A performance comparison between different PWM techniques for the Hybrid Inverter Drive

Variable Speed Drives (VSDs) allow energy savings for loads where operation below the grid frequency may be required. However, when operating the motor load at the grid frequency, they introduce, compared to grid-connected operation, energy losses and Electromagnetic Interference (EMI). The Hybrid Inverter Drive (HID) offers maximum efficiency at either mode of operation. With the HID the motor load is operated in inverter-driven mode for motor frequencies below grid frequency and operated in direct grid-connected mode for operation at grid frequency. This eliminates inverter losses and EMI at the grid frequency. In previous work [5], the HID and its semi-closed transitions were introduced. A performance comparison of the HID operation using pure Sinusoidal PWM (SPWM), Space Vector PWM (SVPWM) and the injection of the DC-link mid-point voltage into the SPWM reference signals during semi-closed transitions is presented in this paper. The HID is modelled in MATLAB Simulink.