Multilevel Inverter Shepwm Technique Research Based On Genetic Algorithm

With the development of the power device, multilevel inverter is widely used in the fieldof high voltage and high power. Its advantage is that can reduce the total harmonic distortionrate, improve the power factor, reduce the device’s current stress and be convenient formodular design. So there is an important significance to research the multilevel inverter.Based on cascaded H bridge and diode clamped multilevel inverter as the research object,this paper discusses the application of SHEPWM technique. The main research contents andinnovation points are as follows:The three most widely used of multilevel inverter topology are introduced, their workingprinciple are analyzed, the advantages and disadvantages are compared, and the SHEPWMtechnology based on cascaded H bridge and diode clamped multilevel is researched. Then theladder wave SHEPWM nonlinear equations is derived and established, and aiming at theproblem of limited modulation ratio, an unified mode of multiband is presented to expandmodulation to the range of0~1.In view of the SHEPWM nonlinear equations, an innovative genetic algorithm isintroduced. Relative to the traditional numerical algorithm’s shortcomings of depending onthe initial value selecting, genetic algorithm does not need any given initial value, and hasgood searching capability and convergence. But there are exists precocious and slow speedevolution in the genetic algorithm. On the basis of development of GA, PSGA and MPGA areput forward in this paper. Good effect is achieved in solving process, the precision ofreconciliation and the evolution speed are improved. And the situation that the DC voltages ofcascaded H bridge inverter are not completely equal in the practical application is discussed.It points out that must do some appropriate adjustments when the angle deviation is huge.This method can suit the requirements of harmonic elimination.The calculation results above are processed, angle trajectory figures are drawn, anddistribution and multiplicity of solutions are analyzed and discussed. Then the circuitsimulation experiment is done by using MATLAB/Simulink software, the distributionregularity of harmonic is analyzed. At the last, the experimental results are verified byexperiment platform.