Due to the low impedance characteristic of the high voltage direct current(HVDC)grid,the fault current rises extremely fast after a DC-side fault occurs,and this phenomenon seriously endangers the safety of the HVDC g...Due to the low impedance characteristic of the high voltage direct current(HVDC)grid,the fault current rises extremely fast after a DC-side fault occurs,and this phenomenon seriously endangers the safety of the HVDC grid.In order to suppress the rising speed of the fault current and reduce the current interruption requirements of the main breaker(MB),a fault current limiting hybrid DC circuit breaker(FCL-HCB)has been proposed in this paper,and it has the capability of bidirectional fault current limiting and fault current interruption.After the occurrence of the overcurrent in the HVDC grid,the current limiting circuit(CLC)of FCL-HCB is put into operation immediately,and whether the protected line is cut off or resumed to normal operation is decided according to the fault detection result.Compared with the traditional hybrid DC circuit breaker(HCB),the required number of semiconductor switches and the peak value of fault current after fault occurs are greatly reduced by adopting the proposed device.Extensive simulations also verify the effectiveness of the proposed FCL-HCB.展开更多
DC series-parallel power flow controller(SP-PFC)is a highly efficient device to solve the problem of uncontrolled line current in the bipolar DC distribution system.However,its potential in fault current limiting is n...DC series-parallel power flow controller(SP-PFC)is a highly efficient device to solve the problem of uncontrolled line current in the bipolar DC distribution system.However,its potential in fault current limiting is not fully explored.In this paper,a self-adaptive action strategy(SAAS)and a parameter optimization method of SP-PFC in bipolar DC distribution systems are proposed.Firstly,the common-and different-mode(CDM)equivalent circuits of the bipolar DC distribution system with SP-PFC in different fault stages are established,which avoids the line coupling inductance.Based on this,the influence of different parameters and line coupling inductance on the fault current limiting capability are investigated.It is found that the SP-PFC has the best fault current limiting capability when the capacitance and inductance of filter are inversely proportional.To realize the adaptability of fault current limiting capability under different fault severities,the SAAS of SP-PFC is proposed.The validity of the CDM equivalent circuits and parameter optimization method,and the effectiveness of the SAAS are verified by simulations and experiments.展开更多
Fault current limiting is a critical technology to en sure the safe operation of modular multilevel converter based multi-terminal direct current(MMC-MTDC)grids.This paper proposes a fault severity classification base...Fault current limiting is a critical technology to en sure the safe operation of modular multilevel converter based multi-terminal direct current(MMC-MTDC)grids.This paper proposes a fault severity classification based coordination con trol strategy of fault current limiter(FCL)and MMC for adap tive fault current limiting.The proposed strategy reduces the in vestment in FCL,and keeps the bus voltages of non-faulty lines at reasonable values.Firstly,a rapid fault circuit parameter esti mation(FCPE)method using initial fault current information is proposed.With this method,the fault distance and fault transi tion resistance can be quickly estimated,which are used for a quantitative indication of the fault severity.Subsequently,the coordination control strategy of FCL and MMC is proposed,in which the FCL action is prioritized,while the control of MMC is complementary for current limiting.Based on the proposed strategy,fault severity phase planes(FSPPs)are constructed to assess fault severity and calculate the activation time of FCL and voltage regulation factor of MMC.Therefore,the FCL acti vation and MMC control are matched to the fault severity.The effectiveness and advantages of the proposed strategy are vali dated by the simulations in PSCAD/EMTDC.展开更多
In order to overcome the problems of power flow control and fault current limiting in multi-terminal high voltage direct current(MTDC)grids,this paper proposes a modular multi-terminal DC power flow controller(MM-DCPF...In order to overcome the problems of power flow control and fault current limiting in multi-terminal high voltage direct current(MTDC)grids,this paper proposes a modular multi-terminal DC power flow controller(MM-DCPFC)with fault current limiting function.The topology structure,operation principle,and equivalent circuit of MM-DCPFC are introduced,and such a structure has the advantages of modularity and scalability.The power balance mechanism is studied and a hierarchical power balance control strategy is proposed.The results show that MM-DCPFC can achieve internal power exchange,which avoids the use of external power supply.The fault characteristics of MM-DCPFC are analyzed,fault current limiting and self-protection methods are proposed,and the factors affecting the current limiting capability are studied.The simulation models are established in PLECS,and the simulation results verify the effectiveness of MM-DCPFC in power flow control,fault current limiting,and scalability.In addition,a prototype is developed to validate the function and control method of MM-DCPFC.展开更多
