In nuclear fusion power supply systems, the thyristors often need to be connected in parallel for sustaining large current. However, research on the reverse recovery transient of parallel thyristors has not been repor...In nuclear fusion power supply systems, the thyristors often need to be connected in parallel for sustaining large current. However, research on the reverse recovery transient of parallel thyristors has not been reported yet. When several thyristors are connected in parallel,they cannot turn-off at the same moment, and thus the turn-off model based on a single thyristor is no longer suitable. In this paper, an analysis is presented for the reverse recovery transient of parallel thyristors. Parallel thyristors can be assumed as one virtual thyristor so that the reverse recovery current can be modeled by an exponential function. Through equivalent transformation of the rectifier circuit, the commutating over-voltage can be calculated based on Kirchhoff’s equation. The reverse recovery current and commutation over-voltage waveforms are measured on an experiment platform for a high power rectifier supply. From the measurement results, it is concluded that the modeling method is acceptable.展开更多
Because of their economy and applicability,high-power thyristor devices are widely used in the power supply systems for large fusion devices.When high-dose neutrons produced by deuterium–tritium(D–T)fusion reactions...Because of their economy and applicability,high-power thyristor devices are widely used in the power supply systems for large fusion devices.When high-dose neutrons produced by deuterium–tritium(D–T)fusion reactions are irradiated on a thyristor device for a long time,the electrical characteristics of the device change,which may eventually cause irreversible damage.In this study,with the thyristor switch of the commutation circuit in the quench protection system(QPS)of a fusion device as the study object,the relationship between the internal physical structure and external electrical parameters of the irradiated thyristor is established.Subsequently,a series of targeted thyristor physical simulations and neutron irradiation experiments are conducted to verify the accuracy of the theoretical analysis.In addition,the effect of irradiated thyristor electrical characteristic changes on the entire QPS is studied by accurate simulation,providing valuable guidelines for the maintenance and renovation of the QPS.展开更多
Thyristors have longer lifetimes,higher reliability,and very high voltage and current ratings and they require less maintenance than other high-power semiconductor devices.As a result,they are particularly suitable fo...Thyristors have longer lifetimes,higher reliability,and very high voltage and current ratings and they require less maintenance than other high-power semiconductor devices.As a result,they are particularly suitable for quench protection systems(QPSs),which protect the superconducting magnets in large fusion devices from damage.In this paper,we propose a design for a 100 k A/10 k V thyristor stack supported by both theoretical and simulation-based analyses as well as experimental verification.Due to the ultrahigh electrical performance requirements imposed on the QPS by the Comprehensive Research Facility for Fusion Technology(CRAFT),three main issues must be considered:the voltage-balancing problem caused by multiple thyristors in a series structure,the increased junction temperature problem caused by extremely high currents,and the reverse recovery phenomenon that arises from the thyristor’s physical structure.Hence,a series of detailed theoretical analyses,simulations,and experiments,including a thyristor junction temperature prediction method and reverse recovery process modeling,were carried out to optimize the design.Finally,the reliability and stability of the thyristor stack were verified by a series of prototype experiments.The results confirmed the correctness and accuracy of the proposed thyristor stack design method and also indicated that the proposed thyristor stack can meet the application conditions of a 100 k A QPS in the CRAFT project.展开更多
High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs...High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs during the underwater high voltage pulse discharge process, which brings security risks to the stability of the pulse fracturing system. In order to solve this problem, an underwater pulse power discharge system was established, the circuit oscillation generation conditions were analyzed and the circuit oscillation suppression method was proposed. Firstly, the system structure was introduced and the charging model of the energy storage capacitor was established by the state space average method. Next, the electrode high-voltage breakdown model was established through COMSOL software, the electrode breakdown process was analyzed according to the electron density distribution image, and the plasma channel impedance was estimated based on the conductivity simulation results. Then the underwater pulse power discharge process and the circuit oscillation generation condition were analyzed, and the circuit oscillation suppression strategy of using the thyristor to replace the gas spark switch was proposed. Finally, laboratory experiments were carried out to verify the precision of the theoretical model and the suppression effect of circuit oscillation. The experimental results show that the voltage variation of the energy storage capacitor, the impedance change of the pulse power discharge process, and the equivalent circuit in each discharge stage were consistent with the theoretical model. The proposed oscillation suppression strategy cannot only prevent the damage caused by circuit oscillation but also reduce the damping oscillation time by77.1%, which can greatly improve the stability of the system. This research has potential application value in the field of underwater pulse power discharge for reservoir reconstruction.展开更多
