A Novel Control System for Current Source Converter Based Variable Speed PM Wind Power Generators

Abstract

A novel control scheme for permanent magnet synchronous generator (PMSG) is proposed in this paper, where high power current source converter (CSC) is employed as the connection between direct-driven generator and grid for wind energy applications. In medium voltage high power range, PWM current source inverter (CSI) shows its advantages when connected to grid: simple topology, small Alter, smooth power output and proved short circuit protection. However, it also presents some challenges for control scheme development. The input filter capacitor would result in load dependent power factor at the grid side and variable minimum dc link current in order to achieve unity power factor. The proposed control scheme is developed to incorporate both maximum power tracking and output power factor control. By independently control the real power and reactive power, unity power factor control is achieved at grid side in spite of the CSI output capacitors. By controlling the inverter modulation index at the highest possible level, the proposed control scheme keeps the dc link current at a minimum value with various wind speeds and therefore greatly reduces the converter power loss at lower power levels. Simulation and experimental results verify the control scheme proposed for CSI based direct-drive wind generation system.