Typology and working mechanism of a hybrid power router based on power-frequency transformer electromagnetic coupling with converters

Abstract The power router (PR) is a promising piece of equipment for realizing multi-voltage level interconnection and flexible power control in the future distribution power grid. In this paper, a hybrid PR (HPR) topology based on power-frequency transformer electromagnetic coupling with converters is proposed for the medium distribution power grid. The power-frequency transformer is used to undertake power transmission, voltage conversion, and other main tasks, while the power electronic converters are combined to achieve active control. Equivalent magnetic and electrical circuit models are established to help discuss the operating principle of the proposed HPR. Additionally, the power flow and control principle of the HPR in different operating conditions are analyzed, with the control system design scheme presented. The theoretical analysis results are verified by MATLAB/Simulink + Plecs simulation and a controller hardware-in-the-loop study, as well as a down-scale experimental test, indicating that the proposed HPR is flexible in active voltage support and current control

Extendable space-type switched-capacitor multilevel inverter with fault-tolerant capability

Low reliability is one of the main concerns in terms of multilevel inverters (MLI) due to the presence of a large number of switches and capacitors. Therefore, the fault-tolerant operation of MLIs has recently gained a great deal of attention. An extendable space-type switched-capacitor MLI topology with fault-tolerant characteristics is proposed in this paper. The proposed inverter employs a single direct-current voltage source and three capacitors to output staircase voltage levels with low distortion. The proposed topology is capable of tolerating open-circuit faults due to the separated charging paths of the inverter. Under pre-fault and post-fault operations, it preserves capacitor voltage balancing, voltage boost capability, as well as the ability to supply inductive loads. Furthermore, the voltage stresses of the switches and the voltage ripples of the capacitors are decreased or remain under post-fault operations. The proposed topology has been validated with a laboratory prototype in both dynamic and steady-state operations