DC-Link Capacitor and Inverter Current Ripples in Anisotropic Synchronous Motor Drives Produced by Synchronous Optimal PWM

An accurate approximation of the dc-link capacitor current is crucial for the design of the dc-link capacitor as the capacitor current ripple affects lifetime, size, weight, and cost of the voltage source inverter (VSI). In this article, analytical expressions for the dc-link capacitor current and the inverter current are derived for two-level VSIs feeding anisotropic interior permanent magnet synchronous machines (IPMSMs) controlled by synchronous optimal pulsewidth modulation (SOPWM). The magnetic anisotropic properties of the IPMSM are considered and half-wave symmetric SOPWM signals are utilized. Experimental results evaluate the effect of various pulse patterns on the produced inverter current and dc-link capacitor current ripples and validate the correctness of the derived expressions.