Power equipment vibration visualization using intelligent sensing method based on event-sensing principle

Vibration measurements can be used to evaluate the operation status of power equipment and are widely applied in equipment quality inspection and fault identification.Event-sensing technology can sense the change in surface light intensity caused by object vibration and provide a visual description of vibration behavior.Based on the analysis of the principle underlying the transformation of vibration behavior into event flow data by an event sensor,this paper proposes an algorithm to reconstruct event flow data into a relationship correlating vibration displacement and time to extract the amplitude-frequency characteristics of the vibration signal.A vibration measurement test platform is constructed,and feasibility and effectiveness tests are performed for the vibration motor and other power equipment.The results show that event-sensing technology can effectively perceive the surface vibration behavior of power and provide a wide dynamic range.Furthermore,the vibration measurement and visualization algorithm for power equipment constructed using this technology offers high measurement accuracy and efficiency.The results of this study provide a new noncontact and visual method for locating vibrations and performing amplitude-frequency analysis on power equipment.

Aggregator-based demand response mechanism for electric vehicles participating in peak regulation in valley time of receiving-end power grid

With the increase in the power receiving proportion and an insufficient peak regulation capacity of the local units, the receiving-end power grid struggles to achieve peak regulation in valley time. To solve this problem while considering the potential of the large-scale charge load of electric vehicles(EVs), an aggregator-based demand response(DR) mechanism for EVs that are participating in the peak regulation in valley time is proposed in this study. In this aggregator-based DR mechanism, the profits for the power grid’s operation and the participation willingness of the EV owners are considered. Based on the characteristics of the EV charging process and the day-ahead unit generation scheduling, a rolling unit commitment model with the DR is established to maximize the social welfare. In addition, to improve the efficiency of the optimization problem solving process and to achieve communication between the independent system operator(ISO) and the aggregators, the clustering algorithm is utilized to extract typical EV charging patterns. Finally, the feasibility and benefits of the aggregator-based DR mechanism for saving the costs and reducing the peak-valley difference of the receiving-end power grid are verified through case studies.

Trust evaluation model of power terminal based on equipment portrait

As the number of power terminals continues to increase and their usage becomes more widespread,the security of power systems is under great threat.In response to the lack of effective trust evaluation methods for terminals,we propose a trust evaluation model based on equipment portraits for power terminals.First,we propose an exception evaluation method based on the network flow order and evaluate anomalous terminals by monitoring the external characteristics of network traffic.Second,we propose an exception evaluation method based on syntax and semantics.The key fields of each message are extracted,and the frequency of keywords in the message is statistically analyzed to obtain the keyword frequency and time-slot threshold for evaluating the status of the terminal.Thus,by combining the network flow order,syntax,and semantic analysis,an equipment portrait can be constructed to guarantee security of the power network terminals.We then propose a trust evaluation method based on an equipment portrait to calculate the trust values in real time.Finally,the experimental results of terminal anomaly detection show that the proposed model has a higher detection rate and lower false detection rate,as well as a higher real-time performance,which is more suitable for power terminals.

Double-ring high-frequency common-mode switching oscillation current sensor for inverter-fed machine winding insulation monitoring

Insulation failure significantly contributes to the unpredictable shutdown of power equipment.Compared to the partial discharge and high-frequency(HF)injection methods,the HF common-mode(CM)leakage current method offers a non-intrusive and highly sensitive alternative.However,the detection of HF CM currents is susceptible to interference from differential-mode(DM)currents,which exhibit high-amplitude and multifrequency components during normal operation.To address this challenge,this paper proposes a double-ring current sensor based on the principle of magnetic shielding for inverter-fed machine winding insulation monitoring.The inner ring harnesses the magnetic aggregation effect to isolate the DM current magnetic field,whereas the outer ring serves as the magnetic core of the Rogowski current sensor,enabling HF CM current monitoring.First,the magnetic field distributions of the CM and DM currents were analyzed.Then,a correlation between the sensor parameters and signal-to-noise ratio of the target HF CM current was established.Finally,an experimental study was conducted on a 3-kW PMSM for verification.The results indicate that the proposed double-ring HF CM sensor can effectively mitigate DM current interference.Compared to a single-ring sensor,a reduction of approximately 40%in the DM component was achieved,which significantly enhanced the precision of online insulation monitoring.

