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Transformer-less photovoltaic grid connection detection system and detection method

A detection system and transformer technology, applied in the direction of photovoltaic power generation, single-net parallel feeding arrangement, etc., can solve the problems of not using positive feedback, poor timeliness, and large grid-connected waveform THD, so as to improve the quality of grid-connected and prevent islanding phenomenon, the effect of fast phase lock

Inactive Publication Date: 2014-05-28
DONGHUA UNIV
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  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] This grid-connected method has some defects: (1) Due to the interference of small voltage, the THD of the grid-connected waveform becomes larger, which affects the power supply quality; (2) Positive feedback is not used in the output voltage disturbance, resulting in too slow islanding detection speed, The timeliness is poor; (3) Although the zero-crossing phase detection + genlock algorithm achieves the minimum overshoot, the phase lock takes a long time

Method used

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  • Transformer-less photovoltaic grid connection detection system and detection method

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Embodiment 1

[0024] like figure 1 As shown in the figure, a transformerless photovoltaic grid-connected detection system provided by the present invention includes a full-bridge inverter, and the full-bridge inverter consists of a field effect transistor Q1, a field effect transistor Q2, a field effect transistor Q3 and a field effect transistor. composed of transistor Q4. The output end of the full-bridge inverter is connected to a filter circuit, which is composed of an inductor L1 and a capacitor C22. DC voltage of the front stage After full-bridge inverter and filter circuit, it is converted into power frequency sinusoidal alternating current. The first output end of the filter circuit is connected in series with the current transformer L8 and the relay RE1 in sequence, and then connected to the first port 4 of the two user load access ends. The control unit captures the current through the current transformer L8. The inverter output control signal terminal of the control unit is ...

Embodiment 2

[0037] In this embodiment, the control unit adopts a DSP and an intelligent power module (abbreviated as IPM in English) to realize grid-connected operation. After the DSP control unit captures the zero-crossing signal, it applies the above-mentioned 25-cycle detection grid connection method, which makes the detection time shorter, and the island is found and phase-locked more quickly. The application of IPM module makes the whole circuit simpler. In this way, the grid connection quality and reliability of the inverter will be higher. Other structures and steps are the same as in Example 1.

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Abstract

The invention provides a transformer-less photovoltaic grid connection detection system which is characterized by comprising a full-bridge inverter; the fore direct current voltage is inverted by the full-bridge inverter and filtered, and power frequency sine alternating current is obtained; and an inversion mode can make the inverter work in a grid connection mode or an independent power supply mode on demand, and the switching of the two modes is realized by the control of a controller to a relay. The invention also provides a method which adopts the system, which adopts a continuous and active detecting island, i.e. an active disturbance system which controls the output of a grid connection inverter in each cycle. The invention has the advantages that: the grid connection quality of the inverter and the reliability of a photovoltaic system can be effectively improved.

Description

technical field [0001] The invention relates to a grid-connected detection system of a household inverter (1kW-10kW) in a photovoltaic power generation system and a method for using the system. Background technique [0002] Due to the gradual exhaustion of conventional energy and the gradual increase of environmental pollution, the development and application of new energy has received extensive attention from all over the world. With the country's proposal of the concept of smart grid and the requirements for building high-quality and high-reliability power systems, inverters are an indispensable and important equipment in new energy systems, and their performance stability, superiority, especially The requirements for grid connection quality are also getting higher and higher. Phase-locked loop and islanding detection are important links to ensure high quality and high reliability of grid connection. [0003] The islanding detection methods include passive islanding dete...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38
CPCY02E10/563Y02E10/56
Inventor 孙以泽王强陈玉洁孟婥
Owner DONGHUA UNIV
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