Hasil untuk "Distribution or transmission of electric power"

Abduljalil S. Aljadani, Firdous U. Nazir, Bikash C. Pal et al.

The large penetration of distributed generations impacts both the secondary low-voltage (LV) and the primary medium-voltage (MV) segments of the distribution network. Optimizing power flow calculations for the integrated MV/LV networks is crucial for the real-time management of modern distribution networks. Traditional methods in symmetrical coordinates are primarily limited to the three-wire model of three-phase networks, often leading to inaccuracies in power flow calculations when applied to three-phase four-wire LV segments. This paper introduces a novel power flow method for integrated three-wire MV and four-wire LV networks. Using eigenvector decomposition to diagonalize the admittance matrix of four-wire LV lines, the proposed method improves the computational efficiency of power flow calculations and accurately calculates the neutral-to-ground voltage. The results of the case studies show over 50\% reduction in the number of non-zero elements in the LU factors of the bus admittance matrix, and speed-up factors of 2.78 on the IEEE 123-node test system and 3.63 on the IEEE 8500-node test system in execution times for Volt/Var control (VVC), compared to the phase coordinates model.

Yufei Chen, Yong Wei, Jinxin Cao et al.

Fatemeh Esmaeili, Hamid Reza Koofigar

Abstract Herein, the load power control of the stand‐alone photovoltaic‐battery hybrid power system (HPS) has been investigated. The underlying HPS consists of a boost DC‐DC converter, a non‐isolated bidirectional half‐bridge converter, a photovoltaic (PV) panel, and a battery pack. On the PV side, a disturbance observer‐based finite‐time terminal sliding mode control (FTSMC) is used to regulate the DC bus to the desired voltage, in the presence of irradiation variation and load changes. On the battery side, the load power control system is constructed, based on a model predictive control (MPC) algorithm, with constraints on state‐of‐charge (SOC) and maximum current value of the battery to improve the battery life cycle and high reliability of the system. To highlight the benefits of the closed‐loop system, the analytical proofs and numerical analysis are presented from a comparative viewpoint. The experimentally derived results, by implementation on TMS320F28335 digital signal processing (DSP), are also presented and discussed for practical justification.

Mohammad Hasan Hemmatpour

Abstract In power systems, voltage collapse during overload can be a significant threat. Accurate forecasting of critical operational conditions within power grids is crucial for preventing such situations. Precise predictions of voltage collapse enable operators to monitor the system closely and implement necessary corrective measures promptly, avoiding potential issues. However, monitoring networks can be costly due to the numerous loads and transformers in the distribution system. A comprehensive approach known as the voltage stability index (VSI) forecast without measurement buses (VFWMB) has been introduced to address this challenge. This approach involves innovative methods, including the seeking observation zone with weight least square (SOZWLS) technique for determining the number and location of measurements in the network based on its topology. Additionally, short‐term load forecasting is performed using the long short‐term memory (LSTM) forecasting method, followed by voltage estimation for buses without measurements. Finally, the proposed method calculates the modern voltage stability index for distribution systems (MVSIDS) for upcoming hours. All indicators and techniques in the VFWMB method have been validated. The algorithm has been thoroughly tested on various networks, including small and large, balanced and unbalanced, and both real and test networks, showing high efficiency in the electricity industry.

Atul S. Koshti, Aanchal Verma, Rajesh Arya et al.

Abstract This paper presents a novel tolerable random interruption duration (TRID) concept for estimation of reliability indices of stand‐alone hybrid renewable energy system (SAHRES) during down time. This concept utilizes the ignorance of interruption duration if it is tolerable in event of failure. It uses a framework using network reduction technique and sequential Monte Carlo simulation (SMCS) suitable for present research whereas the solution in such cases is not feasible with analytical method. Thus reliability indices such as mean up time, mean down time, failure frequency, system failure rate, interruption duration and system unavailability are estimated using SMCS. Modelling aspects are considered for load, capacity, renewable energy system and TRID due to network outage. The impact of considering random tolerable interruption duration has been demonstrated on the reliability indices and case study is presented to show the effect of change of TRID on reliability indices. A sample SAHRES has been considered for the study.