This work proposes a novel approach for multi-type optimal placement of flexible AC transmission system(FACTS) devices so as to optimize multi-objective voltage stability problem. The current study discusses a way for...This work proposes a novel approach for multi-type optimal placement of flexible AC transmission system(FACTS) devices so as to optimize multi-objective voltage stability problem. The current study discusses a way for locating and setting of thyristor controlled series capacitor(TCSC) and static var compensator(SVC) using the multi-objective optimization approach named strength pareto multi-objective evolutionary algorithm(SPMOEA). Maximization of the static voltage stability margin(SVSM) and minimizations of real power losses(RPL) and load voltage deviation(LVD) are taken as the goals or three objective functions, when optimally locating multi-type FACTS devices. The performance and effectiveness of the proposed approach has been validated by the simulation results of the IEEE 30-bus and IEEE 118-bus test systems. The proposed approach is compared with non-dominated sorting particle swarm optimization(NSPSO) algorithm. This comparison confirms the usefulness of the multi-objective proposed technique that makes it promising for determination of combinatorial problems of FACTS devices location and setting in large scale power systems.展开更多
A bridge arm prototype of ITER poloidal field (PF) converter modules has been designed and fabricated. Non-cophase counter parallel connection is chosen as the arm structure of the prototype. Among all factors affec...A bridge arm prototype of ITER poloidal field (PF) converter modules has been designed and fabricated. Non-cophase counter parallel connection is chosen as the arm structure of the prototype. Among all factors affecting current sharing, arm structure is the main one. During the design of the arm prototype, a novel method based on inductance matrixes is employed to improve the current sharing of the bridge arm. The test results on the prototype show that the current sharing performance of the arm prototype is much better than relevant design requirement, and that the matrix method is very effective to analyze and solve the current sharing problems of thyristor converters.展开更多
To overcome hole-injection limitation of p^+-n emitter junction in 4H-SiC light triggered thyristor, a novel high- voltage 4H-SiC light triggered thyristor with double-deck thin n-base structure is proposed and demon...To overcome hole-injection limitation of p^+-n emitter junction in 4H-SiC light triggered thyristor, a novel high- voltage 4H-SiC light triggered thyristor with double-deck thin n-base structure is proposed and demonstrated by two- dimensional numerical simulations. In this new structure, the conventional thin n-base is split to double-deck. The hole- injection of p^+-n emitter junction is modulated by modulating the doping concentration and thickness of upper-deck thin n- base. With double-deck thin n-base, the current gain coefficient of the top pnp transistor in 4H-SiC light triggered thyristor is enhanced. As a result, the triggering light intensity and the turn-on delay time of 4H-SiC light triggered thyristor are both reduced. The simulation results show that the proposed 10-kV 4H-SiC light triggered thyristor is able to be triggered on by 500-mW/cm^2 ultraviolet light pulse. Meanwhile, the turn-on delay time of the proposed thyristor is reduced to 337 ns.展开更多
A new 4 H–SiC light triggered thyristor(LTT) with 7-shaped thin n-base doping profile is proposed and simulated using a two-dimensional numerical method. In this new structure, the bottom region of the thin n-base ...A new 4 H–SiC light triggered thyristor(LTT) with 7-shaped thin n-base doping profile is proposed and simulated using a two-dimensional numerical method. In this new structure, the bottom region of the thin n-base has a graded doping profile to induce an accelerating electric field and compensate for the shortcoming of the double-layer thin n-base structure in transmitting injected holes. In addition, the accelerating electric field can also speed up the transmission of photongenerated carriers during light triggering. As a result, the current gain of the top pnp transistor of the SiC LTT is further increased. According to the TCAD simulations, the turn-on delay time of the SiC LTT decreases by about 91.5% compared with that of previous double-layer thin n-base SiC LTT. The minimum turn-on delay time of the SiC LTT is only 828 ns,when triggered by 100 mW/cm^2 ultraviolet light. Meanwhile, there is only a slight degradation in the forward blocking characteristic.展开更多
