Adaptive Space-Vector Hysteresis-Based Control with Constant Switching-Frequency for Three-Level Shunt Active Power Filters

摘要

This paper proposes a new constant-frequency space-vector hysteresis current control (CF-SVHCC) technique for three-level neutral-point diode-clamped (TL-NPC) inverters in shunt active power filter applications when applied to three-phase isolated neutral point (INP) systems. The proposed techniques is developed based on two recognized modulation methods, space-vector pulsewidth modulation and adaptive hysteresis-band current control. The proposed technique consists of two alternating adaptive hysteresis-band strategies around the error-current vector in the αβ stationary reference frame (SRF). The first strategy is designed with the purpose of utilizing the medium- and large-voltage vectors of the TL-NPC inverter to keep the error-current vector within the adaptive hysteresis boundary, while the second one is designed according to the small-voltage vectors of the TL-NPC inverter to balance its neutral point voltage. The main part of this proposed technique is a supervisory controller that operates in SRF to effectively avoid inter-phase dependency. This smart controller systematically uses the zero-voltage vectors and the nonzero-voltage vectors associated with the alternating adaptive hysteresisband strategies in order to prevent high switching frequency and maintain the switching frequency constant in INP systems, respectively. The proposed CF-SVHCC performance is validated by extensive simulation studies for both steady-state and transient conditions.