Efficiency Analysis of Vienna Rectifier-Based Grid interface Systems for Low-Power PM WECS

Abstract

Losses of power semiconductor switching devices used in grid-connected wind energy conversion systems (WECSs) are regarded as one of the main issues to be considered when comparing different types of grid interface systems (GISs). This loss is more highlighted for low-power applications, because it directly affects the reliability and efficiency of the system. Recently, a GIS using Vienna rectifier (VR) as generator-side converter is investigated for a permanent magnet synchronous generator-based WECS. Due to its cost advantage, this reduced switch count rectifier is specifically attractive for low-power applications. In this study, the analytical relations for switching and conduction losses of a VR-based GIS are derived and compared to conventional back-to-back systems. As for the grid-side converter, two types of inverters, conventional six-switch inverter and B4 inverter, are considered and the efficiency of GIS is investigated analytically. In order to derive the loss equations for VR, a new current PWM method is presented explaining the formulas required for its implementation. Finding the relations for switching loss and efficiency, different GISs are compared and the most efficient ones are determined for different ratings. The GISs are also simulated, and their switching power losses for different operating points are shown.