In order to test the superconducting magnet performance for the Comprehensive Research Facility for Fusion Technology(CRAFT)project of China,a power supply converter needs to be designed.In this paper,short circuits u...In order to test the superconducting magnet performance for the Comprehensive Research Facility for Fusion Technology(CRAFT)project of China,a power supply converter needs to be designed.In this paper,short circuits upstream and downstream of the direct current(DC)reactor are analyzed,and the thyristor style and the parallel number are determined by the limit analysis of junction temperature and fault current I^2t.On this basis,the over current and voltage verification of fast fuse are finished to protect the thyristor at fault cases by considering the short circuit of the bridge arm.Then,the resistor and capacitor parameters of thyristor snubber are committed to decreasing the reverse over voltage.These analysis results will be used as the preliminary design of high power magnet converter for CRAFT.展开更多
For a single machine infinite power system with thyristor controlled series compensation(TCSC) device, which is affected by system model uncertainties, nonlinear time-delays and external unknown disturbances, we prese...For a single machine infinite power system with thyristor controlled series compensation(TCSC) device, which is affected by system model uncertainties, nonlinear time-delays and external unknown disturbances, we present a robust adaptive backstepping control scheme based on the radial basis function neural network(RBFNN). The RBFNN is introduced to approximate the complex nonlinear function involving uncertainties and external unknown disturbances, and meanwhile a new robust term is constructed to further estimate the system residual error,which removes the requirement of knowing the upper bound of the disturbances and uncertainty terms. The stability analysis of the power system is presented based on the Lyapunov function,which can guarantee the uniform ultimate boundedness(UUB) of all parameters and states of the whole closed-loop system. A comparison is made between the RBFNN-based robust adaptive control and the general backstepping control in the simulation part to verify the effectiveness of the proposed control scheme.展开更多
Thyristor valve is one of the key equipments for ultra high voltage direct current(UHVDC) power transmission projects.Before being installed on site,they need to be tested in a laboratory in order to verify their oper...Thyristor valve is one of the key equipments for ultra high voltage direct current(UHVDC) power transmission projects.Before being installed on site,they need to be tested in a laboratory in order to verify their operational performance to satisfy the technical specification of project related.Test facilities for operational tests of thyristor valves are supposed to enable to undertake more severe electrical stresses than those being applied in the thyristor valves under test(test objects).On the other hand,the stresses applied into the test objects are neither higher nor lower than specified by the specification,because inappropriate stresses applied would result in incorrect evaluation of performance on the test objects,more seriously,would cuase the damage of test objects with expensive cost losing.Generally,the process of operational tests is complicated and performed in a complex synthetic test circuit(hereafter as STC),where there are a lot of sensors used for measuring,monitoring and protection on line to ensure that the test circuit functions in good condition.Therefore,the measuring systems embedded play a core role in STC,acting like "eyes".Based on the first project of building up a STC in China,experience of planning measuring systems is summarized so as to be referenced by related engineers.展开更多
An ultra-high voltage 4H-silicon carbide(Si C) gate turn-off(GTO) thyristor for low switching time is proposed and analyzed by numerical simulation. It features a double epitaxial p-base in which an extra electrical f...An ultra-high voltage 4H-silicon carbide(Si C) gate turn-off(GTO) thyristor for low switching time is proposed and analyzed by numerical simulation. It features a double epitaxial p-base in which an extra electrical field is induced to enhance the transportation of the electrons in the thin p-base and reduce recombination. As a result, the turn-on characteristics are improved. What is more, to obtain a low turn-off loss, an alternating p^+/n^+region formed in the backside acts as the anode in the GTO thyristor. Consequently, another path formed by the reverse-biased n^+–p junction accelerates the fast removal of excess electrons during turn-off. This work demonstrates that the turn-on time and turn-off time of the new structure are reduced to 37 ns and 783.1 ns, respectively, under a bus voltage of 8000 V and load current of 100 A/cm^2.展开更多
