Hasil untuk "Distribution or transmission of electric power"

Yanling Lin, Jianhui Wang, Meng Yue

Christoph Becker, Tobias Rebentisch, Markus Zdrallek et al.

This contribution presents a method for automated strategic network planning for electric distribution networks across voltage levels. Three approaches for cross-voltage-level planning using level-separate network-datasets are presented. Advantages and disadvantages for all approaches are compared. The approach of successive automated strategic network planning starting with the lower voltage level is selected. The contribution then describes the underlying method and its implementation into two existing software solutions. The implementation is then tested by performing strategic network planning for two network areas with medium- and low-voltage networks from a German distribution system operator. The emerging results show that cross-voltage-level planning leads to a significant reduction of reinforcement expenses for both network areas. The contribution concludes that using the presented approach could lead to lower estimated reinforcement expenses in distribution networks, but further analyses on the impact of different constellations are necessary.

N. Sinthuja, M. Senthilvelan, K. Murali

In this paper, we report the emergence of breather and super rogue waves in a modified Noguchi electrical transmission line and demonstrate that both phenomena arise from baseband modulational instability. We then systematically examine the influence of three key parameters and time that appear in the solutions, on the structure and behavior of breathers and super rogue waves, how they control waveform amplitude, localization, and intensity. We also explore the intricate dynamics of wave propagation in nonlinear electrical line. Our findings provide valuable insights into the role of network parameters, such as inductances, capacitances, and nonlinear coefficients, in shaping wave behavior, offering not only practical guidelines for the design, stability, and experimental investigation of electrical transmission systems but also provides practical approaches for controlling and managing breather and super rogue wave phenomena in the transmission lines.

Weilun Wang, Zhentong Shao, Yikui Liu et al.

To facilitate the integration of distributed energy resources (DERs) into the wholesale market while maintaining the tractability of associated market operation tools such as unit commitment (UC), existing DER aggregation (DERA) studies usually consider that each DERA is presented on a single node of the transmission network. Nevertheless, the increasing scale and geographical distribution of DERs spur the emergence of DERAs covering multiple transmission nodes, posing new challenges in modeling such multi-transmission-node DERAs (M-DERAs). Indeed, assessing the aggregated impact of an M-DERA on power flows is a non-trivial task, because the sensitivities of each transmission line to DERs at different transmission nodes are not identical. Inspired by the distribution factor (DF) based shift factor (SF) aggregation strategy in industry practice, this paper proposes a novel DF-based chance-constrained UC (CCUC) model to determine system optimal operation plans with M-DERAs. DFs, treated as uncertain parameters to describe possible responses of DERs against aggregated dispatch instructions from regional transmission organizations, are modeled via a bounded hetero-dimensional mixture model (BHMM) by leveraging historical DF records distributed on multiple hyperplanes in a bounded space. With this, power flow limits are modeled as chance constraints in CCUC, which is reformulated into a scenarios-based stochastic form and solved by Benders decomposition. The proposed method is tested on an IEEE 24-bus system to illustrate its effectiveness in managing M-DERA integration while ensuring operational economics and mitigating the overloading of transmission lines.

Qiao Li, Linlin Wu, Xiao Wang et al.

Abstract This paper presents an analytical examination of the small‐single stability (SSS) criterion of the permanent magnet synchronous generator (PMSG)‐based wind power delivery system via voltage source converter‐based high voltage direct current (VSC‐HVDC). First, a small‐signal model of the PMSG‐based WPDS is developed. Then, the SSS criterion, driven by the phase‐locked loop of the PMSG in the sub‐synchronous timescale, is derived. The derived SSS criterion provides analytical insights into why and how the loading condition, the grid connection, and the control parameters affect the system’s SSS. It is unambiguously revealed that increasing loading conditions of the PMSG or/and the grid connection of the WPDS to VSC‐HVDC shall bring about a higher risk of oscillatory instability. Hence, analytical derivation of the SSS criterion helps better understand the instability mechanism in the PMSG‐based WPDS via VSC‐HVDC. In addition, while the derivation of the SSS criterion presupposes identical dynamics among PMSGs, this derived criterion can still be approximately utilized to assess the SSS of the PMSG‐based WPDS via VSC‐HVDC, irrespective of whether the dynamics of the PMSGs are similar or different. Finally, the SSS criterion is demonstrated and evaluated through three examples of the PMSG‐based WPDS via VSC‐HVDC.

Shuai Yuan, Bing Wen, Jian‐Ying Zhang et al.

