A Digital Twin-Based Model Construction and Parameter Identification Method for MMC Half-Bridge Submodule

Modular multilevel converter (MMC) is widely used in high-power motor drive, energy storage, and flexible dc power transmission and distribution system, and the parameter identification for submodule (SM) is essentially important for reliable operation of MMC. This article proposes a digital twin (DT)-based method for model construction and parameter identification of the MMC half-bridge SM (HBSM). First, the DT model of the HBSM is built, which consists of a simplified MMC SM equivalent model and an arm current simulator-based mission profile emulator (MPE). Second, a modified particle swarm optimization (MPSO) algorithm is proposed to achieve the online identification of internal parameters in the HBSM, further achieving the real–virtual interaction feedback for real-time sensing of the operation state of the HBSM. Finally, a nonintrusive DT MPE for the HBSM is constructed in MATLAB. The simulation and experimental results show that the average errors of the actual and model-calculated capacitor voltage values are within 0.1%, and the parameter identification results combined error is less than 1%. The DT model established by the proposed method can effectively identify the parameters of MMC SMs under different operating conditions.