In the voltage source converter based high-voltage direct current(VSC-HVDC)grids,fast and reliable protections are the key technologies.The traditional protection schemes are easily affected by fault resistance,line d...In the voltage source converter based high-voltage direct current(VSC-HVDC)grids,fast and reliable protections are the key technologies.The traditional protection schemes are easily affected by fault resistance,line distributed capacitance,etc.Meanwhile,the influence of fault current limiting strategy(FCLS)has not been fully considered.In this paper,the fault characteristics under FCLS and the feasibility of traditional travelling wave protections are analyzed.To improve the reliability and sensibility,a similarity comparison based pilot protection scheme is proposed,which focuses on the relationship between the fault characteristics and the state of the protected transmission line,with the establishment of a precise frequencydependent transmission line model.The criteria based on the similarity comparison calculated by cross-wavelet can identify the fault effectively.Meanwhile,the protection scheme can also endure the influence of error synchronization.Finally,the protection performance is verified in the PSCAD/EMTDC under different fault conditions.展开更多
The series voltage source converter(SVSC)is widely used in the power electronic equipment,such as series active power filter,dynamic voltage restorer,unified power flow controller and so on.However,while the SVSC is m...The series voltage source converter(SVSC)is widely used in the power electronic equipment,such as series active power filter,dynamic voltage restorer,unified power flow controller and so on.However,while the SVSC is more vulnerable to the impact of fault current,its applications are increasing,bringing huge challenges to the safe operation of the grid.In recent years,the topology and control strategy of the series voltage source converter with fault current limiting(SVSC-FCL)are a research hotspot.In this paper,it suggests classifying SVSC-FCL based SVSC into two groups:the control scheme optimization group and the existing topology improvement group.The research challenges and perspectives of the SVSC-FCL are introduced in detail.This paper aims to illustrate current research progress on SVSC-FCL and enrich the available pool of the multi-functional power electronic equipment.展开更多
A novel magnetic-controlled switcher type fault current limiter (FCL) based on the topology of the saturated iron core high temperature superconducting FCL is proposed. The magnetic field distribution of the FCL iron ...A novel magnetic-controlled switcher type fault current limiter (FCL) based on the topology of the saturated iron core high temperature superconducting FCL is proposed. The magnetic field distribution of the FCL iron core is analyzed by FEA software ANSYS. The current limiting characteristic is investigated by both 3-D field-circuit coupled simulation and Matlab. The experiments on the 220 V/50 A test model show that the FCL can limit the fault current swiftly and effectively,and the FCL has the advantages of simple and reliable structure, flexible control strategy. The simulation and experimental results prove that the theoretical expectation and current limiting performance is satisfactory for practical use.展开更多
This paper presents a new type of fault current limiter (FCL) based on fast closing switch, which is composed of a capacitor bank and a reactor in series. The main control component is a fast closing switch connecte...This paper presents a new type of fault current limiter (FCL) based on fast closing switch, which is composed of a capacitor bank and a reactor in series. The main control component is a fast closing switch connected in parallel with the capacitors, which is driven by the electromagnetic repulsion force. It can response the order within 1 ms. When fault occurs, the switch closes and the capacitors are bypassed, and the fault current is limited by the reactor. Simulation analysis and experiment show that the electromagnetic repulsion force actuator can meet the demand of fast closing switch, it is feasible to develop the FCL with low cost and high reliability.展开更多
The liquid metal current limiter(LMCL)is regarded as a viable solution for reducing the fault current in a power grid.But demonstrating the liquid metal arc plasma self-pinching process of the resistive wall,and reduc...The liquid metal current limiter(LMCL)is regarded as a viable solution for reducing the fault current in a power grid.But demonstrating the liquid metal arc plasma self-pinching process of the resistive wall,and reducing the erosion of the LMCL are challenging,not only theoretically,but also practically.In this work,a novel LMCL is designed with a resistive wall that can be connected to the current-limiting circuit inside the cavity.Specifically,a novel fault current limiter(FCL)topology is put forward where the novel LMCL is combined with a fast switch and current-limiting reactor.Further,the liquid metal self-pinch effect is modeled mathematically in three dimensions,and the gas-liquid two-phase dynamic diagrams under different short-circuit currents are obtained by simulation.The simulation results indicate that with the increase of current,the time for the liquid metal-free surface to begin depressing is reduced,and the position of the depression also changes.Different kinds of bubbles formed by the depressions gradually extend,squeeze,and break.With the increase of current,the liquid metal takes less time to break,but breaks still occur at the edge of the channel,forming arc plasma.Finally,relevant experiments are conducted for the novel FCL topology.The arcing process and current transfer process are analyzed in particular.Comparisons of the peak arc voltage,arcing time,current limiting efficiency,and electrode erosion are presented.The results demonstrate that the arc voltage of the novel FCL topology is reduced by more than 4.5times and the arcing time is reduced by more than 12%.The erosions of the liquid metal and electrodes are reduced.Moreover,the current limiting efficiency of the novel FCL topology is improved by 1%–5%.This work lays a foundation for the topology and optimal design of the LMCL.展开更多