An analysis model of the dV/dt capability for a metal-oxide-semiconductor (MOS) controlled thyristor (MCT) is developed. It is shown that, in addition to the P-well resistance reported previously, the existence of...An analysis model of the dV/dt capability for a metal-oxide-semiconductor (MOS) controlled thyristor (MCT) is developed. It is shown that, in addition to the P-well resistance reported previously, the existence of the OFF-FET channel resistance in the MCT may degrade the dV/dt capability. Lower P-well and N-well dosages in the MCT are useful in getting a lower threshold voltage of OFF-FET and then a higher dV/dt immunity. However, both dosages are restricted by the requirements for the blocking property and the forward conduction capability. Thus, a double variable lateral doping (DVLD) technique is proposed to realize a high dV/dt immunity without any sacrifice in other properties. The accuracy of the developed model is verified by comparing the obtained results with those from simulations. In addition, this DVLD MCT features mask-saving compared with the conventional MCT fabrication process. The excellent device performance, coupled with the simple fabrication, makes the proposed DVLP MCT a promising candidate for capacitor discharge applications.展开更多
For three fundamental input-protection schemes suitable for high-frequency CMOS ICs, which utilize protection devices such as NMOS transistors, thyristors, and diodes, we attempt an in-depth comparison on HBM ESD robu...For three fundamental input-protection schemes suitable for high-frequency CMOS ICs, which utilize protection devices such as NMOS transistors, thyristors, and diodes, we attempt an in-depth comparison on HBM ESD robustness in terms of lattice heating inside protection devices and peak voltages developed across gate oxides in input buffers, based on DC, mixed-mode transient, and AC analyses utilizing a 2-dimensional device simulator. For this purpose, we construct an equivalent circuit model of input HBM test environments for CMOS chips equipped with input ESD protection circuits, which allows mixed-mode transient simulations for various HBM test modes. By executing mixed-mode simulations including up to six active protection devices in a circuit, we attempt a detailed analysis on the problems, which can occur in real tests. In the procedure, we suggest to a recipe to ease the bipolar trigger in the protection devices and figure out that oxide failure in internal circuits is determined by the peak voltage developed in the later stage of discharge, which corresponds to the junction breakdown voltage of the NMOS structure residing in the protection devices. We explain strength and weakness of each protection scheme as an input ESD protection circuit for high-frequency ICs, and suggest valuable guidelines relating design of the protection devices and circuits.展开更多
Power electronic zigzag transformer is an attractive solution for the flexible interconnection of smart distribution networks.It is constituted by slow-response and low-precision thyristor converters and fast-response...Power electronic zigzag transformer is an attractive solution for the flexible interconnection of smart distribution networks.It is constituted by slow-response and low-precision thyristor converters and fast-response and high-accuracy voltage source converters.This paper models its primary circuit and addresses its basic operation mechanism.Then a dual-timescale control scheme is investigated to realize the coordinated regulation of both types of converter.A simulation case is established in PSCAD containing interconnected mid-voltage distribution networks.Simulations with poor-and well-matched control timescales are both carried out.And accordingly,the power flow controllability under these conditions is compared.When the shorter control timescale is no more than tenth of the longer one,the power electronic zigzag transformer will operate with satisfying performances.展开更多
With the growth of capacity of high voltage direct current(HVDC) transmission lines,the ratings of thyristor valves,which are one of the most critical equipments,are getting higher and higher.Verification of performan...With the growth of capacity of high voltage direct current(HVDC) transmission lines,the ratings of thyristor valves,which are one of the most critical equipments,are getting higher and higher.Verification of performance of thyristor valves particularly designed for HVDC project plays an important role in the handover of products between the manufacturer and the client.Conventional test facilities based on philosophy of direct test cannot meet the requirements for modern thyristor valves.New test facilities with high ratings are necessarily built based on philosophy of synthetic test.Over the conventional direct test circuit,the later is an economical and feasible solution with less financial investment and higher test capability.However,the equivalency between the synthetic test and the direct test should be analyzed technically in order to make sure that the condition of verification test in a synthetic test circuit should satisfy the actual operation condition of thyristor valves existing in a real HVDC project,just as in a direct test circuit.Equivalency analysis is focused in this paper,covering the scope of thyristor valves' steady state,and transient state.On the basis of the results achieved,a synthetic test circuit of 6 500 A/50 kV for operational tests of thyristor valves used for up to UHVDC project has newly been set up and already put into service in Xi'an High Voltage Apparatus Research Institute Co.,Ltd.(XIHARI),China.Some of the results have been adopted also by a new national standard of China.展开更多
