Acta Energiae Solaris Sinica•2026•DOI: 10.19912/j.0254-0096.tynxb.202608_9665
This paper addresses the prevalent design deficiency in two-stage power conversion systems (PCS), where single-stage converter stability is prioritized over cascaded coupling effects, leading to reduced system stability and DC bus voltage oscillations. By establishing bidirectional impedance models for the DC-side ports of both the front-end bidirectional DC/DC converter and the rear-end voltage source converter (VSC), the influence of power magnitude and direction on port impedance characteristics is systematically investigated. A novel impedance optimization control strategy based on capacitor current observation is proposed. This strategy reshapes the impedance models of both stages, reducing the resonant peak of the source converter's output impedance and mitigating the negative impedance characteristic of the load converter's input impedance, thereby preventing magnitude intersection of input and output impedances and expanding the stable operating range of the cascaded system. A state observer replaces high-precision current sensors for capacitor current measurement, reducing hardware cost. Simulation and experimental results validate the effectiveness of the proposed control strategy, demonstrating suppression of bus voltage oscillations under rated power conditions. The study reveals that stability margins differ between forward and reverse power flow: forward power flow induces negative input impedance in the VSC, causing instability, while reverse power flow yields positive output impedance, ensuring better stability margins. Future work will address transient stability under non-rated conditions such as continuous power fluctuations and weak grid with nonlinear loads.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4197-4
Deep-blue organic light-emitting diodes (OLEDs) remain the most challenging primary-color emitters due to stringent exciton energy requirements. We strategically designed two innovative deep-blue emitters, SCZ-4AnCN and STPA-4AnCN, via systematic functionalization of an anthracene core with arylamino-decorated spirofluorene donors and cyano-substituted phenyl acceptors. Comprehensive theoretical and experimental analyses demonstrate that these spirofluorene-anthracene hybrids adopt precisely engineered distorted configurations, effectively suppressing detrimental intermolecular π–π stacking in condensed phases. The sp3-hybridized bridgehead carbons in spirofluorene units play a pivotal role by simultaneously restricting π-conjugation extension and fine-tuning donor–acceptor interactions, thereby stabilizing the lowest excited singlet (S1) state with dominant local excitation (LE) character. This molecular engineering yields exceptional deep-blue emission with remarkable efficiency. Notably, the materials exhibit unique high-lying reverse intersystem crossing (hRISC) behavior, enabling efficient triplet harvesting. Optimized doped devices incorporating SCZ-4AnCN achieve outstanding performance, including a maximum external quantum efficiency (EQE_max) exceeding 10% and CIE coordinates (0.154, 0.052) approaching the BT.2020 blue standard. Nondoped devices maintain impressive performance with an EQE_max of 7.51% and superior operational stability, demonstrating less than 10% efficiency roll-off at 1000 cd m−2. This work validates anthracene-based molecular architectures for deep-blue electroluminescence and establishes a transformative design paradigm for next-generation OLED emitters.
SCIENCE CHINA Materials•2025•DOI: 10.1007/s40843-025-3732-2
The exploration and utilization of marine resources demand advanced operational tools. At present, deep-sea vehicles equipped with manipulators serve as the primary platforms for underwater exploration. However, the pressure sensors responsible for detecting the subtle gripping forces of these manipulators still face significant technical challenges, primarily due to the extreme hydrostatic pressure, corrosive seawater environment, and stringent mechanical strength requirements. A dual-curing, waterproof digital light processing (DLP) resin has been developed to achieve micron-scale printing accuracy, excellent seawater resistance, and mechanical properties comparable to those of thermoplastic resins. More importantly, the deep-sea pressure sensor (DSPS) features a unique printed lattice structure that allows seawater to penetrate and equilibrate the internal and external pressures, effectively mitigating the effects of deep-sea hydrostatic pressure. Experimental results demonstrate that the sensor exhibits a wide detection range and high sensitivity, with a measured sensitivity of 0.77 kPa−1 under 30 MPa hydrostatic pressure and a signal fluctuation below 1.48%. Furthermore, both the sensitivity and detection range of the sensor can be tuned by adjusting the lattice parameters, providing a robust foundation for the advancement of marine resource exploration.