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In this article, a series hybrid circuit breaker based on a flying capacitor multilevel injector (FCM-SHCB) is proposed for MVDC and LVDC, which utilizes the multilevel characteristic of FCM to realize the fault-current-limitation modulation and extend operation windows for mechanical switch (MS). Meanwhile, by fully exploring the redundant states of the FCM structure, the proposed FCM-SHCB can avoid the high-frequency operation of one single device in conventional S-HCBs, realizing balanced switching operation of the power semiconductor devices and reducing switching frequency without sacrificing the injection performance. The operation principle and parameters design consideration are detailed. A proof-of-concept FCM-SHCB prototype experimentally demonstrates the proposed solution can maintain the high-speed fault-current breaking ability (150 V/15 A/ $6~\mu $ s) while obtaining balanced switching operation (half-reduced switching frequency) and current limiting capability.

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.

The Si/WBG hybrid half-bridge (HHB) converter with hybrid frequency interleaved operation (HFIO) aims to offer an improved cost-performance tradeoff but suffers from uncompensable and low-frequency fluctuations in power quality issues and complicated control design. In this article, an Si/wide-bandgap (WBG) coupled half-bridge (CHB) is proposed, which coordinates the hybrid-frequency interleaved Si and WBG phase operation by a coupled inductor. By optimal configuring the coupling coefficient, the un-compensable, and low-frequency fluctuations of power quality issues can be completely addressed. Meanwhile, the HFIO controller is redesigned from the perspective of the modulated model predictive control, and the implementation can be greatly simplified under the selected optimal coefficient. A 3.3 kW Si insulated gate bipolar transistor (IGBT)/SiC mosfet CHB totem-pole bridgeless PFC (TPBPFC) prototype is built as a case study to validate the proposed design concept. In comparison to conventional Si/SiC HHB TPBPFC, the proposed Si/SiC CHB TPBPFC can achieve a maximum 64.7% total harmonic distortion (THD) reduction, demonstrating the same low ripple and THD performance as full high-frequency two-phase all-SiC design in all operating ranges while with 16.7% cost reduction.