Three-phase Three-level Inverter Research Articles

Modulação space vector para inversores alimentados em tensão: uma abordagem unificada

O objetivo deste trabalho é de que ele possa ser utilizado como tutorial da modulação space vector para profissionais da área de Eletrônica de Potência. Nesse sentido, este artigo apresenta uma abordagem unificada para a modulação space vector aplicada a inversores alimentados em tensão. Cinco inversores de tensão são apresentados para exemplificar a metodologia proposta, são eles: inversor monofásico em ponte completa, inversor trifásico a três fios de dois e três níveis, inversor trifásico a quatro fios de três e quatro braços. Para cada um dos inversores são apresentados os vetores de comutação, os planos de separação, os planos limites para operação na região linear, bem como algumas possíveis seqüências de comutação. Resultados experimentais são apresentados para validar a metodologia proposta.

Control of Cascaded Multilevel Inverters

A new type of multilevel inverter is introduced which is created by cascading two three-phase three-level inverters using the load connection, but requires only one dc voltage source. This new inverter can operate as a seven-level inverter and naturally splits the power conversion into a higher-voltage lower-frequency inverter and a lower-voltage higher-frequency inverter. This type of system presents particular advantages to Naval ship propulsion systems which rely on high power quality, survivable drives. New control methods are described involving both joint and separate control of the individual three-level inverters. Simulation results demonstrate the effectiveness of both controls. A laboratory set-up at the Naval Surface Warfare Center power electronics laboratory was used to validate the proposed joint-inverter control. Due to the effect of compounding levels in the cascaded inverter, a high number of levels are available resulting in a voltage THD of 9% (without filtering).

Two-phase modulation technique for three-level inverter-fed AC drives

Two-phase dipolar and unipolar modulation techniques for three-level three-phase inverters are suggested and compared with conventional three-phase pulsewidth modulation (PWM) techniques. Two-phase PWMs with 60/spl deg/ (0/spl deg/ and /spl plusmn/30/spl deg/ shift) and 120/spl deg/ cycles are investigated from the point of view of harmonic losses, motor voltage spectra, and torque pulsations. It is shown that two-phase dipolar PWMs have no advantages in comparison with three-phase PWMs, while two-phase unipolar PWMs-in contrast with three-phase PWMs-considerably decrease the motor harmonic losses and torque pulsations in the whole motor voltage region. At the same time, the inverter neutral point control requires reversing to three-phase PWM technique for the duration of the control.