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Detection method, equipment and system of one-phase island of three-phase grid-connected inverter

A detection method and detection equipment technology, applied in the field of electric power system, can solve the problems of false triggering of communication, failure to accurately and timely detect single-phase or two-phase isolated islands, high cost, etc., and achieve the effect of small harmonic content

Active Publication Date: 2013-07-24
HUAWEI DIGITAL POWER TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0023] However, this method increases equipment investment, the cost is too high, and there may be false triggers in the communication
[0024] In summary, none of the islanding detection methods for three-phase grid-connected inverters provided in the prior art can accurately and timely detect the occurrence of single-phase or two-phase islanding, thereby disconnecting the inverter from the load, thereby Avoid the hazards of isolated islands

Method used

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  • Detection method, equipment and system of one-phase island of three-phase grid-connected inverter
  • Detection method, equipment and system of one-phase island of three-phase grid-connected inverter
  • Detection method, equipment and system of one-phase island of three-phase grid-connected inverter

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Effect test

Embodiment 1

[0057] see figure 2 , which is a flow chart of Embodiment 1 of a method for detecting single-phase islanding of a three-phase grid-connected inverter provided by an embodiment of the present invention.

[0058] S201: Calculate the phase difference between every two phases of the three-phase grid voltage

[0059] It should be noted that before the reactive current is injected, if no island is generated, the phase difference between every two phases of the three-phase grid voltage is determined by the grid voltage, that is, the phase difference is 120 degrees (between A and B phases between phases B and C, between phases A and C).

[0060] S202: Inject reactive current into the output current of the inverter;

[0061] In the embodiment of the present invention, the reactive current is injected into the output current of the inverter because:

[0062] If no reactive current is injected into the output current of the inverter, when islanding occurs, the resonant frequency ma...

Embodiment 2

[0074] see image 3 , which is a flow chart of Embodiment 2 of the method for detecting single-phase islanding of a three-phase grid-connected inverter provided by the present invention.

[0075] The following takes the inverter as a photovoltaic inverter as an example for introduction.

[0076] The inverter power is 20kW, taking full load output as an example. Of course, the inverter can also output at no load, and output at full load is only one of the working conditions. For example, the inverter output is only 10kW, and the load consumption of a certain phase is exactly 3.333kW. At this time, the consumption is equal to the output, and the load is matched.

[0077] A single-phase RLC equivalent load is connected between the inverter and the grid. It should be noted that the load may not be an RLC, but it can be equivalent to an RLC load according to the working principle of the circuit. The test circuit is shown as figure 1 shown.

[0078] The power consumed by R here...

Embodiment 3

[0127] see Figure 8 , which is a schematic diagram of Embodiment 3 of a single-phase or two-phase island detection device for a three-phase grid-connected inverter provided by an embodiment of the present invention.

[0128] In this embodiment, an implementation manner of the reactive current injection unit 200 is mainly introduced.

[0129] The reactive current injection unit 200 in this embodiment includes a driving control signal sending subunit 201, which is used to send a driving control signal to the inverter to change the output current of the inverter so that the output current of the inverter becomes an inverted The superposition of the original output current of the device and the injected reactive current.

[0130] It should be noted that the power part of the inverter is mainly realized by the power tube. The drive control signal sending sub-unit 201 generates a PWM pulse signal, which controls the switch state of the power tube in the inverter, so that the inve...

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Abstract

The invention discloses a detection method, equipment and system of a one-phase island of a three-phase grid-connected inverter. Reactive currents are injected into output currents of the inverter, the phase difference between every two phases of voltages in a three-phase voltage is calculated before the reactive currents are injected, then the phase difference between every two phases of voltages in the three-phase voltage is calculated after the reactive currents are injected, and when the sum of phase difference values are greater than a set phase threshold value, the fact that the island happens is judged. By means of the method, the fact that whether the island happens or not can be judged accurately and effectively through the phase difference values, furthermore, due to the fact that the reactive currents are injected into the output currents of the inverter, the harmonic content of output wave forms is little, and only tiny reactive power change can be achieved in the grid-connecting process of the inverter. Compared with a disturbance method based on frequency or active power in the prior art, the injected reactive currents can not influence generating capacity.

Description

technical field [0001] The present invention relates to the technical field of power systems, and more specifically, to a detection method, device and system for a single-phase island of a three-phase grid-connected inverter. Background technique [0002] At present, with the shortage of energy in the world, the application of wind power generation and photovoltaic power generation is becoming more and more extensive. Both wind power and photovoltaic power generation need to feed the electric energy generated by wind turbines and photovoltaic modules to the AC grid. Since the electric energy generated by wind turbines and photovoltaic modules is DC, when it is fed back to the AC grid, a grid-connected inverter needs to be used to convert the DC into AC and then feed it to the AC grid. [0003] see figure 1 , which is a working diagram of a three-phase grid-connected inverter in the prior art. [0004] The AC grid side includes grid 1 (three-phase A, B, and C) and grid-sid...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/00
Inventor 肖永利侯坤郑越
Owner HUAWEI DIGITAL POWER TECH CO LTD
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