Direct Power Control of Neutral-Point-Clamped PWM Converter

This paper describes direct power control of a neutral-point-clamped PWM converter. The key of this strategy is a direct selection of switching modes on the basis of instantaneous control errors of active and reactive power. In addition, this paper discusses neutral point voltage control and PWM pattern equalization schemes. The validity of the proposed technique was examined by computer simulations and experiments after theoretical analyses. Through several experimental tests, it was confirmed that total input power factor and efficiency were more than 99% and 97% over the load power range from 400 to 2000W, respectively. The experimental results demonstrated excellent performance of the proposed method, compared with a conventional control technique of the neutral-point-clamped PWM converter.