Bidirectional Five-Level Asymmetric T-Type Converter with Dual-Interval Current Sensorless Control Strategy

This paper proposes a dual-interval current sensorless control strategy for bidirectional five-level asymmetric T-type converters to reduce the cost, hardware complexity, and measurement errors associated with conventional current sensors. A mathematical model and bidirectional power control scheme are first established, and a current estimation mechanism is developed to replace physical current sensors for closed-loop current control under grid-connected operation. The proposed strategy is experimentally validated using a bidirectional five-level asymmetric T-type converter prototype in rectifier and inverter modes at 500 W and 1 kW. Experimental results show that the rectifier mode achieves a minimum input current total harmonic distortion (THDi) of 3.254% and a maximum power factor (PF) of 0.9986. In the inverter mode, the converter achieves a minimum THDi of 5.008% and PF ranging from 0.9948 to 0.9934. The results demonstrate that the proposed current sensorless control strategy can maintain satisfactory current quality, power factor, and bidirectional power conversion performance without physical current sensors, demonstrating its feasibility for grid-connected power conversion applications.