Jingxin Zhang, Uzair Bin Tahir, Richard Manasseh

The reactive Power Take Off (PTO) force is the key to maximizing mechanical power absorption and electric power generation of Wave Energy Converters (WECs) from ocean waves with variable frequency, but its study is limited due to its difficulty in physical realization. This paper presents a simple yet effective $LC$-tuned WEC that generates a tunable reactive PTO force from tunable inductor $L$ and capacitor $C$ in the WEC. A complete closed loop system model of the WEC is derived first, then three quantitative rules are obtained from analyzing the model. These rules are used to tune the $LC$ network, and hence the reactive PTO force that drives the WEC, to resonate with the input wave force and generate maximal electric power over a range of wave frequencies. Mathematical analysis of the WEC and tuning rules reveals the analytical and quantitative descriptions of the WEC's mechanical power absorption, active and reactive electric power generation and power factor, optimal electric resistance load, and the generator and $LC$ capacity requirements. Simulation results show the effectiveness and advantages of the proposed WEC and verify the analysis results.

Yingrui Zhuang, Lin Cheng, Ning Qi et al.

Scenario reduction (SR) aims to identify a small yet representative scenario set to depict the underlying uncertainty, which is critical to scenario-based stochastic optimization (SBSO) of power systems. Existing SR techniques commonly aim to achieve statistical approximation to the original scenario set. However, SR and SBSO are commonly considered as two distinct and decoupled processes, which cannot guarantee a superior approximation of the original optimality. Instead, this paper incorporates the SBSO problem structure into the SR process and introduces a novel problem-driven scenario reduction (PDSR) framework. Specifically, we project the original scenario set in distribution space onto the mutual decision applicability between scenarios in problem space. Subsequently, the SR process, embedded by a distinctive problem-driven distance metric, is rendered as a mixed-integer linear programming formulation to obtain the representative scenario set while minimizing the optimality gap. Furthermore, <i>ex-ante<i> and <i>ex-post<i> problem-driven evaluation indices are proposed to evaluate the SR performance. Numerical experiments on two two-stage stochastic economic dispatch problems validate the effectiveness of PDSR, and demonstrate that PDSR significantly outperforms existing SR methods by identifying salient (e.g., worst-case) scenarios, and achieving an optimality gap of less than 0.1% within acceptable computation time.

Heshmatollah Nourizadeh, Mostafa Ghadiri, Hassan Bashiri et al.

Yousef Fattahyan, Nabiollah Ramezani, Iraj Ahmadi

Abstract Generally, wind speed alters continuously during a day and leads to fluctuating output power of a wind farm (WF). Connecting such a WF to the transmission line of grid causes a malfunction in the performance of the backup zone of the distance relays due to the random nature of generation and the number of connected wind turbines (WF penetration). In this study, a new adaptive setting groups‐based method has been proposed to set the second zone of the distance relay in the grid with a WF equipped with a doubly fed induction generator. In this method, the authors have also taken into account the uncertainty of wind fluctuations and the availability of WT. A Markov model is developed to implement these features. To determine the impedance setting of each of the set groups of the second zone in the distance relays of the remote bus, the obtained impedances are clustered in four clusters by using the combination of K‐means and particle swarm optimization algorithms. Finally, the details of the analysis results of this issue have been compared with other methods available in the literature. The validity and accuracy of the proposed approach also have been assayed and confirmed.

Hui Ma, Yu Du, Jingyu Shen et al.

Abstract The objective of this paper is to determine the transient characteristics and sites of the pre‐breakdown (pre‐BD) in the spark conditioning under power frequency voltage (PFV) in vacuum. A multi‐angle optical path system was designed and made the determination of the pre‐BD sites in spark conditioning possible, through one camera at two viewing angles. The experimental results indicate that, in the spark conditioning under PFV, the pre‐BDs continuously occurred at a random moment. Within several half‐waves, the number of the pre‐BDs could reach dozens of times, which was the key for the treatment of the electrode surface in conditioning. Under the application of PFV, the single pre‐BD occurred at a random moment, in which it would last for several microseconds and the peak value of the current would reach several amperes. Moreover, the pre‐BD sites randomly distributed in the surface of the electrode and almost covered the whole surface of the electrode. The pre‐BDs took place independently in both time and space, in which there should be no effect between each other of two sequential pre‐BDs. To sum up, the transient characteristics and the sites of the pre‐BDs determined in this paper could reveal the physical mechanism of the pre‐BD on the treatment of electrode surface in the conditioning process, which is quite significant to improve the BD voltage of vacuum interrupter.

