Annular direct current micro-grid single-end current type distance measurement method based on control and protection cooperation

Abstract

The invention relates to an annular direct current micro-grid single-end current type distance measurement method based on control and protection cooperation. The method comprises the following steps that a hybrid current limiter composed of a hybrid direct current circuit breaker and a current limiting resistor is connected to a VSC outlet in series; a boundary inductor and a boundary resistor are additionally arranged in the annular direct-current micro-grid; a current break variable and a voltage break variable of a direct current side capacitor branch of each converter are configured as a protection starting criterion condition; when the inter-electrode fault of the annular DC micro-grid is detected, single-end fault distance measurement is realized; when the fault distance measurement result is smaller than the length of the local end line, it can be judged that the fault occurs in the area, then a tripping signal is sent to the second rapid isolation switch, fault clearing is achieved, and power supply is restored; if it is judged that the fault occurs outside the area, when the current is zero, a first rapid isolation switch in the hybrid rapid isolation switch is switched on, the normal state is recovered, and when the fault current cannot be detected in the line, the VSC is recovered, and power supply is recovered.

Description

technical field [0001] The invention belongs to the field of relay protection of electric power systems, and in particular relates to a single-end current distance measuring technology of a circular DC micro-network based on coordination of control and protection. Background technique [0002] The DC microgrid based on pulse width modulation (PWM) has the advantages of low network loss, large transmission capacity, fewer conversion links and high power quality. One of the networking methods. However, in the low-voltage DC system, there are still many key problems to be solved, and there are also many technical difficulties in the aspects of fault current limiting, location and isolation. [0003] At present, the research programs on DC system protection at home and abroad are mainly divided into two categories. The first type is a protection scheme based on single-ended quantities. Due to the unknown problem of the opposite-end electrical quantities, accurate fault locatio...

AI Technical Summary

Problems solved by technology

The first type is a protection scheme based on single-ended quantities. Due to the unknown electrical quantities at the opposite end, accurate fault location cannot be achieved.

The second type is communication-based protection schemes, which can effectively overcome the shortcomings of single-ended protection principles in multi-terminal power supply systems, and have strong anti-transition resistance capabilities, but have high requirements for communication synchronization and lay a large number of The communication device does not meet the requirements of economy

Images