Reserach On Multilevel Inverter Shepwm Technology Based On Intelligent Algorithm

Multilevel inverters have received more and more attention in high voltage and high power applications and power system due to the advantage of large output capacity,low switching frequence, good quality of the output voltage waveform and high power factors.In this paper SHEPWM is studied because of its advantage such as simple control,high waveform quality and can eliminate the harmonic selectively,the main research contents and innovation points are as follows.In view of solving the SHEPWM nonlinear equations,this paper proposes PSO with dynamic change of inertia weights and real coding GASA,which are less dependent on initial value,and the former overcomes the shortcoming of easily falling into the local optimum,the number of iterations is greatly reduced,and effectively balances the searching performance and convergence speed of the algorithm,the latter makes full use of the global optimization of GA and the local serach performance of SA,can be more effectively converged at optimum,and uses the real coding to save the individual to improve calculation accurace.Based on the H cascaded multilevel inverter as the research object,the SHEPWM harmonic elimination strategy and the SHEPWM power balance strategy are established,on the premise of the output phase voltage waveform to meet the 1/4 cycle symmetry,the output voltage waveform of each H brideg is changed to achieve power balance,compared with the simulation results,the SHEPWM power balance strategy can achieve power balance on the basis of reducing the harmonic elimination equations.Aiming at the problem of low harmonic content in the cascaded multilevel inverter,combines the SHEPWM with phase shift modulation,the output voltage amplitude and the output voltage phase of the H bridge model are controlled synthetically,and a large number of low harmonics can be eliminated by the calculation of the 3 switching angles,the lowerset order harmonic of the output line voltage is 23 times,which significantly improves the quality of the waveform.According to the above results,the switching angles trajectories are drawn,the simulation platform is built by using Matlab/Simulink software,the voltage waveform and spectrum are simulated and verified,and the feasibility of the control strategy and the correctness of the algorithm are proved.