Research On Five-phase Three-level Indirect Matrix Converter

Nowadays, the development of AC drives is going into the field of high power andmedium-high voltage. Meanwhile, AC drives are inevitable fed by power converters.Multi-phase AC drives have many advantages over traditional three-phase AC drives:high power density under voltage limited conditions, reduced torque pulsations andimproved fault tolerance. Multi-level technology makes it possible for voltage limiteddevices to achieve high voltage with the quality of output waveform being improved.Indirect matrix converter (IMC), which performs high-efficiency ac-ac convertionflexibly, is a power converter with great development potential. By using five-phasethree-level indirect matrix converter as a typical application of multi-phase multi-leveltechnology, this paper enrichs the theory of power converters.The rectification stage of IMC and the control strategy were first studied, anddiode-clamped topology of five-phase three-level voltage source inverter (FPTL-VSI)was examined, and then the simplified FPTL-VSI topology was proposed. Finally, thetopology of five-phase three-level IMC (FPTL-IMC) was presented. In terms of controlsimplicity and cost, the simplified topology was determined as the research subject.The distribution of space vectors in simplified FPTL-VSI was studied, includingthe vectors in the fundamental wave space and the third harmonic wave space. Theselection of basic vectors was simplified, and nearest three vectors modulation schemewas proposed. In order to eliminate the reference vector in third harmonic wave space,the nearest four vectors modulation scheme was also proposed. The balance of neutralpoint was considered in the schemes. By adjusting the effective time of the redundantvectors, the potential of the neutral point can be ballanced.The modulation scheme of simplified FPTL-IMC was proposed. The modulationscheme of rectification stage enabled maximum dc voltage output, while the inversionstage exploited the modulation scheme of VSI as illuminated before. To overcome theunfixed amplitude of basic space vectors resulted by fluctuant dc-link voltage, thevirtual vector was proposed to converter the unfixed vector to fixed vector. Finally, thesynchronization control schemes between the rectification and inversion has beenstudied, including zero current commutation and non-zero current commutation.The experimental plantform based on DSP and CPLD was built. The experiment ofrectification stage, FPTL-VSI and FPTL-IMC were carried out. The feasibility ofproposed topology and the effectiveness of the modulation scheme were proved bysimulation and experimental results.