A Survey on Space-Vector Pulse Width Modulation for Multilevel Inverters

Abstract

Abstract-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.Index Terms-g-h frame, imaginary coordinate system, K-L frame, multilevel inverters, space vector pulse width modulation (SVPWM), α'-β' frame. I. IntroductIonN OWADAYS, the extensive use of multilevel inverters in high power and high voltage applications has made it a point of attraction for the researchers because of their remarkable performance. As compared with two-level inverters, multilevel inverters have various advantages, e.g. less harmonics in output current and voltages, reduced voltage stress across switching devices, lower dv/dt, better output wave form quality and lower common mode voltages [1], [2]. The diode-clamped 3 level neutral-point clamped (NPC) topology, as shown in Fig. 1 has been the most widely used one among all multilevel inverter topologies that have been proposed in literature [3]- [5].By using an appropriate PWM technique, from discrete voltage levels, multilevel inverters generate the sinusoidal output voltages of different frequencies. Multilevel inverter's output performance depends on modulation algorithm and various PWM algorithms have been developed so far to fulfill the following objectives: less total harmonic distortion (THD), wider linear modulation range, lower switching losses and easy implementation. Among these, the two most popular PWM generation algorithms for multilevel inverters are sinusoidal carrier-based PWM (SPWM) and space vector PWM (SVPWM). In engineering applications, SPWM algorithms maintained their credibility for a long period [6]-[10] but with the development of microcontrollers, SVPWM took place due to its easy digital implementation, better harmonics performance, high DC voltage utilization ratio, reduced switching losses and convenience for capacitor voltage balancing. Moreover, the SVPWM has 15% higher linear modulation range than that of SPWM [11]. However, by increasing the number of...

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