The Research On Diode-Clamped Three-Level Inverter

Compared with traditional converter, multilevel converter has obvious advantages in high power application field, for the voltage applying to each switch transistor and switching loss are decreased, electromagnetic interference is alleviated as well. Under this background, a series of research on diode-clamped three-level inverter have been presented in this paper.Firstly the topology of diode-clamped three-level inverter is introduced and analyzed, and its characteristics are emphasized. At same time, some problems and research directions are proposed.Secondly, two kinds of modulation strategies of three-level inverter are studied. For SPWM modulation, traditional method is presented and its difficulty of application in digital system has been pointed out. To solve this problem, an improved SPWM method has been given. For SVPWM modulation, after a detailed introduction, the problem of complex calculation is pointed out and a method about 60°coordinate transformation is introduced. Both strategies have been simulated in MATLAB, and their validities have been proved.Experimental platform is also established. The parameters of hardware have been determined, including DC side capacitors and parameters of IGBT and clamping diodes. Control system of three-level inverter, which is composed of DSP and its peripheral circuit, IGBT driver, connection circuit and protection circuit, is designed. Based on experimental platform, the improved SPWM modulation strategy is tested, and the results have been given, which can prove the correctness of the circuit and control system design, as well as attest the validity of application of improved SPWM modulation in diode-clamped three-level inverter.