In a poloidal field (PF) converter module, fuse protection is of great importance to ensure the safety of the thyristors. The fuse is pre-selected in a traditional way and then verified by finite element analysis. A...In a poloidal field (PF) converter module, fuse protection is of great importance to ensure the safety of the thyristors. The fuse is pre-selected in a traditional way and then verified by finite element analysis. A 3D physical model is built by ANSYS software to solve the thermal- electric coupled problem of transient process in case of external fault. The result shows that this method is feasible.展开更多
A high-current pulse forming network (PFN) has been developed for applications to artificial solar-wind generation. It is switched by staticinduction thyristor (SIThy) and is capable of generating pulsed current of ~...A high-current pulse forming network (PFN) has been developed for applications to artificial solar-wind generation. It is switched by staticinduction thyristor (SIThy) and is capable of generating pulsed current of ~9.7 kA for a time duration of ~1 ms. The SIThy switch module ismade that it can be controlled by an optical signal and it can be operated at elevated electrical potential. The experiments reported in this paperused two switch modules connected in series for maximum operating voltage of 3.5 kV. The experimental results have demonstrated a pulsedhigh-current generator switched by semiconductor devices, as well as the control and operation of SIThy for pulsed power application.展开更多
基金supported by the International Thermonuclear Experimental Reactor Project of China(No.2008 GB104000)
文摘In nuclear fusion power supply systems, the thyristors often need to be connected in parallel for sustaining large current. However, research on the reverse recovery transient of parallel thyristors has not been reported yet. When several thyristors are connected in parallel,they cannot turn-off at the same moment, and thus the turn-off model based on a single thyristor is no longer suitable. In this paper, an analysis is presented for the reverse recovery transient of parallel thyristors. Parallel thyristors can be assumed as one virtual thyristor so that the reverse recovery current can be modeled by an exponential function. Through equivalent transformation of the rectifier circuit, the commutating over-voltage can be calculated based on Kirchhoff’s equation. The reverse recovery current and commutation over-voltage waveforms are measured on an experiment platform for a high power rectifier supply. From the measurement results, it is concluded that the modeling method is acceptable.
基金supported by the Fundamental Research Funds for the Central University(No.JZ2023HGTA0182)Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)。
文摘Because of their economy and applicability,high-power thyristor devices are widely used in the power supply systems for large fusion devices.When high-dose neutrons produced by deuterium–tritium(D–T)fusion reactions are irradiated on a thyristor device for a long time,the electrical characteristics of the device change,which may eventually cause irreversible damage.In this study,with the thyristor switch of the commutation circuit in the quench protection system(QPS)of a fusion device as the study object,the relationship between the internal physical structure and external electrical parameters of the irradiated thyristor is established.Subsequently,a series of targeted thyristor physical simulations and neutron irradiation experiments are conducted to verify the accuracy of the theoretical analysis.In addition,the effect of irradiated thyristor electrical characteristic changes on the entire QPS is studied by accurate simulation,providing valuable guidelines for the maintenance and renovation of the QPS.
基金supported by National Key Research and Development Program of China(Nos.2017YFE0300504 and 2017YFE0300500)the Comprehensive Research Facility for the Fusion Technology Program of China(No.2018000052-73-01-001228)。
文摘Thyristors have longer lifetimes,higher reliability,and very high voltage and current ratings and they require less maintenance than other high-power semiconductor devices.As a result,they are particularly suitable for quench protection systems(QPSs),which protect the superconducting magnets in large fusion devices from damage.In this paper,we propose a design for a 100 k A/10 k V thyristor stack supported by both theoretical and simulation-based analyses as well as experimental verification.Due to the ultrahigh electrical performance requirements imposed on the QPS by the Comprehensive Research Facility for Fusion Technology(CRAFT),three main issues must be considered:the voltage-balancing problem caused by multiple thyristors in a series structure,the increased junction temperature problem caused by extremely high currents,and the reverse recovery phenomenon that arises from the thyristor’s physical structure.Hence,a series of detailed theoretical analyses,simulations,and experiments,including a thyristor junction temperature prediction method and reverse recovery process modeling,were carried out to optimize the design.Finally,the reliability and stability of the thyristor stack were verified by a series of prototype experiments.The results confirmed the correctness and accuracy of the proposed thyristor stack design method and also indicated that the proposed thyristor stack can meet the application conditions of a 100 k A QPS in the CRAFT project.
