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Transformer-less photovoltaic grid connection detection system and detection method

A detection system and transformer technology, applied in photovoltaic power generation, single-grid parallel feeding arrangement, etc., can solve the problems of no positive feedback, poor timeliness, and large THD of grid-connected waveforms, so as to improve grid-connected quality and prevent islanding. Phenomenon, the effect of fast lock-in

Inactive Publication Date: 2012-06-27
DONGHUA UNIV
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  • Description
  • 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
  • Transformer-less photovoltaic grid connection detection system and detection method

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Embodiment 1

[0024] Such as figure 1 As shown, a transformerless photovoltaic grid-connected detection system provided by the present invention includes a full-bridge inverter, and the full-bridge inverter is composed 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, and the filter circuit is composed of an inductor L1 and a capacitor C22. The DC voltage of the front stage After the full-bridge inverter and filter circuit, it is converted into industrial frequency sinusoidal alternating current. The first output terminal 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 terminals. The control unit captures the current through the current transformer L8. The inverter output control signal t...

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-period detection grid-connection method to make the detection time shorter, and find the island more quickly and synchronize the phase lock. The application of the IPM module makes the whole circuit simpler. In this way, the grid-connected quality and reliability of the inverter will be higher. Other structures and steps are the same as in Embodiment 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 type inverter (1kW-10kW) in a photovoltaic power generation system and a method for using the system. Background technique [0002] Due to the gradual depletion of conventional energy sources and the gradual aggravation of environmental pollution, the development and application of new energy sources have attracted widespread attention from all over the world. With the introduction of the concept of smart grid by the country and the requirements for building high-quality and high-reliability power systems, inverters, as an indispensable and important device in new energy systems, have great The requirements for grid connection quality are getting higher and higher. The phase-locked loop and island detection are important links to ensure high quality and high reliability of grid connection. [0003] Islanding detection methods include passive islanding detection and active islan...

Claims

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Application Information

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Patent Type & Authority Applications(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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