Research On Three-Level Half-Bridge Inverters

In this thesis, the topologies and working principles of Three-Level Half-Bridge (TL-HB) inverters are introduced. The stability and the principles of loop design of voltage-current dual-loop control strategy are studied. The stability and astringency of error signals of repetitive control are strudied, and the principles of parameters design are presented. According to the analyses of voltage-current dual-loop control and repetitive control, a hybrid control strategy based on voltage-current dual-loop control and repetitive control is proposed, which will efficiently improves the static precision and overcome the repetitive distortion.The reasons why the neutral point voltage turns to be unbalanced are anlysised in detail. Various strategies for balancing the neutral point voltage are investigated, and a new strategy is proposed to balance the neutral point voltage in this thesis. Finally, a 600VA prototype based on DSP is build and the design methods of hardware circuit and software program are presented. The experimental results based on this prototype are provided,by which the validity and feasibility of the proposed control scheme are verified.