基金financially supported by the National Science and Technology Major Project(No.2016ZX05034004)。
文摘High voltage fracturing technology was widely used in the field of reservoir reconstruction due to its advantages of being clean, pollution-free, and high-efficiency. However, high-frequency circuit oscillation occurs during the underwater high voltage pulse discharge process, which brings security risks to the stability of the pulse fracturing system. In order to solve this problem, an underwater pulse power discharge system was established, the circuit oscillation generation conditions were analyzed and the circuit oscillation suppression method was proposed. Firstly, the system structure was introduced and the charging model of the energy storage capacitor was established by the state space average method. Next, the electrode high-voltage breakdown model was established through COMSOL software, the electrode breakdown process was analyzed according to the electron density distribution image, and the plasma channel impedance was estimated based on the conductivity simulation results. Then the underwater pulse power discharge process and the circuit oscillation generation condition were analyzed, and the circuit oscillation suppression strategy of using the thyristor to replace the gas spark switch was proposed. Finally, laboratory experiments were carried out to verify the precision of the theoretical model and the suppression effect of circuit oscillation. The experimental results show that the voltage variation of the energy storage capacitor, the impedance change of the pulse power discharge process, and the equivalent circuit in each discharge stage were consistent with the theoretical model. The proposed oscillation suppression strategy cannot only prevent the damage caused by circuit oscillation but also reduce the damping oscillation time by77.1%, which can greatly improve the stability of the system. This research has potential application value in the field of underwater pulse power discharge for reservoir reconstruction.
文摘This work proposes a novel approach for multi-type optimal placement of flexible AC transmission system(FACTS) devices so as to optimize multi-objective voltage stability problem. The current study discusses a way for locating and setting of thyristor controlled series capacitor(TCSC) and static var compensator(SVC) using the multi-objective optimization approach named strength pareto multi-objective evolutionary algorithm(SPMOEA). Maximization of the static voltage stability margin(SVSM) and minimizations of real power losses(RPL) and load voltage deviation(LVD) are taken as the goals or three objective functions, when optimally locating multi-type FACTS devices. The performance and effectiveness of the proposed approach has been validated by the simulation results of the IEEE 30-bus and IEEE 118-bus test systems. The proposed approach is compared with non-dominated sorting particle swarm optimization(NSPSO) algorithm. This comparison confirms the usefulness of the multi-objective proposed technique that makes it promising for determination of combinatorial problems of FACTS devices location and setting in large scale power systems.
文摘A bridge arm prototype of ITER poloidal field (PF) converter modules has been designed and fabricated. Non-cophase counter parallel connection is chosen as the arm structure of the prototype. Among all factors affecting current sharing, arm structure is the main one. During the design of the arm prototype, a novel method based on inductance matrixes is employed to improve the current sharing of the bridge arm. The test results on the prototype show that the current sharing performance of the arm prototype is much better than relevant design requirement, and that the matrix method is very effective to analyze and solve the current sharing problems of thyristor converters.
基金supported by the National Natural Science Foundation of China(Grant No.51677149)
文摘To overcome hole-injection limitation of p^+-n emitter junction in 4H-SiC light triggered thyristor, a novel high- voltage 4H-SiC light triggered thyristor with double-deck thin n-base structure is proposed and demonstrated by two- dimensional numerical simulations. In this new structure, the conventional thin n-base is split to double-deck. The hole- injection of p^+-n emitter junction is modulated by modulating the doping concentration and thickness of upper-deck thin n- base. With double-deck thin n-base, the current gain coefficient of the top pnp transistor in 4H-SiC light triggered thyristor is enhanced. As a result, the triggering light intensity and the turn-on delay time of 4H-SiC light triggered thyristor are both reduced. The simulation results show that the proposed 10-kV 4H-SiC light triggered thyristor is able to be triggered on by 500-mW/cm^2 ultraviolet light pulse. Meanwhile, the turn-on delay time of the proposed thyristor is reduced to 337 ns.
基金Project supported by the National Natural Science Foundation of China(Grant No.51677149)
文摘A new 4 H–SiC light triggered thyristor(LTT) with 7-shaped thin n-base doping profile is proposed and simulated using a two-dimensional numerical method. In this new structure, the bottom region of the thin n-base has a graded doping profile to induce an accelerating electric field and compensate for the shortcoming of the double-layer thin n-base structure in transmitting injected holes. In addition, the accelerating electric field can also speed up the transmission of photongenerated carriers during light triggering. As a result, the current gain of the top pnp transistor of the SiC LTT is further increased. According to the TCAD simulations, the turn-on delay time of the SiC LTT decreases by about 91.5% compared with that of previous double-layer thin n-base SiC LTT. The minimum turn-on delay time of the SiC LTT is only 828 ns,when triggered by 100 mW/cm^2 ultraviolet light. Meanwhile, there is only a slight degradation in the forward blocking characteristic.
