Current limiting method suitable for grounding fault in alternating-current microgrid

Abstract

The invention relates to a current limiting method suitable for a grounding fault in an AC microgrid. The method comprises the following steps of S1, improving the design of optimal parameters of droop control, constructing a Bode diagram according to a droop control transfer function equation containing a washout filter, and selecting optimal parameters through simulation comparison; S2, an instantaneous power theory being improved, specifically, based on the fact that a traditional instantaneous power theory is only suitable for a single-phase earth fault, the instantaneous power theory containing a double rated current amplitude limiting link being constructed, wherein the instantaneous power theory can be suitable for a two-phase earth fault and a three-phase earth fault; S3, voltage and current double-loop control, utilizing the static error-free tracking performance of a quasi-PR controller, and utilizing quasi-PR control to realize accurate tracking of reference voltage by an outer loop; aiming at a problem that traditional passive control is greatly influenced by parameter disturbance, an inner loop adopts improved passive control to realize accurate tracking of filter inductance current, and voltage and current control is carried out on a converter in a microgrid in combination with an SPWM modulation algorithm. Compared with the prior art, the method has the advantages of being good in fault current asymmetry degree, high in fault recovery speed and the like.

Description

technical field [0001] The invention relates to the technical field of micro-grid current-limiting control, in particular to a current-limiting control method suitable for grounding faults in AC micro-grids. Background technique [0002] In recent years, distributed generation systems based on renewable energy have contributed more and more to the total global energy production. Among them, wind power and photovoltaic power generation are considered as reliable energy sources that should be further developed to achieve maximum efficiency and overcome the world's growing electricity demand. There are two main operating modes of distributed power generation, one is island operation, and the other is grid-connected operation. Regardless of the mode of operation, most researchers focus on power quality and voltage regulation. However, with the increase in the proportion of photovoltaic and wind power generation, the technical problems of distributed power generation systems ha...

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Problems solved by technology

According to the technical report provided by the British Electric Power Company, the direct cause of the accident was that the continuous tripping of gas turbines and wind turbines caused a large power shortage of the system, which further reduced the frequency of the system, triggered the low-frequency load shedding device, and eventually led to a partial power outage in the area; the indirect reason was Large-scale wind turbines shut down due to overcurrent protection problems

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