High-sensitive state perception method for inverter-fed machine turn insulation based on FrFT-Mel

Amidst the swift advancement of new power systems and electric vehicles,inverter-fed machines have progressively materialized as a pivotal apparatus for efficient energy conversion.Stator winding turn insulation failure is the root cause of inverter-fed machine breakdown.The online monitoring of turn insulation health can detect potential safety risks promptly,but faces the challenge of weak characteristics of turn insulation degradation.This study proposes an innovative method to evaluate the turn insulation state of inverter-fed machines by utilizing the fractional Fourier transform with a Mel filter(FrFT-Mel).First,the sensitivity of the high-frequency(HF)switching oscillation current to variations in turn insulation was analyzed within the fractional domain.Subsequently,an improved Mel filter is introduced,and its structure and parameters are specifically designed based on the features intrinsic to the common-mode impedance resonance point of the electrical machine.Finally,an evaluation index was proposed for the turn insulation state of inverter-fed machines.Experimental results on a 3kW permanent magnet synchronous machine(PMSM)demonstrate that the proposed FrFT-Mel method significantly enhances the sensitivity of turn insulation state perception by approximately five times,compared to the traditional Fourier transform method.

Analysis of basic conditions of the power grid interconnection among Xinjiang, Pakistan, and five Central Asian countries

Inter-regional and transnational grid interconnection is necessary for energy development. Xinjiang, which is rich in renewable energy resources, is adjacent to countries in Central Asia and has great potential for interconnection with its neighbors. This paper outlines China's relevant policies for transnational power interconnection, and introduces the energy structure, load demand endowments, and power supply status of Xinjiang, Pakistan, and five Central Asian countries. Further, it analyzes the advantages of the multinational power interconnection from the aspects of power supply and load complementation. Finally, from the perspective of technical support and practical basis, the feasibility of interconnection between Xinjiang, Pakistan, and five Central Asian countries have been analyzed. This paper provides a theoretical basis for promoting and implementing China's "Belt and Road" power transnational interconnected development strategy.

Insulation Diagnosis of Service Aged XLPE Power Cables Using Statistical Analysis and Fuzzy Inference

Cables that have been in service for over 20 years in Shanghai, a city with abundant surface water, failed more frequently and induced different cable accidents. This necessitates researches on the insulation aging state of cables working in special circumstances. We performed multi-parameter tests with samples from about 300 cable lines in Shanghai. The tests included water tree investigation, tensile test, dielectric spectroscopy test, thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), and electrical aging test. Then, we carried out regression analysis between every two test parameters. Moreover, through two-sample t-Test and analysis of va- riance (ANOVA) of each test parameter, we analyzed the influences of cable-laying method and sampling section on the degradation of cable insulation respectively. Furthermore, the test parameters which have strong correlation in the regression analysis or significant differ- ences in the t-Test or ANOVA analysis were determined to be the ones identifying the XLPE cable insulation aging state. The thresholds for distinguishing insulation aging states had been also obtained with the aid of statistical analysis and fuzzy clustering. Based on the fuzzy in- ference, we established a cable insulation aging diagnosis model using the intensity transfer method. The results of regression analysis indicate that the degradation of cable insulation accelerates as the degree of in-service aging increases. This validates the rule that the in- crease of microscopic imperfections in solid material enhances the dielectric breakdown strength. The results of the two-sample t-Test and the ANOVA indicate that the direct-buried cables are more sensitive to insulation degradation than duct cables. This confirms that the tensile strength and breakdown strength are reliable functional parameters in cable insulation evaluations. A case study further indicates that the proposed diagnosis model based on the fuzzy inference can reflect the comprehensive aging state of cable insulation well, and that the cable service time has no correlation with the insulation aging state.

