Single-DC-source five-level CHB inverter with sensor-less voltage balancing

A single-dc-source 5-level cascaded H-bridge (CHB) inverter is studied in this paper. All possible switching sequences are analyzed and a sensor-less voltage balancing approach is proposed that regulates the second dc bus (capacitor) voltage at half of the first dc bus amplitude (isolated dc source). The output voltage levels include zero, capacitor voltage and the dc source amplitude. The simple sensor-less voltage balancing technique is integrated into switching method which makes it easy to implement using even cheap microcontrollers. Simulation results validate the good dynamic performance of the proposed sensor-less voltage controller in regulating the capacitor voltage at the desired level to generate 5-level asymmetric voltage waveform at the inverter output low harmonics contents.