MULTILEVEL CONVERTERS - A NEW BREED OF POWER CONVERTERS

Multilevel voltage source converters are emerging as a new breed of po wer converter options for high-power applications, The multilevel volt age source converters typically synthesize the staircase voltage wave from several levels of de capacitor voltages, One of the major limitat ions of the multilevel converters is the voltage unbalance between dif ferent levels, The techniques to balance the voltage between different Levels normally involve voltage clamping or capacitor charge control, There are several ways of implementing voltage balance in multilevel converters, Without considering the traditional magnetic coupled conve rters, this paper presents three recently developed multilevel voltage source converters: 1) diode-clamp, 2) flying-capacitors, and 3) casca ded-inverters with separate de sources. The operating principle, featu res, constraints, and potential applications of these converters will be discussed.