Symmetrical monopolar configuration is the prevailing scheme configuration for modular multilevel converter based high-voltage direct current(MMC-HVDC) links, in which severe DC overvoltage or overcurrent can be cause...Symmetrical monopolar configuration is the prevailing scheme configuration for modular multilevel converter based high-voltage direct current(MMC-HVDC) links, in which severe DC overvoltage or overcurrent can be caused by the DC faults. To deal with the possible asymmetry in the DC faults and the coupling effects of the DC lines, this paper analyzes the DC fault characteristics based on the phase-mode transformation. First, the DC grid is decomposed into the common-mode and the differential-mode networks. The equivalent models of the MMCs and DC lines in the two networks are derived, respectively. Then, based on the state matrices, a unified numerical calculation method for the fault voltages and currents at the DC side is proposed. Compared with the time-domain simulations performed on PSCAD/EMTDC, the accuracy of the proposed method is validated. Last, the system parameter analysis shows that the grounding parameters play an important role in reducing the severity of the pole-to-ground faults, whereas the coupling effects of the DC lines should be considered when calculating the DC fault currents associated with the pole-to-pole faults.展开更多
针对模块化多电平换流器(modular multilevel converter,MMC)直流配电网发生单极接地故障时,故障特征量小、故障线路与非故障线路故障特征区别不明显、干扰因素多、保护准确性较低等问题,提出一种基于多重综合判据的单端MMC直流配电网...针对模块化多电平换流器(modular multilevel converter,MMC)直流配电网发生单极接地故障时,故障特征量小、故障线路与非故障线路故障特征区别不明显、干扰因素多、保护准确性较低等问题,提出一种基于多重综合判据的单端MMC直流配电网单极接地保护方法。首先计算各线路正负极电流之间的相似性故障判据、本线路与其他线路故障极电流之间的相似性故障判据、本线路与其他线路正负极电流和之间的相似性故障判据,然后综合这3种判据,构建基于多重综合判据的单极接地保护方法。在实时数字仿真系统(real time digital simulation system,RTDS)软件中搭建仿真模型进行验证,结果表明所提方法可以减少干扰因素的影响,具有较高的准确性和可靠性。展开更多
Based on satisfactory control strategy,a new method for robust passive fault tolerant controller is proposed for a class of uncertain discrete-time systems subject to actuator faults.The state-feedback gain matrix is ...Based on satisfactory control strategy,a new method for robust passive fault tolerant controller is proposed for a class of uncertain discrete-time systems subject to actuator faults.The state-feedback gain matrix is calculated by linear matrix inequality(LMI)technique.The designed controller guarantees that the closed-loop system meets the pre-specified consistent constraints on circular pole index and steady-state variance index simultaneously for normal case and possible actuator fault case.The consistency of the performance indices is discussed.Furthermore,with the mentioned indices constraints,a solution is obtained by convex optimal technique for the robust satisfactory fault-tolerant controller with optimal control-cost.展开更多
This paper presents the behavior analysis of modular multilevel converter under DC pole-to-pole short-circuit fault, which is an important issue in fault management, electrical system design and MMC based power system...This paper presents the behavior analysis of modular multilevel converter under DC pole-to-pole short-circuit fault, which is an important issue in fault management, electrical system design and MMC based power system protection and control. Firstly, the transient behavior is analyzed and the conduction overlap- ping angle γ, is defined. Secondly, seven possible short-circuit current paths induced by different γ values are identified, and the corresponding engineering short-circuit current calculation methods for both AC and DC sides are proposed. And then, the influences of impedance distribution factor κ and equivalent short-circuit resistance Rsc on short-circuit currents are elaborated the proposed analysis methods. Finally, case study is used to verify the effectiveness of展开更多
文摘Symmetrical monopolar configuration is the prevailing scheme configuration for modular multilevel converter based high-voltage direct current(MMC-HVDC) links, in which severe DC overvoltage or overcurrent can be caused by the DC faults. To deal with the possible asymmetry in the DC faults and the coupling effects of the DC lines, this paper analyzes the DC fault characteristics based on the phase-mode transformation. First, the DC grid is decomposed into the common-mode and the differential-mode networks. The equivalent models of the MMCs and DC lines in the two networks are derived, respectively. Then, based on the state matrices, a unified numerical calculation method for the fault voltages and currents at the DC side is proposed. Compared with the time-domain simulations performed on PSCAD/EMTDC, the accuracy of the proposed method is validated. Last, the system parameter analysis shows that the grounding parameters play an important role in reducing the severity of the pole-to-ground faults, whereas the coupling effects of the DC lines should be considered when calculating the DC fault currents associated with the pole-to-pole faults.
文摘针对模块化多电平换流器(modular multilevel converter,MMC)直流配电网发生单极接地故障时,故障特征量小、故障线路与非故障线路故障特征区别不明显、干扰因素多、保护准确性较低等问题,提出一种基于多重综合判据的单端MMC直流配电网单极接地保护方法。首先计算各线路正负极电流之间的相似性故障判据、本线路与其他线路故障极电流之间的相似性故障判据、本线路与其他线路正负极电流和之间的相似性故障判据,然后综合这3种判据,构建基于多重综合判据的单极接地保护方法。在实时数字仿真系统(real time digital simulation system,RTDS)软件中搭建仿真模型进行验证,结果表明所提方法可以减少干扰因素的影响,具有较高的准确性和可靠性。
基金Supported partly by the National Natural Science Foundation of China(60574082)the China Postdoctoral Science Foundation(20070411178)the Research Foundation of DML-HIT(HGDML-0502)
文摘Based on satisfactory control strategy,a new method for robust passive fault tolerant controller is proposed for a class of uncertain discrete-time systems subject to actuator faults.The state-feedback gain matrix is calculated by linear matrix inequality(LMI)technique.The designed controller guarantees that the closed-loop system meets the pre-specified consistent constraints on circular pole index and steady-state variance index simultaneously for normal case and possible actuator fault case.The consistency of the performance indices is discussed.Furthermore,with the mentioned indices constraints,a solution is obtained by convex optimal technique for the robust satisfactory fault-tolerant controller with optimal control-cost.
文摘This paper presents the behavior analysis of modular multilevel converter under DC pole-to-pole short-circuit fault, which is an important issue in fault management, electrical system design and MMC based power system protection and control. Firstly, the transient behavior is analyzed and the conduction overlap- ping angle γ, is defined. Secondly, seven possible short-circuit current paths induced by different γ values are identified, and the corresponding engineering short-circuit current calculation methods for both AC and DC sides are proposed. And then, the influences of impedance distribution factor κ and equivalent short-circuit resistance Rsc on short-circuit currents are elaborated the proposed analysis methods. Finally, case study is used to verify the effectiveness of
