Positive and negative sequence extraction method

Abstract

The invention discloses a positive and negative sequence extraction method comprising low-pass filtering, constant-power park conversion, geometric coordinate conversion and geometric coordinate solving. The method has the same quickness as an instantaneous value analytical settlement method. The low-pass filter is added into the analytical process to deal with work conditions like harmonic, sampling error and sudden frequency change conditions, so that the good quickness and stability are realized. Positive and negative sequence components of the grid voltage are extracted quickly and stably.The method has the important significance in the new energy industry. When a grid failure occurs, an inverter is able to deal with the grid failure quickly; a corresponding reactive support is sent out or absorbed based on a corresponding requirement to realize grid recovery, so that a power generating unit passes through the grid failure successfully. The adaptability to the grid is high; stepout of the power generating unit is reduced; and thus worsening of the grid failure is avoided.

Description

technical field [0001] The invention relates to the field of three-phase electrical signal processing, in particular to a method for extracting positive and negative sequences of three-phase electrical signals. Background technique [0002] Grid voltage asymmetry is a common phenomenon. In power system power quality detection, motor vector control, new energy power generation and other projects, it is often necessary to extract the positive and negative sequence components of three-phase AC voltage and current, and suppress the negative sequence components in the current. At present, in the signal extraction device of the three-phase system, the SRF-PLL (PhsaeLocked Loop Based On Synchronization Reference Frace) structure based on d-q coordinate axis transformation has good dynamic response speed. The positive sequence component of the fundamental wave can be better detected under symmetrical ideal conditions. However, under the non-ideal working conditions of grid voltage ...

AI Technical Summary

Problems solved by technology

However, under the non-ideal working conditions of grid voltage asymmetry, when the SRF-PLL structure is used, the negative sequence component will produce 100Hz 2 times the power frequency fluctuation in the d-q axis component, which not only affects the amplitude extraction of the positive sequence component , will also cause errors in the phase detection

In order to solve this problem, the influence of 2 times the power frequency fluctuation component can be suppressed by reducing the bandwidth of the SRF-PLL feedback loop filter, but this will reduce the dynamic response speed, and it can also be eliminated by adding a specific frequency notch filter 2 times power frequency fluctuation in the d-q axis component when the grid voltage is asymmetrical

However, the filtering effect of the notch filter will be affected when the frequency changes, and this scheme cannot detect the amplitude and phase of the negative sequence component of the fundamental wave

[0003] Chinese patent (application number: 201610338901.0) discloses a multi-channel power grid voltage synchronization signal extraction device and method. The multi-channel power grid voltage synchronization signal extraction device and method include an α-β static coordinate system transformation circuit T αβ , different frequency positive and negative sequence d-q synchronous rotating coordinate system transformation circuit e jωt 、e -jωt 、e j5ωt and e -j7ωt , Subtractor, PI regulator, integrator, proportional operator; the disadvantages of this invention: 1. It is necessary to obtain the phases of different frequency signals, and there is a delay in this process, and the real-time performance is not good enough; 2. The extraction of signals of different frequencies is restricted Due to the sampling frequency, the higher the signal frequency, the higher the sampling frequency required. This solution is applied at a low sampling frequency, and the extraction error is very large.

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