The Research On H Bridge Cascaded Multilevel Inverter Based On Chaotic SPWM Control

With the application of power electronic technology in the fields of high voltage and high power frequency conversion,high voltage direct current transmission,static var compensator and active filter,multilevel inverter has attracted more and more attention.Multilevel technology can improve the withstand voltage and frequency of power switching devices.Meanwhile,it can reduce the electromagnetic interference of high frequency devices,which makes the system more stable.At present,clamp type and cascade type are two main topologies of multilevel inverter,and there are many control methods to cooperate with different topologies.This paper is mainly about the pulse width modulation control of H bridge cascaded inverter.Firstly,the research background,significance and the research situation are briefly introduced,including some main topologies and their operational principle.The control methods of multilevel inverter and their application fields are also presentsd.With the analysis of the merits and drawbacks of topologies and control methods,the advantages of H bridge cascaded SPWM inverter are concluded.Secondly,the working theory of carrier phase shift SPWM(CSP-SPWM)control for H bridge cascaded inverter is elaborated in detail.Harmonic analysis of CSP-SPWM control is put forward.Combining CSP-SPWM with chaotic theory,a new kind of control method which is called chaotic SPWM(CSPWM)is proposed in this paper to reduce the infulence of harmonic.Thirdly,the simulation model of H bridge cascaded multilevel inveter is established in Matlab/Simulink,and the sub-modules are introduced.The voltage,current waveform and spectrum are analyzed under different cascade number,carrier frequency and modulation.The output performance of H bridge cascaded multilevel inverter is compared under traditional CSP-SPWM and two kinds of CSPWM.The simulation results show that CSPWM has uniform spectrum which reduces the harmonic amplitude and has some inhibition of harmonic.Based on previous research,output filter is designed,and the simulation result is given.At last,based on the theoretical research and simulation analysis,the hardware of H bridge cascaded five-level inverter control by DSP and FPGA is designed,and the software is written.Using FPGA to produce multiplex PWM,and realize PWM simulation on Quartus ?.Finally,H bridge cascaded five-level inverter operates well under traditional CPS-SPWM and CSPWM.From the experiment result,the ouput voltage and current is nearly sinusoidal with little harmonic.The main harmonic amplitude of ouput waveform has reduced,which improves the anti-electromagnetic interference of the system.