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A detection method and device for an inverter grid-connected AC relay

A technology of AC relay and detection method, applied in circuit breaker testing, instrumentation, measuring electricity and other directions, can solve problems such as inconsistency, relay adhesion, short-circuit three-phase grid impedance, etc.

Active Publication Date: 2020-07-07
SUNGROW POWER SUPPLY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, it often happens that the live wire of a certain phase is short-circuited to the ground or the impedance of the three-phase grid to the ground is inconsistent. At this time, the voltage of the live wire of the phase to the ground is zero or other low values. , it will falsely detect that the relay is stuck and fails

Method used

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  • A detection method and device for an inverter grid-connected AC relay
  • A detection method and device for an inverter grid-connected AC relay
  • A detection method and device for an inverter grid-connected AC relay

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0075] see figure 2 , is a flowchart of a detection method for an inverter grid-connected AC relay provided in this embodiment.

[0076] The first end of the AC relay is connected to the output end of the inverter, and the second end of the AC relay is connected to the AC grid. The method includes:

[0077] Step 201: Detect a first voltage difference between the first terminal and the second terminal of the AC relay.

[0078] Use the voltage measuring device to detect the voltage of the AC relay on the output side of the inverter and the voltage of the AC relay on the AC grid side, that is, use the voltage measuring device to detect the voltages of the first terminal and the second terminal of the AC relay respectively, and convert the voltage of the first terminal to Make a difference with the voltage at the second terminal to obtain a first voltage difference.

[0079] Step 202: When it is judged that the absolute value of the first voltage difference is smaller than the ...

Embodiment 2

[0090] Such as image 3 As shown, it is a topological structure diagram of a three-phase inverter in a power supply neutral point ungrounded system, in which a first controllable switch S4 and an additional resistor R1 are added.

[0091] A first controllable switch S4 and an additional resistor R1 are connected in series between the positive input terminal of the inverter 301 and the ground.

[0092] By controlling the switching state of the first controllable switch S4, the voltage of the midpoint NE of the DC bus at the input end of the inverter 301 to the ground is changed.

[0093] It should be noted that, in the three-phase circuit, the AC relays are arranged between the output terminal of the inverter and the input terminal of the AC grid, which are respectively S1, S2 and S3.

[0094] Specifically, calculate the difference between the voltage of the AC relay on the inverter output side and the voltage of the AC relay on the AC grid side, first control the first contro...

Embodiment 3

[0108] Such as Figure 5 Shown is a topological structure diagram of a three-phase inverter in a power supply neutral point ungrounded system using the second method.

[0109] A bus discharge circuit is added in this structure.

[0110] A bus discharge circuit is connected between the positive bus or negative bus and the midpoint NE of the DC bus, and the voltage of the midpoint NE of the DC bus to ground is changed by controlling the conduction state of the bus discharge circuit.

[0111] Specifically, the bus discharge circuit may be composed of a controllable switch S5 connected in series with an additional resistor R2. When the controllable switch S5 is turned off, it is judged whether the absolute value of the first voltage difference between the first end and the second end of the AC relay is less than the first threshold, and when the absolute value of the first voltage difference is less than the first threshold, the bus discharge is closed The controllable switch S5...

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Abstract

The invention discloses a detection method of an inverter grid-connected alternating-current relay. The first end of the alternating-current relay is connected with the output end of an inverter; thesecond end of the alternating-current relay is connected with an alternating-current grid; when the alternating-current relay is detected, a first voltage difference between the first end and second end of the alternating-current relay is detected at first; when it is judged that the absolute value of the first voltage difference is smaller than a first threshold value, the direct-current bus-barneutral point voltage to earth of an inverter input end is changed; a second voltage difference between the first end and second end of the alternating-current relay is detected again; and if the absolute value of the second voltage difference is smaller than a second threshold value, it can be determined that an adhesion fault occurs on the alternating-current relay. With the method adopted, theshort circuit to earth of a certain phase of a live line, the inconsistency of the earth impedance of a three-phase power grid, or other conditions can be prevented, and the accuracy of the detectionof the adhesion failure of the alternating-current relay can be improved.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a detection method and equipment for an inverter grid-connected AC relay. Background technique [0002] In the field of photovoltaic grid-connected technology, after the direct current output by the solar panel is processed by the inverter, the alternating current that can be incorporated into the alternating current grid can be obtained. There is a relay between the alternating current grid and the inverter. When the relay is closed, the inverter The AC output from the converter can be incorporated into the AC grid. [0003] In the prior art, when the relay is disconnected, the function of the relay is detected, specifically, the difference between the voltage on the AC grid side and the voltage on the inverter side is calculated, and whether the relay is directly judged based on the difference Sticking occurs. [0004] However, it often happens that the live wire of...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/327
CPCG01R31/3278
Inventor 张涛耿后来徐清清郑大龙
Owner SUNGROW POWER SUPPLY CO LTD
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