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Amplitude Algorithm of Step-Up Variable Differential Protection of Pumped Storage Static Frequency Converter

A static frequency converter, differential protection technology, applied in instruments, measuring electrical variables, complex mathematical operations, etc., to achieve the effect of improving calculation accuracy, shortening fault judgment time, and improving rapidity

Active Publication Date: 2019-09-24
NARI TECH CO LTD +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

When the output voltage frequency of the static frequency converter is higher than a specified value (such as 5Hz, this article takes 5Hz as an example), the transformer is connected in series to the circuit and starts to work. Therefore, during the motor starting process, the transformer has a wide operating frequency range. Conventional differential protection The method of current amplitude calculation in the method is no longer applicable

Method used

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  • Amplitude Algorithm of Step-Up Variable Differential Protection of Pumped Storage Static Frequency Converter
  • Amplitude Algorithm of Step-Up Variable Differential Protection of Pumped Storage Static Frequency Converter
  • Amplitude Algorithm of Step-Up Variable Differential Protection of Pumped Storage Static Frequency Converter

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Embodiment Construction

[0019] Embodiments of the present invention will be described in detail below in conjunction with the drawings and specific implementation methods.

[0020] Please combine image 3 As shown, the step-up variable differential protection amplitude algorithm of the pumped storage static frequency converter disclosed in the present invention is carried out in the controller interrupt subroutine, and the algorithm includes the following steps:

[0021] Step 1: Calculate the frequency through the transformer secondary voltage (motor terminal voltage) and update it in real time

[0022] Digital frequency measurement methods include full-wave digital frequency measurement, half-wave digital frequency measurement, and 1 / 4 wave digital frequency measurement. Taking full-wave digital frequency measurement as an example, its basic principle is to detect the time interval between two adjacent rising edges crossing zero. The zero-crossing judgment can be determined by the sampling value o...

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Abstract

The invention discloses a pumped storage static frequency converter step-up transformer differential protection amplitude algorithm. Through real-time motor-side voltage frequency measurement and updating, a Fourier calculation point number and a calculation step are determined according to the voltage frequency; according to the Fourier calculation step and a former sampling sequence participating in Fourier operation, a next sampling sequence participating in operation is determined; an interpolation method is adopted to calculate the current value of the next sampling sequence participatingin operation; and according to the current calculation point number, a Fourier formula is adopted to calculate the current amplitude. The algorithm has the beneficial effects of improving the calculation precision and improving the protection response speed.

Description

technical field [0001] This patent relates to transformer differential protection technology under wide frequency range. Background technique [0002] Most of the large-scale pumped storage power stations use the static frequency converter (Static Frequency Converter, SFC) start-up mode when the water pump is running. The static frequency converter with a high-low-high structure is a voltage signal with a gradually increasing output frequency that is applied to the motor stator through a step-up transformer. , drag the motor to the rated frequency until it is connected to the grid. When the output voltage frequency of the static frequency converter is higher than a certain value (such as 5Hz, this article takes 5Hz as an example), the transformer is connected in series to the circuit and starts to work. Therefore, during the motor starting process, the transformer has a wide operating frequency range. Conventional differential protection The method of current amplitude calc...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R19/00G06F17/14
Inventor 郑玉平李延新杨合民简优宗方存洋刘育鑫胡静
Owner NARI TECH CO LTD
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