Fault detection in multilevel cascaded inverter using park´s vector approach with balanced battery power usage

Among the multilevel converter topologies the cascaded H-bridge converter (MCHBC) differs from other topologies by having series connections of several power cells, producing a better voltage quality and higher voltage output range, and using the same voltage power supply levels. This characteristic adds several benefits as it allows a modular system, the use of low voltage power supplies, and output voltage waveforms with low level of harmonic distortion. Having more semiconductors than a conventional 2-level voltage source inverter (VSI) the probability of a fault occurrence is bigger, and therefore the importance of having a system that can pinpoint the malfunctioning device is higher. This paper presents an integrated method to control a 3-phase MCHBC capable of distributing the energy uniformly by all batteries and simultaneously diagnose isolated gate bipolar transistors (IGBTs) open-circuit faults in the converter cells, using the phase voltage Park´s Vector components of the star connected MCHBC. Simulation and experimental results of the proposed control are presented for a three-phase induction motor load.