Working method of active power filter DC side voltage fluctuation absorbing circuit

Abstract

The present invention relates to the application field of electric power technology, in particular to a working method of an active power filter DC side voltage fluctuation absorbing circuit that effectively absorbs voltage fluctuations on the DC side of an active power filter and enables the active power filter system to operate stably. It includes an active power filter system, a DC side ripple circuit of a parallel active power filter system, each DC side ripple compensation circuit, and a control loop circuit controlling each DC side ripple compensation circuit, the parallel active power filter The system includes a parallel three-phase balance circuit, a filter circuit and a nonlinear load, and its working method includes utilizing the fluctuation of the capacitance of the DC side fluctuation compensation circuit to absorb the voltage fluctuation of the active power filter system.

Description

technical field [0001] The invention relates to the application field of electric power technology, in particular to a working method of a DC side voltage fluctuation absorbing circuit of an active power filter. Background technique [0002] When the conventional active power filter compensates the three-phase balanced harmonic load, the DC side fluctuation is very small, but with the development of the active power filter, the requirements for its compensation effect are getting higher and higher, so the active power filter The power filter needs to compensate the reactive power and unbalance of the load under certain circumstances. In addition, the phase separation control of the three-phase four-wire system also requires the active power filter to have the ability to compensate for unbalance. At this time, when the active power filter is working normally, there will inevitably be a problem of voltage ripple on the DC side. For asymmetrical loads, the voltage ripple on the...

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Problems solved by technology

[0030] That is, the DC side voltage fluctuation will inject an additional 3rd harmonic current into the compensation current, which will affect the output compensation accuracy

[0031] Similarly, the DC side voltage fluctuations caused by other sub-harmonics will also inject additional harmonic currents into the output current through the DC side voltage stabilization loop. Instead, it will inject additional harmonics into the grid and become a harmonic source that needs to be controlled

[0032] In addition, assuming that the parallel-connected active power filter system adopts SPWM modulation, when the modulated wave is per unitized, the DC side voltage reference value is generally used for per unit conversion. At this time, due to the existence of DC side fluctuations, the inverter There is a fluctuation error between the output voltage of the converter and the ideal output voltage, and the accumulation of this error will lead to a decrease in control accuracy and even lead to overmodulation, which will affect the stable operation of the parallel active power filter system

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