Multi-level Inverter Structure And Control Research

In recent years, multi-level inverters are widely recognized, and get a certain application. Multi-level inverters output can have more levels of output voltage waveform, harmonic content is small, close to the sine wave, inverters performance is better, more suitable for large-capacity high-voltage power electronic equipment.The paper summary and comparison a variety of basic topology of multi-level inverters features,these topologies contains NPC multi-level inverters, flying-clamped multi-level inverters,self-voltage balancing type multi-level inverters and cascaded multi-level inverters.Mathematical model is constructed when inverter is in active and passive inverting state.the multi-level inverters switching modulation strategy and the mid-point potential balance problems is the key point potential study. In the NPC three-level inverters, the detailed description of the space vector modulation SVPWM basic principle was shown, given a way of calculating each vector time when a set of space voltage vector into each of the small triangle, written out of the table of switching sequence, then analyzed using the algorithm on how to improve and keep the neutral point voltage balance, finally made a simulation experiment and the simulation results show that the control algorithm can maintain a neutral point voltage balance.A novel dead-time compensation method of the inverter base on SVPWM is presented,This method can avoid the current zero-crossing problems, derived a theoretical formula, prove that they can be interchangeable between two-level and multi-level.Finally hardware and software of the multi-level inverter control system were design, form induction motor control system.