Research On Carrier Phase Shifted SPWM Modulation Strategy Of Cascaded Inverter

It has important significance for energy savings and industry control to develop high voltage high power drive systems. The Cascaded Inverter with Separate DC sources (CISDCS) which is the one of the most popular multilevel topologies, has been applied widely in the high voltage and high power drive fields. In this thesis, the several main topologies of multilevel inverter have been compared;their respective advantages and disadvantages were analyzed carefully. Base on the analysis of operation principle for the cascaded inverter, the modulation principle of carrier-based Phase Shifted SPWM (PS SPWM) has been explained in detail, and the superiority of harmonic elimination under this SPWM modulation has been demonstrated also. The advantages of the PS SPWM applied in the cascaded inverter were also presented.The simulation of cascaded inverter under the PS SPWM modulation by MATLAB was finished, the simulation results proved the feasibility and applicability of the PS SPWM modulation strategy. The experiment equipment of cascaded inverter with three power cells cascaded every phase was set up, which is composed of main circuit, control circuit and state monitor system. The core of the controller was made up of Digital Signal Processor (DSP) and Complex Programmable Logic Device (CPLD) devices. The software and hardware was debugged, no-load test of asynchronous motor driven by the inverter is performed. These works will make basis for next study in the control scheme and modulation strategy of cascaded inverter' s application.