基金supported by the National Key R&D Program of China(No.2017YFE0300504)Comprehensive Research Facility for Fusion Technology(No.2018-00005273-01-001228).
文摘In order to test the superconducting magnet performance for the Comprehensive Research Facility for Fusion Technology(CRAFT)project of China,a power supply converter needs to be designed.In this paper,short circuits upstream and downstream of the direct current(DC)reactor are analyzed,and the thyristor style and the parallel number are determined by the limit analysis of junction temperature and fault current I^2t.On this basis,the over current and voltage verification of fast fuse are finished to protect the thyristor at fault cases by considering the short circuit of the bridge arm.Then,the resistor and capacitor parameters of thyristor snubber are committed to decreasing the reverse over voltage.These analysis results will be used as the preliminary design of high power magnet converter for CRAFT.
基金supported in part by the National Natural Science Foundation of China(61433004,61703289)
文摘For a single machine infinite power system with thyristor controlled series compensation(TCSC) device, which is affected by system model uncertainties, nonlinear time-delays and external unknown disturbances, we present a robust adaptive backstepping control scheme based on the radial basis function neural network(RBFNN). The RBFNN is introduced to approximate the complex nonlinear function involving uncertainties and external unknown disturbances, and meanwhile a new robust term is constructed to further estimate the system residual error,which removes the requirement of knowing the upper bound of the disturbances and uncertainty terms. The stability analysis of the power system is presented based on the Lyapunov function,which can guarantee the uniform ultimate boundedness(UUB) of all parameters and states of the whole closed-loop system. A comparison is made between the RBFNN-based robust adaptive control and the general backstepping control in the simulation part to verify the effectiveness of the proposed control scheme.
基金Project Supported by National Development and Reform Commission(No.[2006]2709)
文摘Thyristor valve is one of the key equipments for ultra high voltage direct current(UHVDC) power transmission projects.Before being installed on site,they need to be tested in a laboratory in order to verify their operational performance to satisfy the technical specification of project related.Test facilities for operational tests of thyristor valves are supposed to enable to undertake more severe electrical stresses than those being applied in the thyristor valves under test(test objects).On the other hand,the stresses applied into the test objects are neither higher nor lower than specified by the specification,because inappropriate stresses applied would result in incorrect evaluation of performance on the test objects,more seriously,would cuase the damage of test objects with expensive cost losing.Generally,the process of operational tests is complicated and performed in a complex synthetic test circuit(hereafter as STC),where there are a lot of sensors used for measuring,monitoring and protection on line to ensure that the test circuit functions in good condition.Therefore,the measuring systems embedded play a core role in STC,acting like "eyes".Based on the first project of building up a STC in China,experience of planning measuring systems is summarized so as to be referenced by related engineers.
基金Project supported by the National Natural Science Foundation of China(Grant No.51677149)
文摘An ultra-high voltage 4H-silicon carbide(Si C) gate turn-off(GTO) thyristor for low switching time is proposed and analyzed by numerical simulation. It features a double epitaxial p-base in which an extra electrical field is induced to enhance the transportation of the electrons in the thin p-base and reduce recombination. As a result, the turn-on characteristics are improved. What is more, to obtain a low turn-off loss, an alternating p^+/n^+region formed in the backside acts as the anode in the GTO thyristor. Consequently, another path formed by the reverse-biased n^+–p junction accelerates the fast removal of excess electrons during turn-off. This work demonstrates that the turn-on time and turn-off time of the new structure are reduced to 37 ns and 783.1 ns, respectively, under a bus voltage of 8000 V and load current of 100 A/cm^2.
基金supported by the National Natural Science Foundation of China(Grant No.U1330114)the Advance Research Program,China(GrantNo.51308030407)the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory,China(Grant No.ZHD201201)
文摘An analysis model of the dV/dt capability for a metal-oxide-semiconductor (MOS) controlled thyristor (MCT) is developed. It is shown that, in addition to the P-well resistance reported previously, the existence of the OFF-FET channel resistance in the MCT may degrade the dV/dt capability. Lower P-well and N-well dosages in the MCT are useful in getting a lower threshold voltage of OFF-FET and then a higher dV/dt immunity. However, both dosages are restricted by the requirements for the blocking property and the forward conduction capability. Thus, a double variable lateral doping (DVLD) technique is proposed to realize a high dV/dt immunity without any sacrifice in other properties. The accuracy of the developed model is verified by comparing the obtained results with those from simulations. In addition, this DVLD MCT features mask-saving compared with the conventional MCT fabrication process. The excellent device performance, coupled with the simple fabrication, makes the proposed DVLP MCT a promising candidate for capacitor discharge applications.
