A Space Vector PWM Scheme for Multi-Frequency Output Voltage Generation with Multi-Phase Voltage Source Inverters

Multiphase variable-speed drives, supplied from two-level voltage-source inverters (VSIs), are nowadays considered for various industrial applications. Depending on the drive structure and/or the motor design, the VSI is required to generate either sinusoidal voltages or voltages that contain a certain number of sinusoidal components (“multifrequency output voltages”). The existing space vector pulsewidth-modulation (SVPWM) schemes are based on selection of (n − 1) active space vectors (for odd phase numbers) within a switching period and they yield either sinusoidal voltage or sinusoidal fundamental voltage in combination with a limited amount of other harmonic terms. This paper develops a SVPWM scheme, which enables multifrequency output voltage generation with arbitrary values of various sinusoidal components in the output voltage. The method is based on initial selection of (n − 1)2/2 active space vectors within a switching period, instead of the common (n − 1) active vectors. By properly arranging the sequence of the vector application, it is possible to provide an automatic postreduction of the number of applied active vectors to (n − 1), thus maintaining the same switching frequency as with the existing schemes while simultaneously avoiding the limiting on the generated sinusoidal output voltage components. Theoretical considerations are detailed using a five-phase VSI. The experimental verification isprovided using a five-phase two-motor series-connected induction motor drive, supplied from a custom-designed five-phase DSP–controlled VSI.