A sliding mode control approach to suppress power quality challenges in single-phase variable frequency drives within the constant power region

This paper proposes a variable frequency drive (VFD) for single-phase induction motors that features power factor correction (PFC) and addresses power quality issues, including current and voltage harmonic distortion on the grid and load sides. The proposed VFD topology employs a two-stage architecture: a front-end totem-pole PFC stage for controlling the DC-link voltage and a subsequent neutral point clamped (NPC) inverter to supply the induction motor with the commanded output voltage waveform. To ensure robust performance, the front-end converter employs an adaptive gain super-twisting sliding mode control (SSMC). This approach concurrently achieves the unity power factor and minimizes the total harmonic distortion (THD) in the grid current and voltage. The NPC stage switches are governed/driven by a controller based on the unipolar selective harmonic elimination (SHE) technique to satisfy the load-side voltage quality specifications. Simulation results confirm that the designed VFD complies with relevant power quality standards across the entire constant power operating region of a typical single-phase induction motor. Furthermore, a comprehensive report covers the designed VFD performance across various frequencies of the output voltage. Results verify the superiority of the SSMC hysteresis current control over the PI peak current control within the power quality characteristics.