最新刊期
卷 45 ， 期 6 ， 2024
- 摘要：With the increasing proportion of centralized and distributed new energy in the distribution network，the fluctuation and intermittency characteristics of these new energy cause more significant impact on the distribution network，which leads to frequent voltage fluctuations in the distribution network and brings unprecedented challenges to the reactive power support and voltage stability. In this paper，the voltage stability of the power grid operation due to the withdrawal of the reactive power compensation device of the new energy station is studied. The permitted maximum power generation output of the new energy station is studied from the aspects of theoretical compensation and system simulation when the static var generator of new energy station is removal from operation due to the maintenance or fault and also with consideration of the voltage variation of the gird connection point. The simulation results show that after the out of operation of the reactive power compensation device of the new energy station for some reason，the maximum active output of the photovoltaic power station is about 20% of the total installed capacity when the peak power load of the new energy station is required to give full play to the peak role. This conclusion can effectively guide the power dispatching agency to accurately control the power generation output of the new energy station so to improve operation efficiency and voltage stability of the power grid，and enhance the coordination and management ability of the dispatching agency to the power grid and the power supply.关键词：new energy;reactive power compensation;power grid operation;voltage stability42|135|0更新时间：2024-12-27
Reactive Power Compensation and Filter
- 摘要：Film capacitor，as a basic electronic component，is widely used in fields such as energy，military and medical treatment. The metallized film capacitor，compared to foil film capacitor，exhibits excellent features such as small size，low loss and high reliability. However，there are currently some difficulties in thickness measurement，microstructure observation and stress detection for metallized films used in capacitors. In this paper，the research progress and existed specific problems of the metallized films for capacitors in above aspects are summarized and corresponding suggestions are proposed in order to provide theoretical guidance for the development of metallized film capacitors.关键词：film capacitors;metallized films;film thickness measurement;microstructure;stress detection53|108|0更新时间：2024-12-27
- 摘要：Film capacitor is the key component of power electronic system and its reliability is highly related to the stable operation of the power equipment. However，voltage and temperature are the critical factors affecting aging of the capacitor. In this paper，the polypropylene film capacitor is taken as the object. The electrothermal stress accelerated aging test platform is set up，the life of the film capacitor is extracted under different temperatures and voltages and the Arrhenius model and exponential model are combined to study the life prediction of the film capacitor. The study results show that with the increase of temperature and voltage the life of the capacitor is reduced significantly，in which the influence of voltage on the aging of the film capacitor is more significant than that of the temperature. This study helps to further analyze the mechanism of electrothermal stress on the aging of thin film capacitor and can be used for life prediction to improve reliability of the system.关键词：film capacitor;accelerated aging;voltage;temperature40|186|0更新时间：2024-12-27
- 摘要：In this paper，a case of negative dielectric loss duringon-site hand-over test of a parallel capacitor for 500 kV circuit breaker is introduced. It is found through on-site inspection and principle analysis that the wood support structure beneath the parallel capacitor is damped and T-type network is formed.，causing the measured dielectric loss to be negative. In order to explore the influence of each parameter of this T-type network on the capacitance and dielectric loss of the tested object，an equivalent circuit analysis is performed on the T-type network. Matlab is used for simulation analysis. It is found that the measurement error of the capacitance and dielectric loss of the tested object is increased with the increase of stray resistance to ground. With the increase of stray capacitance，the error of dielectric loss is increased firstly and then decreased. The error of capacitance is continued to increase，and the influence of stray resistance is opposite to that of stray capacitance. As for the test environment at site，the corresponding specific measures are proposed so to provide experience reference for the on-site testing of the relevant equipment.关键词：negative dielectric loss;supporting structure;T-type network;simulation analysis;error18|24|0更新时间：2024-12-27
Capacitor
- 摘要：Capacitive voltage transformer is an important detection and protection equipment in substation. In this paper，related suggestions of such aspects as design，operation and maintenance of the capacitive voltage transformer are provided through analysis of the multiple types of faults of the capacitive voltage transformer in operation. Firstly，5 types of typical fault and 1 type of misdiagnosis phenomena of capacitive voltage transformers in 500 kV、±500 kV and 1 000 kV substations are analyzed. Then，the causes of such faults as oil leakage of the capacitive voltage transformer，abnormity of capacitor unit and electromagnetic unit are deeply analyzed in accordance with the real fault example of the voltage transformer at site and also in combination with its working principle，operating condition，diagnostic data and disassembly at the factory etc. Finally，as for the misjudgement of self excitation of dielectric electric bridge，the cause of its occurrence is analyzed by reasonable calculation，and verified by Matlab/Simulink simulation model and field test. The experimental results are consistent with the theoretical calculation.关键词：capacitive voltage transformer;fault;capacitor unit;electromagnetic unit;abnormal voltage;self-excitation30|142|0更新时间：2024-12-27
