Performance enhancement and comparison of discrete time current regulators for parallel active filters

Discrete time linear and hysteresis current regulators (CR) for three-phase parallel active filters (PAF) are reviewed and evaluated. A novel discrete time hysteresis current regulation method with current oversampling and flexible PWM release capability, DHCR3, which has superior overall performance and simple implementation (no additional hardware) is proposed. Switching ripple filters (SRF) suitable for each CR type are designed. A DSP controlled PAF is designed and built for a three-phase 10 kW diode rectifier load. The CR and PAF performances are verified by means of theory, simulations, and experiments and strong correlation is obtained. The study shows that of various CRs, the synchronous frame resonant filter CR and DHCR3 with appropriate SRF types perform satisfactorily and the latter has much lower implementation complexity and reduced switching losses.