Results of Investigation of Multicell Converters With Balancing Circuit—Part II

This paper presents an investigation of a multilevel multicell ac/ac converter. The converter employs flying capacitors, whose voltages should remain in a constant relation to the input ac voltage. An inadequate relation between the voltages across the flying capacitors (the imbalance state) results in an increase of voltages across the switches above their rated values. An RLC series circuit (a balancing circuit) with a properly selected resonance frequency was connected in parallel to the load in order to eliminate the imbalance. The balancing process with the use of a passive RLC depends on the configuration and parameters of the balancing circuit, the parameters of the converter, as well as on the operating conditions. This paper focuses on the impact of these parameters on the operation of the converter. Furthermore, the principle of operation of the multilevel multicell ac/ac converter with an application of the natural balancing process is described.