Considerations for multi-carrier modulations of parallel-connected five-level PWM inverters

The five-level PWM inverters have significant advantages such as an ability to operate the motor with nearly sinusoidal current waveforms and higher output voltages. In order to increase the inverter size, the parallel connection method would be effective for the present whose voltage waveform becomes nine voltage level. In high-power applications, for instance, the carriers should be synchronized to modulating sinusoidal waves. Moreover, for the interphase reactor, lower order harmonic application is prohibited. To improve the harmonic characteristic of the parallel-connected five-level inverters, various modulation strategies are proposed and discussed