Universal MNRV DPWM Methodology for Effective Voltage Balancing in Diode-Clamped Multilevel Topologies

This paper presents the multi-neighboring reference vector discontinuous PWM (MNRV DPWM) methodology for effectively controlling DC-link voltage imbalance in multilevel diode-clamped topologies. MNRV DPWM utilizes multiple neighboring reference voltage vectors to balance capacitor charging while ensuring volt-time compliance through the additional degrees of freedom provided by outermost voltage vectors. A duty compensation mechanism further simplifies closed-loop control and enhances system stability. The proposed approach is applied to three-phase PWM inverters and full-bridge (FB) LLC resonant converters, demonstrating its effectiveness in DC/AC and DC/DC power conversion systems. By interpreting FB circuits as two symmetric half-bridge circuits, MNRV DPWM can be efficiently implemented through offset voltage (Voffset) injection. Experimental results confirm the effectiveness of MNRV DPWM in mitigating voltage imbalance and enhancing power conversion efficiency. This study highlights the broad applicability of MNRV DPWM across multilevel DC/AC, AC/DC, and DC/DC converters and its potential for high-voltage, high-power conversion systems.