Current source converters; nonlinear control; power quality (PQ); unified power-quality conditioner (UPQC) Control schemes; Current source converters; Current-source topology; Dc current; Design and control; Design procedure; Displacement power factor; Load power factor; Low switching frequency; Non linear control; On currents; Point of common coupling; Ridethrough capability; Selection procedures; unified power-quality conditioner (UPQC); Voltage disturbances; Voltage-source converter; Electric fault currents; Power quality; Quality control