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Island detection method based on reactive current and voltage frequency feedback

A technology of voltage frequency and island detection, which is applied in the direction of measuring electricity, measuring devices, measuring electrical variables, etc., can solve problems affecting power quality, detection blind spots, etc., and achieve the effect of small impact and high efficiency

Inactive Publication Date: 2019-11-29
SHANGHAI CHURUI ENERGY TECH CO LTD
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Problems solved by technology

[0003] The invention discloses a new scheme based on the islanding detection method based on reactive current and voltage frequency feedback, and uses a tangent function to realize the positive feedback between voltage frequency and given reactive current, which solves the problem of existing detection blind spots or affecting power quality in existing schemes question

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  • Island detection method based on reactive current and voltage frequency feedback
  • Island detection method based on reactive current and voltage frequency feedback
  • Island detection method based on reactive current and voltage frequency feedback

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Embodiment Construction

[0021] In order to reduce the detection blind area during the island detection of the grid-connected inverter and minimize the impact of the island detection on the output power, this scheme proposes an island detection method with positive feedback of reactive current frequency, and deduces that the positive feedback is established Parameter conditions, and the acquisition methods of each parameter were analyzed. Simulation and experiments have proved that this method has almost no impact on the system when the grid is normal, but once the grid is islanded, the positive feedback between reactive current and frequency will make the frequency change rapidly in one direction until the islanding protection is triggered. This scheme proposes an islanding detection method based on reactive current frequency positive feedback on a three-phase photovoltaic grid-connected inverter platform. The photovoltaic grid-connected inverter system consists of two stages, the former stage is a B...

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Abstract

The invention relates to an island detection method based on reactive current and voltage frequency feedback. Phase-locked loop control is adopted, so that a phase-locked angle can be obtained; phasedifference exists between the phase-locked angle and the voltage phase angle of a power grid; a relation among reactive current, active current and voltage frequency are obtained according to a relation between the power of a load and the output power of an inverter under a steady state after the power outage of the power grid; positive feedback between the frequency and given reactive current isachieved through a tangent function; the voltage frequency deviates towards the same direction all the time through the positive feedback, so that the phase difference can be eliminated; when the power of the power grid is normal, the voltage frequency of a common point is stabilized at 50Hz or has very small fluctuation, the disturbance of applied reactive current is very small, and influence onthe power factor of a system is relatively small; and if an island condition appears in the power grid, the positive feedback between the reactive current and the frequency enables the frequency to quickly change towards one direction until island protection is triggered. The method has the advantages of small influence and high efficiency.

Description

technical field [0001] The invention relates to an island detection method, in particular to an efficient island detection method based on reactive current and voltage frequency feedback, which belongs to the field of grid-connected power generation. Background technique [0002] Island detection is an essential function of photovoltaic grid-connected power generation systems. In large-scale photovoltaic power generation systems, three-phase grid-connected inverters are an important part of the power generation system. The inverter converts light energy into electrical energy and transmits it to the grid. In the process of power generation, we not only need to detect the quality of the inverter output power, but also need to consider the island state formed when the grid is powered off. When the inverter is isolated, the continuous grid-connected operation of the inverter will cause potential harm to the power supply equipment and personnel, so there are many methods of isla...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/08
CPCG01R31/088
Inventor 郑文祺邵冲
Owner SHANGHAI CHURUI ENERGY TECH CO LTD
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