Based On The Three-level Ac Variable Speed System

This paper proposes a new strategy for balancing the neutral point voltage in the process of the three-level inverter vector controlling.Three-level inverter is also named as Neutral Point Clamped inverter. It is very suitable for using in higher voltage condition. Three-level inverter reduced the harmonic content of generated voltage or current waveforms. The harmonic content of such a voltage is greatly reduced if compared with a two-level waveform. In the main circuit of three-level inverter, diode-clamped and flying-capacitor are used equally sharing the input voltage, so the input voltage can be much higher than two-level inverter even using the same device. However, the neutral point voltage always fluctuate when the inverter running.In this paper, a new method was developed for limiting the voltage fluctuating of the neutral point, and it was proved correct through experiment. It was also introduced that how to produce the control pulses used in vector control.Three-level inverter is one type of the multilevel inverter , also most pragmatism. In my experiments, a inverter control-circuit was built, which can limiting the neutral point voltage fluctuating properly. Based on the DSP chip, the main controller of the circuit is TMS320LF2407A controller, produced by TI corporation.Through the experiment, a result can be concluded that the novel method can balancing the neutral point voltage properly.