A Bidirectional Single Capacitor Unit Based Hybrid T-Type Converter Topology With Sensor-Less Voltage Balancing Capabilities

This study introduces a novel bidirectional hybrid T-type converter configuration named the single-capacitor unit-based hybrid T-type converter (SCU-HTC). This innovative architecture employs a single capacitor, leading to a 50% reduction in total capacitor count when compared to conventional T-type inverters. The design operates in two primary modes: buck mode and normal mode. In buck mode, the single capacitor’s voltage is maintained at half of the DC link voltage, resulting in lower output voltage magnitude and improved total harmonic distortion. This outcome is distinct from standard T-type inverters. Conversely, during normal mode, the topology functions either as a three-phase two-level inverter or a three-phase three-level inverter. To facilitate seamless operation in both buck and normal modes, a new switching strategy is proposed. This strategy ensures balanced capacitor voltage, enhancing the stability of the DC link voltage. The proposed architecture also exhibits power factor correction (PFC) capabilities. Unlike many PFCs that struggle with maintaining unity power factor (UPF) across various power levels, often necessitating additional circuitry and control complexity, the suggested topology for rectifier mode offers sensor-less self-balancing that consistently upholds UPF. Notably, this topology also effectively addresses issues related to capacitor voltage balance. Experimental validation of the proposed concept underscores its viability.