The effectiveness of a combination of fault current limiter and thyristor controlled braking resistor on power system stability enhancement and damping turbine shaft torsional oscillations has been studied. If both de...The effectiveness of a combination of fault current limiter and thyristor controlled braking resistor on power system stability enhancement and damping turbine shaft torsional oscillations has been studied. If both devices operate at the same bus, the stabilization control scheme can be carried out continuously and with flexibility. As a result, the fault currents are limited, and the generator disturbances and the turbine shaft torsional oscillations are converged quickly. In this paper, the effectiveness of the combination of both devices has been demonstrated by considering 3LG （three-lines-to-ground） fault in a two-machine infinite bus system. Also, temperature rise effect of both devices with various resistance values and weights has been demonstrated. Simulation results indicate a significant power system stability enhancement and damping turbine shaft torsional oscillations as well as with allowable temperature rise.展开更多
The fault current limiter(FCL)is an effective measure for improving system stability and suppressing short-circuit fault current.Because of space and economic costs,the optimum placement of FCLs is vital in industrial...The fault current limiter(FCL)is an effective measure for improving system stability and suppressing short-circuit fault current.Because of space and economic costs,the optimum placement of FCLs is vital in industrial applications.In this study,two objectives with the same dimensional measurement unit,namely,the total capital investment cost of FCLs and circuit breaker loss related to short-circuit currents,are considered.The circuit breaker loss model is developed based on the attenuation rule of the circuit breaker service life.The circuit breaker loss is used to quantify the current-limiting effect to avoid the problem of weight selection in a multi-objective problem.The IEEE 10-generator 39-bus system in New England is used to evaluate the performance of the proposed genetic algorithm(GA)method.Comparative and sensitivity analyses are performed.The results of the optimized plan are validated through simulations,indicating the significant potential of the GA for such optimization.展开更多
A novel magnetic-controlled switcher type fault current limiter （FCL） for high voltage electric network is presented. The current limiting principle of the FCL and the bias current influence on the characteristic of...A novel magnetic-controlled switcher type fault current limiter （FCL） for high voltage electric network is presented. The current limiting principle of the FCL and the bias current influence on the characteristic of the FCL axe discussed. The experiments on the 220 V/50 A test model show that the FCL can limit the fault current swiftly and effectively. Under the normal state, the bias current adjustment can change the FCL voltage loss; under the fault state, the steady fault current can be easily adjusted to the preset level by bias current regulating. The experimental result is in accordance with the principle analysis and the FCL has the advantages of flexible control strategy and simple and reliable structure.展开更多
A deregulated power market is making short-circuit currents likely to exceed the thermal or mechanical permissible limits of switchgear. Consequently fault current limiters （FCL） become more necessary in power syste...A deregulated power market is making short-circuit currents likely to exceed the thermal or mechanical permissible limits of switchgear. Consequently fault current limiters （FCL） become more necessary in power systems. The use of FCLs has an impact on the protection schemes and functions in power systems. Thus, before FCLs can be applied in the network, the impacts on existing protection system must be understood. Depending on the current limiting technique used, today＇s protection concepts may have to be adapted or revised to ensure proper network protection selectivity. A relationship between fault current limiters and protection schemes should be established by taking into account both protection and network specific issues, such as the impact of different FCL technologies, existing and new protection concepts, selectivity and innovative network. This paper is presenting a frame work for accomplishing this task.展开更多