Abstract This paper presents a state‐space average model of a three‐level photovoltaic (PV) inverter to understand short‐circuit currents transient characteristics. Analytical solution of the model is also derived. The proposed model is validated with PV system controller hardware in‐loop (HIL) test method. The errors between simulation and HIL tests results under various conditions are evaluated, testifying the validity of the proposed model. With the model and analytical solution, the decaying time constants of sub‐transient and transient processes are derived, which shows that the time constants of a three‐level PV inverter are not fixed and they vary with voltage dips. The analytical expression of short‐circuit currents is also formulated. The findings from this study are essential to short‐circuit current calculations of a power grid with large‐scale PV plants, coordination of power system protections, and grid planning.

Leen Al Homoud, Katherine Davis, Shamina Hossain-McKenzie et al.

Modern-day power systems have become increasingly cyber-physical due to the ongoing developments to the grid that include the rise of distributed energy generation and the increase of the deployment of many cyber devices for monitoring and control, such as the Supervisory Control and Data Acquisition (SCADA) system. Such capabilities have made the power system more vulnerable to cyber-attacks that can harm the physical components of the system. As such, it is of utmost importance to study both the physical and cyber components together, focusing on characterizing and quantifying the interdependency between these components. This paper focuses on developing an algorithm, named CyberDep, for Bayesian network generation through conditional probability calculations of cyber traffic flows between system nodes. Additionally, CyberDep is implemented on the temporal data of the cyber-physical emulation of the WSCC 9-bus power system. The results of this work provide a visual representation of the probabilistic relationships within the cyber and physical components of the system, aiding in cyber-physical interdependency quantification.

Amna Aljubor, Salma Al Sheblawi

The research aims to study the electrical energy problems in the Najaf and Haidariah gas stations, as well as study the effects resulting from those problems, including health, environmental and economic problems. The problems that this energy sector suffers from vary, including problems of production, distribution, power transmission and others, and we will discuss that in some detail in the folds of this research The study aims to know the most important problems facing electrical energy and the resulting air pollution in the study area. The main problem of the research was represented by the following question: What are the electrical energy problems in the Najaf and Haidariah gas stations and what are the damages resulting from them. Expanding the establishment of new stations or increasing the capacities of the current stations and maintenance work for them on a regular basis, and there is a big difference between the actual (equipped) and consumed electric energy and the governorate’s need for this energy, and the consumption of electric energy in the governorate is characterized by fluctuation In general, this oscillation is related to power supply for various reasons.

Chao Dong, Ke Zhang, Zhiyuan Xie et al.

Abstract Overhead transmission line detection based on deep learning of aerial images taken by UAVs has been widely investigated. Despite its success, it is limited by several factors, including inappropriate evaluation criteria and dramatic scaling of components in the images. To mitigate these issues, a relative mean Average Precision evaluation index is proposed to accurately measure the model's detection performance for smaller objects. A data enhancement strategy including multi‐scale transformation is adopted to alleviate the problem of drastic scaling. The existing Cascade RCNN target detection technology is enhanced by incorporating Swin‐v2 and a balanced feature pyramid to improve feature characterization capabilities, while side‐aware boundary localization is utilized to improve the positioning accuracy of the model. Experimental results demonstrate that the proposed method outperforms state‐of‐the‐art methods on CPLID and achieves 7.8%, 11.8%, and 5.5% higher detection accuracy than the baseline for mAP50, relative small and medium mAP, respectively. Additionally, the paper discusses the influence of adopted data enhancement on the robustness of the model.

Moslem Dehghani, Taher Niknam, Mina GhasemiGarpachi et al.

Abstract The purpose of this paper is to examine cyber security issues related to smart grids (SGs), such as prior cyber‐attacks, possible vulnerability issues, and enhanced cyber‐security procedures for SGs on a technical and management basis. When designing public policies for SGs, it is important to consider both the motivations and obstacles to cyber protection and socio‐economic conditions. Furthermore, the importance of suggested policies is viewed from various perspectives. The present paper provides an assessment of a group of policies specified by various stakeholders as having the potential for developing SG cyber security. The methodology for the formation of such a group of policies includes a perfect examination of global experience and meetings with experts from various fields. Subsequently, such policies are evaluated using a Delphi questionnaire aimed at assessing their advantages in pursuing investment goals for cyber security. The first result is that every policy is considered a positive effect of all goals, different in the priority assigned to each of them. The policies that received the most attention were: “regulatory changes policy to foster innovation in cyber security of SGs,” “regulation of new business models to improve cyber security and detect malicious attacks” and “establish a cyber‐security governance strategy.”

