Islanding detection method and device for a three-phase grid-connected inverter

Abstract

The invention discloses an isolated island detection method and device for a three-phase grid connected inverter. The method comprises the steps of injecting reactive current Iq1 and Iq2 to the output current of the inverter, wherein Iq2 is equal to Id*(F-FN)*K; judging whether the variations of the phase angles between every two phases of the last semiaxis and the current semiaxis meet the condition that the variation of the first phase angle and the variation of the Iq1 of the current semiaxis and the variation of the Iq1 of the last semiaxis are in direct proportion and are same in direction, the variation of the second phase angle and the variation of the Iq1 are in direct proportion and opposite in direction and the variation of the third phase angle is not influenced by the Iq1; if yes, judging that single-phase or two-phase isolated island occurs; calculating the three-phase voltage frequency condition of grid connected points and judging whether the three-phase voltage frequency exceeds the preset voltage frequency threshold value; if the three-phase voltage frequency exceeds the preset voltage frequency threshold value, judging that the three-phase isolated island occurs; if the three-phase voltage frequency does not exceed the preset voltage frequency threshold value, calculating the average value F of the three-phase voltage frequency of the grid connected points to calculate the corresponding Iq2. The isolated island detection method and device can be used for detecting the single-phase, two-phase and three-phase isolated island states at the same time.

Description

technical field [0001] The invention relates to the field of island detection, in particular to an 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 caused by unplanned island...

AI Technical Summary

Problems solved by technology

However, in the actual three-phase grid-connected inverter, single-phase, two-phase and three-phase island faults may occur in the system, and the system can only judge single-phase, two-phase islands or only three-phase island-to-island detection is not enough

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