In this work discrete time current regulation methods for three-phase parallel active filters (PAF) are investigated. With emphasis on PAF applications, linear and hysteresis current regulation methods are studied and improvements on the discrete time implementation of the latter type without any additional analog hardware are provided. The dependency of the switching ripple filter (SRF) type on the PAF current regulator (CR) type is considered and design methods provided. A PAF is designed for a three-phase 10 kW diode rectifier load and studies are investigated through this system. The CR and PAF performances are studied by means of theory, simulations, and laboratory experiments. A DSP controlled PAF system is built and all the algorithms are experimentally verified. The study shows that the resonant filter linear current regulator and the improved discrete time hysteresis current regulator with appropriate SRF types perform satisfactorily.