Multilevel SVPWM algorithm used in cascade H bridge STATCOM has the advantage of high DC voltage utilization

providing good voltage waveform. But the complexity of the traditional algorithm will rises rapidly due to a large amount of redundant space vectors appearing when the number of level becomes larger. To solve the problem of difficult in implementing the traditional algorithm

a simplified multilevel modulation algorithm used in STATCOM is proposed

which combines with zerosequence voltage injection

the DC voltage balance between three phrases. A two-module STATCOM model is built in Simulink

and the simulation results shows that the STATCOM has good ability of reactive current and harmonic current compensation. The multilevel SVPWM algorithm is simplified and the simplified alg-orithm. The results verifies the validity and feasibility of the proposed algorithm.