- 摘要：A discharge accident of the electromagnetic unit of 110 kV capacitive voltage transformer（CVT）is introduced in this paper. It is judged throughout such analysis as appearance inspection，oil spectrum test，electrical test and internal disassembly of the electromagnetic unit of the faulty CVT that the accident is caused by the lax seal due to foreign objects at the flange connection between the capacitor unit and the electromagnetic unit. The moisture penetrating into the electromagnetic unit causes the insulation to become damp，thus reducing strength and resulting in discharge. The fault reflects the deficiencies in the overall testing and foreign object detection methods during the production stage of the equipment，and specific sug-gestions and preventive measures are proposed for safe operation of CVT in the future.关键词：CVT;electromagnetic unit;discharge19|69|0更新时间：2024-12-27
- 摘要：In view of overheating，insulation cracking and even damage of instrument transformer due to ferromagnetic resonance of the dead tank electromagnetic potential transformer（PT）in the gas insulated metal enclosed switchgear（GIS），a method for identifying the ferromagnetic resonance of the instrument transformer in GIS is proposed. Firstly，aiming at the problem that ferroresonance fault is easily disturbed by uncertain noise and causes signal feature drowning，the frequency band of fast spectral kurtosis is refined by interpolation，the sub bands is used to enhance of decomposition of the high-frequency part，and keep the expression of the high frequency part of the signal in the kurtosis graph more sufficient，and the characteristics of the ferromagnetic resonance signal is preserved in the form of images. Then，on this basis，the structure of GoogLeNet convolutional neural network is adjusted in two aspects：on the one hand，the convolution operation is added to enhance the network’s ability to extract potential features；on the other hand，reducing the number of sampling layers solves the problem of insufficient measured data. Finally，the method is verified by using simulation and laboratory monitoring data，and the results show its effectiveness in improving fault identification accuracy and saving training time.关键词：GIS;electromagnetic voltage transformer;ferromagnetic resonance;parameter matching9|54|0更新时间：2024-12-27
Voltage Transformer
- 摘要：For solving the problem that the unbalanced high voltage of the power grid easily leads to off grid accidents of direct-drive permanent magnet wind turbine，the optimal strategy in combination of sliding mode control，virtual synchronous generator technology and the positive and negative sequence voltage and current double closed-loop PWM control is proposed. By decoupling the positive and negative sequences of the grid-side voltage and current in the dq coordinate system，the relationship between the sequential component current and power under asymmetrical faults is set up，the command values of the positive and negative sequence currents is obtained by calculation，the active power is controlled to reduce the frequency fluctuation of the system，and the reactive power is regulated to support the voltage recovery at the grid-connected point. The output of the current inner-loop is taken as the input to the part of the voltage outer-loop control，the inner-loop PI control of the current is optimized into sliding-mode control so to enhance stability of the grid-connected inverter. The simulation experiment shows the effectiveness of the optimized control method. The fault ride through ability and operation stability of the permanent magnet direct drive wind power grid connected system in case of unbalanced high voltage are improved.关键词：direct-drive wind turbine;high voltage ride-through;asymmetric fault;virtual synchronization technology;sliding mode control9|92|0更新时间：2024-12-27
- 摘要：For assuring the reliability of traction power supply，it is necessary to do the maintenance in the case of daily power outage of the contact network. Mastering the status of ground wire operators in real time helps to assure the personal safety of the maintenance staff and improve the safety management level of the outage maintenance site at contact network. In view of lack of state perception of the ground wire operators during the grounding wire hanging operations，a kind of wearable device designed for grounding wire operators has been developed. The wearable device can perceive the health status of ground wire operators in real-time，thus assuring their safety and maintenance efficiency. Through LoRa self-organizing network communication with the original system，remote monitoring of ground wire operator information in the background can be achieved. The experimental results indicate that the device can achieve the monitoring of the health status of ground wire operators.关键词：power outage maintenance of contact network;hanging the grounding wire;operators;wearable device;status perception11|34|0更新时间：2024-12-27
- 摘要：The 10 kV line of new distribution network is equipped with a large number of intelligent switches（FTU）. The FTU，in case of a single-phase ground fault on the line，can quickly monitor the zero-sequence voltage and current electrical volume. The phase relationship of zero sequence voltage and current of faulty line and section is analyzed and compared with that of non fault line and section，which can quickly select line and section positioning. In this paper，zero-sequence network analysis for faulty sections containing FTUs on both sides is made，the node voltage equation is written so that the analytical formula of the fault distance and the zero-sequence voltage current on both ends can be obtained. The fault distance obtained by the formula is free from the influence of ground resistance and the calculated fault distance is more accurate. Through simulation and analysis，the effectiveness of single-phase grounding fault line selection，location and distance measurement by using zero-sequence voltage current under the new type of distribution network is verified. Finally，the handling flow chart of single phase ground fault of new type of distribution network is given，which can provide reference for actual single-phase grounding faults.关键词：new distribution network;FTU;single-phase ground fault;zero-sequence network;fault location and ranging;zero-sequence voltage and current15|167|0更新时间：2024-12-27
