Definite-time zero-sequence over-current protection is presently used in systems whose neutral point is grounded by a low resistance(low-resistance grounding systems).These systems frequently malfunction owing to thei...Definite-time zero-sequence over-current protection is presently used in systems whose neutral point is grounded by a low resistance(low-resistance grounding systems).These systems frequently malfunction owing to their high settings of the action value when a high-impedance grounding fault occurs.In this study,the relationship between the zero-sequence currents of each feeder and the neutral branch was analyzed.Then,a grounding protection method was proposed on the basis of the zero-sequence current ratio coefficient.It is defined as the ratio of the zero-sequence current of the feeder to that of the neutral branch.Nonetheless,both zero-sequence voltage and zero-sequence current are affected by the transition resistance,The influence of transition resistance can be eliminated by calculating this coefficient.Therefore,a method based on the zero-sequence current ratio coefficient was proposed considering the significant difference between the faulty feeder and healthy feeder.Furthermore,unbalanced current can be prevented by setting the starting current.PSCAD simulation results reveal that the proposed method shows high reliability and sensitivity when a high-resistance grounding fault occurs.展开更多
A new system-corrected CMOS audio power AMP is presented. Consisting of four single-end OPAs,this structure is a pseudo-differential system. Compared to conventional CMOS power AMPs, it has the merits of low power con...A new system-corrected CMOS audio power AMP is presented. Consisting of four single-end OPAs,this structure is a pseudo-differential system. Compared to conventional CMOS power AMPs, it has the merits of low power consumption, extremely low THD,easy compensation, and good driving capability. With 1st silicon 0.25μm 1P4M CMOS technology and a 3V power supply,the output range can be 4Vpp when driving an 8Ω‖ 300pF load, while its power dissipation is less than 3mW. The THD is better than 0. 003% at 1kHz. A new over-current protection circuit, which can effectively protect the power output circuits on the chip, is also demonstrated.展开更多
This paper introduces the design of the TZ-2 high voltage modulator for electron cyclotron resonance heating （ECRH） on HL-2A tokamak. The high voltage power supplies （HVPS） for the cyclotron have to operate advant...This paper introduces the design of the TZ-2 high voltage modulator for electron cyclotron resonance heating （ECRH） on HL-2A tokamak. The high voltage power supplies （HVPS） for the cyclotron have to operate advantageously and flexibly, with high stabilization and good insulation to high-voltage. Moreover, the HVPS must carry out the function of protection quickly, for insure the security of people and devices in the experiment on HL-2A. In this year, the HVPS with these modulators satisfies the requirement of the experiment of HL-2A.展开更多
基金supported in part by National Key Research and Development Program of China(2016YFB0900603)Technology Projects of State Grid Corporation of China(52094017000W).
文摘Definite-time zero-sequence over-current protection is presently used in systems whose neutral point is grounded by a low resistance(low-resistance grounding systems).These systems frequently malfunction owing to their high settings of the action value when a high-impedance grounding fault occurs.In this study,the relationship between the zero-sequence currents of each feeder and the neutral branch was analyzed.Then,a grounding protection method was proposed on the basis of the zero-sequence current ratio coefficient.It is defined as the ratio of the zero-sequence current of the feeder to that of the neutral branch.Nonetheless,both zero-sequence voltage and zero-sequence current are affected by the transition resistance,The influence of transition resistance can be eliminated by calculating this coefficient.Therefore,a method based on the zero-sequence current ratio coefficient was proposed considering the significant difference between the faulty feeder and healthy feeder.Furthermore,unbalanced current can be prevented by setting the starting current.PSCAD simulation results reveal that the proposed method shows high reliability and sensitivity when a high-resistance grounding fault occurs.
文摘A new system-corrected CMOS audio power AMP is presented. Consisting of four single-end OPAs,this structure is a pseudo-differential system. Compared to conventional CMOS power AMPs, it has the merits of low power consumption, extremely low THD,easy compensation, and good driving capability. With 1st silicon 0.25μm 1P4M CMOS technology and a 3V power supply,the output range can be 4Vpp when driving an 8Ω‖ 300pF load, while its power dissipation is less than 3mW. The THD is better than 0. 003% at 1kHz. A new over-current protection circuit, which can effectively protect the power output circuits on the chip, is also demonstrated.
文摘This paper introduces the design of the TZ-2 high voltage modulator for electron cyclotron resonance heating （ECRH） on HL-2A tokamak. The high voltage power supplies （HVPS） for the cyclotron have to operate advantageously and flexibly, with high stabilization and good insulation to high-voltage. Moreover, the HVPS must carry out the function of protection quickly, for insure the security of people and devices in the experiment on HL-2A. In this year, the HVPS with these modulators satisfies the requirement of the experiment of HL-2A.
