Hybrid SVM for Enhanced Efficiency of 3L ANPC Inverter With Full ZVS Range

The zero-voltage-switching variable frequency (ZVS-VF) control can achieve ZVS without auxiliary circuit. Nevertheless, it will increase switching losses under light load and conduction losses under heavy load, thus affecting efficiency. This is particularly evident in scenarios with varying dc side voltage and load power (e.g., photovoltaic systems). To address this issue, our proposed continuous space vector modulation (CSVM)-improved discontinuous space vector modulation (IDSVM) hybrid strategy can improve the efficiency at both light and heavy loads under various dc side voltages when employing ZVS-VF to a 3L inverter. This is achieved by leveraging the losses performance of diverse modulations, and CSVM is chosen to reduce switching losses under light load, while IDSVM is selected to limit conduction losses under heavy load. Additionally, with the proposed hybrid modulation, the full ZVS range can be realized in the 3L inverter. The modulation transition point is determined by the power losses analysis, ZVS range analysis, and smooth transition constraint. It can be adaptively adjusted to achieve smooth transition of different modulation methods under varying operating conditions. The experimental results from a 10-kW 3L active neutral-point-clamped (ANPC) inverter demonstrate that the proposed strategy improves efficiency by 3.7% for light load and 1.94% for full load compared to the conventional constant frequency control.