Poria Astero, Feifei Bai, Vahid Disfani et al.

Yijun Chen, Kanghong Shi, Ian R. Petersen et al.

In the transition to net zero, it has been suggested that a massive expansion of the electric power grid will be required to support emerging renewable energy zones. In this paper, we propose the use of battery-based feedback control and nonlinear negative imaginary systems theory to reduce the need for such an expansion by enabling the more complete utilization of existing grid infrastructure. By constructing a novel Lur'e-Postnikov-like Lyapunov function, a stability result is developed for the feedback interconnection of a nonlinear negative imaginary system and a nonlinear negative imaginary controller. Additionally, a new class of nonlinear negative imaginary controllers is proposed to deal with actuator saturation. We show that in this control framework, the controller eventually leaves the saturation boundary, and the feedback system is locally stable in the sense of Lyapunov. This provides theoretical support for the application of battery-based control in electrical power systems. Validation through simulation results for single-machine-infinite-bus power systems supports our results. Our approach has the potential to enable a transmission line to operate at its maximum power capacity, as stability robustness is ensured by the use of a feedback controller.

Charleston Dale M. Ambatali, Shinichi Nakasuka, Bo Yang et al.

The retrodirective antenna array is considered as a mechanism to enable target tracking of a power receiver for long range wireless power transfer (WPT) due to its simplicity in implementation using only analog circuits. By installing the retrodirective capability on both the generator and rectenna arrays, a feedback loop that produces a high efficiency WPT channel is created. In this paper, we characterize the dynamics of this phenomenon using a discrete-time state-space model based on S-parameters and show that the system can naturally achieve maximum theoretical WPT efficiency. We further confirmed the theoretical analysis through a hardware experiment using a 12-port circuit board with measurable S-parameters mimicking a static wireless channel. The results collected from the hardware experiment show agreement with the proposed theoretical framework by comparing the theoretical efficiency with the measured efficiency and by showing that the collected data points follow the predicted condition to achieve maximum efficiency.

Vasileios A. Evangelopoulos, Pavlos S. Georgilakis

Se Hoon Baik, Yong Tae Yoon, Young Gyu Jin et al.

Abstract Imbalance band market is an alternative to traditional market structures which is proposed to ensure that system frequency remains within acceptable bounds. In an imbalance band market environment, the load‐serving entities (LSEs) can purchase bands or reduce the load deviation by operating a battery energy storage system (BESS) to avoid the penalty for causing imbalance. The market concept would be effective in sharing balancing responsibility between a system operator (SO) and load‐serving entities. In this study, the authors proposed a planning framework for a load serving entity (LSE) considering cloud energy storage (CES) business as a useful resource in the imbalance band market environment. The term of cloud energy storage is used as a platform that the operator owns and operates the storage, while subscribed clients pay a service fee for requesting charging and discharging operations. The simulation results show that operating cloud energy storage business is economically rational strategy for the LSE. The authors verified that a LSE operating the cloud energy storage business under an imbalance band market environment to pursue its own benefit better performs a part of the balance‐maintaining obligation of the SO compared with a LSE not operating the cloud energy storage business.

Lizhou Jiang, Xin Li, Tao Long et al.

Abstract The large‐scale blackouts of distribution systems (DS) caused by extreme natural disasters have aroused a lot of attention. To enhance the resilience of DSs, a novel service restoration and recovery model to minimize the system‐wide load loss is proposed here, where reconfiguration systems and two kinds of moveable resources, that is, mobile sources (MS) and repair crews (RC), are considered. Then, time‐space network (TSN) is applied to model the movement of MSs and RCs over the real‐world transportation networks (TN). However, the introduction of TSN makes solving the model become a time‐consuming task as plenty of variables are involved by it. To tackle this challenge which may lead to the impracticability of the model, a Floyd‐algorithm based TN simplification method is proposed to reduce the variables without sacrificing the equivalence of the TNs before and after the transformation. Finally, the applicability and effectiveness of the proposed model are verified on a 33‐bus test DS and a real‐world DS with complicated TNs.

Xingwu Yang, Zhicheng Meng, Xinyi He et al.