- 摘要：The increasing complexity of the grid structure and the variation of the operation mode have a significant impact on the voltage stability of the system，and the traditional voltage control method is difficult to accurately identify the voltage dominant node，which restricts the effective control of the local voltage. In view of this issue，a sub-regional dominant node optimal identification method considering the neighbourhood coupling degree is proposed in this paper. The method is based on a reasonable division of the grid，the sub-regions reflecting the local voltage control characteristics is obtained，and the voltage dominant nodes in each sub-region is accurately located by constructing the dominant node optimal identification model. Firstly，the full-dimensional extension matrix model of electrical distance is constructed through considering the control characteristics of reactive power sources，and the hierarchical clustering algorithm is used to achieve the sub-regional classification of the grid；Then，combining the principle of connectivity of the region，the power-voltage coupling relationship between controllable nodes in the sub-region and adjacent regions is analyzed，and a comprehensive sensitivity index considering the neighbourhood coupling degree is constructed，and the dominant node in each sub-region is identified in accordance with the results of the index calculations. At the same time，the variation of dominant node under different operation modes of the grid is studied to verify the flexibility and adaptability of the proposed identification method. Finally，the IEEE 39 node system is used for simulation analysis. The results show that the proposed method takes the coupling degree of neighbouring nodes into account，and is more reliable than the traditional dominant node selection method. In addition，the method not only adapts to the flexible and variable grid operation mode，but also provides effective support for the reactive power compensation capacity planning of complex networks.关键词：grid partitioning;integrated sensitivity;dominant node optimal identification;voltage stability8|44|0更新时间：2024-12-27
Research on System Application
- 摘要：As for the randomness and fluctuation of output power in grid-connected photovoltaic system，a single energy storage form cannot meet simultaneously the common needs of both power type and energy type. In this paper，a kind of compound energy storage control strategy based on SOC value of super capacitor for photovoltaic power generation system is proposed so to achieve smooth grid connection of photovol-taic output. Firstly，the effect of compound energy storage on the stability of PV grid connection is ana-lyzed. Then，the compound energy storage control strategy based on SOC value of super capacitor is intro-duced in detail. Finally，a simulation model is set up in Matlab/Simulink to simulate photovoltaic smooth grid-connection and constant power grid-connection. The feasibility of the composite energy storage control strategy is verified by the simulation result，which can cooperate well with photovoltaic grid-connection and play a prominent role in smooth fluctuation and peak cutting and valley filling.关键词：photovoltaic grid-connected;compound energy storage;control strategy;smooth grid connection11|94|0更新时间：2024-12-27
- 摘要：The multi-terminal VSC-HVDC transmission technology is developing rapidly and its reliability analysis is a prerequisite to ensure the safe and stable operation of the DC transmission system. Due to the lack of qualitative and quantitative assessment and study of improvement methods for the reliability of multi-terminal DC transmission systems at present，a kind of reliability modeling method for multi-terminal VSC-HVDC systems based on status spacial method and step-by-step combination model is proposed in this paper. The various practical operating status of multi-terminal VSC-HVDC transmission projects are considered in this method，the status transition models for DC line and subsystem of converter station are set up respectively. The correctness and feasibility of this method are verified by solving such reliability in-dicators as power supply availability and annual equivalent outage time. Finally，an analytical expression for the sensitivity of reliability index to component failure rates is set up by using the hierarchical equiva-lence method，and the weakest link of system reliability is quantitatively analyzed. The research can pro-vide some reference for the reliability assessment of actual VSC-HVDC projects.关键词：multi-terminal VSC-HVDC trnsmission;operation mode;status-spacial method;reliability;sensitivity12|173|0更新时间：2024-12-27
- 摘要：For improving the issue of the frequency modulation capability and frequency stability reduction of power grid system at a high penetration rate of new energy，while taking into account the economic benefits of the system，a capacity optimized configuration scheme for frequency support of collaboration between flywheel energy storage and wind turbines based on typical wind power scenario probability is proposed in this paper. Firstly，the improved K-means clustering algorithm is used to process the annual historical processing data of wind power，and four typical operating scenarios and their probabilities of wind power are obtained. Then，the operational model and frequency regulation control strategy of the wind-storage integrated system are set up based on the characteristics of wind turbines and flywheel energy storage. Finally，a capacity optimized configuration model for wind-storage integrated system is set up with the objective function of maximizing annual economic benefits，and the optimized configuration model is solved by using the particle swarm optimization（PSO）algorithm. The configuration scheme is compared with the scenario of only having wind turbines through simulation. The results show that the proposed configuration scheme has great improvement in annual economic benefits and frequency modulation completion rate and the rationality and effectiveness of the scheme are proved.关键词：wind-storage integrated;K-means clustering;wind power scenario probability;flywheel energy storage system;frequency support;particle swarm optimization（PSO）algorithm17|162|0更新时间：2024-12-27
Application Technology in the Field of Clean Energy
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