Simple Control Algorithm to Balance the DC-Link Voltage in Multilevel Four-Leg Four-Wire Diode Clamped Converters

Multilevel converters and specially multilevel four-leg four-wire converters actually are an important focus of researchers. Applications as harmonic compensation and energy quality are the major objectives of this type of converters. The balancing of the DC-Link capacitors voltage is a critical problem in multilevel converters and the first control strategy based on using the redundant vectors in a Space Vector Modulation scheme for four-leg four-wire Diode Clamped converters is presented. The balancing algorithm was simulated and finally successfully implemented in a real prototype. It is important to notice that the proposed method is completely generalized an due to it, it is independent of the load and independent of the number of levels of the converter. Besides, the proposed balancing control algorithm works with balanced or unbalanced loads. Experimental results are presented using a 50KW prototype.