Single-Phase Three-Wire Power Converters Based on Two-Level and Three-Level Legs Using a Space-Vector PWM-Based Voltage Balancing

This article proposes four converters for interfacing a single dc power source and loads of a single-phase three-wire system. The topologies of the proposed converters are based on two-level (2L) and three-level neutral point clamped (NPC) legs. For regulating the dc-link capacitors of the NPC-based converters, a dc-link voltage-balancing technique is proposed to balance the neutral-point voltage using the space-vector pulsewidth modulation, considering the harmonic distortion of the output voltages and the semiconductor losses from an algorithm that defines the vector sequences to be applied. These characteristics make the proposed converters suitable for applications in microgrid employing dc distributed energy resources or ac power supply by adding ac-dc stage. The proposed converters are compared to a conventional 2 L converter from simulated results for evaluating the semiconductor losses in balanced and unbalanced load scenarios. Experimental results are presented to verify the effectiveness of the proposed voltage-balancing technique and to validate the converters.