A novel orthogonal-vectors-based topology of multilevel inverters

This paper presents a novel proposal of developing converter output voltage waveforms and novel converter topologies. The main idea is based on the assumption that the total converter output space vector is composed of two orthogonal space vectors. Two basic proposals are discussed. The first one is related to a converter built of two standard inverters: a main inverter (MI) and an auxiliary one. The converter output voltage space vector is composed of two orthogonal vectors generated by the respective inverters. The total power of the auxiliary inverter does not exceed 20% of the MI power. Thanks to the presented control method, the harmonic content of the output voltage is significantly reduced. The second proposal is related to a novel converter topology denoted as OVT-IHC. The converter is built of one two-level inverter and three isolated H-bridge circuit units. The structure and its performance are also discussed in the paper. The converter in question is able to generate 133 different output space vectors and permits achievement of a stepped adjustment of the RMS output voltage. Both topologies presented in the paper indicate some characteristics and advantages of multilevel inverters. The converters acting on the basis of the orthogonal vectors idea possess promising properties and are suitable to applications in medium-power converters. The paper presents main features and contribution to the theory.