文摘For three fundamental input-protection schemes suitable for high-frequency CMOS ICs, which utilize protection devices such as NMOS transistors, thyristors, and diodes, we attempt an in-depth comparison on HBM ESD robustness in terms of lattice heating inside protection devices and peak voltages developed across gate oxides in input buffers, based on DC, mixed-mode transient, and AC analyses utilizing a 2-dimensional device simulator. For this purpose, we construct an equivalent circuit model of input HBM test environments for CMOS chips equipped with input ESD protection circuits, which allows mixed-mode transient simulations for various HBM test modes. By executing mixed-mode simulations including up to six active protection devices in a circuit, we attempt a detailed analysis on the problems, which can occur in real tests. In the procedure, we suggest to a recipe to ease the bipolar trigger in the protection devices and figure out that oxide failure in internal circuits is determined by the peak voltage developed in the later stage of discharge, which corresponds to the junction breakdown voltage of the NMOS structure residing in the protection devices. We explain strength and weakness of each protection scheme as an input ESD protection circuit for high-frequency ICs, and suggest valuable guidelines relating design of the protection devices and circuits.
基金This work was supported by the National Natural Science Foundation of China(51490680,51490683).
文摘Power electronic zigzag transformer is an attractive solution for the flexible interconnection of smart distribution networks.It is constituted by slow-response and low-precision thyristor converters and fast-response and high-accuracy voltage source converters.This paper models its primary circuit and addresses its basic operation mechanism.Then a dual-timescale control scheme is investigated to realize the coordinated regulation of both types of converter.A simulation case is established in PSCAD containing interconnected mid-voltage distribution networks.Simulations with poor-and well-matched control timescales are both carried out.And accordingly,the power flow controllability under these conditions is compared.When the shorter control timescale is no more than tenth of the longer one,the power electronic zigzag transformer will operate with satisfying performances.
基金Project Supported by National Development and Reform Commission(No.[2006]2709)
文摘With the growth of capacity of high voltage direct current(HVDC) transmission lines,the ratings of thyristor valves,which are one of the most critical equipments,are getting higher and higher.Verification of performance of thyristor valves particularly designed for HVDC project plays an important role in the handover of products between the manufacturer and the client.Conventional test facilities based on philosophy of direct test cannot meet the requirements for modern thyristor valves.New test facilities with high ratings are necessarily built based on philosophy of synthetic test.Over the conventional direct test circuit,the later is an economical and feasible solution with less financial investment and higher test capability.However,the equivalency between the synthetic test and the direct test should be analyzed technically in order to make sure that the condition of verification test in a synthetic test circuit should satisfy the actual operation condition of thyristor valves existing in a real HVDC project,just as in a direct test circuit.Equivalency analysis is focused in this paper,covering the scope of thyristor valves' steady state,and transient state.On the basis of the results achieved,a synthetic test circuit of 6 500 A/50 kV for operational tests of thyristor valves used for up to UHVDC project has newly been set up and already put into service in Xi'an High Voltage Apparatus Research Institute Co.,Ltd.(XIHARI),China.Some of the results have been adopted also by a new national standard of China.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2010GB108001 and 2013GB113003)
文摘In a poloidal field (PF) converter module, fuse protection is of great importance to ensure the safety of the thyristors. The fuse is pre-selected in a traditional way and then verified by finite element analysis. A 3D physical model is built by ANSYS software to solve the thermal- electric coupled problem of transient process in case of external fault. The result shows that this method is feasible.
文摘A high-current pulse forming network (PFN) has been developed for applications to artificial solar-wind generation. It is switched by staticinduction thyristor (SIThy) and is capable of generating pulsed current of ~9.7 kA for a time duration of ~1 ms. The SIThy switch module ismade that it can be controlled by an optical signal and it can be operated at elevated electrical potential. The experiments reported in this paperused two switch modules connected in series for maximum operating voltage of 3.5 kV. The experimental results have demonstrated a pulsedhigh-current generator switched by semiconductor devices, as well as the control and operation of SIThy for pulsed power application.