High efficiency, hybrid Selective Harmonic Elimination phase-shift PWM technique for Cascaded H-Bridge inverters to improve dynamic response and operate in complete normal modulation indices

Abstract

Selective Harmonic Elimination PWM (SHE-PWM) method has slow dynamic response, due to using the Fourier transform before the Look-Up Tables (LUTs) in practices. Also, in some cases, the SHE-PWM cannot find any solutions in normal modulation ranges. On the other hand, Phase-Shift PWM (PSPWM) does not need Fourier transform in practice to operate, but it has lower efficiency than SHE-PWM. Furthermore, the PSPWM can work properly in all of the normal modulation indices. Using the combination of these two methods can achieve high efficiency and fast dynamic response at the same time. Moreover, the inverter can work in all of the normal modulation indices. To reach these goals, a hybrid Selective Harmonic Elimination PWM with Phase-Shift Pulse Width Modulation (HSHE-PSPWM) is introduced by applying SHE-PWM in steady state condition and applying PSPWM in dynamic conditions. Also, for some modulation indices that the SHE-PWM does not have any solutions, the PSPWM has been applied to the Cascaded H-Bridge (CHB) inverter. A controller is also proposed to switch between the SHE-PWM and PSPWM. Also, a RLC low pass filter is designed to attenuate high order harmonics of the proposed HSHE-PSPWM and it will be shown that the proposed technique can fully meet the IEEE-519 2014 in steady state and transient conditions. Finally, to verify the effectiveness and applicability of the proposed method, simulation and experimental results are obtained from a 7-level Cascaded H-Bridge inverter.