This paper proposes a joint limiting control strategy for suppressing DC fault current and arm current in modular multilevel converter-based high-voltage direct current(MMC-HVDC) systems, which includes two target-ori...This paper proposes a joint limiting control strategy for suppressing DC fault current and arm current in modular multilevel converter-based high-voltage direct current(MMC-HVDC) systems, which includes two target-oriented current limiting controls. To limit the DC fault current in the early fault stage, an equivalent modular multilevel converter(MMC) impedance is obtained, and its high-frequency part is reshaped by introducing virtual impedance, which is realized by adjusting the inserted submodules adaptively. Following the analysis of MMC control characteristics, the arm current limiting strategy is investigated, with results showing that the inner-loop control has significant effects on arm current and that a simple low-pass filter can reduce the arm current in the fault period. Finally, by combining the virtual impedance shaping and innerloop control, the fault currents of DC lines and MMC arms can be suppressed simultaneously, which can not only alleviate the interrupting pressure of the DC circuit breaker, but also prevent the MMC from being blocked by the arm overcurrent. Theoretical analysis conclusions and the proposed strategy are verified offline by a digital time-domain simulation on Power Systems Computer Aided Design/Electromagnetic Transients including DC platform, and experiment on a real-time digital simulator platform.展开更多
This paper proposes a novel directional pilot protection method based on the transient energy for bipolar HVDC line.Supposing the positive direction of current is from DC bus to the DC line,in the case of an internal ...This paper proposes a novel directional pilot protection method based on the transient energy for bipolar HVDC line.Supposing the positive direction of current is from DC bus to the DC line,in the case of an internal line fault,the transient energies detected on both sides of the line are all negative within a short time,which denotes the positive direction fault;while for an external fault,the transient energy on one end is positive,which means a negative direction fault,but the transient energy on the opposite end is negative,which indicates that the fault direction is positive.According to these characteristics,an integration criterion identifying fault direction is constructed.In addition,through setting a fixed energy threshold,the faulted line and lightning disturbance can also be discriminated.Simulation results from UHVDC transmission system show the validity of the proposed protection method.展开更多
As it is crucial to protect the transmission line from inevitable faults consequences,intelligent scheme must be employed for immediate fault detection and classification.The application of Artificial Neural Network(A...As it is crucial to protect the transmission line from inevitable faults consequences,intelligent scheme must be employed for immediate fault detection and classification.The application of Artificial Neural Network(ANN)to detect the fault,identify it’s section,and classify the fault on transmission lines with improved zone reach setting is presented in this article.The fundamental voltage and current magnitudes obtained through Discrete Fourier Transform(DFT)are specified as the inputs to the ANN.The relay is placed at section-2 which is the prime section to be protected.The ANN was trained and tested using diverse fault datasets;obtained from the simulation of different fault scenarios like different types of fault at varying fault inception angles,fault locations and fault resistances in a 400 kV,216 km power transmission network of CSEB between Korba-Bhilai of Chhattisgarh state using MATLAB.The simulation outcomes illustrated that the entire shunt faults including forward and reverse fault,it’s section and phase can be accurately identified within a half cycle time.The advantage of this scheme is to provide a major protection up to 99.5%of total line length using single end data and furthermore backup protection to the forward and reverse line sections.This routine protection system is properly discriminatory,rapid,robust,enormously reliable and incredibly responsive to isolate targeted fault.展开更多
Prognostics and health management （PHM） is very important to guarantee the reliability and safety of aerospace systems, and sensing and test are the precondition of PHM. Integrating design for testability into early...Prognostics and health management （PHM） is very important to guarantee the reliability and safety of aerospace systems, and sensing and test are the precondition of PHM. Integrating design for testability into early design stage of system early design stage is deemed as a fundamental way to improve PHM performance, and testability model is the base of testability analysis and design. This paper discusses a hierarchical model-based approach to testability modeling and analysis for heading attitude system health management. Quantified directed graph, of which the nodes represent components and tests and the directed edges represent fault propagation paths, is used to describe fault-test dependency, and quantitative testability information is assigned to nodes and directed edges. The fault dependencies between nodes can be obtained by functional fault analysis methodology that captures the physical architecture and material flows such as energy, heat, data, and so on. By incorporating physics of failure models into component, the dynamic process of a failing or degrading component can be projected onto system behavior, i.e., system symptoms. Then, the analysis of extended failure modes, mechanisms and effects is utilized to construct fault evolution-test dependency. Using this integrated model, the designers and system analysts can assess the test suite＇s fault detectability, fault isolability and fault predictability. And heading attitude system application results show that the proposed model can support testability analysis and design for PHM very well.展开更多
基金supported in part by the Fundamental Research Funds for the Central Universities (No.2022SCU12005)the General Project of Natural Science Foundation of Sichuan Province (No.2022NSFSC0262)。
文摘This paper proposes a joint limiting control strategy for suppressing DC fault current and arm current in modular multilevel converter-based high-voltage direct current(MMC-HVDC) systems, which includes two target-oriented current limiting controls. To limit the DC fault current in the early fault stage, an equivalent modular multilevel converter(MMC) impedance is obtained, and its high-frequency part is reshaped by introducing virtual impedance, which is realized by adjusting the inserted submodules adaptively. Following the analysis of MMC control characteristics, the arm current limiting strategy is investigated, with results showing that the inner-loop control has significant effects on arm current and that a simple low-pass filter can reduce the arm current in the fault period. Finally, by combining the virtual impedance shaping and innerloop control, the fault currents of DC lines and MMC arms can be suppressed simultaneously, which can not only alleviate the interrupting pressure of the DC circuit breaker, but also prevent the MMC from being blocked by the arm overcurrent. Theoretical analysis conclusions and the proposed strategy are verified offline by a digital time-domain simulation on Power Systems Computer Aided Design/Electromagnetic Transients including DC platform, and experiment on a real-time digital simulator platform.
