Research On SVM Of Nine Bidirectional Switches Integrated Into One Module For Matrix Converter

As a new type of AC-AC "green converter" in electric power industrial control, matrix converter has many advantages over conventional inverter: such as compact structure, high power density, high input power factor, low grid harmonic pollution, theoretically unlimited output frequency, no intermediate large-capacity storage device links, etc. It has become the focus of many scholars.Firstly, this article starts from the basic structure, basic principle, mathematical modeling and control method of research object, emphatically analyzes the modulation process of modular MC by double space vector modulation algorithm, including the "virtual rectifier stage" space vector modulation and "virtual inverter stage" space vector modulation two parts, as well as the synthesis of two parts, then derives 36 kinds of effective combination of switches and corresponding duty cycle time, getting the nine-sequence pulse width distribution method by optimizing the combination of switches, thus the switching losses are reduced.Then, combined with double space vector control strategy, Matlab / Simulink simulation software is used for MC modeling and simulation analysis, respectively programming the virtual rectifier stage and the virtual inverter stage. After this two processes are combined to output the switch control table. The simulation uses a modular thought and selects the actual IGBT module to build the main circuit, which is very close to the actual circuit. And it is solved the problem of slow simulation speed caused by the delay of the filter.Thus the simulation experiment has verified the correctness and feasibility of the control strategy and optimization of pulse width allocation method.Thereafter, the nine bidirectional switches combined into one matrix converter is equivalently decomposed into three separate converter units. These three units are three-phase input single phase output ones and their commutation algorithms are same. Therefore, this article only analyses and discusses the four-step commutation of one unit in detail, to obtain the MC switch commutation state diagram and the detailed switch table of commutation control, And Quartus II 9.0 software is used to write optimized VHDL commutation program according to the principle of the four step commutation algorithm. The simulation results have verified the correctness, feasibility and reliability of the four step commutation.Finally, based on the analysis of related MC technology above, a MC prototype experiment system is designed, which uses DSP( TMS320F28335) +CPLD(EPM570T144C5N)as the control core, including hardware design and software design. The hardware part includes the main circuit, the sampling circuit, the main control board, the driving circuit and the clamp circuit and so on, Software part deduces and first publishes the decoding expressions of nine bidirectional switches. The solution method is suitable for any switching sequence table of an AC- AC matrix converter. And it can be extended to the solution of the switching commutation decoding of any other matrix converters and other converters. Some experiments are done on this platform, and the waveforms of voltage and current of two different output frequencies are obtained. The experimental results have verified the correctness and feasibility of the control strategy and system scheme.