Abstract: A novel optimal switching systems algorithm, referred to as 3-segment space vector pulse width modulation (SVPWM), was developed to solve the problem that the traditional 7-segment SVPWM is limited largely in high-level electric inverters application. The optimal algorithm adopts a novel triangular dividing method and 60° coordinate system. The cause and minimization principle of additional switching were analyzed. The design steps of 3-segment switching sequence were given detailedly with some examples. In contrast to that of 7-segment SVPWM, the switching sequence design of the proposed 3-segment SVPWM is more flexible, and it could minimize the switching frequency, decreasing switching loss. The proposed modulation strategy was simulated on a 5-level cascaded H-bridge inverter. Simulation results verified its validity and superiority.