Performance Analysis of Five Phase NPC MLI with Phase Shifting Carrier Pulse Width Modulation

Abstract

The multi-level inverters (MLI) are used in most of the power electronic industries for its better harmonics performance, lower switching stress, lower losses etc. Generally, the 3-phase motors are in practice, but in recent years the multi-phase motors are gaining attraction due to its lower switching stress, reduced current per phase and better harmonic performances. The 5-phase motors are preferred among multi-phase motors for its better reliability and robust control [1]. The 5-phase Neutral Point Clamped Multi Leve Inverter (NPC MLI) are used for driving the 5-phase motors [2]. The controlling of MLI is done by multi-carrier Pulse Width Modulation (PWM) techniques which is categorised as Level Shifting Carrier PWM and Phase Shifting Carrier (PSC) PWM [3]. The Level Shifting PWM is classified as Phase Disposition (PD) PWM, Phase Opposition Disposition (POD) PWM and Alternate Phase Opposition Disposition (APOD) PWM. The amplitude and frequency of carrier signal are same for all the above mentioned PWM techniques. The position of carrier signal is displaced in PD PWM, while the phase angle of carrier signal below the zero reference is shifted by 180^o in POD PWM techniques and the phase angle of alternate carrier signals are shifted by 180^o in APOD PWM techniques [4]. In PSC PWM techniques, the phase angles of each carrier signal are shifted by particular degrees while the amplitude, frequency and position are same for all carrier signal [5]. This angle shift of each carrier signal is selected based on the number of levels in inverter.