Analysis, design and simulation of digital controlled symmetrical seven levels inverter

Cajethan M. Nwosu – Cosmas U. Ogbuka – Stephen E. Oti

   An analysis, design and simulation of digital controlled symmetrical seven levels inverter is presented in this paper. Against the contemporary use of two asymmetrical DC sources with two H-bridge cells to generate seven levels inverter two DC sources of equal voltage ratings are used through digital control strategy to realize seven levels output voltage. By utilizing limited number of active switching components and avoiding the usual complex PWM control techniques for multilevel inverters by way of digital control strategy, high efficiency multilevel inverter systems due to reduction in total harmonic distortion and switching losses is guaranteed. Owing to symmetry of the H-bridge cells, a simple and single programmed counter built around J-K flip is required irrespective of number of cascades. The analyzed and designed system has been simulated in MATLAB/SIMULINK environment. With an R-L load of 200 ohm and 200 mH, improved total harmonic distortions (THDs) for the inverter current and voltage are 7.59 % and 16.89 % respectively. The obtained results show that the control-circuit-based multilevel inverter topology is most suited for applications in solar powered inverter systems.

Keywords: seven level inverter, cascaded H-bridge, J-K flip-flop, transition table, digital control

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