New neutral point balancing strategy for five-level diode clamped converters used in STATCOM of wind energy conversion systems

This paper presents a new neutral point balancing strategy for the five-level diode clamped converter (DCC) which can be used in STATCOM (static synchronous compensator) of wind energy conversion systems (WECS), with lower switching frequency below 1 kHz. The proposed space vector modulation (SVM) strategy reduces voltage variations at the converter neutral point, with no need for additional controls or auxiliary devices. The redundant switching states are utilized to generate the switching sequence in this strategy. The new algorithms are implemented in Matlab/Simulink and PLECS co-simulation platform on a 6 MW, 6.9 KV, five-level NPC (neutral point clamped) STATCOM. The simulation results demonstrate the capabilities of the proposed strategy to effectively maintain voltage balance of the dc link capacitors.