Research On Repetitive Control Of Shunt Active Power Filter In Three-Phase Three-Wire System

In recent years, with the extensive application of power electronics device, it has become the most serious and most prominent harmonic source, which causing serious harmonic pollution to the power system, therefore harmonic suppression has become very real and valuable. At present, the active power filter is one of the most effective during many kinds of harmonic suppression methods.This paper, first of all, briefly introduces the definition and harm of harmonic, by contrasting to the existing harmonic suppression methods, exposits the advantages and theoretical foundation of active power filter. Then in the shunt three-phase three-wire APF mathematical model foundation, does a further introduction to the extraction of harmonic instruction and generation of compensation instruction. Then the current loop control mode is chosen as its centre content with detailed analysis on PI control and repetitive control.By contrast, this paper adopts d-q detection method based on park transformation and low-pass digital filtering based on sliding window iterative method to realize the extraction of harmonic current, and makes a more detailed introduction to space vector pulse width modulation principle of generating compensation current.By establishing the mathematical model of APF system and using state feedback method to achieve d axis and q axis decoupling, the PI controllers of current loop and voltage loop are designed in this paper. Through the simulation, we analyze the influence of changing circuit parameters on the system performance, and point out the inherent limitations of using pure PI control in the APF. Then this paper proposes a way of adding the repetitive control system to the current loop control to improve the steady state characteristics of APF, and gives the detailed designing process of the repetitive controller. Through parameter tuning, the last PI and repetitive paralleled hybrid control simulation results show that the proposed control method on harmonic in this paper has a very good suppression effect.