With the level number of the cascaded H-bridge inverter increasing

it becomes complex for the spacevector pulse width modulation（SVPWM）algorithm to determine the position of the reference voltage vector. Accord-ingly

this paper proposes a method for decomposing a reference vector into multilevel basic vector and two-level ref-erence vector. The small hexagonal region

where the two-level reference voltage vector nearest the reference vectorend locates

is selected

and the two-level reference vector is synthesized using the improved seven-segment two-lev-el method. Then

the two-level switching sequence is combined with the multilevel basic vector to get multilevelswitching sequence. The improved two-level SVPWM omits the sector identification to simplify the complex opera-tion of the action time. Application of this method to the cascaded H-bridge shunt active power filter（SAPF）canachieve simple control logic and lower harmonic content in inverter output. The effectiveness of the proposed methodis verified by simulation and experiment.