Predicting of Power Quality Steady State Index Based on Chaotic Theory Using Least Squares Support Vector Machine

An effective power quality prediction for regional power grid can provide valuable references and contribute to the discovering and solving of power quality problems. So a predicting model for power quality steady state index based on chaotic theory and least squares support vector machine (LSSVM) is proposed in this paper. At first, the phase space reconstruction of original power quality data is performed to form a new data space containing the attractor. The new data space is used as training samples for the LSSVM. Then in order to predict power quality steady state index accurately, the particle swarm algorithm is adopted to optimize parameters of the LSSVM model. According to the simulation results based on power quality data measured in a certain distribution network, the model applies to several indexes with higher forecasting accuracy and strong practicability.

Research on power electronic transformer applied in AC/DC hybrid distribution networks

The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/DC hybrid distribution network is put forward according to the demands of power grid, with advantages of accepting DG and DC loads, while clearing DC fault by blocking the clamping double sub-module(CDSM) of input stage. Then, this paper shows the typical structure of AC/DC distribution network that is hand in hand. Based on the new topology, this paper designs the control and modulation strategies of each stage, where the outer loop controller of input stage is emphasized for its twocontrol mode. At last, the rationality of new topology and the validity of control strategies are verified by the steady and dynamic state simulation. At the same time, the simulation results highlight the role of PET in energy regulation.

The Visualization Analysis of Research Hotspot and Frontier Technology of the Smart Power Distribution and Utilization Based on the Cite Space

In order to make an intensive study of the development of smart power distribution and utilization technology in China, their research hotspots and frontier technology are selected out through combining the informatics method, and using the CiteSpace which can take keyword cooccurrence analysis and draw the visualization graph. According to this result, we can infer the development trend of smart power distribution and utilization in the future, and providing reference for the researcher whose engage in this domain. The electric related literature was collected from the CNKI database in China. Under the smart power distribution and utilization domain, we also analyze the development of the power quality and the energy internet in detail.

Research on Power Quality Evaluation Based on Radar Chart Method and Fuzzy Membership Degree

Aiming at the current limit value of six steady-state energy indexes, the current radar method is used for reference. A method of comprehensive evaluation of power quality based on improved radar method is proposed, which improves the power quality index Type radar pattern to represent the steady-state indicator. Each of the main indicators corresponds to a partial ring, and the angle of the annular portion is mainly affected by the size of the weight. Compared with the previous radar map method to maintain the independence of the indicators and a single indicator of the binding data assessment. The method has the advantages of good feasibility.

Repulsive firefly algorithm-based optimal switching device placement in power distribution systems

To achieve optimal configuration of switching devices in a power distribution system,this paper proposes a repulsive firefly algorithm-based optimal switching device placement method.In this method,the influence of territorial repulsion during firefly courtship is considered.The algorithm is practically applied to optimize the position and quantity of switching devices,while avoiding its convergence to the local optimal solution.The experimental simulation results have showed that the proposed repulsive firefly algorithm is feasible and effective,with satisfying global search capability and convergence speed,holding potential applications in setting value calculation of relay protection and distribution network automation control.

Research on the Effects of the Most Used Market Power Mitigation Mechanisms Considering Different Market Environments

The market power mitigation method of the supply-side has become one of the key points affecting the stability of the electricity spot market.Different mitigation mechanisms are used in the current mature electricity markets of the world.However,the same market power mitigation mechanism shows different effects in different market environments.Every market operator in the world needs the most efficient way to mitigate market power.Considering that there is no relevant literature discussing the market power effects of different mitigation methods in detail,the mitigation effects need to be discussed and further researched.So,we analyze the effects of the most utilized market power mitigation mechanisms while considering different market environments.Firstly,we establish a Nash-Stackelberg interactive game model to simulate the competitive strategies of power suppliers.Secondly,the different market power mitigation approaches are modeled.Then,a multi-agent system(MAS)genetic interior-point algorithm is proposed to solve the problem of suppliers.Finally,through the simulation analysis,the market power mitigation effects of different mechanisms while considering three operation states of the system in two market structures are all analyzed.

