Multilevel converters have made many advances in high power applications and renewable energies due to their ability to generate multiple voltage levels. One of the most widely used multilevel converters is the Cascaded H-Bridge Converter (CHB). This converter is made of serializing several H-bridge cells in each phase that produce the desired voltage, and serializing these bridges has made it possible to use redundancy in this converter. The large number of semiconductor switches used in these converters increases the probability of fault in these converters. To ensure that the converter continues to operate in the event of short-circuit and open-circuit faults and to prevent their spread, it is essential to find a suitable solution for the converter to continue operating. In this essay, a method will be presented to improve a cascaded H-bridge converter’s performance after a fault in the application of photovoltaics. This method is based on injecting more active and reactive power into the grid and tries to achieve this goal based on the characteristics of solar panels and by increasing the total voltage generated by the panels compared to the complete elimination of the defective cell, the system’s ability to inject reactive power to the grid increases. In this method, after the fault occurs, only the defective leg is left out, and the other leg continues to work. Also, in order not to produce DC voltage at the voltage generated by the cells, the complementary leg of the defective leg from another healthy cell treats like the defective leg to create a symmetrical voltage at the output. This increases the faulty cell voltage and injects more active power into the grid than completely eliminating the faulty cell. Also, to increase the active power injected into the grid, the modulation coefficient of the defective cell is increased as much as possible, which also increases the active injecting power but reduces the output voltage of the panels. The modulation used is a combination of LSPWM and PSPWM modulations, which has led to the use of both positive features for this system.