FCL （fault current limiter） is used to solve relays miscoordination problem arises from DG （distributed generation） installation. In most published researches, different optimization methods are developed to obtai...FCL （fault current limiter） is used to solve relays miscoordination problem arises from DG （distributed generation） installation. In most published researches, different optimization methods are developed to obtain optimal relay settings to achieve coordination in case of not installing DG, then depending on the achieved optimal obtained relay settings, FCL impedance is deduced to ensure relays coordination restoration in case of installing DG. Based on original optimal relay settings, obtained FCL impedance is not the minimum one required to achieve relay coordination. The contribution of this paper is the generation of multi sets of original relay settings that increase the possibility of finding FCL impedance of minimum value which is lower than the calculated value based on original optimal relay settings. The proposed method achieves better economic target by reducing FCL impedance. The proposed approach is implemented and tested on IEEE-39 bus test system.展开更多
Virtual synchronous generators(VSGs)can provide voltage and frequency support to power systems due to their inertial and damping features.Unfortunately,power angle stability and fault current limitations are still cha...Virtual synchronous generators(VSGs)can provide voltage and frequency support to power systems due to their inertial and damping features.Unfortunately,power angle stability and fault current limitations are still challenging aspects of VSGs under large disturbances.Power angle stability and fault current limitations are indispensable for the safe operation of a VSG.However,in existing studies,these aspects are mostly solved as two independent problems.In this paper,the comprehensive transient stability enhancement(CTSE)control strategy for a VSG,considering power angle stability and fault current limitations is proposed.With a CTSE control,VSG's transient power angle stability is guaranteed.In addition,the steady-state and impulse components of the fault current are fully limited.Furthermore,CTSE control parameters adapted to different fault degrees are presented.Finally,simulation and experimental tests are performed to validate the performance of the proposed method.展开更多
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
With the development of power electronic technologies and distributed power generation,DC distribution networks attract increasing attention due to their various advantages compared with traditional AC distribution ne...With the development of power electronic technologies and distributed power generation,DC distribution networks attract increasing attention due to their various advantages compared with traditional AC distribution networks.However,DC fault protection is one of the major issues in DC distribution networks.To improve their reliability and protect the semiconductor devices under DC faults,a current-limiting and energy-transferring DC circuit breaker topology is proposed in this paper.By applying passive components and thyristors,the proposed topology is capable of quickly limiting the fault current and transferring the faulty energy.The working principle,mathematical model and parameter designing method of the proposed topology are presented in this paper.The simulation results verify that the proposed DC circuit breaker could effectively limit the fault current and quickly interrupt the fault current.Cost and conduction power loss evaluation proves the practicality of the proposed topology in medium-voltage DC distribution networks.展开更多
Modular multilevel converter(MMC)is increasingly being applied to high voltage direct current(HVDC)systems.However,dc short circuit situations restrain the application of a conventional half bridge MMC system.In this ...Modular multilevel converter(MMC)is increasingly being applied to high voltage direct current(HVDC)systems.However,dc short circuit situations restrain the application of a conventional half bridge MMC system.In this paper,a new sub-module topology with inserted thyristor can help the MMC system clear a dc side fault.Working states and devices voltage stress of the proposed topology are analyzed and the conduction loss comparison between the proposed topology with several existing topologies with dc fault blocking capability is carried out.Results show the proposed topology is superior to other topologies in terms of conduction loss while using the same voltage rating devices.Besides,compared with traditional half bridge topology,only thyristors and diodes are added in the proposed topology.Therefore,cost of the proposed topology can be lower than conventional hybrid MMC sub-modules.At last,the fault blocking capability of the proposed topology is verified in the simulation.展开更多
The modular multilevel converter(MMC)based DC grid is considered as a future solution for bulk renewable energy integration and transmission.However,the high probability of DC faults and their rapid propagation speed ...The modular multilevel converter(MMC)based DC grid is considered as a future solution for bulk renewable energy integration and transmission.However,the high probability of DC faults and their rapid propagation speed are the main challenges in the development of DC grids.Existing research primarily focuses on the DC fault clearance methods,while the fault current suppression methods are still barely researched.Additionally,the coordination method of fault current suppression and clearance needs to be optimized.In this paper,the technical characteristics of the current suppression methods are studied,and the coordinated methods of fault current suppression and clearance are proposed.At last,a cost comparison of these methods is presented.The research results show that the proposed strategies can reduce the cost of the protection equipment.展开更多
基金This project is funded by the Dongying Science Development Fund Project(DJ2021013).
