Research On Three-Level Inverter And Its Neutral Point Potential Balance Control

With the development of power electronics technology, the high-voltage high-power multi-level inverter gradually becomes a hot topic. Compared with the two-level, multi-level inverter widely used, because of its low-voltage devices availableto achieve relatively high voltage output, device loss, the output waveformharmonic small. At the same time, multi-level inverter also has a correspondinginadequacy. For example, switch device under voltage imbalance, DC sidecapacitor voltage fluctuation reduces the life of the capacitance, and the inverteroutput voltage waveform distortion. As the study object of diode clamp three-levelinverter, this paper analysis problem and solutions of neutral point potentialbalancing. The three-level inverter is developed. It has already been put intoproduction. The main contents of this paper are as follows:At the beginning, the topology of NPC three-level inverter and how the NPCthree-level inverter work are studied in this paper.Secondly, from the hardware structure, software control strategies andcomponents, the reasons of imbalanced neutral point potential are studied in detail.In view of neutral point voltage balance problems, several kinds of neutral-pointpotential balancing control strategy are studied deeply and a variety of software andhardware of balance control strategies are compared and analyzed.In the end, three-level inverter experiment equipments are designed for projectdemanding, and hardware and software are designed. The main circuit of three-levelinverter is build; driving and protecting circuit and auxiliary power are designed.For solving power source of system, the project designed three switching supplypowers. The midpoint potential balancing control algorithm and control programsare written and finally some experiments related hardware and software verificationis done. And the system is tested by doing experiments.