Five-Level ANPC Inverter With Full DC-Bus Utilization

This letter presents an improved hybrid active neutral point clamped (IHANPC) five-level (5L) inverter as an upgrade/replacement for a conventional 5L ANPC inverter. Unlike the conventional ANPC inverters, the proposed inverter doubles the utilization of the dc-link voltage, eliminating the need for an additional boosting stage. By charging the switched capacitor (SC) to half the input voltage, it doubles the rms output voltage for a given dc voltage. Also, a tiny inductor is incorporated to limit the prevailing SC impulse charging current without affecting the inverter operation. Moreover, the proposed IHANPC inverter can also self-start and self-balance the voltages of the SC and the dc-link capacitor voltages without any external circuits or balancing techniques. Due to the lower required dc-link voltage and limited SC charging current, devices with lower voltage and current ratings can be selected. Design considerations and a comparative analysis with other current topologies are discussed in detail. The comparison shows that the proposed IHANPC requires the least number of parts to achieve the same performance and output quality. To validate the effectiveness and practicality of the proposed IHANPC inverter, the experimental results for a 1.2-kW system are presented.