A DC side voltage control method of a three-phase four-bridge active power filter

Abstract

The invention discloses a direct current side voltage control method of a three-phase four-leg active power filter. The method comprises the following steps: establishing a state space model of the three-phase four-leg active power filter under dq0 coordinates, using a d-axis control quantity to control direct current side voltage, using q-axis and 0-axis control quantities to control alternatingcurrent output current and selecting q-axis and 0-axis output current and the direct current side voltage as system output; defining an error vector, selecting the sliding mode surface and deriving ad-axis current command value; adding the d-axis current command value to output of a harmonic wave detection circuit and taking the sum as total d-axis reference current; and introducing an integral term into the sliding mode surface so as to improve the control precision. When voltage or load of a power grid is unbalanced, two filters are increased, one is a wave trap for filtering out second harmonic waves in voltage at a common connection point, the other one is a low-pass filter for filtering out the harmonic waves contained in a voltage measured value on the direct current side and then accurate compensation of the active power filter can be realized. By adopting the method, the problem of poor effects of conventional PI (proportional and integral) control is solved, and the method further has the advantages of fast response, strong robustness, capability of removing adverse effects of an outer ring on an inner ring and the like.

Description

technical field [0001] The invention relates to a voltage control method, in particular to a voltage control method of a three-phase four-arm active power filter. Background technique [0002] The three-phase four-wire system is widely used in industrial and civil power systems. The main load of the system is a single-phase load with low power, but due to the increasing number, the harmonics, neutral current and three-phase imbalance caused by them The problem is getting worse, causing various accidents. Therefore, it is of great practical significance to compensate the above-mentioned distortion in the three-phase four-wire system. Active power filter (APF) is a new type of power electronic device used to dynamically suppress harmonics and compensate reactive power. It can compensate harmonics and reactive power that vary in size and frequency. It is an important way to solve power quality problems, which can quickly and flexibly compensate various distortions of the powe...

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Problems solved by technology

[0004] In view of the above problems, the purpose of the present invention is to provide a DC side voltage control method of a three-phase four-arm active power filter, which can solve the problem of poor control effect of conventional PI control, and also has fast response, robustness Strong rod, can remove the bad influence of the outer ring on the inner ring, etc.

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