Development of a novel SPWM technique for multilevel inverters

In the control of multilevel inverters, SPWM, SVPWM, and SHE-PWM are widely used. In contrast of others, it is hard to utilize the SPWM algorithm in real time application since it does require pre-calculations and switching angle calculations. It is also a disadvantage of regular SPWM unable to eliminate side band harmonics. SPWM can be utilized up to a limited range in over modulation area besides linear modulation. If this is the case, the output voltage level will be generated between 86% and 109% of input line voltage. The SPWM method implemented in this thesis is designed in order to eliminate THD ratios caused by carrier frequencies and side band harmonics of carrier signal. The Bessel function which is the most effective digital filtering method among others is used in the developed SPWM technique. The analytical equation of the modulation technique is arranged by adding Bessel functions in order to eliminate interferences occurred in the carrier signal and it?s side bands. In this way, an SPWM modulation technique is obtained which is not only eliminating the interferences caused by modulation index but also eliminating the interferences caused by side bands. The SPWM modulator which carries out the digital filtering in its analytical equations is applied by generating switching signals with TMS320F2812 DSP to control a full bridge and an H-bridge inverter in various modulation indexes and switching frequencies. The measured THDv, THDi, values in phase and line of the inverter topologies are found lower than international standards. In addition, the developed technique provided lower THD ratios compared to previous studies which are based on various control techniques in the literature.