Multi-level Converter Topology And Modulation Algorithms

Recently, multilevel converter has been one of research hot points in high-voltage and high-power fields. Based on the three-level diode-clamped DC/AC converter, this thesis focuses on topological structure and modulation algorithms for use in multilevel converter.I. The analysis of multilevel converters topologiesThe basic principle of multilevel converters is introduced. Thereby, several primary circuits of multilevel converter are also introduced and their merits and demerits are analysed in detail. And then, the thorny problem on the research of multilevel converter is pointed out,II. Design of a three-level SVPWM algorithmThis thesis discusses several primary modulation algorithms of multilevel converter and analyses their merits and demerits. PWM modulation algorithms are extensively studied. Accordingly, this thesis points out the key factors which reduce common-mode voltage and point potential fluctuations, and also establishes mathematical model of NPC's neutral point potential fluctuations. Based on the mathematical model, a three-level SVPWM algorithm is proposed which can reduce common-mode voltage and depress neutral point potential fluctuations. This algorithm also inexistences vector abrupt change, and is very simple. .III. The circuit designing of multilevel converterIn order to explore a feasible way for the application of multilevel converter, this thesis focuses on the points of circuit designing, including the choice power of circuit topology and electronics device, the circuit designing of snubber buffer circuits, filter circuit, and drive circuit, and the DSP-based control circuit designing.