Novel hysteresis current control for modular multilevel converters using acceleration slope

This paper presents a novel acceleration slope-based hysteresis current control strategy for modular multilevel converters (MMCs). This approach enables the MMC to function as a high-bandwidth, high-precision current source while still retaining the low inherent harmonic generation and low losses of the MMC. Unlike traditional hysteresis current control in two-level voltage-source converters (VSCs), which toggle between two output voltage levels, the MMC’s multiple voltage levels offer more flexible current slope control with fewer switching actions. The proposed control is compared to other voltage generation techniques, such as nearest-level control, showing that the resulting losses are similar to those of traditional voltage-controlled MMCs. The paper also demonstrates the application of this strategy in a STATCOM with active filtering, highlighting faster response times. Additionally, a current source type Grid Forming Converters (GFMs), e.g., Virtual Synchronous Generator (VSG), is presented, illustrating how the proposed control enhances stability in both weak and strong ac grids. The effectiveness of the proposed method and two applications are validated through electromagnetic transient (EMT) simulations and hardware-in-loop (HIL) simulation.