A SVPWM Scheme To Reduce The Common Mode Voltage In A Dual-two Level Inverter Under High DC Voltage Utilization

The Dual two-level inverter system is a popular topology in the field of multi-level inverters in recent years.When the star-connected stator windings are opened,two inverters can be employed to feed the open-end winding motor,which is equivalent to a three-level Inverter.The dual two-level inverter system shows advantages in DC voltage utilization,fault tolerance and convenient control.The dual two-level inverter system with a single power supply is of a simpler structure,lower cost of the supply,and a more complex common-mode voltage(CMV)problem.Based on this topology,the study of this thesis proposes a pulse width modulation(PWM)strategy which can suppress the CMV under high DC voltage utilization.First of all,the research background of multilevel inverter and the dual two-level inverter system are introduced.After that,the main three types of topology structure are discussed.Then,the current research on the modulation strategies,which are aimed to suppress the CMV of the dual two-level inverter system,are reviewed.And these strategies are divided into three groups: the zero mean CMV strategies;the strategies of zero instantaneous value of CMV;and the others are aimed to achieve a balance between the suppression of CMV and the DC voltage utilization.Based on that,the mathematical model of the system is studied,and the output CMV of different topology structures is analyzed,which lays the foundation for the follow-up research.After analyzing the pros and cons of the current mainstream modulation strategies like180° decoupled space vector pulse width modulation(SVPWM)scheme,alternate subhexagonal center PWM switching scheme and maximum modulation range SVPWM,a novel SVPWM modulation strategy based on nonzero vector theory is proposed,which can not only suppress the CMV,but also make sure the dual two-level inverter is under high DC voltage utilization.In the meanwhile,considering that dead time should be added in practical application,the effect of dead time on CMV suppression is analyzed,and then acompensation strategy is applied to reduce the side effect of dead time.After theoretical deduction,a simulation model is built and simulated based on MATLAB/SIMULINK.The simulation results are compared with other modulation strategy,and the performance of nonzero vector SVPWM strategy is verified by the simulations.Finally,an experimental platform is built based on digital signal processor TMS320F28335 and intelligent power module(IPM),then the program is developed.Experiment has been conducted to verify the feasibility of the strategy with comparative analysis.