Direct-current microgrid fault isolation method based on alternating-current circuit breaker removal

Abstract

The invention relates to a direct-current microgrid fault isolation method based on alternating-current circuit breaker removal. The method comprises the following steps of: 1, alternating-current circuit breakers are installed at the two ends of a circuit, and topological transformation is conducted on a VSC at the same time as follows: in six bridge arms of three phases of the VSC, two thyristors are used for replacing antiparallel diodes in an upper bridge arm and a lower bridge arm of any one phase, the two thyristors are conducted all the time, and thyristor conduction signals at the positions are cancelled after protection is started, for the remaining four bridge arms of the two phases, in any group of upper and lower bridge arm branches belonging to the two different phases, a thyristor is used for replacing an antiparallel diode, the thyristors at the two positions are conducted all the time, and thyristor conduction signals at the positions are cancelled after protection is started, for the remaining two bridge arms which are not operated and belong to different two phases, the antiparallel diodes in the two bridge arms are respectively connected with the thyristors in parallel, the conduction forward direction is opposite to the direction of the corresponding antiparallel diode, and after the protection is started, the two thyristors are always conducted.

Description

technical field [0001] The invention belongs to the field of relay protection of electric power systems, and in particular relates to a DC micro-grid fault isolation scheme based on the removal of an AC circuit breaker. Background technique [0002] With the growth of social economy and the enhancement of human awareness of environmental protection, new energy has become a hot spot of widespread concern in the power and energy industry and has been widely promoted. In addition, the proportion of some DC loads such as electric vehicles, frequency conversion equipment, LED lighting, information equipment, etc. is increasing day by day. However, based on the voltage source converter (Voltage Source Converter, VSC) using pulse width modulation (PWM) to realize the DC microgrid mixed with the AC system, as the main grid, distributed power supply and DC load are higher The efficient access form has the advantages of high efficiency, large power supply capacity, good anti-interfer...

AI Technical Summary

Problems solved by technology

However, when the periodic minimum value of the fault current generated by the above method will be very large, even greater than the current during normal operation of the system, then the auxiliary arc extinguishing device and the AC circuit breaker will most likely fail, which will make the use of the method based on this method The reliability of the protection scheme of removing the AC circuit breaker is greatly reduced, and the system will have potential safety hazards in relay protection

[0005] Considering this, at the same time, the theoretical research and practical application of DC circuit breakers are not yet mature at this stage. Therefore, it is of great engineering significance to propose a transitional fault isolation scheme based on the high reliability of AC circuit breakers to remove fault lines. Urgent demand for microgrid system development and promotion

Images