Sensorless Control on a Dual-Fed Flux Modulated Electric Motor

This paper proposes the operation principle and a new flux estimation method for sensorless control strategy for the dual-fed flux modulated electric motor(DFFM).The DFFM is designed based on the flux modulation theory,it includes two stator windings and one rotor which simplify the mechanical structure.The rotor has only modulation iron and no permanent magnets on it,so there is no cogging torque problem in this motor.With adjustment of the outer and inner stator flux rotating frequency and amplitude,different rotation speed and torque of the sandwiched rotor can be gained for the DFFM.Furthermore,an improved flux estimation based sensorless control strategy is performed on the proposed machine to fit the two winding set control situation.The startup and performance of the proposed control strategy is verified by the simulation and experiments.

Endogenous Security-Aware Resource Management for Digital Twin and 6G Edge Intelligence Integrated Smart Park

The integration of digital twin(DT)and 6G edge intelligence provides accurate forecasting for distributed resources control in smart park.However,the adverse impact of model poisoning attacks on DT model training cannot be ignored.To address this issue,we firstly construct the models of DT model training and model poisoning attacks.An optimization problem is formulated to minimize the weighted sum of the DT loss function and DT model training delay.Then,the problem is transformed and solved by the proposed Multi-timescAle endogenouS securiTy-aware DQN-based rEsouRce management algorithm(MASTER)based on DT-assisted state information evaluation and attack detection.MASTER adopts multi-timescale deep Q-learning(DQN)networks to jointly schedule local training epochs and devices.It actively adjusts resource management strategies based on estimated attack probability to achieve endogenous security awareness.Simulation results demonstrate that MASTER has excellent performances in DT model training accuracy and delay.

Current Control Strategy of Chain Circuit STATCOM

在链式静止同步补偿器（static synchronous compen-sator,STATCOM）小信号交流模型的基础上,提出简化的STATCOM电流控制闭环系统;分别对典型Ⅰ型、典型Ⅱ型控制系统的电流调节器进行参数优化及比较,分析表明,对于电流阶跃响应,系统处于线性控制状态时超调量相对百分比不变,处于限幅非线性状态时超调量绝对值不变;采用比例调节器的典型I型系统稳态精度稍差,但动态控制精度较高,适合用于链式STATCOM工程装置;在a-b-c坐标系下仿真表明,应用优化设计的典型Ⅰ型系统控制参数,链式STATCOM输出电流可以快速跟踪参考值变化,具有良好的稳定性和跟踪精度。

用于现场老化交联聚乙烯电力电缆的降解评估参数（英文）

The cables are more likely to deteriorate after several years of service in Shanghai,a city with a humid climate and abundant rainfall.Before assessing the aging status of those cables,it is critical to present effective test parameters which are sensitive to the aging process under special field conditions.Therefore,we have performed water tree investigation,tensile test,and differential scanning calorimetry(DSC)test on hundreds of cable samples removed from service.A large number of typical bowtie water trees were found in cable insulation and the water tree content was proposed to characterize the degree of water treeing.Based on Arrhenius Equation and equivalent thermal history parameters estimated from DSC profiles,we also proposed a new parameter ln(t/τθ)to characterize the aging status of cable insulation,Where,t is treated duration andτθis the thermal life under treated temperature.The applicabilities of water tree content,tensile strength,and ln(t/τθ)are tested using the analysis of variance(ANOVA).Then we investigated the relationship between the tensile strength and the water tree content using regression analysis,and analyzed the relationship between ln(t/τθ)and the tensile strength.The results indicated that each of these parameters performs differently with cables which experienced different degrees of age related degradation,and can be used to identify the aging status of field aged cables.The tensile strength can reflect the water treeing condition of field aged cables very well as a commonly used functional parameter.Since ln(t/τθ)is strongly related to the tensile strength,it is an effective parameter to characterize the aging status of field aged cable insulation.Using this newly proposed parameter is more time saving because of the convenience in sampling.