基金National Natural Science Foundation of China(51677109)National Key Research and Development Program of China(2016YFB0906003).
文摘This paper proposes a novel directional pilot protection method based on the transient energy for bipolar HVDC line.Supposing the positive direction of current is from DC bus to the DC line,in the case of an internal line fault,the transient energies detected on both sides of the line are all negative within a short time,which denotes the positive direction fault;while for an external fault,the transient energy on one end is positive,which means a negative direction fault,but the transient energy on the opposite end is negative,which indicates that the fault direction is positive.According to these characteristics,an integration criterion identifying fault direction is constructed.In addition,through setting a fixed energy threshold,the faulted line and lightning disturbance can also be discriminated.Simulation results from UHVDC transmission system show the validity of the proposed protection method.
基金support of Chhattisgarh Council of Science&Technology(CGCOST)Raipur for funding the project No.8062/CGCOST/MRP/13,dtd.27.12.2013.
文摘As it is crucial to protect the transmission line from inevitable faults consequences,intelligent scheme must be employed for immediate fault detection and classification.The application of Artificial Neural Network(ANN)to detect the fault,identify it’s section,and classify the fault on transmission lines with improved zone reach setting is presented in this article.The fundamental voltage and current magnitudes obtained through Discrete Fourier Transform(DFT)are specified as the inputs to the ANN.The relay is placed at section-2 which is the prime section to be protected.The ANN was trained and tested using diverse fault datasets;obtained from the simulation of different fault scenarios like different types of fault at varying fault inception angles,fault locations and fault resistances in a 400 kV,216 km power transmission network of CSEB between Korba-Bhilai of Chhattisgarh state using MATLAB.The simulation outcomes illustrated that the entire shunt faults including forward and reverse fault,it’s section and phase can be accurately identified within a half cycle time.The advantage of this scheme is to provide a major protection up to 99.5%of total line length using single end data and furthermore backup protection to the forward and reverse line sections.This routine protection system is properly discriminatory,rapid,robust,enormously reliable and incredibly responsive to isolate targeted fault.
基金supported by National Natural Science Foundation of China (No. 51175502)
文摘Prognostics and health management （PHM） is very important to guarantee the reliability and safety of aerospace systems, and sensing and test are the precondition of PHM. Integrating design for testability into early design stage of system early design stage is deemed as a fundamental way to improve PHM performance, and testability model is the base of testability analysis and design. This paper discusses a hierarchical model-based approach to testability modeling and analysis for heading attitude system health management. Quantified directed graph, of which the nodes represent components and tests and the directed edges represent fault propagation paths, is used to describe fault-test dependency, and quantitative testability information is assigned to nodes and directed edges. The fault dependencies between nodes can be obtained by functional fault analysis methodology that captures the physical architecture and material flows such as energy, heat, data, and so on. By incorporating physics of failure models into component, the dynamic process of a failing or degrading component can be projected onto system behavior, i.e., system symptoms. Then, the analysis of extended failure modes, mechanisms and effects is utilized to construct fault evolution-test dependency. Using this integrated model, the designers and system analysts can assess the test suite＇s fault detectability, fault isolability and fault predictability. And heading attitude system application results show that the proposed model can support testability analysis and design for PHM very well.