Elmer Sorrentino, Andres Vera

Abstract This article shows a comparison of peak values of measured and computed waveforms of induction motor currents during nearby three‐phase short circuits with the results from the standardized calculations of those currents. The methods for computing short‐circuit currents according to IEC and ANSI standards are based on phasors at grid frequency, and the correspondent transient result is approximated to a simple sine wave plus a decaying DC component. However, the measured and simulated waveforms are far away from those simple waveforms. Thus, the peak values computed by standardized methods must be obviously different than the peak values of measured and simulated waveforms. It is herein shown that these differences are larger in smaller motors, and it is also shown that standardized methods to compute these motor currents are accurate enough although they are simply based on phasors at grid frequency. On the other hand, the maximum value of the first peak of motor contribution does not necessarily occur at the same time of the maximum first peak of grid contribution. This fact had been rarely mentioned, and an analysis about its influence was not found in the literature. Herein, it is shown that the influence of this point is not very important in the analyzed cases.

Alexandre Bach, Trung Dung Le, Marc Petit

Abstract This paper extends the study of a zero‐sequence impedance‐based fault location method (FLM) designed for medium voltage (MV) distribution feeders whose principle has been presented in a previous work Bach et al. This method is able to locate any type of earth fault with any type of neutral grounding inside a convex set of nodes forming the solution area. The total length of the lines inside this area is statistically computable a priori and depends only on the number and location of additional voltage measurements deployed on some remote end secondary substations. To be efficiently applied to the most challenging rural feeders presenting a lot of ramifications, simulations have shown a need for synchronized measurements, such as the ones obtained using phasor measurement units. Besides, this paper addresses the coupling potential of this method with more traditional ones such as Takagi‐based FLMs to enhance the performances of both, solving the multiple estimation problem while potentially locating the fault within one node. Finally, an extensive sensitivity analysis has been carried out, showing a good robustness with respect to impedance estimation errors or fault impedance values while showing the need for synchronization, especially on some remote measurement locations.

Rong Zeng, Jinliang He, Zhanqing Yu et al.

Qiang Fan, Jianzhong Xu, Tian Liang et al.

Abstract Modular multi‐level converters (MMCs) are a mainstay in many HVDC transmission projects worldwide. Half‐bridge MMC (HB‐MMC) is mostly used in the current project. The large capacitor of sub modules (SMs) is often required in MMC to ensure the low voltage ripple. Here, the three‐stage switching MMC (TSS‐MMC) topology is proposed, which can greatly reduce the capacitor voltage ripple of SMs by dynamically adjusting the position of inductance on the upper and down bridge arms. The principle of reducing capacitor voltage ripple based on equal capacitance theory is introduced. The selection of the inductance value of each part in TSS‐MMC is introduced. The start‐up process strategy, capacitor voltage ripple reduction strategy in steady‐state operation, and DC fault ride‐through strategy of TSS‐MMC are proposed. The effectiveness and engineering practicability of the proposed TSS‐MMC is verified by transient simulation program built on PSCAD/EMTDC. The simulation results show that compared with MMC with circulating current suppressing controller (CCSC), it can effectively reduce the capacitor voltage ripple by over 50%. Furthermore, the total used inductance of TSS‐MMC can also be reduced. A comprehensive assessment of TSS‐MMC is also carried out.

Zihao Xie, Zhaobin Du, Weixian Zhou et al.

Abstract With large‐scale wind farms connected to AC/DC network, the transient stability assessment (TSA) of the power system becomes more and more difficult. Among them, estimating the region of attraction (ROA) of the equilibrium point is a traditional but still challenging problem. Based on the Lyapunov stability theory, this paper proposes a new approach to obtain the enlarged estimation of the ROA. The optimization and updating strategy of shape function in the sum of squares (SOS) optimization problem are studied to reduce the conservatism of estimation result. In the proposed method, the gravitational search algorithm (GSA) is employed to optimize the coefficients of initial shape function to improve estimation performance. Based on the time‐domain simulation (TDS) of expected faults, the fitness value for shape function optimization is calculated using the values of state variables at the fault clearing time and the system stability information. Furthermore, the optimal Lyapunov function is computed by introducing the update condition of shape function and adjusting the iteration strategy of the ROA estimation algorithm. Finally, the proposed method is applied to a two‐machine‐infinite‐bus system and a more complex nine‐bus AC/DC system with wind power. And the effectiveness of the proposed method is verified by comparing with the existing ROA estimation methods.

