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Island detection method of photovoltaic grid-connected system

An island detection and photovoltaic technology, which is applied in the direction of measuring electricity, measuring devices, and measuring electrical variables, etc., can solve the problems that it is not suitable to be used alone, the system is unstable, and the time to detect islands is long, so as to reduce detection blind spots and improve safety performance , Accurate and fast island effect

Inactive Publication Date: 2013-05-08
TIANJIN UNIVERSITY OF TECHNOLOGY
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Problems solved by technology

However, this kind of disturbance will cause system instability, and it will take a long time to detect the island, so it should not be used alone

Method used

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  • Island detection method of photovoltaic grid-connected system
  • Island detection method of photovoltaic grid-connected system
  • Island detection method of photovoltaic grid-connected system

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Embodiment Construction

[0023] An islanding detection method for a photovoltaic grid-connected system according to the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] 1. Use the over / under voltage and over / under frequency methods to detect the islanding effect and detect the frequency of the PCC. For inverters, unipolar PWM modulation technology has better harmonic current and smaller switching loss than bipolar PWM modulation technology. The inverter injects unity power factor current into the grid. A 1.5KW photovoltaic system is connected to the public grid and local loads. The output active power and reactive power of the photovoltaic system are the same as those of the load. The load is modeled by RLC with a fixed frequency of 50HZ, and the quality factor Q f =2.5. The grid is a voltage source of Thevenin impedance. The specific parameter settings are shown in Table 2.

[0025] Table 2

[0026] param...

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Abstract

The invention relates to an island detection method of a photovoltaic grid-connected system. In views of the problems that independently-adopted passive detection mode is effective only when effective when mismatching degrees of source and load are large and a large non-detection zone (NDZ) can be accordingly provided; and when an active detection mode is independently-adopted, the system is disturbed, and therefore the disturbance results in instability of the system, and accordingly over-voltage / under-voltage is provided. An over-frequency / under-frequency detection method is combined with an improved impedance detection method to conduct island detection to the system, and therefore the NDZ is reduced to a minimum, quality of electric energy is improved and total harmonic distortion (THD) is reduced.

Description

technical field [0001] The invention relates to an island detection method of a photovoltaic grid-connected system, which can quickly and accurately detect the occurrence of the island effect when the power grid is abnormal or disconnected, and belongs to the detection field of photovoltaic power generation systems. Specifically, it involves an improved impedance detection method that combines over / under voltage and over / under frequency to accurately determine whether the islanding effect occurs in the system, and is mainly used in photovoltaic grid-connected inverters. Background technique [0002] In the 21st century, the demand for energy is becoming more and more urgent, and solar energy, as one of the renewable energy sources, has attracted increasing attention from governments and energy experts around the world in recent years. In China, power shortage is already a very serious problem. Photovoltaic power generation, as one of the ideal and environmentally friendly f...

Claims

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Application Information

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IPC IPC(8): G01R31/00
Inventor 袁其平李称鑫
Owner TIANJIN UNIVERSITY OF TECHNOLOGY
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