文摘Due to the low impedance characteristic of the high voltage direct current(HVDC)grid,the fault current rises extremely fast after a DC-side fault occurs,and this phenomenon seriously endangers the safety of the HVDC grid.In order to suppress the rising speed of the fault current and reduce the current interruption requirements of the main breaker(MB),a fault current limiting hybrid DC circuit breaker(FCL-HCB)has been proposed in this paper,and it has the capability of bidirectional fault current limiting and fault current interruption.After the occurrence of the overcurrent in the HVDC grid,the current limiting circuit(CLC)of FCL-HCB is put into operation immediately,and whether the protected line is cut off or resumed to normal operation is decided according to the fault detection result.Compared with the traditional hybrid DC circuit breaker(HCB),the required number of semiconductor switches and the peak value of fault current after fault occurs are greatly reduced by adopting the proposed device.Extensive simulations also verify the effectiveness of the proposed FCL-HCB.
基金supported by the National Natural Science Foundation of China(No.52207126)the Natural Science Foundation of Sichuan Province(No.2023NSFSC0296)the Joint Funds of the National Natural Science Foundation of China(No.U22B6006).
文摘DC series-parallel power flow controller(SP-PFC)is a highly efficient device to solve the problem of uncontrolled line current in the bipolar DC distribution system.However,its potential in fault current limiting is not fully explored.In this paper,a self-adaptive action strategy(SAAS)and a parameter optimization method of SP-PFC in bipolar DC distribution systems are proposed.Firstly,the common-and different-mode(CDM)equivalent circuits of the bipolar DC distribution system with SP-PFC in different fault stages are established,which avoids the line coupling inductance.Based on this,the influence of different parameters and line coupling inductance on the fault current limiting capability are investigated.It is found that the SP-PFC has the best fault current limiting capability when the capacitance and inductance of filter are inversely proportional.To realize the adaptability of fault current limiting capability under different fault severities,the SAAS of SP-PFC is proposed.The validity of the CDM equivalent circuits and parameter optimization method,and the effectiveness of the SAAS are verified by simulations and experiments.
基金supported in part by the National Natural Science Foundation of China(No.52207126)the Natural Science Foundation of Sichuan Province(No.2024NSFSC0869)the Joint Funds of the National Natural Science Foundation of China(No.U22B6006).
文摘Fault current limiting is a critical technology to en sure the safe operation of modular multilevel converter based multi-terminal direct current(MMC-MTDC)grids.This paper proposes a fault severity classification based coordination con trol strategy of fault current limiter(FCL)and MMC for adap tive fault current limiting.The proposed strategy reduces the in vestment in FCL,and keeps the bus voltages of non-faulty lines at reasonable values.Firstly,a rapid fault circuit parameter esti mation(FCPE)method using initial fault current information is proposed.With this method,the fault distance and fault transi tion resistance can be quickly estimated,which are used for a quantitative indication of the fault severity.Subsequently,the coordination control strategy of FCL and MMC is proposed,in which the FCL action is prioritized,while the control of MMC is complementary for current limiting.Based on the proposed strategy,fault severity phase planes(FSPPs)are constructed to assess fault severity and calculate the activation time of FCL and voltage regulation factor of MMC.Therefore,the FCL acti vation and MMC control are matched to the fault severity.The effectiveness and advantages of the proposed strategy are vali dated by the simulations in PSCAD/EMTDC.
