Distributed Event-Triggered Consensus Control for Modular Multilevel Converters

The modular multilevel converter (MMC) is a prominent topology for medium to high-voltage, high-power conversion applications. This converter has a modular construction based on building blocks named submodules (SMs). However, the large number of SMs required in a typical application makes operating the MMC through a centralized control architecture difficult. Recently, distributed control schemes have been proposed to provide a modular hardware and software development solution for the MMC. This control architecture allows a two-level hierarchy, in which there are distributed low-level control tasks among local controllers (LCs) placed in the converter SMs, while central controller (CC) undertakes high-level control tasks. Under this scheme, both LCs and the CC could execute their control algorithms at different time steps, optimizing the control hardware utilization: this has not been previously reported for MMC operating with a distributed control approach. Based on that, this article proposes an event-triggered distributed control scheme for regulating the capacitor voltages in the MMC. Contrary to previously reported works, the proposal only updates the control actions of LCs when a trigger event occurs, notably reducing the LCs hardware utilization. Real-time hardware-in-the-loop simulation studies validate the proposal's effectiveness, and its performance is compared with traditional consensus-based distributed approach, showing superior performance.