This paper presents an optimized modulation method to increase the DC-link voltage utilization in DC to AC converters. Inspired by third-harmonic injection method, several zero-sequence harmonic components are injected to the reference voltage waveform to enhance the DC-link voltage utilization factor. For this purpose, the amplitude of the fundamental component as well as the other components are extracted to obtain the maximum output voltage without overmodulation. This problem is defined as an optimization problem with inequality constraints and solved by the particle swarm optimization (PSO) algorithm. Consequently, the DC-link voltage utilization factor is enhanced. The zero-sequence components, also, are eliminated automatically in the line-to-line voltages. The performance of the proposed method is investigated using simulation and experimental results.