基金supported in part by National Key R&D Program of China(No.2018YFB0904600)National Natural Science Foundation of China(No.51807053)。
文摘In order to overcome the problems of power flow control and fault current limiting in multi-terminal high voltage direct current(MTDC)grids,this paper proposes a modular multi-terminal DC power flow controller(MM-DCPFC)with fault current limiting function.The topology structure,operation principle,and equivalent circuit of MM-DCPFC are introduced,and such a structure has the advantages of modularity and scalability.The power balance mechanism is studied and a hierarchical power balance control strategy is proposed.The results show that MM-DCPFC can achieve internal power exchange,which avoids the use of external power supply.The fault characteristics of MM-DCPFC are analyzed,fault current limiting and self-protection methods are proposed,and the factors affecting the current limiting capability are studied.The simulation models are established in PLECS,and the simulation results verify the effectiveness of MM-DCPFC in power flow control,fault current limiting,and scalability.In addition,a prototype is developed to validate the function and control method of MM-DCPFC.
基金supported by National Natural Science Foundation of ChinaState Grid Joint Fund for Smart Grid(No.U2066210)National Natural Science Foundation of China(No.52007003)。
文摘In the voltage source converter based high-voltage direct current(VSC-HVDC)grids,fast and reliable protections are the key technologies.The traditional protection schemes are easily affected by fault resistance,line distributed capacitance,etc.Meanwhile,the influence of fault current limiting strategy(FCLS)has not been fully considered.In this paper,the fault characteristics under FCLS and the feasibility of traditional travelling wave protections are analyzed.To improve the reliability and sensibility,a similarity comparison based pilot protection scheme is proposed,which focuses on the relationship between the fault characteristics and the state of the protected transmission line,with the establishment of a precise frequencydependent transmission line model.The criteria based on the similarity comparison calculated by cross-wavelet can identify the fault effectively.Meanwhile,the protection scheme can also endure the influence of error synchronization.Finally,the protection performance is verified in the PSCAD/EMTDC under different fault conditions.
基金Supported by National Natural Science Foundation of China 51707014in part by Scientific Research Fund of Hunan Provincial Education Department 17C0040+1 种基金in part by Key Laboratory of Renewable Energy Electric-Technology of Hunan Province 2017ZNDL005in part by Open Research Project of the State Key Laboratory of Industrial Control Technology(Zhejiang University)(ICT170316).
文摘The series voltage source converter(SVSC)is widely used in the power electronic equipment,such as series active power filter,dynamic voltage restorer,unified power flow controller and so on.However,while the SVSC is more vulnerable to the impact of fault current,its applications are increasing,bringing huge challenges to the safe operation of the grid.In recent years,the topology and control strategy of the series voltage source converter with fault current limiting(SVSC-FCL)are a research hotspot.In this paper,it suggests classifying SVSC-FCL based SVSC into two groups:the control scheme optimization group and the existing topology improvement group.The research challenges and perspectives of the SVSC-FCL are introduced in detail.This paper aims to illustrate current research progress on SVSC-FCL and enrich the available pool of the multi-functional power electronic equipment.
基金Major State Basic Research Development Program of China ( No.2005CB221505)Research Foundation for the Doctoral Programof Higher Education of China(No.20050248058)
文摘A novel magnetic-controlled switcher type fault current limiter (FCL) based on the topology of the saturated iron core high temperature superconducting FCL is proposed. The magnetic field distribution of the FCL iron core is analyzed by FEA software ANSYS. The current limiting characteristic is investigated by both 3-D field-circuit coupled simulation and Matlab. The experiments on the 220 V/50 A test model show that the FCL can limit the fault current swiftly and effectively,and the FCL has the advantages of simple and reliable structure, flexible control strategy. The simulation and experimental results prove that the theoretical expectation and current limiting performance is satisfactory for practical use.
文摘This paper presents a new type of fault current limiter (FCL) based on fast closing switch, which is composed of a capacitor bank and a reactor in series. The main control component is a fast closing switch connected in parallel with the capacitors, which is driven by the electromagnetic repulsion force. It can response the order within 1 ms. When fault occurs, the switch closes and the capacitors are bypassed, and the fault current is limited by the reactor. Simulation analysis and experiment show that the electromagnetic repulsion force actuator can meet the demand of fast closing switch, it is feasible to develop the FCL with low cost and high reliability.
