Design of fault-tolerant cascaded H-Bridge multilevel inverter with output-side transformers using bidirectional switches

Globally increasing energy demand, running short of fossil fuels and researches for finding environment friendly choices strengthen a solution of local electricity production, especially from renewable energy sources. In this type of systems, inverters play a key role by providing power transforms. Multilevel inverters can achieve very low total harmonic distortion (THD) values at low switching frequencies without using any filtering units when compared with classic two-level inverters. However, multilevel inverters use high number of semiconductor elements, which increases the probability of any fault in the circuit, which may cause the whole system stopping for a long time. This is very critical issue for the buildings that have vital importance like hospitals or the industries where faults cost large amounts of money. In this work, a Fault-tolerant cascaded H-Bridge quasi-eight-level multilevel inverter with a single DC source and with output-side transformers was designed and application of reconfiguration technique was shown. The proposed inverter system can continue working if a fault occurs in one of H-Bridges with a one-level decrement in the output voltage in quarter period.