoo et al.

In this article, a broad overview of the current research trends in power-electronic innovations in cyber–physical systems (CPSs) is presented. The recent advances in semiconductor device technologies, control architectures, and communication methodologies have enabled researchers to develop integrated smart CPSs that can cater to the emerging requirements of smart grids, renewable energy, electric vehicles, trains, ships, the Internet of Things (IoT), and so on. The topics presented in this article include novel power-distribution architectures, protection techniques considering large renewable integration in smart grids, wireless charging in electric vehicles, simultaneous power and information transmission, multihop network-based coordination, power technologies for renewable energy and smart transformer, CPS reliability, transactive smart railway grid, and real-time simulation of shipboard power systems. It is anticipated that the research trends presented in this article will provide a timely and useful overview to the power-electronics researchers with broad applications in CPSs.

Hejun Yang, Lei Wang, Yinghao Ma et al.

Abstract Time of use pricing strategy can not only reduce the load fluctuation but also improve the power system reliability. Generally, before carrying out a time of use pricing optimization, it needs to perform a period partition optimization for dividing peak‐valley periods. In existing researches, however, the period partition optimization and the time of use pricing optimization are implemented independently. Although the output of period partition optimization is used as the input of time of use pricing optimization, the bidirectional feedback effect between period partition optimization and time of use pricing optimization is not considered, which will lead to the existing time of use pricing optimization may not be the globally optimal solution. Therefore, this paper investigates a new optimization method for time of use pricing optimization with the consideration of bidirectional feedback effect, establishes a comprehensive customer satisfaction degree model considering the customer load proportion coefficient, and defines an elastic cofactor to describe the electricity price response difference of multiple types of customers. The Roy Billinton test system is used to verify the correctness and effectiveness of the proposed method in this paper.