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: step 1, connecting a bidirectional Buck type active power decoupling circuit in parallel on the direct current side of a traditional parallel active power filter; and step 2, by controlling the bidirectional Buck circuit, transferring the low-frequency fluctuation power of the direct-current side of the active power filter to the 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 fluctuations of the direct-current side voltage of the parallel active power filter are suppressed, so that a low-pass filter in a direct-current side voltage control link of the active power filter is omitted, and the corresponding speed of a system is increased. In addition, a thin film capacitor with a small capacitance value can be utilized to replace a traditional electrolytic capacitor under the condition of small fluctuation of the direct current side voltage, and the reliability of the system is improved.

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] With the development of power electronics technology, many nonlinear loads in power distribution systems such as rectifiers, inverters, uninterruptible power supplies, and electric arc furnaces are increasing, and harmonic pollution in power grids is becoming increasingly serious. Harmonics can cause problems such as transformer overheating, protection equipment failure, harmonic resonance and communication network interference. In addition, with the development of technology and industry, large-capacity reactive devices such as high-power motors and transformers appear in power systems. Make the grid power factor low. Low power factor will lead to increased line loss, lower grid efficiency, and even grid collapse. The shunt active power filt...

AI Technical Summary

Problems solved by technology

[0003] The DC side voltage of SAPF has inherent low-frequency fluctuations such as 6 times frequency, 12 times frequency, and 18 times frequency. The traditional method is to connect a large-capacity electrolytic capacitor in parallel on the SAPF DC side to reduce fluctuations, but large-value The electrolytic capacitor affects the response speed of the system. In addition, the fluctuating current frequently charges and discharges the capacitor, which accelerates the volatilization of the electrolyte and the aging of the capacitor, seriously affecting the reliability of the device. At the same time, in the DC side voltage control link, in order to avoid the impact of the DC side voltage fluctuation The output current is affected, and a low-pass filter with a very low cut-off frequency needs to be added, which greatly reduces the response speed of the system

[0004] At present, a small number of scholars have suppressed the fluctuation of the SAPF DC side voltage by introducing a resonant controller, 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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