Parallel active power filter direct current side voltage low-frequency ripple suppression method

Abstract

The invention discloses a parallel active power filter direct current side voltage low-frequency ripple suppression method, and belongs to the field of power electronic control. The method comprises the following steps: 1, connecting a bidirectional Buck-Boost active power decoupling circuit in parallel on the direct current side of a traditional parallel active power filter; 2, by controlling the bidirectional Buck-Boost active power decoupling circuit, transferring the low-frequency fluctuation power of the direct-current side of the active power filter to an auxiliary capacitor, thereby realizing low-frequency ripple suppression of the voltage of the direct-current side of the active power filter. Based on an active power decoupling technology, 6-frequency-multiplication, 12-frequency-multiplication, 18-frequency-multiplication and 24-frequency-multiplication fluctuation of the direct-current side voltage of the parallel active power filter is suppressed, a thin-film capacitor with a small capacitance value can be used for replacing a traditional electrolytic capacitor under the condition that the direct-current side voltage fluctuation is small, and the reliability of a system is improved. In addition, a low-pass filter in a direct-current side voltage control link of the active power filter is omitted, and the corresponding speed of the system is increased.

Description

technical field [0001] The invention relates to the field of power electronic control, in particular to a method for suppressing low-frequency ripples of DC side voltage of a parallel active power filter. Background technique [0002] The active power filter takes into account the functions of fast harmonic compensation and reactive power compensation. It is an important device in power quality management. It can well compensate the harmonics caused by nonlinear loads such as various rectifiers and inverters, and improve power quality. . Among them, the shunt active power filter (SAPF) is easily disconnected from the power grid in the event of a fault without affecting the operation of other equipment, and is currently widely used in power systems. [0003] The load harmonics in the three-phase symmetrical power grid mainly include 6k+1 (k=1,2,...(natural number)) positive sequence harmonics and 6k+5 (k=0,1,...(natural number)) negative sequence harmonics Harmonics, when S...

AI Technical Summary

Problems solved by technology

The amplitude of the voltage fluctuation on the DC side greatly affects the quality of the SAPF output current. In order to suppress the voltage fluctuation on the DC side, the traditional method is to connect a large-capacity electrolytic capacitor in parallel on the DC side of the SAPF to slow down the fluctuation, but there is an electrolyte in the electrolytic capacitor. Volatility and short life, especially when the fluctuating voltage is large, the fluctuating current repeatedly charges and discharges the electrolytic capacitor, which accelerates the aging of the capacitor and requires frequent replacement of the electrolytic capacitor, which affects the reliability of the device. At the same time, the large capacity The value of the electrolytic capacitor greatly affects the response speed of the DC side voltage

In addition, in order to avoid the impact of the fluctuation voltage on the DC side on the output current of the SAPF, a low-pass filter with a very low cut-off frequency needs to be added, which further reduces the response speed of the system

[0004] At present, some scholars have introduced a resonant controller to suppress the fluctuation of the SAPF DC side voltage, but the effect is very small, and it will also have a certain impact on the output current of the SAPF.

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