Abstract: An space vector pulse width modulation（SVPWM） modulation was proposed to solve the problem of DC voltage imbalance in the single-phase cascaded neutral-point-clamped H-bridge inverter. To avoid the harm of module port voltage level-skip, the transition states were introduced in the redundant vector selection, which made the current vector gradually switching to the vector with the strongest voltage balance ability, and reduced the switching frequency of the converter. The selection method of the optimal transition was given. Meanwhile, a digital SVPWM algorithm based on the programmable logic device was designed. Finally, the experimental results of two-cascade-module based prototype were presented to verify the voltage balance ability and the steady-state and dynamic performances of this modulation strategy.