Design of a new DC link voltage controller for universal power quality controllers

In this paper, an outer loop model for DC link voltage control in a three-phase three-wire universal power quality controller (UPQC) is prpposed based on the equilibrium of instantaneous power in parallel active power filter. According to the small signal model, a new controller for DC link voltage control has been designed. It is expected to improve the system performances in both reference following and disturbance suppression. Computer simulations and hardware prototype experiments demonstrate that compared with conventional P controller and PI controller, this new controller has better performances for DC link voltage control and guarantees a good compensation while voltage sags occur in the power supply.