Voltage sag detection method

Abstract

The invention relates to a voltage sag detection method. The method comprises the following steps: (1) when a voltage sag fault is caused, the system three-phase voltage containing positive-sequence component, negative-sequence component and fifth harmonic component is sent in a dq coordinate transformation module; (2) after coordinate transformation, the positive-sequence component is DC component, the negative-sequence component is 100Hz component, the fifth harmonic component is 300Hz component, the 100Hz component and 300Hz component are filtered by an equivalence filter network to obtain the DC components of the d axis and the q axis, the sum of squares of the two DC components is calculated, then the root-mean-square value is calculated, finally system positive-sequence voltage amplitude is obtained; and (3) 90% of rated voltage amplitude is selected to be the threshold value of voltage sag, the system positive-sequence voltage amplitude is compared with the threshold value, when the positive-sequence voltage amplitude is less than the threshold value, voltage sag occurs; and when the positive-sequence voltage amplitude is more than or equal to the threshold value, the voltage sag does not occur. The invention adopts the equivalence filter network to solve the harmonic enlargement problem. The invention can be widely used for the voltage fault detection of various power systems.

Description

technical field [0001] The invention relates to a detection method in a power system, in particular to a voltage sag detection method. Background technique [0002] With the development of modern science and technology, more and more industrial production processes and assembly lines (such as semiconductor manufacturing, computer integrated manufacturing, paper industry, etc.) Several cycles of power interruption or voltage sag will affect the normal operation of these devices. Therefore, high-quality power supply has become the basic condition for normal production and life in modern society. At present, in the study of power quality problems, voltage sag has been considered to be the most serious dynamic power quality problem that affects the normal and safe operation of many electrical equipment. Statistics show that for large-scale power users, the annual occurrence rate of sudden drops exceeding 20% ​​is about 10 to 20 times. In many highly automated continuous produc...

AI Technical Summary

Problems solved by technology

However, these methods either have poor real-time performance or complex calculations, so they are limited to software simulation and test prototype simulation.

Among them, the detection algorithm based on "abc-dq" transformation is currently the most researched algorithm. The conventional algorithm of this method needs to separate the DC component through a low-pass filter or a sliding window, which has a delay and is difficult to guarantee real-time performance.

Later, someone improved the detection algorithm of "abc-dq" transformation, and separated the DC component by replacing the filter with differential operation, which improved the real-time performance, but the improved algorithm has the disadvantage of harmonic amplification

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