A Virtual Space Vector PWM with Active Neutral Point Voltage Control and Common Mode Voltage Suppression for Three-level NPC Converters

Virtual space vector pulse width modulation (VSVPWM) provides a new approach to neutral point voltage (NPV) control and common mode voltage (CMV) suppression. Few values of coefficients configured in the virtual vectors cannot adjust the NPV continuously. An improved VSVPWM (IVSVPWM) with active neutral point voltage control (ANPVC) and CMV suppression is proposed in this paper. Continuously variable coefficients configured in the virtual vectors adjust the NPV actively and continuously for any load power factor over the full modulation indexes. Failure of CMV suppression is analyzed, and the undesired vectors with high CMV are avoided by limiting the range of the variable coefficients. The limited variable coefficients and the selected basic vectors with low CMV suppress the CMV effectively. Simulation and experimental results are given to validate the proposed novel IVSVPWM which can achieve quicker ANPVC and reduce CMV to half of the conventional VSVPWM simultaneously.