Elena Gutierrez-Ballesteros, Sarah K. Ronnberg, Aurora Gil-De-Castro

The topology of a device will determine the impact said device has on the grid and how immune that device is for disturbances in the grid. LED lamps are very commonly used devices, with different topologies available in the market, each topology showing different behavior when connected to a grid. For power quality studies, it is important to classify LED lamps, without breaking them to know the topology. Several classification methods are found in the literature with this purpose. In this paper, four methods from different papers for classifying LED lamps have been applied to a group of 21 LED lamps with active power consumption below 25 W. It has been observed that the applicability of the methods may lead to a gap of knowledge needed for classification, leaving space for personal criteria when classifying, that can be afforded using unsupervised Machine Learning. Two unsupervised Machine Learning methods were applied using the electrical parameters and statistics proposed in literature.

Michael Abdelmalak, Narayan Bhusal, Mukesh Gautam et al.

This paper provides a strategy to identify layers and sub-layers of cyber-physical power systems (CPPS) and characterize their inter- and intra-actions. The physical layer usually consists of the power grid and protection devices whereas the cyber layer consists of communication, and computation and control components. Combining components of the cyber layer in one layer complicates the process of modeling intra-actions because each component has different failure modes. On the other hand, dividing the cyber layers into a large number of sub-layers may unnecessarily increase the number of system states and increase the computational burden. In this paper, we classify system layers based on their common, coupled, and shared functions. Also, interactions between the classified layers are identified, characterized, and clustered based on their impact on the system. Furthermore, based on the overall function of each layer and types of its components, intra-actions within layers are characterized. The strategies developed in this paper for comprehensive classification of system layers and characterization of their inter- and intra-actions contribute toward the goal of accurate and detailed modeling of state transition and failure and attack propagation in CPPS, which can be used for various reliability assessment studies.

Kejun Chen, Yu Zhang

Probabilistic power flow (PPF) analysis is critical to power system operation and planning. PPF aims at obtaining probabilistic descriptions of the state of the system with stochastic power injections (e.g., renewable power generation and load demands). Given power injection samples, numerical methods repeatedly run classic power flow (PF) solvers to find the voltage phasors. However, the computational burden is heavy due to many PF simulations. Recently, many data-driven based PF solvers have been proposed due to the availability of sufficient measurements. This paper proposes a novel neural network (NN) framework which can accurately approximate the non-linear AC-PF equations. The trained NN works as a rapid PF solver, significantly reducing the heavy computational burden in classic PPF analysis. Inspired by residual learning, we develop a fully connected linear layer between the input and output in the multilayer perceptron (MLP). To improve the NN training convergence, we propose three schemes to initialize the NN weights of the shortcut connection layer based on the physical characteristics of AC-PF equations. Specifically, two model-based methods require the knowledge of system topology and line parameters, while the purely data-driven method can work without power grid parameters. Numerical tests on five benchmark systems show that our proposed approaches achieve higher accuracy in estimating voltage phasors than existing methods. In addition, three meticulously designed initialization schemes help the NN training process converge faster, which is appealing under limited training time.

Behzad Moradi, Abbas Kargar, Sayed Yaser Derakhshandeh et al.

Abstract Transient stability is one of the major features of power systems operation which can be also considered an objective function in the flexible AC transmission systems (FACTS) allocation problem. This paper introduces a general multi‐level multi‐objective optimisation framework and its application on optimising the size and location of the improved hybrid flow controller (IHFC). IHFC is a new member of the FACTS family whose ability to control power flow and improve power system stability has been investigated. The optimisation problem considers economic and stability‐based objective functions simultaneously, and the allocation problem is formulated as a non‐linear programming (NLP) problem. The New England 39‐bus system has been used as a case study to demonstrate that the proposed framework can provide efficient and economically viable solutions to the allocation problem.

Lin Yang, Zhihao Hu, Lupeng Nian et al.

Abstract Freezing fraction and collision coefficient are the key parameters in the ice accretion model, which should be calculated to predict the icing trend for transmission lines. Here a mathematical relation between freezing fraction and collision coefficient was derived using the simplified head balance model of transmission lines icing. Combined with the empirical formula of the liquid water content in air, a calculation method of the freezing fraction and collision coefficient was proposed using the ice surface temperature of transmission lines and the icing mass growth rate. The method to measure the icing mass growth rate based on online monitoring data and icing experiments was proposed. The icing experiments were carried out in the low‐temperature ice chamber with the same parameters as the online monitoring environmental parameters. The values of the freezing fraction and collision coefficient were calculated by using the online monitoring data and icing experiments data respectively, the calculation results were compared. The maximum relative differences between the calculation results from the online monitoring data and the icing experiments data do not exceed 18%, which proves the validity of the calculation method of the freezing fraction and collision coefficient in ice accretion model of transmission lines.