Detection method for islanding effect of grid-connected inverter

Abstract

The invention relates to the technical field of grid-connected inverters, and discloses a detection method for an islanding effect of a grid-connected inverter. The method comprises the following steps of: detecting a voltage frequency f(n-1) of a grid-connected port in a previous power grid cycle; detecting a voltage frequency f(n) of the grid-connected port in the present power grid cycle; calculating the absolute value |Delta| of the difference between the power grid frequencies of the two adjacent cycles, wherein the |Delta| is equal to |f(n) - f(n-1)|; adding 1 to a count value when the |Delta| is determined to be outside a range from 0.1Hz to 0.3Hz; and judging that an islanding effect is generated in case that the count value is greater than N / 2 within continuous N cycles. According to the technical scheme of the invention, the islanding effect can be detected by controlling the added frequency disturbance to be within a range from 0.3Hz to 0.5Hz, and the detection time is short; and moreover, via the method, the output of harmonic waves from the inverter to a power grid can be effectively reduced, so a system is relatively stable.

Description

technical field [0001] The invention relates to the technical field of grid-connected inverters, and more particularly to an islanding effect detection method for grid-connected inverters. Background technique [0002] The island effect means that when the grid is powered off, the grid-connected inverter power supply still maintains the state of continuing to supply power to a certain part of the line in the voltage-loss grid. When a certain area in the grid is in the island state of photovoltaic power generation, the grid will not Then control the voltage and frequency in the island area. The voltage or frequency drift in this area will not only damage the user equipment, but also may affect the recovery of the power supply system in this area, and even threaten the personal safety of the staff in severe cases. Therefore, the grid-connected inverter needs to prevent the island effect, Ensure system security and stability. [0003] So how do you detect the islanding effect...

AI Technical Summary

Problems solved by technology

However, after the grid is powered off, due to the unpredictability and complexity of the load in the photovoltaic power generation island area, the detected port voltage and output frequency fluctuations will be very small, so the active island detection method also has detection blind spots

Although increasing the frequency disturbance can reduce the detection blind zone, excessive frequency disturbance will aggravate the distortion of the output current waveform. When power quality control is required, the disturbance will also have a serious impact on the harmonic compensation effect

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