Abstract LCL grid‐connected inverter is good at suppressing the high frequency current, but the inherent resonance frequency of the filter will lead to the resonance peak. Therefore, the active damping is commonly used to suppress the resonance effect. Since the weighted average current control can provide better bandwidth for the system with high frequency and has the characteristics of system reduction, it is often used to replace the traditional dual‐loop current control in the application of LCL grid‐connected inverter. However, the reduction of current resonance peak at the grid side by the weighted average current control is limited, so it is necessary to combine the grid voltage and capacitor current feedback loop to achieve the ideal results. In weak grid, the newly added feedback path would easily lead to the loss of system reduction, which results in the existence of transient variables in the transfer function affecting the stability of the control strategy. To solve this technical problem, this paper addresses a new control method of LCL grid‐connected inverter based on weighted average current control. By adding a capacitor current feedback path, pole‐zero cancellation of the control system is realised as to reduce the systematic order and improve the robustness of the controller under the time‐varying weak grid.

Ziyu Wang, Jingyu Wang, Dongyuan Shi et al.

Abstract Extensive adoption of Information and Communication Technologies makes power systems and communication systems more tightly coupled to form cyber‐physical power systems. It causes power systems to be growingly susceptible to cyber contingencies. Cyber contingencies may sabotage measurement availability, further disrupt the observability analysis in state estimation, and thus threaten the stable operation of power systems. This paper investigates the impact of cyber contingencies on measurement availability. A workflow is presented to achieve accurate and meticulous impact identification under intricate communication architectures with various cyber contingencies. And a set of indicators are proposed to quantitatively evaluate measurement availability. Case studies demonstrate that the proposed method is effective in identifying and assessing the impact of cyber contingencies on measurement availability. Meanwhile, the proposed workflow and indicators can also be employed to dynamically evaluate the system's resilience in protecting measurement transmission against hypothetical cyber contingencies, which could benefit the offline planning and online operation of cyber‐physical power systems

Yixiang CHEN, Qibo HUANG, Xiaoqun QIN et al.

Based on hydrodynamic conditions of the shallow karst groundwater seepage, we mainly study the natural polarization phenomenon of geological structures in water-enriched karst induced by the action of groundwater seepage and distribution characteristics of the natural electric field therefrom. By comprehensive prospecting with the combination of self-potential method and high-density electronic resistivity method, we analyse and evaluate the application effect of the combination on the exploration of karst groundwater in different hydrogeological environments of middle and lower reaches of Xijiang River. In this study, we also integrate geophysical prospecting results with the data derived from exploration & production wells in the survey project of hydrogeological environment initiated and supported by China Geological Survey. Study results show that induced electrical methods, such as transient electromagnetic method, audio magnetotelluric sounding method, ground nuclear magnetic resonance method, induced polarization method, sonic frequency geoelectric field method, VLF electromagnetic method, etc., are seriously affected by electromagnetic fields like power transmission and communication network. The high-density resistivity method shows a strong anti-interference ability and high signal-to-noise ratio. But its exploration depth is relatively shallow, and it is easily disturbed by ore bodies with high conductivity such as charry limestones or karst minerals. The self-potential method is used in the situation of polarization of geological structures in water-enriched karst caused by groundwater migration. Anomalies of the natural electric field are closely related to the groundwater recharge and migration. The complementation of self-potential method and high-density electronic resistivity method in groundwater exploration can contribute to the mutual corroboration of prospecting results, hence improving prospecting resolution and precision.

Jing Ma, Jiaming Zhang, Wangyang Du et al.

Abstract Concerning the difficulty in determining the restart strategy for AC/DC interconnected systems, this paper proposes a method of calculating the optimal restart strategy for AC/DC interconnected systems based on dynamic energy. First, a dynamic energy function that characterises the stability of system is constructed. Then, the analytical expressions of the dynamic energy function are calculated separately for the deionisation stage, the restart stage, and the alpha retard stage of the entire restart process. On this basis, the variation rate of the system dynamic energy is defined as the energy accumulation rate, which quantifies the accumulation or consumption of dynamic energy during the restart process, and facilitates detailed analysis of the effects of the restart time and restart duration on the stability of system. Then, a method to calculate the optimal restart time is proposed with the goal of minimising the dynamic energy accumulated in the system. Finally, hardware‐in‐the‐loop tests are carried out on the RT‐LAB platform for simulation verification. The experimental results show that the dynamic energy function constructed in this paper can reflect the stability of system. Using the proposed optimal restart strategy can reduce the accumulation of dynamic energy and improve the stability of system.