The Summary of HVDC Commutation Failure and Example Analysis

2013 ◽  
Vol 446-447 ◽  
pp. 853-857
Author(s):  
Qian Jin Wu ◽  
Xue Zhi Wang
Keyword(s):  
Power System ◽  
Preventive Measures ◽  
Power Grid ◽  
Large Area ◽  
Hvdc System ◽  
Identification Method ◽  
Commutation Failure ◽  
The Common ◽  
The Stability

Commutation Failure is the common fault of HVDC, continuous commutation failure may lead to HVDC block and affect the stability of the power system. Especially in southern power grid, china, its special that the end of four HVDC system are all in Guangzhou. If the AC system occurs serious fault, all of the HVDC system may occur commutation Failure, HVDC block, even occurs large area blackout. So how to avoid continuous commutation failure and restore the stability of HVDC is important for AC and DC parallel power system. This paper based on the mechanism of commutation failure, analyze the reason of commutation failure and identification method, preventive measures. At last, this paper uses actual recorded wave to analyze the diversification of system after commutation failure.

Reliable Analysis on Fast Valving of Ultra-Supercritical Unit Under Transient Fault Conditions

2017 ◽  
Author(s):  
Yu Cai ◽  
Wei Li ◽  
Bao Zhang ◽  
Wenjian Wu ◽  
Deren Sheng ◽  
...  
Keyword(s):  
Power System ◽  
Steam Turbine ◽  
Dynamic Model ◽  
Transient Stability ◽  
Power Grid ◽  
Load Shedding ◽  
Control Mode ◽  
Normal Operation ◽  
Transient Fault ◽  
The Stability

Fast valving of ultra-supercritical unit has great effects on over-speed prevention, load-shedding control, transient stability analysis of electrical system and other security problems. The purpose of fast valving is to maintain the stability of power system once fault or load shedding of unit occurs in the electric power system. Therefore, it is of great significance to study the reliability of fast valving for ultra-supercritical unit. In this paper, the KU ( short shedding) logic condition of SIEMENS T3000 system is analyzed as the research object of fast valving. The unit can be avoided over speed by monitoring the unit load and fast valving under faulty grid conditions based on the KU control. A series of measures will be taken after KU is triggered, for instance the governing valving will be closed quickly and the DEH (digital electro-hydraulic) control of the steam turbine will be switched to speeding control mode. On the other hand, the unit will return to normal operation if the transient fault of power grid disappears. The key contributions of this thesis include three parts: Firstly, based on the analysis of control characteristics of ultra-supercritical unit and protective logic and triggered conditions of KU function, a novel dynamic model by coupling the fast valving of steam turbine and the transient stability of generator is established by applying the PSCAD software. Then, the dynamic response process of ultra-supercritical unit is simulated and calculated by adopting the coupling dynamic model when KU function is triggered. Also the influence factors and reliability of fast valving are analyzed under transient fault conditions. Finally, two optimized measures by increasing the time delay and the speed of quantitative judgment are put forward to reduce risks and avoid the misoperation of signal distortion which may be caused by the power transmitter under transient fault conditions. The results of this study can not only help to evaluate the reliability of fast valving function scientifically in power grid transient fault, but also guide the technicians to analyze the stability of the power grid.

Mid-Term Stability Assessment of Jiangxi Power Grid

2013 ◽  
Vol 732-733 ◽  
pp. 882-887
Author(s):  
Yong Chun Su ◽  
Hao Wei Jia
Keyword(s):  
Power System ◽  
Power Grid ◽  
Assessment Method ◽  
Control Measures ◽  
Assessment Process ◽  
Jiangxi Province ◽  
Stable Operation ◽  
Stability Assessment ◽  
Term Stability ◽  
The Stability

Mid-term stability assessment is an important work to support power system operation in a province power grid of China every year. The stability assessment method and process was introduced in this paper. As an example, the stability of Jiangxi province power system was evaluated in the following two years. Weak area and weak transmission line were found out in each power supply area. Prevention and control measures were proposed. According to problems among the assessment process and using the state monitoring data, an approach was discussed to increase the assessment result accuracy. The analysis conclusion provides the reference to the safe and stable operation of Jiangxi power system.

The Study of Chopper in the LVRT of Direct-Drive Wind Energy Generation System

2014 ◽  
Vol 950 ◽  
pp. 314-320 ◽  
Author(s):  
Jun Jia ◽  
Xin Xin Hu ◽  
Ping Ping Han ◽  
Yan Ping Hu
Keyword(s):  
Power System ◽  
Wind Power ◽  
Wind Turbines ◽  
Reactive Power ◽  
Power Grid ◽  
Synchronous Generator ◽  
Direct Drive ◽  
Fault Ride Through ◽  
Wind Power System ◽  
The Stability

