A look-up table based method for voltage balancing of neutral-point in five-level ANPC converter

In this paper, an easily implementable method based on look-up tables is presented for balancing the neutral-point (NP) voltage in a five-level Active NPC topology for space vector modulation (SVM). In the proposed method, by utilizing the direction of output phase currents, operating region is divided into six zones. In each zone, there are two look-up tables; one for increasing the NP voltage and the other for decreasing the NP voltage. Since some look-up tables in different zones are identical, six individual look-up tables are obtained for controlling the NP voltage. In the proposed method, just few comparative operators and six look-up tables are utilized; therefore this method has proper implementation capability. Also, the proposed method is experimentally implemented on an active NPC converter which drives an induction motor via rotor field oriented control (RFOC) method. Experimental results verify performance, good dynamic response and effectiveness in balancing the NP voltage in low and high modulation index.