Performance improvement for cascaded multilevel inverters under battery outage condition

This paper is about a battery outage compensation scheme for cascaded inverters, which allows achieving good harmonic performance. The basic gate generation circuit consists of a hybrid modulation controller which combines FPWM & MSPWM for each inverter cell operation, so that the output inherits the features of switching loss reduction from FPWM, and a good harmonic performance from MSPWM. A sequential switching scheme is embedded with this hybrid modulation in-order to overcome unequal switching losses, and therefore, differential heating among the power devices. A simple base PWM circulation scheme is also to be used to get resultant hybrid PWM circulation so as to make the power dissipation balanced among the modules. The sequential switching hybrid modulation switching scheme was implemented with base PWM generation using Alternate Phase Opposition Disposition (APOD) method. The system is simulated for various frequency modulation indices and the harmonic performances are analysed. The inverters implemented using HAPOD and SHE techniques were simulated and their performances are compared under both normal condition and contingency condition with battery outage compensation.