Research progress of the electrochemical impedance technique applied to the high-capacity lithium-ion battery

The world's energy system is changing dramatically.Li-ion battery,as a powerful and highly effective energy storage technique,is crucial to the new energy revolution for its continuously expanding application in electric vehicles and grids.Over the entire lifetime of these power batteries,it is essential to monitor their state of health not only for the predicted mileage and safety management of the running electric vehicles,but also for an"end-of-life"evaluation for their repurpose.Electrochemical impedance spectroscopy(EIS)has been widely used to diagnose the health state of batteries quickly and nondestructively.In this review,we have outlined the working principles of several electrochemical impedance techniques and further evaluated their application prospects to achieve the goal of nondestructive testing of battery health.EIS can scientifically and reasonably perform real-time monitoring and evaluation of electric vehicle power batteries in the future and play an important role in vehicle safety and battery gradient utilization.

Investigation of the performance of CF3I/c-C4F8/N2 and CF3I/c-C4F8/CO2 gas mixtures from electron transport parameters

CF3I gas mixtures have attracted considerable attention as potential environmentally-friendly alternatives to SF6 gas,owing to their excellent insulating performance.This paper attempts to study the CF3I ternary gas mixtures with c-C4F8 and buffer gases N2 and CO2 by considering dielectric strength from electron transport parameters based on the Boltzmann method and synergistic effect analysis,compared with SF6 gas mixtures.The results confirm that the critical electric field strength of CF3I/c-C4F8/70%CO2 is greater than that of 30%SF6/70%CO2 when the CF3I content is greater than 17%.Moreover,a higher content of c-C4F8 decreases the sensitivity of gas mixtures to an electric field,and this phenomenon is more obvious in CF3I/c-C4F8/CO2 gas mixtures.The synergistic effects for CF3I/c-C4F8/70%N2 were most obvious when the c-C4F8 content was approximately 20%,and for CF3I/c-C4F8/70%CO2 when the c-C4F8 content was approximately 10%.On the basis of this research,CF3I/c-C4F8/70%N2 shows better insulation performance when the c-C4F8 content is in the15%–20%range.For CF3I/c-C4F8/70%CO2,when the c-C4F8 content is in the 10%–15%range,the gas mixtures have excellent performance.Hence,these gas systems might be used as alternative gas mixtures to SF6 in high-voltage equipment.

Research on characteristics of acoustic signal of typical partial discharge models

The pulse current method,acoustic and ultrasonic partial discharge(PD)detection,and voiceprint PD detection are commonly used detection methods for the PD detection of power equipment.To study the characteristics of PD signals of typical discharge models based on the principles of the above three detection methods,an acoustic detection experimental system consisting of a needle-tip model and a surface model was built.Acoustic tests were carried out on needle-tip models with different curvature radii and surface discharge models with different lengths of conductive paste.The experimental results showed that acoustic and ultrasonic PD detection and voiceprint PD detection exhibited different sensitivities to the needle-tip discharge models,and the combination of acoustic and ultrasonic PD and voiceprint PD detection was more beneficial for the comprehensive detection of cable PD signals.Based on voiceprint recognition technology,this study drew FFT(Fast Fourier Transformation)diagrams of different types of PD acoustic signals and analyzed the differences in the ultrasonic signal frequency distribution.The frequency band of the voiceprint PD signal of the needle-tip discharge models was concentrated in the range 17-27 kHz,and the frequency band of the voiceprint PD signal of the conductive paste discharge models was concentrated in the range 20-25 kHz.The measurement of voiceprint PD signals in these frequency bands were strengthened when the PD of a cable was detected on-site,which provides the basis for the use of the cable model for on-site PD detection.