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Leakage current detection protection method and device

A leakage current detection and leakage current technology, applied in emergency protection circuit devices, circuit devices, emergency protection devices with automatic disconnection, etc., can solve the problems of ignoring the AC component of resistive leakage current and the defects of calculation formulas.

Active Publication Date: 2020-10-30
TONGJI UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0009] This leakage current protection method ignores the AC component of the resistive leakage current, and the calculation formula is flawed when the resistive and capacitive leakage currents change suddenly at the same time, so this method has great limitations in use.

Method used

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  • Leakage current detection protection method and device
  • Leakage current detection protection method and device

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Embodiment 1

[0053] This embodiment provides a leakage current detection and protection method, which accurately detects continuous and sudden leakage currents without increasing hardware costs, and can not only protect in time when the protection conditions are met, but also prevent false protection when the protection conditions are not met.

[0054] The theoretical basis and specific methods of the method in this embodiment will be described in detail below.

[0055] 1. Theoretical basis

[0056] The inverter undergoes DC-AC conversion. The main components of the common-mode voltage between the DC side and the AC side are DC and low-frequency AC. The frequency of the low-frequency AC in a single-phase system is consistent with the fundamental frequency of the power grid. The frequency of the quantity is consistent with the 3rd harmonic frequency of the power grid. The main component of the common-mode voltage determines that the main components of the resistive common-mode leakage curr...

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Abstract

The invention relates to a leakage current detection protection method and device. The method comprises the following steps: a leakage current sampling step: carrying out discrete sampling on leakagecurrent; a leakage current calculation step: calculating a total leakage current effective value and a resistive leakage current effective value according to the sampling data; a continuous leakage current protection step: judging whether the main component of the leakage current is capacitive or resistive according to the effective value of the resistive leakage current, and then respectively taking corresponding continuous leakage current protection measures; and an abrupt change leakage current protection step: calculating the abrupt change amount and the abrupt change speed of the leakagecurrent according to the effective value of the resistive leakage current so as to calculate the abrupt change time reaching the abrupt change amount, and carrying out abrupt change leakage current protection according to the abrupt change time. Compared with the prior art, the method and the device have the advantages of high detection protection accuracy, good real-time performance, low hardwarecost and the like.

Description

technical field [0001] The invention relates to the field of leakage current detection, in particular to a leakage current detection and protection method and device. Background technique [0002] For non-isolated grid-connected photovoltaic inverters, the corresponding standards (such as German VDE0126-1-1) stipulate the leakage current protection standard, and the continuous and sudden leakage current must meet the corresponding protection threshold and protection time requirements. The specific requirements are shown in the table 1. [0003] Table 1 [0004] [0005] Generally, a sensor is added to the output side of the inverter to sample the leakage current, and the sampled value is calculated and processed in the controller to determine whether the leakage current meets the protection condition. Grid-connected inverter system with leakage current protection function such as figure 1 As shown in the figure, a single-phase inverter is taken as an example, and the r...

Claims

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Application Information

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IPC IPC(8): H02H3/32H02H7/26H02H3/24
CPCH02H3/24H02H3/32H02H7/26
Inventor 康劲松张凤岗
Owner TONGJI UNIV
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