A single-phase and two-phase islanding detection method and device for a three-phase grid-connected inverter

Abstract

The invention discloses a single-phase and double-phase island detection method and device of a three-phase grid-connected inverter. The method comprises the steps of periodically injecting reactive current into output current of the inverter; using a moving average method to calculate the phase angle between every two phases of three-phase power grid voltage of the positive half axis and the negative half axis; calculating the variation of the phase angle between every two phases of the current half axis and the previous half axis; calculating the variation of reactive current of the current half axis and the previous half axis; and determining whether the variation of the phase angle between every two phases of the current half axis and the previous half axis satisfies the conditions that the variation of the first phase angle and the variation of the reactive current are in direct proportion to each other and are identical in direction, the variation of the second phase angle and the variation of the reactive current are in direct proportion to each other and are opposite in direction, and the variation of the third phase angle is independent of the effect of the reactive current. If the variation of the phase angle between every two phases of the current half axis and the previous half axis satisfies the aforementioned conditions, it is determined that an island is generated. With the employment of the single-phase and double-phase island detection method and device, the island state can be detected in a rapid, accurate, and blind area-free manner; and the influence on the quality of electric energy in a power grid can be reduced.

Description

technical field [0001] The invention relates to the field of island detection, in particular to a single-phase and two-phase island detection method and device for a three-phase grid-connected inverter based on reactive power disturbance. Background technique [0002] When solar energy, wind energy, fuel cell and other new energy grid-connected power generation systems are connected to the public grid, after the public grid stops supplying power, the existence of solar energy, wind energy, fuel cell and other new energy grid-connected power generation systems will keep some lines in the power outage area still charged state, forming islands of self-sufficient power supply. In the island state, the power company loses control over the line voltage and frequency, which in turn will bring a series of potential safety hazards and accident disputes. [0003] For this reason, it is necessary to quickly and effectively detect the island state, so as to eliminate the possible harm ...

AI Technical Summary

Problems solved by technology

However, the disturbance introduced by the active frequency shifting and active phase shifting islanding detection methods will cause the degradation of power quality

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