With the scale of wind farm continuously increasing, when grid fault, the influences of the wind turbines connected to the grid on the stability of the power grid can never be ignored. Therefore, there are higher standards of the wind turbines’ abilities of fault ride-through (FRT) and producing reactive power. This paper studies the direct-drive wind power system, and the main point is the fault ride-through (FRT) of the permanent magnetic synchronous generator (PMSG) with Chopper. By establishing the dynamic model of PMSG under the environment of DigSILENT, this paper simulates the fault ride-through (FRT) of the direct-drive wind power system connecting into power grid. During the research, we focus on the stability of voltage about the Chopper to the DC bus under faults. What’s more, in this paper, we analysis the data about how the Chopper help the DC bus to improve its stability. The simulation results show that: when there is a fault on the point of common coupling, the permanent magnetic synchronous generator has the capability of fault ride-through (FRT). Especially when there is a voltage dip on the grid side, the permanent magnetic synchronous generator could produce reactive power for power grid, effectively preventing the system voltage from declining seriously, so as to improve the system stability under faults.

Overview of Generator Out-of-Step Prediction

2014 ◽  
Vol 521 ◽  
pp. 167-172
Author(s):  
Yan Xu ◽  
Guo Lin Huang
Keyword(s):  
Power System ◽  
Power Grid ◽  
Initial System ◽  
System State ◽  
Advantages And Disadvantages ◽  
Fault Severity ◽  
Initial System State ◽  
The Stability

With the development of power system, the main unit is gradually becoming larger and larger, thus length of time that large generators after experiencing disturbances in power grid needed to adjust and maintain the stability is more important than ever. Generator out-of-step prediction which is a part of security and automaticity equipment of power system, sends out the corresponding operation instructions in order to keep the whole system stay stability, according to the initial system state and fault severity. The paper analyzes and classifies several schemes and principles on generator out-of-step prediction. The actual advantages and disadvantages are pointed out. At last, the development of out-of-step prediction is also presented.

Experimental Voltage Stabilization of a Variable Speed Wind Turbine Driving Synchronous Generator using STATCOM based on Genetic Algorithm

2016 ◽  
Vol 17 (5) ◽  
pp. 541-546 ◽  
Author(s):  
Helmy M. El-Zoghby ◽  
Ahmed F. Bendary
Keyword(s):  
Genetic Algorithm ◽  
Power System ◽  
Wind Turbine ◽  
Reactive Power ◽  
Power Grid ◽  
Synchronous Generator ◽  
Voltage Regulation ◽  
Operating Conditions ◽  
Static Synchronous Compensator ◽  
The Stability

Abstract In this paper Static Synchronous Compensator (STATCOM) is used for improving the performance of the power grid with wind turbine that drives synchronous generator. The main feature of the STATCOM is that it has the ability to absorb or inject rapidly reactive power to grid. Therefore the voltage regulation of the power grid with STATCOM device is achieved. STATCOM also improves the stability of the power system after occurring severe disturbance such as faults, or suddenly step change in wind speed. The proposed STATCOM controller is a Proportional-Integral (PI) controller tuned by Genetic Algorithm (GA). An experimental model was built in Helwan University to the proposed system. The system is tested at different operating conditions. The experimental results prove the effectiveness of the proposed STATCOM controller in damping the power system oscillations and restoring the power system voltage and stability.

Analysis and Prevention of Grid Over-Voltage Ferromagnetic Resonance

2014 ◽  
Vol 960-961 ◽  
pp. 929-934
Author(s):  
Ming Jun Lv ◽  
Xin Zhao ◽  
Xiang Dong Zhao ◽  
Jian Guo Liu ◽  
Feng Zhen Liu ◽  
...  
Keyword(s):  
Power System ◽  
Ferromagnetic Resonance ◽  
Preventive Measures ◽  
Power Grid ◽  
Electrical Equipment ◽  
Normal Operation ◽  
Stable Operation ◽  
Power Outages ◽  
The Future ◽  
Great Harm

Over-voltage in the power system can be caused by a lot of reasons , including higher frequency ferromagnetic resonance overvoltage which occurs in normal operation and causes great harm. Overvoltage events often result in damages to electrical equipment or even power outages . In this paper,ferromagnetic resonance is analyzed to study harm , causes, conditions , and phenomena and to handle resonance and develop practical preventive measures. The related analysis is important to work for the future operation of the power grid to prevent and limit the ferromagnetic resonance over voltage which provides some help to further ensure the safety and stable operation of the power grid .

Research on Stability of Power System with Distributed Generation Synthesis Load Model

2013 ◽  
Vol 341-342 ◽  
pp. 1374-1379
Author(s):  
Yang Liu ◽  
Zhen An Zhang ◽  
Wei Liu ◽  
Ya Nan Wang
Keyword(s):  
Power System ◽  
Distributed Generation ◽  
Transient Stability ◽  
Power Grid ◽  
Stable Operation ◽  
Power Network ◽  
Small Hydropower ◽  
Large Power ◽  
Load Model ◽  
The Stability

With different element models and parameters in power system, the transient stability analysis results are also different, especially the model of generator and load. Based on the actual parameters of Hunan power grid, this paper builds the synthesis load model of the distribution network with small hydropower considered, and then the Hunan simulation network can also be got. Using PSASP, analyses the transient stability of Hunan power system with distributed small hydropower under different operation modes systematically and comprehensively. Through an overall check of the stability level in each Hunan area, and then compared with the analysis results of Hunan power grid based on the currently used load model , the influences of the distributed small hydropower on the safe and stable operation of the large power network are summarized.

