Effect of Unipolar and Bipolar SPWM on the Lifetime of DC-link Capacitors in Single-Phase Voltage Source Inverters

This paper explores the impact of different modulation techniques on the lifetime of DC-link capacitors for different modulation indices and varying operating power of voltage source inverter system. The conducted analysis show that the capacitor lifetime improves when using unipolar Sinusoidal pulsewidth modulation (SPWM), which introduces the highest lifetime for DC-link capacitors when a single unit voltage source inverter is used. Likewise, for two paralleled voltage source inverter unit' topology, both units using unipolar SPWM, having the same switching frequency produces the least thermal stress on the capacitor and consequently giving the highest lifetime.