Method for distinguishing free oscillation and forced oscillation of electric power system

Abstract

The invention discloses a method for distinguishing free oscillation and forced oscillation of an electric power system, and belongs to the technical field of electric power system analysis. The method includes the steps: monitoring active power amplitudes of a generator, a transformer and a circuit and analyzing active power data with the maximum amplitude after the system starts oscillation; solving the maximum value and the minimum value of the active power in each oscillation cycle, subtracting the minimum value from the maximum value to obtain an oscillation peak-to-peak value and analyzing a few or a dozen of oscillation cycles with peak-to-peak values increased with time from oscillation starting time; subtracting a previous peak-to-peak value from each peak-to-peak value to obtain the increment of each peak-to-peak value and solving natural logarithms for the increment; and linearly fitting the natural logarithms for the increment of the peak-to-peak values, calculating a slope index and judging that oscillation is free oscillation when the slope index is larger than zero and the oscillation is forced oscillation when the slope index is smaller than zero. By the method, oscillation types are distinguished according to waveform features at an oscillation starting stage, oscillation type distinguishing speed and accuracy are improved, a power grid operator can be helped to timely and accurately distinguish the oscillation types, and targeted measures are taken to calm down oscillation.

Description

technical field [0001] The invention belongs to the technical field of power system analysis, in particular to a method for distinguishing free oscillation and forced oscillation of a power system. Background technique [0002] Low-frequency oscillation is a prominent problem that threatens the safe operation of power systems. When low-frequency oscillation occurs, electrical quantities such as rotor angle, speed, output power, line power, and bus voltage of the generator in the grid will continue to oscillate. The oscillation frequency is generally 0.1-2.5Hz, which seriously threatens the safety of the grid. Once an oscillation occurs, the power grid operation department needs to take effective control measures in time to quickly calm the oscillation. At present, there are two main types of low-frequency oscillations in power grids, one is weakly damped or even negatively damped free oscillations caused by insufficient system damping, and the other is forced oscillations c...

AI Technical Summary

Problems solved by technology

[0012] The purpose of the present invention is to solve the problem that the prior art has no effective method for identifying the oscillation type, and to provide an oscillation type identification method for low-frequency oscillations in power systems, which can quickly and accurately identify whether the oscillation type is free oscillation or forced oscillation after the low-frequency oscillation occurs. oscillation

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