Dead-time effect modeling for hybrid modular multilevel converter using twin mapping

• High-efficiency equivalent model for MMCs considering dead time characteristics. • Detailed analysis of the modal transition of full- and half-bridge submodules during dead time. • Twin mapping method enabling dead-time characteristics in Thevenin equivalent models. • EMT Characteristics validated by comparing with SOTA models and the accuracy and efficiency are demonstrated. • Notches and spikes caused by dead time are accurately regenerated, providing a model foundation for further research. Dead-time control is essential for modular multilevel converters (MMCs), but it negatively impacts MMC performance. To support the development of control strategies to mitigate the adverse effects of dead-time, electromagnetic transient (EMT) simulations are crucial for analyzing MMCs’ dead-time behavior and developing strategies to mitigate these effects. However, simulating the impact of dead-time in high-level MMCs remains a challenge. The complex modular cascaded circuit significantly slows simulation speed, while the freewheeling conduction of submodule diodes during dead-time disrupts the integrity of submodules in each bridge-arm. This makes it difficult to represent the circuit as a unified Thevenin equivalent for simplification. To address the issue, the dead-time effect is modeled using a diode-H-bridge in this paper. Submodules are categorized into those affected by the dead-time effect and those not. This paper also proposes the capacitor state mapping approach, referred to as “twin mapping method”, to restore the submodules’ behavior during and outside the dead-time, eliminating the isolation of submodules and enabling the application of the Thevenin equivalent theorem. Finally, a Thevenin equivalent model (EM) is developed and compared with a detailed model (DM) and state-space model (SSM). PSCAD/EMTDC simulations demonstrate that the proposed EM effectively captures dead-time spikes and notches while significantly accelerating simulation speed.