| As the development of national economic, increasement of electrical load and long-distance and large-capacity power transmission, high voltage direct current (HVDC) power grid is developed quickly. However, there are still no reliable direct current circuit breaker and interrupted method; it is imminently to develop a direct current circuit breaker to interrupt the circurt. In this paper, researches were carried out to study the problems of HVDC interruption based on forced-current zero. By the methods of simulation and experiment, influence of opening speed, commutating frequency and arcing time on the arc appearance and post-arc dielectric strength was carried out besed on a hybrid actuator. The results can guide the design of DC vacuum circuit breaker and its engineering application. The contents and results of this paper are descriped as follows:A two-stage method, which the current was controlled in excitating stage and displacement was controlled in movable stage, was put forward. The closing model was established with proportional-differential (PD) and fuzzy algorithm respectively in the two stages to control the closing time and speed of the hybrid actuator. And the algorithm has been verified effectively by closing experiments with the variation of capacitor voltage, capacitance, ambient temperature and load force. The opening time and speed was controlled by stabilizing the discharged capacitor votage, which was also verified experimentally. Results indicated that closing time difference can be stabilized within ±0.5ms and opening time difference can be stabilized within ±0.3ms.By the combination of circuit and continuous transition model, the simulation of DC interruption was conducted to study the influence of opening speed, arcing time and commutating frequency on post-arc current, sheath increasement and metal vapor attenuation in EMTP/ATP. Qualitative rules have been obtained to guide the parameter selection for DC interruption in theory. It is discoveried that increasing commutating frequency is adverse to the recovery of dielectric strength. Increasing opening speed and decreasing arcing time are benefit for the sheath increasement, metal vapor attenuation and dielectric strength recovery.A system for DC interruption and arc observation was established to investigate the arc appearance by the variation of opening speed, arcing time and commutating frequency. By the method of image processing techniques, area of the arc photos was measured to analyze the relationship between the above three factors and arc appearance. And related laws have been obtained, which can guide the parameter selection for DC interruption experimentally. It is appropriate to select the opening speed with 2.1m/s and arcing time with 2ms under the condition of this paper. Also, commutating frequency can be increased within the breaking capacity of vacuum interrupter. In addition, a new method, arc image pcolor enhancement, was mentioned to process the arc images. And the results were in accordance with these obtained by the area measurement experiments.The method of pulse discharge was adopted to study the inherent dielectric strength by the variation of opening speed, arcing time and commutating frequency in an established measurement system. It is indicated that increasing opening speed, decreasing arcing time and commutating time are useful for the recovery of dielectric strength. Also, the optimal parameters are in accordance with these obtained by the area measurement experiments. |
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