Stefan Capitaneanu

Graphical and algebraic synthesis for PWM methods

Abstract The article proposes an algebraic synthesis for PWM methods, which is based on a graphical representation of the 2 levels VSI (Voltage Source Inverter). This theory can be the starting point for every PWM method representation. In order to understand the historical evolution of the PWM methods the authors propose two classification groups of the main PWM techniques. The main classification is based on the movement of the neutral point (zero-voltage VN0 evolution). The details of PWM methods presented here are also seen from the graphical representation perspective. The equivalence between the well-known SVM (Space Vector Modulation) practically DDT realized (Direct Digital Technique) and the three-phase PWM with a carrier based industrial realization is shown. The principles of the three-phase PWM and the 3rd harmonic injection PWM (THIPWM4, THIPWM6) are compared the same as the DPWM (Discontinuous PWM) methods. These classifications and equivalences between different techniques show that the number of contemporary used PWM principles can be reduced. The general complex space representation and the classifications proposed here are simple to comprehension educational tools and they simply the way towards practical implementation.