A survey on space-vector pulse width modulation for multilevel inverters

The selection of an appropriate modulation scheme plays a vital role to assure the performance of multilevel inverters. Space vector pulse width modulation (SVPWM) is more efficient among all other pulse width modulation (PWM) techniques due to its key characteristics like better DC voltage utilization, switching losses reduction and easiness in digital implementation. The conventional SVPWM scheme presents some computational complexities due to redundant switching states and large number of space vectors. This paper summarizes five different SVPWM techniques for multilevel inverters which are α-β frame, g-h frame, K-L frame, α′-β′ frame and SVPWM based on imaginary coordinate system. g-h frame and K-L frame are based on 60° and 120° coordinates system respectively. To compare the result of these SVPWM schemes, the complex calculations of conventional SVP-WM are converted into simplified line voltages form. The comparison results validate all the SVPWM techniques, but the SVPWM based on imaginary coordinate is found more simple in duty ratio calculations, easier to understand and provides a better control for zero-sequence component for any level of inverter.