Research on Vulnerability Assessment System of Complicated Power System

2011 ◽  
Vol 204-210 ◽  
pp. 622-626 ◽  
Author(s):  
Bo Wang ◽  
Da Hai You ◽  
Xiang Gen Yin
Keyword(s):  
Power System ◽  
Vulnerability Assessment ◽  
Assessment System ◽  
Large Area ◽  
Power Outages ◽  
Analytic Hierarchy ◽  
Factors Analysis ◽  
The Social ◽  
The Government ◽  
The Stability

The factors which lead to large-area power outages are more than ever, when the complexity of the expansion power system is increasing. Therefore, it is important to assess the vulnerability of the complicated power system. This paper first proposes an objective, practical and adaptive vulnerability assessment system of complicated power system by use of Analytic Hierarchy Process, which based on multi-factors analysis of large-area outages. This system can find out the vulnerability point of the power system，and take advantages of the government, who can over-all plan, correspond and organize the social resource to reduce the vulnerability of power system and prevent large-area power outages, and the power enterprises who can maintaining the stability of power system by technology. Finally, the paper gives an assessment example of provincial power system.

Research on Load Models Effect on Stability of Voltage of DC End Power System

2013 ◽  
Vol 347-350 ◽  
pp. 1404-1410 ◽  
Author(s):  
Xiao Ming Liu ◽  
Xin Sheng Niu ◽  
Jie Zhang ◽  
Yi Zhu
Keyword(s):  
Power System ◽  
Induction Motor ◽  
Power Grid ◽  
Load Ratio ◽  
Transient State ◽  
Ratio Distribution ◽  
Load Model ◽  
Load Models ◽  
The Stability ◽  
Simulated Analysis

Load characteristic is one of the vital factors that effect the stability of voltage of power system. As the most important dynamic load in power system, induction motor is one of the most direct reasons which resulting in instability of voltage. In simulated analysis, the establishment of load model, choice of parameter as well as ratio distribution of different kinds of load will lay considerable influence on the stability of system. This thesis establishes the load model of induction motor in stable and transient state and simulates on the basis of Shandong power grid. As the simulating result shows, load ratio of induction motor has fundamental effect on the voltage stability of Shandong power grid. As the load ratio of induction motor increases, the stability of voltage of Shandong power grid decrease and the voltage may even break down.

scholarly journals Infectivity of SARS-CoV-2 and Other Coronaviruses on Dry Surfaces: Potential for Indirect Transmission

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5211
Author(s):  
Max Bueckert ◽  
Rishi Gupta ◽  
Aditi Gupta ◽  
Mohit Garg ◽  
Asit Mazumder
Keyword(s):  
Room Temperature ◽  
Preventive Measures ◽  
Surface Coatings ◽  
Future Research ◽  
Protective Equipment ◽  
Indirect Transmission ◽  
Current State ◽  
The Common ◽  
The Stability ◽  
Indoor Conditions

The unwavering spread of COVID-19 has taken the world by storm. Preventive measures like social distancing and mask usage have been taken all around the globe but still, as of September 2020, the number of cases continues to rise in many countries. Evidently, these measures are insufficient. Although decreases in population density and surges in the public’s usage of personal protective equipment can mitigate direct transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), indirect transmission of the virus is still probable. By summarizing the current state of knowledge on the stability of coronaviruses on dry materials, this review uncovers the high potential for SARS-CoV-2 transmission through contaminated surfaces (i.e., fomites) and prompts future research. Fully contextualized data on coronavirus persistence are presented. The methods and limitations to testing the stability of coronaviruses are explored, and the SARS-CoV-2 representativeness of different coronaviruses is analyzed. The factors which dictate the persistence of coronaviruses on surfaces (media, environmental conditions, and material-type) are investigated, and the review is concluded by encouraging material innovation to combat the current pandemic. To summarize, SARS-CoV-2 remains viable on the timescale of days on hard surfaces under ambient indoor conditions. Similarly, the virus is stable on human skin, signifying the necessity of hand hygiene amidst the current pandemic. There is an inverse relationship between SARS-CoV-2 surface persistence and temperature/humidity, and the virus is well suited to air-conditioned environments (room temperature, ~ 40% relative humidity). Sunlight may rapidly inactivate the virus, suggesting that indirect transmission predominantly occurs indoors. The development of antiviral materials and surface coatings would be an extremely effective method to mitigate the spread of COVID-19. To obtain applicable data on the persistence of coronaviruses and the efficiency of virucidal materials, future researchers should understand the common experimental limitations outlined in this review and plan their studies accordingly.

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