Discontinuous PWM Techniques to Eliminate Over-Charging Effects in Four-Level Five-Phase Induction Machine Drives

摘要

Four-level dual inverter configuration fed five-phase induction motor drive utilizing unequal DC voltages for the dual two-level inverters on both sides of the open-ended stator is discussed in this paper. The DC voltages of the two inverters are maintained in the ratio of 2∶1. By properly adding zero-sequence signals to the reference signals, continuous and discontinuous pulse width modulation (DPWM3) can be generated. But in continuous PWM technique, extensive speed control is not possible since over charging of capacitors and the DC voltage ratio of 2∶1 fail to maintain. To solve this problem, an off-set value addition to the reference modulating signal is implemented. Compared to continuous PWM technique, in DPWM3 techniques, a better improvement in the quality of output voltage and current is observed and is discussed in terms of harmonic order; number of levels in common mode voltage (CMV), total harmonic distortion (THD). The proposed techniques are designed using a simple, easier, scalar-based approach which depends upon instantaneous values of the reference voltages and it does not need complex mathematical calculations. Simulation and experimental studies have been carried to show the efficient performance of the drive.