Variable OFF-Time and Deadtime Scheme With Optimized Control Frequency for Soft-Switching Single-Phase Inverters

摘要

Controlling current at critical conduction mode (CRM) is an effective way to achieve zero voltage switching (ZVS) of switches for inverters. However, the higher reverse inductor current and fixed deadtime in fully digital soft-switching control, such as reverse current boundary-based (RCB-based) schemes, lead to higher rms inductor current and higher power losses. Besides, the digital control frequency for CRM-based inverters is not well designed, resulting in the contradiction between high performance and high digital calculation burden. Therefore, this article proposes a fully digital soft-switching control based on the variable off -time and deadtime with an optimized designed digital control frequency. First, the variable off -time and deadtime design guidelines are addressed with the established mathematical model of the CRM-based inverter. Then, the power losses of the inverter with different digital control frequencies and control schemes are quantitatively analyzed and compared. Finally, a 1 kW single-phase three-level neutral-point-clamped grid-tied inverter was built. Experimental results show that the proposed scheme can achieve the ZVS turn- on of switches without additional components, and the maximum efficiency is 98.3%. Compared with the RCB-based scheme, the proposed method achieves higher efficiency with the same hardware cost.