Multilevel multiphase space vector PWM algorithm with switching state redundancy applied to three-phase converters

Abstract

This paper presents the particularization of a recent multilevel multiphase space vector pulse-width modulation algorithm for three-phase converters. This modulation technique takes advantage of the switching state redundancy, which permits to achieve different goals like extending the modulation index range and reducing the number of switchings. The particularized algorithm is then compared with an existing multilevel space vector modulation technique showing many similarities. Finally, the algorithm is implemented in a low cost FPGA and it is tested in laboratory with a real prototype by using a neutral point clamped inverter. I. INTRODUCTIONThe space vector pulse-width modulation (SVPWM) is a very common modulation technique that is still in focus of the research community attention [1]-[5] because it offers a great flexibility to optimize the switching waveforms. This technique represents the reference voltage and the switching states of the converter in a vectorial space. In this space, the reference vector is approximated by means of a sequence of switching vectors. Complexity and computational cost of traditional multilevel SVPWM techniques increase with the number of levels of the converter, and most of them use trigonometric functions or precomputed tables [6], [7]. In the two-dimensional (2D) and the three-dimensional (3D) SVPWM algorithms proposed in [8] and [9], respectively, the calculation of the switching vectors and the switching times is reduced to a few comparison and addition operations, which do not depend on the number of levels. Consequently, those multilevel techniques are very suitable for real-time implementation [10]. Recently, in [11] and [12], two new multiphase SVPWM techniques with low computational complexity, which makes them suitable for on-line implementation using low-cost devices, were presented. Both techniques can be used with the typical multilevel topologies such as diode-clamped, flying capacitor, cascaded full-bridge or even hybrid converters. The modulation technique of [11] is suitable for converters with neutral wire. In the case of converters with floating neutral, this algorithm shows a poor performance because it does not take into account the switching state redundancy. The

Multilevel multiphase space vector PWM algorithm with switching state redundancy applied to three-phase four-leg converters

“…In four leg converters there are four intervals [q min a , q max a ], [q min b , q max b ], [q min c , q max c ] and [q min n , q max n ] that are calculated by means of (11) and (12) as…”

“…Therefore, the general multilevel multiphase SVPWM techniques developed in [7] and [8] can be applied to solve the space vector modulation problem in four-leg converters. This paper is the last one of a series of four papers that show the application of both multiphase multilevel SVPWM techniques to three-phase converters with three and four legs [9]- [11]. The application of the multiphase modulation technique in [7] to multilevel converters with three legs provides the simple modulation algorithm in [9], which is fully equivalent to the previous threedimensional (3D) SVPWM algorithm presented in [12].…”

“…Such problem is solved by the multilevel multiphase SVPWM technique in [8] that takes advantage of the switching state redundancy. The application of this modulation technique to three-phase three-leg converters provides the very simple algorithm in [11] in which the part devoted to calculate the two-dimensional (2D) space vectors is equivalent to the fast 2D SVPWM algorithm presented in [13]. Consequently, the algorithm in [11] can be considered as an extension of the algorithm in [13] that includes a method to select the redundant switching states.…”