Method for protecting whole-line rapid-cutting and optimizing reclosure of current collection line

Abstract

A method for protecting whole-line rapid-cutting and optimizing reclosure of a current collection line comprises the following steps that firstly, a three-phase current and a zero-sequence current of the protected current collection line of a wind power plant grid-connection transformer substation are measured; secondly, as for an interphase fault, protection configuration of current quick-break protection in the I-section direction is performed; thirdly, a busbar phase voltage of the wind power plant grid-connection transformer substation is measured and used for judging the fault direction; fourthly, as for a grounding fault, protection configuration of I-section zero-sequence current quick-break protection is performed; fifthly, the line is configured with automatic three-phase one-shot reclosure, as for a wind generation set grid-connection current collection line not having the low voltage ride through capability, reclosure is conducted once at 0.5s after the fault, and as for a wind generation set grid-connection current collection line having the low voltage ride through capability, reclosure is conducted once at a time delay t after the fault. The method for protecting whole-line rapid-cutting and optimizing reclosure of a current collection line can achieve rapid power service restoration of the line having a transient fault, lay a foundation for rapid and initiative grid connection of a wind generation set, and enhance safety and stability of a grid-connection electric power system.

Description

technical field [0001] The invention belongs to the technical field of wind power generation, and in particular relates to a full-line speed-cut protection and optimized reclosing method for collector lines compatible with the operating characteristics of wind turbines Background technique [0002] Mainstream wind turbines such as doubly-fed and permanent magnet grid-connected inverters are very sensitive to system voltage drops, which can easily cause large-scale wind power chains to go off-grid, posing a serious threat to the safe and stable operation of the grid-connected power system. This problem is called the low voltage ride through problem of wind turbines. [0003] In fact, the serious voltage drop that really tests the low voltage ride-through ability of wind turbines is basically caused by system failure; the voltage distortion of about 10-15% caused by factors such as wind farm reactive power imbalance or system disturbance, existing The overload capacity of the...

AI Technical Summary

Problems solved by technology

[0008] 1. The protection range of section I unlimited current quick-break protection and I-section zero-sequence current quick-break protection is too small, especially due to the intermittent influence of wind farm output, the system impedance on the back side of 35kV fluctuates greatly, and the actual protection of section I current protection The range is greatly reduced; therefore, most of the faults need to be removed by the protection action of stage II;

[0009] 2. The action delay of stage II time-delayed current quick-break protection is long, and the fault voltage drop exists for a long time. It is required that the wind turbine must have a strong low-voltage ride-through capability, otherwise it will cause a large number of wind turbines to go off-grid;

[0010] 3. The existing wind farm collector line protection is not configured to reclose after a fault, mainly because the operating status of the wind turbine connected to the collector line is unknown after the fault, and the fixed time for arc extinguishment at the fault point cannot be determined; the probability of occurrence on the collector line 80-90% of single-phase instantaneous ground faults cannot achieve self-healing, which prolongs the time for wind turbines to re-connect to the grid for power generation

[0011] The above problems lead to any fault disturbance in the wind power grid-connected system, which will cause a large area of ​​wind turbines to be disconnected from the grid

Therefore, the State Grid Corporation of China's "Technical Regulations for Connecting Wind Farms to the Grid (Revised Edition)" mandates that wind turbines connected to the grid must pass the low-voltage ride-through function; so that the current operating wind turbines have to increase the capacity of the inverter and improve the wind turbine when the voltage drops. Control strategy, but this is a technical transformation method for individual wind turbines, the overall cost is very high, and wind power operators and wind turbine manufacturers lack initiative

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