Investigation on Zero-Sequence Signal Injection for Improved Harmonic Performance in Split-Phase Induction Motor Drives

In three-phase induction motor drives, addition of certain zero-sequence signal which divides the null vector time equally between the two zero states is known to improve the harmonic performance over sinusoidal modulation. Similarly, in split-phase induction motor (SPIM) drives also, addition of such a zero-sequence signal to each set of three-phase sinusoidal modulating waves leads to reduction in total harmonic distortion (THD) in a motor current. However, the above method known as double zero-sequence injection pulse width modulation (DZIPWM) is significantly inferior to four-dimensional 24-sector space vector pulse width modulation (4D24SEC PWM) in terms of THD. This paper investigates and attempts to determine the zero-sequence signal, if any, whose injection could result in a harmonic performance comparable to that of 4D24SEC PWM. Such a zero-sequence signal is determined and is shown to be quite different from that used in DZIPWM. The analytical findings are used to propose a computationally efficient, carrier-based approach to implement the 4D24SEC PWM, whose implementation is otherwise highly resource intensive. The feasibility, computational efficiency, and accuracy of the proposed approach are demonstrated and validated on a 6-kW split-phase motor drive, controlled from a field programmable gate array platform. This paper enables good harmonic performance of the split-phase drive with low computational effort and resources.