Current ripple analysis of PWM methods for open-end winding induction motor

An open-end winding induction motor drive is configured by driving the open-end induction motor using two three-phase inverters connected to a common DC source. This configuration can feed three-level voltage to the stator windings. In addition, it can double switching frequency without increasing switching losses in each single inverter by commutating the two inverters alternately. However, the open-end winding induction motor has a drawback that the zero-sequence voltage will produce zero-sequence current due to the neutral disconnection. Therefore, the balance between its advantage and drawback has to be considered for practical use. There are various PWM methods for open-end winding motor drive because they have high degree of freedom for controlling. The phase difference between the two inverters is one of these degrees of freedom. Another is a choice between switching both the inverters or switching only one of them while keeping the other clamped. In this paper, four PWM methods are implemented by using simple triangular carrier comparison and evaluated by computer simulation. The current total harmonic distortion, the magnitude of d-q current ripple and zero-sequence current of each method are compared. The results showed which PWM method most utilizes the advantage of open-end winding configuration and improves current wave forms even with zero-sequence current.