基金supported by National Natural Science Foundation of China(Nos.51777025,52177131)the Interdisciplinary Program of the Wuhan National High Magnetic Field Center(No.WHMFC202130)Huazhong University of Science and Technology。
文摘The liquid metal current limiter(LMCL)is regarded as a viable solution for reducing the fault current in a power grid.But demonstrating the liquid metal arc plasma self-pinching process of the resistive wall,and reducing the erosion of the LMCL are challenging,not only theoretically,but also practically.In this work,a novel LMCL is designed with a resistive wall that can be connected to the current-limiting circuit inside the cavity.Specifically,a novel fault current limiter(FCL)topology is put forward where the novel LMCL is combined with a fast switch and current-limiting reactor.Further,the liquid metal self-pinch effect is modeled mathematically in three dimensions,and the gas-liquid two-phase dynamic diagrams under different short-circuit currents are obtained by simulation.The simulation results indicate that with the increase of current,the time for the liquid metal-free surface to begin depressing is reduced,and the position of the depression also changes.Different kinds of bubbles formed by the depressions gradually extend,squeeze,and break.With the increase of current,the liquid metal takes less time to break,but breaks still occur at the edge of the channel,forming arc plasma.Finally,relevant experiments are conducted for the novel FCL topology.The arcing process and current transfer process are analyzed in particular.Comparisons of the peak arc voltage,arcing time,current limiting efficiency,and electrode erosion are presented.The results demonstrate that the arc voltage of the novel FCL topology is reduced by more than 4.5times and the arcing time is reduced by more than 12%.The erosions of the liquid metal and electrodes are reduced.Moreover,the current limiting efficiency of the novel FCL topology is improved by 1%–5%.This work lays a foundation for the topology and optimal design of the LMCL.
文摘The effectiveness of a combination of fault current limiter and thyristor controlled braking resistor on power system stability enhancement and damping turbine shaft torsional oscillations has been studied. If both devices operate at the same bus, the stabilization control scheme can be carried out continuously and with flexibility. As a result, the fault currents are limited, and the generator disturbances and the turbine shaft torsional oscillations are converged quickly. In this paper, the effectiveness of the combination of both devices has been demonstrated by considering 3LG （three-lines-to-ground） fault in a two-machine infinite bus system. Also, temperature rise effect of both devices with various resistance values and weights has been demonstrated. Simulation results indicate a significant power system stability enhancement and damping turbine shaft torsional oscillations as well as with allowable temperature rise.
基金supported by State Grid Science and Technology Projects(SGTYHT/17-JS-199)National Natural Science Foundation of China(51577163).
文摘The fault current limiter(FCL)is an effective measure for improving system stability and suppressing short-circuit fault current.Because of space and economic costs,the optimum placement of FCLs is vital in industrial applications.In this study,two objectives with the same dimensional measurement unit,namely,the total capital investment cost of FCLs and circuit breaker loss related to short-circuit currents,are considered.The circuit breaker loss model is developed based on the attenuation rule of the circuit breaker service life.The circuit breaker loss is used to quantify the current-limiting effect to avoid the problem of weight selection in a multi-objective problem.The IEEE 10-generator 39-bus system in New England is used to evaluate the performance of the proposed genetic algorithm(GA)method.Comparative and sensitivity analyses are performed.The results of the optimized plan are validated through simulations,indicating the significant potential of the GA for such optimization.
基金the National Basic Research Program(973) of China (No. 2005CB221505)the Research Fund for Doctoral Program of High Education of China(No. 20050248058)
文摘A novel magnetic-controlled switcher type fault current limiter （FCL） for high voltage electric network is presented. The current limiting principle of the FCL and the bias current influence on the characteristic of the FCL axe discussed. The experiments on the 220 V/50 A test model show that the FCL can limit the fault current swiftly and effectively. Under the normal state, the bias current adjustment can change the FCL voltage loss; under the fault state, the steady fault current can be easily adjusted to the preset level by bias current regulating. The experimental result is in accordance with the principle analysis and the FCL has the advantages of flexible control strategy and simple and reliable structure.
文摘A deregulated power market is making short-circuit currents likely to exceed the thermal or mechanical permissible limits of switchgear. Consequently fault current limiters （FCL） become more necessary in power systems. The use of FCLs has an impact on the protection schemes and functions in power systems. Thus, before FCLs can be applied in the network, the impacts on existing protection system must be understood. Depending on the current limiting technique used, today＇s protection concepts may have to be adapted or revised to ensure proper network protection selectivity. A relationship between fault current limiters and protection schemes should be established by taking into account both protection and network specific issues, such as the impact of different FCL technologies, existing and new protection concepts, selectivity and innovative network. This paper is presenting a frame work for accomplishing this task.
