Torque Ripple Minimization in Six-Step PMSM Drives via Variable and Fast DC Bus Dynamics.

Six-step modulated drive systems have been shown to have higher power density and lower switching loss than pulsewidth modulation drive systems. It has also been shown that by manipulating the dc bus voltage, six-step mode can drive permanent magnet synchronous machines (PMSMs) over a wide speed range, and maintain the machine operating point on the maximum torque per ampere curve below the base speed to reduce the machine copper loss. However, high torque ripple exists while in this type of six-step mode. This paper develops the control design methodologies to leverage the variable and fast dc bus manipulation, provided by two-step finite-settling-step dc-to-dc converter control, to minimize torque ripple in six-step PMSM drives. Two torque control algorithms: existing voltage angle based torque control and deadbeat-direct torque and flux control are used to evaluate torque ripple reduction capability and energy savings potential of six-step PMSM drive systems. [ABSTRACT FROM AUTHOR]