Island detection method based on phase-frequency positive feedback

A technology of island detection and positive feedback, applied in the direction of measuring electricity, measuring devices, measuring electrical variables, etc., can solve the problems of small working dead zone, complex algorithm, power grid harmonic problems, etc., to reduce harmonics, simple calculation, Correct the effect of unreasonable movement

Active Publication Date: 2013-07-17
CHINA AGRI UNIV
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These methods have small working dead zone, fast detection speed and high precision, but the algorith

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  • Island detection method based on phase-frequency positive feedback
  • Island detection method based on phase-frequency positive feedback
  • Island detection method based on phase-frequency positive feedback

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[0041] The following is a phase-based method proposed by the present invention. The islanding detection method of frequency positive feedback is described in detail with reference to the accompanying drawings and embodiments.

[0042] The invention is suitable for a digital control inverter system with grid-connected function. The method of the present invention is based on the phase. The island detection method of frequency positive feedback is mainly to modify the phase-frequency characteristics of the second-order generalized integrator, and perform phase compensation on the output of the phase-locked loop, so that the positive feedback of the phase-locked loop occurs when the inverter works in the island state, and the engineering error is infinite. Zoom in and shift the frequency until it is determined that islanding occurs.

[0043] The bidirectional energy storage inverter is taken as an example below, and other grid-connected photovoltaic power generation systems suc...

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Abstract

The invention provides an island detection method based on phase-frequency positive feedback and relates to the technical field of grid-connected inverter control. The island detection method includes: acquiring voltage signals of inverter grid-connected points through an analog to digital (AD) converter, utilizing a phase-locking ring to perform phase locking, and obtaining power grid frequency f and a voltage phase theta; calculating a power grid frequency average value F through cumulative number N of the power grid frequency f; obtaining an offset angle d theta through calculation according to the power grid frequency average value F, compensating the phase, obtaining a compensated output phase, measuring frequency f' of an inverter grid-connected point according to the output phase, and judging whether an inverter is in an island operation state. Compared with a traditional algorithm, the island detection method cannot be influenced by current, power and load impedance, has no non-detection zone and no artificial disturbance of frequency, the phase and the like, and does not lead harmonic wave toward a power grid. The island detection method is simple, rapid, reliable and accurate and improves island detection speed.

Description

technical field [0001] The invention relates to the technical field of grid-connected inverter control, in particular to an islanding detection method based on phase-frequency positive feedback. Background technique [0002] With the increasingly serious energy shortage and environmental problems, the utilization of renewable energy such as solar energy and wind energy has become a research hotspot all over the world. The function of the distributed power inverter is to convert the electric energy generated by wind turbines, photovoltaic panels and other devices into alternating current that meets the national grid access standards. When the inverter is connected to the grid, an island phenomenon may occur in the power system. The so-called isolated island phenomenon means that when the large power grid loses power, the inverter still transmits electric energy to the large power grid, fails to detect the power failure state of the large power grid and separates from it, and...

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Application Information

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IPC IPC(8): G01R31/00
Inventor 杨仁刚周献飞孙钦斐冯小明王文成唐云峰王江波
Owner CHINA AGRI UNIV
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