Reduced Order Generalized Integrators with Phase Compensation for Three-Phase Active Power Filter

Current regulation is a critical issue for the stable operation of three-phase active power filters (APF). The challenge of the current controller lies in how to track the high slew rate reference with zero steady-state error in a fast and accurate way. Conventionally, multiple paralleled second-order generalized integrators (SOGIs) are utilized to achieve those objectives. However, it will increase the computational burden due to calculation of the multiple paralleled SOGIs. To overcome this issue, phase compensated reduced order generalized integrator (ROGI) is proposed in this paper. Compared with the conventional SOGI, ROGI reduces almost half of computational burden without compromising compensation performance in normal operation conditions. The inherent relationship between SOGI and ROGI is developed, and it is found that one SOGI with a specific resonant frequency is actually constructed by two paralleled ROGIs in positive and negative resonant frequencies. Moreover, the controller parameters are designed and optimized by means of Nyquist diagrams and sensitivity functions in z-domain for directly digital implementation. Finally, the laboratory tests of APF are performed to validate the feasibility and effectiveness of the proposed scheme.