Single-Stage Control System of I-MMC-BasedIsland MVDC Link Receiver With MultipleModulation Freedoms

In the medium-voltage AC/DC distribution networks with distributed renewable sources onislands, a multi-port receiver is the key factor for hybrid power conversion. However, the most used modularmultilevel converter (MMC)-based multi-port converters (MCs) face the coordination and complexitychallenges due to their double-stage control system and voltage-balancing control of capacitors. In particular,the control system is more unstable and complicated when the control of circulating currents is considered.In this paper, an isolated modular multilevel converter (I-MMC) is used as a receiver, and a unifiedcoordinated control scheme based on the multiple modulation freedoms is proposed. Due to the voltageclamping of high-frequency transformers, there is no concern of the capacitors’ voltage-balancing control.Based on the proposed single-stage control system, the unified coordinated control scheme solves thecoordination problem of the MMC-based MCs. The multiple modulation freedoms corresponding to an ACport, two DC ports, and three-phase circulating currents can independently control respective targets. Thecontrol structure is simplified, while the control freedoms are ensured. Experimental results confirming theperformance of the designed control system is shown.     «

In the medium-voltage AC/DC distribution networks with distributed renewable sources onislands, a multi-port receiver is the key factor for hybrid power conversion. However, the most used modularmultilevel converter (MMC)-based multi-port converters (MCs) face the coordination and complexitychallenges due to their double-stage control system and voltage-balancing control of capacitors. In particular,the control system is more unstable and complicated when the control of circulating currents is c...     »