Carrier-Based Discontinuous Modulation for Dual Three-Phase Two-Level Inverters

Dual two-level inverter topology is a simple structure able to produce multilevel output voltage waveforms equivalent to a 3-level inverter. Its modular structure consists of two standard two-level three-phase voltage source inverters (VSI) supplied by two dc supplies. In case of two separate dc supplies an independent modulation of the two inverters can provide arbitrary power sharing between inverters in order to balance their dc voltages. However, proper multilevel voltage waveforms can be obtained only by relatively complex space vector modulation (SVM). This paper proposes two carrier-based modulation techniques for a dual two-level inverter with power sharing capability and proper multilevel voltage waveforms. Their main advantage is a simpler implementation compared to SVM. The proposed algorithms have been verified by numerical tests and preliminary implementation in an industrial DSP.