文摘FCL （fault current limiter） is used to solve relays miscoordination problem arises from DG （distributed generation） installation. In most published researches, different optimization methods are developed to obtain optimal relay settings to achieve coordination in case of not installing DG, then depending on the achieved optimal obtained relay settings, FCL impedance is deduced to ensure relays coordination restoration in case of installing DG. Based on original optimal relay settings, obtained FCL impedance is not the minimum one required to achieve relay coordination. The contribution of this paper is the generation of multi sets of original relay settings that increase the possibility of finding FCL impedance of minimum value which is lower than the calculated value based on original optimal relay settings. The proposed method achieves better economic target by reducing FCL impedance. The proposed approach is implemented and tested on IEEE-39 bus test system.
基金supported by the National Natural Science Foundation of China(51907057,52077072).
文摘Virtual synchronous generators(VSGs)can provide voltage and frequency support to power systems due to their inertial and damping features.Unfortunately,power angle stability and fault current limitations are still challenging aspects of VSGs under large disturbances.Power angle stability and fault current limitations are indispensable for the safe operation of a VSG.However,in existing studies,these aspects are mostly solved as two independent problems.In this paper,the comprehensive transient stability enhancement(CTSE)control strategy for a VSG,considering power angle stability and fault current limitations is proposed.With a CTSE control,VSG's transient power angle stability is guaranteed.In addition,the steady-state and impulse components of the fault current are fully limited.Furthermore,CTSE control parameters adapted to different fault degrees are presented.Finally,simulation and experimental tests are performed to validate the performance of the proposed method.
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This work is supported by National Key R&D Program(2018YFB0904600).
文摘With the development of power electronic technologies and distributed power generation,DC distribution networks attract increasing attention due to their various advantages compared with traditional AC distribution networks.However,DC fault protection is one of the major issues in DC distribution networks.To improve their reliability and protect the semiconductor devices under DC faults,a current-limiting and energy-transferring DC circuit breaker topology is proposed in this paper.By applying passive components and thyristors,the proposed topology is capable of quickly limiting the fault current and transferring the faulty energy.The working principle,mathematical model and parameter designing method of the proposed topology are presented in this paper.The simulation results verify that the proposed DC circuit breaker could effectively limit the fault current and quickly interrupt the fault current.Cost and conduction power loss evaluation proves the practicality of the proposed topology in medium-voltage DC distribution networks.
基金supported by the National Key R&D Program of China(2018YFB1500702)the National Natural Science Foundation of China(52177187).
文摘Modular multilevel converter(MMC)is increasingly being applied to high voltage direct current(HVDC)systems.However,dc short circuit situations restrain the application of a conventional half bridge MMC system.In this paper,a new sub-module topology with inserted thyristor can help the MMC system clear a dc side fault.Working states and devices voltage stress of the proposed topology are analyzed and the conduction loss comparison between the proposed topology with several existing topologies with dc fault blocking capability is carried out.Results show the proposed topology is superior to other topologies in terms of conduction loss while using the same voltage rating devices.Besides,compared with traditional half bridge topology,only thyristors and diodes are added in the proposed topology.Therefore,cost of the proposed topology can be lower than conventional hybrid MMC sub-modules.At last,the fault blocking capability of the proposed topology is verified in the simulation.
基金This work was supported by National Key Research and Development Program under Grant No.2018YFB0904600the National Natural Science Foundation of China under Grant No.51777072.
文摘The modular multilevel converter(MMC)based DC grid is considered as a future solution for bulk renewable energy integration and transmission.However,the high probability of DC faults and their rapid propagation speed are the main challenges in the development of DC grids.Existing research primarily focuses on the DC fault clearance methods,while the fault current suppression methods are still barely researched.Additionally,the coordination method of fault current suppression and clearance needs to be optimized.In this paper,the technical characteristics of the current suppression methods are studied,and the coordinated methods of fault current suppression and clearance are proposed.At last,a cost comparison of these methods is presented.The research results show that the proposed strategies can reduce the cost of the protection equipment.
