A three-phase inverter with neutral-line voltage injection is proposed to improve the output voltage waveform. This inverter consists of a three-phase inverter and a single-phase inverter. The former is referred to as the main inverter, which operates in the 120° conduction mode, and the latter is called the auxiliary inverter, which serves as a wave shaper injecting voltages of three-time and higher-order frequencies (odd triples) of the main frequency with PWM operation. The main inverter converts almost all the input DC power to AC power in the discontinuous rectangular waveform. The auxiliary inverter is applied to lower the total harmonic distortion (THD) of the output voltage. The design of the proposed inverter is presented in this paper. A digital-signal-processor (DSP) is used as a controller. The performance of the entire inverter is investigated in both theoretically and experimentally. The output three-phase voltages had a THD of approximately 4.3% in the experiment. The practicability of the control method is confirmed.
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