Design and evaluation of a PWM rectifier control system for testing renewable DC sources connected to the grid

Voltage source PWM rectifiers connected to the AC grid are increasingly used in different applications like stand alone power supplies, high-efficiency regenerative AC drives and grid-connected renewable energies. Fast dynamics, sinusoidal input current, and unity power factor justify its wide application. The overall system performance is strongly dependent on the PWM rectifier characteristics. The main performance indices are related to the DC voltage regulation and input current dynamics and steady state properties like total harmonic distortion (THD) and robustness to grid disturbances. Three main controllers exist in the PWM converter: DC voltage, AC current and synchronizer. Using a virtual-flux-based synchronizer and a PI voltage controller, the paper presents a DSP-based discrete hysteresis current controller with limited switching frequency. Complete simulation results under nominal and abnormal grid conditions are presented; an experimental prototype was developed to implement and test the overall control system