Proportional-Integral Control of Three-Phase Neutral-Point-Clamped Converters

Two-level converters are widely applied in middle and high voltage fields. In high voltage applications, though the over-voltage problem can be mitigated by using multiple switches in series and/or parallel, this evokes other problems like dynamic and/or static voltage and current sharing problems of the switches, which increases uncertain factors in technology and decreases system stability. To solve this problem, three and higher level converters (i.e., multiple-level converters) have been investigated by researchers, to suit the high-voltage and high-power systems. Multiple level converters can greatly reduce the current THD of the input current, decrease the electromagnetic interference of system, achieve less power loss and improve energy efficiency. Therefore, multiple-level converters is the future trend.