Robust flux weakening scheme for surface-mounted permanent-magnet synchronous drives employing an adaptive lattice-structure filter

An advanced control structure for surface-mounted permanent-magnet synchronous (SMPMS) drives provides a stable, high performance operation in the flux weakening region, utilizing the over-modulation and six-step modes of the space vector modulation (SVM). An automatic transition into flux weakening is achieved by controlling the reference voltage magnitude. The fifth and seventh stator current harmonics of the fundamental frequency, generated in the over-modulation and six-step modes, propagate through the current control loops, resulting in the sixth harmonic in the reference voltage and deteriorating drive performance. To filter the sixth harmonic, an adaptive lattice-structure allpass-based notch filter is employed, providing minimal phase delay and complete attenuation of the sixth harmonic.