Island detection method of photovoltaic grid connected system

An island detection and photovoltaic technology, applied in photovoltaic power generation, single-network parallel feeding arrangement, fault location, etc., can solve the problems of reducing active power output of photovoltaic grid-connected inverter, reducing power generation efficiency, etc., to reduce blind spots, small impact, Detect fast effects

Inactive Publication Date: 2011-11-23
SOUTHEAST UNIV
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Problems solved by technology

This method does not have detection blind spots, but reduces the active power output of

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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

[0027] The present invention is specifically realized through the following technical solutions:

[0028] Step 1 sets the initial value of n to 0 and n is an integer;

[0029] Step 2 Through the zero-crossing detection circuit, the voltage u at the common coupling point PCC pcc The rising edge or falling edge signal is sent to the digital processor at zero crossing, and the voltage period T at the common coupling point PCC is calculated in real time u , and then get the voltage frequency f at the point of common coupling PCC u ; Described zero-crossing detection circuit is known technology at present, for example can adopt literature (Zheng Fei, Fei Shumin, Zhou Xingpeng, Wang Xin. Based on the photovoltaic grid-connected control of FPGA digital phase-locked loop [J]. Power Electronics Technology , 2010, 44(6):53-54) on page 54 figure 2 The block diagram of the zero-crossing detection circuit shown;

[0030] Step 3 If the voltage frequency at the point of public coupling ...

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Abstract

The invention discloses an island detection method of a photovoltaic grid connected system in the field of application of a photovoltaic grid connected system control technology. The island detection method is characterized in that a frequency deviation positive feedback coefficient k is self-adaptively regulated by sections through detecting a change time n of a voltage frequency fu at a point of common coupling (PCC) towards a certain direction, thus frequency deviation is accelerated; and if the absolute value of the change time n exceeds 12, the voltage frequency fu at the PCC does not exceed the limit, two continuous working frequency periods of negative pulse current amplitude interference are applied and low-voltage protection is triggered, thus an island is detected. The method has the advantages of little influence on power grid harmonic waves and active output of the photovoltaic grid connected system and high detection speed.

Description

technical field [0001] The invention relates to an island detection method of a photovoltaic grid-connected system, belonging to the application field of photovoltaic grid-connected system control technology. Background technique [0002] The islanding phenomenon of photovoltaic grid-connected inverters means that when the power grid is interrupted due to electrical failure or natural factors, the inverter still transmits power to the grid, and together with the local load, forms a self-sufficient power supply island that cannot be controlled by the public grid system. The island detection method on the inverter side can be divided into two types: passive (passive) and active (active) according to whether artificial disturbance is applied. Passive detection refers to detecting whether the voltage at the common point is abnormal and can be divided into overvoltage / Under voltage, over frequency / under frequency island detection method, phase mutation detection method, voltage ...

Claims

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Application Information

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IPC IPC(8): H02J3/38G01R31/08
CPCY02E10/563Y02E10/56
Inventor 郑飞费树岷周杏鹏
Owner SOUTHEAST UNIV
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