The Research On Three-phase Three-wire Shunt Three-level Active Power Filter

Nowdays, active power filter mainly concentrated in low-voltage distribution side application and in small and medium capacity. But a large amount of power electronic devices and nonlinear loads are parallel in the gird, currently active power filter has been unable to meet demand on the market of both the large-capacity and high-pressure applications. Multi-level technology opens a channel for solving such demand, studying how to achieve three-level active power filter is the main problem described in this article.This paper discusses the problem from both principle and application.In principle aspect, a switching function model was established in abc coordinate. With the use of ip-iq harmonic current detection method based on instantaneous reactive theory, instruction current signal was obtained. Several three-level SVPWM algorithms were discussesed, and the differences between several algorithms were pointed out, the modulation algorithm based on 60°coordinates was adopted. The mechanism of the three-level DC-side midpoint potential imbalance was analyzed and several midpoint balancing algorithms were compared, the balance algorithm based on charge balance was selectd after synthesizing the difficult degree and balancing effect. On the basis of previous research, the appropriate output filter parameters were selected. In control, PI control was used to keep the DC side voltage constant. PI+ Repetitive Control was adopted to track the instruction current and the specific parameter tuning method was given.In application aspect, a active power filter prototype of 50A output current was built. Its hardware and software were also designed. In hardware part, some sampling conditioning circuit and driving circuit were designed. And the prototype hardware architecture was planed. In spftware part, some software flow was given.All principle questions adopted in this article have detailed theoretical analysis, formula deduction and simulation verification. Application issues covered engineering problems in three-level active power filter implementation. This paper has some significance for the application of three-level active power filter.