Photovoltaic microgrid fault isolation method based on fault state

Abstract

For the single-phase grounding fault and instant fault of a power distribution network including a photovoltaic microgrid, the invention discloses a photovoltaic microgrid fault isolation method based on a fault state. The method includes the following steps of (1) partitioning the microgrid; (2) isolating the fault sections; (3) cutting off a single-phase grounding fault wire; and (4) recovering the power supply of fault microgrid partitions. The microgrid is reasonably partitioned, the fault sections are isolated through a boundary switch, and the power-off range is reduced. By the full use of the anti-islanding protection function of a photovoltaic inverter, a fault line is selected through S transform after the photovoltaic power supply and the power grid are isolated, so that the reliability of relay protection and the accuracy of line selection are improved, and the problem that the power distribution network including the photovoltaic power supply is unreliable in relay protection due to the bidirectional flow of power is solved. The photovoltaic microgrid fault isolation method has better protection effects on the single-phase grounding fault and other instant faults in the power distribution network.

Description

technical field [0001] The invention relates to a fault processing method of a distribution network, in particular to a photovoltaic micro-grid fault isolation method based on a fault state, and belongs to the technical field of new energy power generation. Background technique [0002] With the continuous improvement of modern power users' requirements for power supply continuity and reliability and the increasing emphasis of power supply enterprises on user satisfaction, how to analyze the cause of the fault, select the fault feeder, isolate the faulty station area and recover after the distribution network fails. Quick restoration of power is becoming increasingly important. On the other hand, with the development of industry, a large number of nonlinear loads such as rectifiers, electric arc furnaces, frequency conversion devices, etc. The structure of the distribution network will be changed, and the original one-way power flow of the distribution network will be chang...

AI Technical Summary

Problems solved by technology

[0003] The connection of distributed power generation devices such as photovoltaics and wind power to the distribution side changes the structure of the distribution network, and changes the original one-way power flow of the distribution network into a two-way power flow, which will result in the protection and fault diagnosis of the distribution network. more complicated

The traditional relay protection method cannot quickly locate and eliminate the fault of the distribution network connected to the distributed power supply, which will lead to an excessively large power outage and it is difficult to determine the location of the fault

In the event of an unplanned island, there is a risk that the distributed power inverter will continue to operate in parallel with the grid, which will cause hidden dangers for equipment maintenance in the distribution network failure state

[0004] In the medium and low voltage distribution network, more than 80% of the faults are single-phase ground faults. Unlike the high-current grounding system of the transmission network, the neutral point of the distribution network is usually not grounded, or grounded through arc suppression coils and high impedance, Both are low-current grounding systems. When a single-phase grounding fault occurs, since a short-circuit circuit cannot be formed, although the line voltage remains normal at this time, it can still supply power to users for more than one hour, but the phase voltage of the unfaulted phase will increase by 1.732 times , which seriously threatens the insulation performance of the system

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