A multi-level inverter configuration for 4n pole induction motor drive by using conventional two-level inverters

A multi-level inverter configuration for 4n pole induction motor drive is presented in this paper. This topology is developed using three two-level inverters and two isolated dc sources. Among these three two-level inverters one inverter is switched at fundamental frequency and remaining two inverters are switched at higher frequency. Two isolated dc sources with equal magnitude are used in this topology to block the path for zero sequence currents. Low frequency operated inverter is connected to one dc source and high frequency operated inverters are connected to other dc source. The magnitude of dc source voltage required in this topology is four times lesser than the dc source required in conventional five-level NPC inverter configuration. The first center band harmonics are cancelled by providing 180⁰ phase shift between the high frequency carrier signals. This topology can be operated during the failure of any one inverter switches or any one dc source which will increase the reliability of the system. The number of switching devices used in this configuration is considerably less compared to conventional five-level inverters. This configuration is best suitable for high power applications where low frequency operated inverter can use thyristors as switching devices. The proposed topology is simulated in MATLAB/Simulink with (5HP) four pole induction motor and results are presented to show the validity of this configuration.